In the South and Southwestern regions of Nigeria, this woody plant is an important component of rural architecture. Natives used to construct life fences (Fongod et al., 2014). In South Africa and DR Congo, A. laxiflora is reported to be used as an anti-venom for snake bites (Molander et al., 2014). Similarly, the whole plant has been reported for the treatment of malaria, pile, dysentery, eczema, cough, and high fever in the Ekiti state of Nigeria (Jayeoba et al., 2012; Adeniran, 2015).

Leaves are the most frequently used plant part in folk medicine preparations, taken orally in most instances as an infusion, decoction, or juice, followed by the stems, branches, and roots. Leaves crushed in water are sometimes applied externally to treat skin diseases (Ajibesin et al., 2007). Similarly, the leaves of A. laxiflora are squeezed and mixed with milk or cheese (wara). A cup of the resultant mixture is suggested to be taken twice a week as a remedy for anemia by the Yoruba tribe of southwest Nigeria (Fabeku and Akinsulire, 2008). For managing uterine contraction and prevention of miscarriages, traditional healers in the south of Nigeria use A. laxiflora leave concoction prepared by squeezing leaves in water, filtering them, and mixing them with calabash chalk or calabash clay, taken twice a day after conception for 6 months (Bafor et al., 2018). Moreover, in the food industry, A. laxiflora leaves are used as wraps to preserve Kola nuts (Garcinia kola) and other perishable food items (Ihejirika et al., 2015).

The stem branches are used as Chewing sticks (local toothbrushes) for cleaning teeth in Nigeria (Farombi et al., 2003). Stem bark and branches have also been used in traditional medicine for various purposes, notably for malaria, anemia, emmenagogue, ringworm, venereal disease, typhoid fever, antioxidant, infertility in females, infectious diseases, tumor, inflammation, teething problems, and toothache in South Africa, Ghana, and Nigeria (Dzoyem and Eloff, 2015; Kaur et al., (2012); Obodai and Nsor, 2009).

In the Ogun and Osun states of Nigeria, the roots and fruits are used as ethnomedicine to treat fibroids (Oyeyemi et al., 2019). In the Edo state of Nigeria, the root bark of A. laxiflora is boiled with an egg from local chicken and eaten as a remedy for hemorrhoids (Ugbogu and Chukwuma, 2019). The traditional practitioners in the Ekiti state of Nigeria also prescribe root decoction for lowering blood pressure and reducing incidences of heart failure (Adeniran and Falemu, 2017).

Traditional use of A. laxiflora is limited to Africa, with lots of similarities in therapeutic applications, possibly due to the shared cultural exchange of its ethnobotanical use. Table 1 shows the ethnomedicinal uses of A. laxiflora in different African countries, regions, and communities, together with the plant parts used.

Flavonoids are the most common group of natural polyphenolic substances found in all fruits and vegetables. The flavonoids reported in A. laxiflora are in the form of flavanol and glycoside. From the ethyl acetate soluble fraction of the crude methanolic leaf extract of A. laxiflora, one novel acetylated flavonoid quercetin-3,4′-diacetate and three known flavonoid glycosides, quercetin, quercitrin, and rutin, were isolated (Ogundipe et al., 2001b). Concurrently, two novel sulfated flavonoids were isolated for the first time in the genus Alchornea and the family Euphorbiaceae, namely, quercetin-7,4′-disulphate and quercetin-3′,4′-disulphate (Ogundipe et al., 2001a). In another study, taxifolin glycosides were isolated from an n-butanol fraction of crude 50% ethanol aqueous leaf extract by AGC and SLHC chromatography characterized by spectroscopy techniques such as MS, ¹H, and ¹³C NMR (Adeloye et al., 2005). Oloyede et al. (2011) reported that A. laxiflora leaves’ ethanol extract on fractionation and characterization yielded two new flavonoids, namely, quercetin-3-O-β-D-glucopyranoside and quercetin-3,7.3′,4′-tetrasulphate. Lately, five known flavonoid glycosides (hyperoside, reynoutrin, guaijaverin, taxifolin-3-O-β-D-xylopyranoside, taxifolin-3-O-β-D-galactopyranoside) and two megastigmane glycosides (byzantionoside B and leeaoside) together with one steroidal glycoside (β-sitosterol-β-D-glucoside) and one lignan glycoside (syringaresinol-β-D-glucoside) were isolated from the methanolic leaf extract of A. laxiflora (Tapondjou et al., 2016). Interestingly, flavonoids were reported mainly from the leaves, but other parts of the plant have not been investigated yet, and quercetin sounds to be the most abundant and common monomer in the plant (Table 2; Supplementary Figure S1).

The leaves of A. laxiflora have demonstrated a higher concentration of phenolic compounds than the other parts (Table 2). The phytochemical investigation of methanolic extract from the stem bark of A. laxiflora resulted in the isolation of eight compounds, including ellagic acid, 3-O-methylellagic acid, and 3-O-methylellagic acid-3-O-α-rhamnopyranoside (Sandjo et al., 2011). A novel ellagic acid derivative, namely, 3,4,3′-tri-O-methylellagic acid, was isolated from the methanolic extract obtained from the A. laxiflora stem bark (Mbaveng et al., 2015). In another study, Morah and Uduagwu (2017) separated several phenolic compounds, namely, phenol, 2,4-bis(1,1-dimethylethyl)-; phenol, 2,6-bis(1,1-dimethylethyl)-; phthalic acid, butyl undecyl ester; diisooctyl phthalate and bis[di(trimethylsiloxy) phenylsiloxy] trimethylsiloxy phenyl siloxane from the petroleum ether; and ethanol extract of A. laxiflora leaves. In addition, Okokon et al. (2017b) isolated butylated hydroxy anisole (BHA), pyrogallol, 1,2-benzenedicarboxylic acid; 4-((1E)-3-hydroxy-1-propenyl)-2-methoxyphenol; 2-methoxy-4-vinylphenol; and 4-vinylphenol as major constituents of A. laxiflora leaves. 1,1′-Biphenyl-3,4,4′-trimethoxy-6′-formyl-; phenol, 3-[(trimethylsilyl)oxy]-; and zeranol were reported to be isolated from the A. laxiflora root ethyl acetate fraction (Okokon et al., 2017a) (Table 2; Supplementary Figure S2).

Many terpenoids (22 compounds), including seven triterpenoids, two diterpenoids, one sesquiterpene, five carotenoids, and seven steroids, have been isolated from the leaves, stem bark, and root extracts of A. laxiflora (Table 2; Supplementary Figure S3). Triterpenoids are represented by four pentacyclic triterpenoids (3-acetyloleanolic acid, 3-acetoxyursolic acid, adipedatol, and betulin) and two squalene types (squalene and 2,2,4-trimethyl-3-(3,8,12,16-tetramethyl-heptadeca-3,7,11,15-tetraenyl)-cyclohexanol) triterpenoid. Diterpenoids isolated from A. laxiflora leaves’ methanol and petroleum ether extracts are 17-hydroxyingenol and 3,7,11,15-tetramethyl-2-hexadecen-1-ol (Sandjo et al., 2011; Tapondjou et al., 2016; Okokon et al., 2017b; 2017a; Morah and Uduagwu, 2017; Bafor et al., 2018). Morah and Uduagwu (2017) investigated five carotenoid pigments (astaxanthin, lycoxanthin, rhodopin, dimethoxy-lycopene, and anhydrorhodovibrin), one sesquiterpene (hexahydrofarnesyl acetone), and five steroids (glycocholic acid, ethyl iso-allocholate, 7,8-epoxylanostan-11-ol, 3-acetoxy-, and 4-vinylcholestan-3-ol) from leaves of A. laxiflora using petroleum ether and ethanol fraction and structure confirmed by GS-MS. Sandjo et al. (2011) and Tapondjou et al. (2016) isolated and established the structure of a known steroidal glycoside, β-sitosterol-3-O-β-D-glucopyranoside from the methanol extract of stem bark and leaves, respectively. Likewise, another steroid cholest-4-en-3-one was isolated and characterized by Okokon et al. (2017a) from A. laxiflora ethanol root extract. In an attempt to isolate some antimalarial and antiplasmodial constituents from A. laxiflora, leaves and root ethanol extract on fractionation resulted in the isolation of three terpenoids, namely, 2,6,10-trimethylundecan-(5E)-2,5,9-trien-4-one; 3,7,11,15-tetramethyl-2-hexadecen-1-ol and 2(4H)-benzofuranone, 5,6,7,7A-tetrahydro-6-hydroxy-4,4,7- (Okokon et al., 2017b; 2017a).

Recently, essential oil from A. laxiflora leaves hydro-distillate on GC-MS analysis offered three long-chain aliphatic acids (palmitic, oleic, and petroselinic) (Otuechere et al., 2019). In another study, the crude methanolic extract of A. laxiflora leaves was subjected to column chromatographic separation and HR-ESI-TOF-MS analysis, resulting in the isolation of one novel fatty acid ester, namely, (10Z)-tetradec-10-enoic acid-(2S)-2-carboxy-2-hydroxyethyl ester, and one new ceramide, (2R)-2-hydroxy-N-[(2S,3S,4R,15Z)-1,3,4-trihydroxy-15-triaconten-2-yl]octacosamide (Sandjo et al., 2011). Morah and Uduagwu (2017) studied the GC-MS of petroleum ether and ethanol extracts of the A. laxiflora leaves and identified twelve fatty acid derivatives, namely, ethyl linoleate, icosyl oleate, oleyl palmitoleate, methyl palmitate, ethyl palmitate, cyclopropanedodecanoic acid, 2-octyl-, methyl ester; methyl isostearate, 1-heptatriacotanol; ethanol, 2-(9,12-octadecadienyloxy)-, (Z,Z)-; 9-octadecene, 1,1′-[1,2-ethanediylbis(oxy)] bis-, (Z,Z)-; 9-desoxy-9x-chloroingol 3,7,8,12-tetraacetate and one lactone fatty acid ester tricyclo [20.8.0.0(7,16)]triacontane, 1(22),7(16)-diepoxy- (Table 2; Supplementary Figure S4). Moreover, Okokon et al. (2017b) also isolated thirteen saturated and unsaturated fatty acids and esters, namely, pentadecanoic acid, stearic acid, 2-hydroxyethyl oleate, henicosyl formate, methyl ricinoleate, methyl linoleate, methyl elaidolinolenate, 1,3-diacetyloxypropan-2-yl icosanoate, 1-tetradecanol, 1-hexadecanol, dimethyl undecanedioate, 1-heptacosanol, and Z,E-2,13-octadecadien-1-ol. Okokon et al. (2017a) isolated and characterized a multitude of fatty acids from A. laxiflora root ethyl acetate fraction, including ethyl oleate, methyl oleate, α-linoleic acid, propyl linoleate, methyl palmitate, ethyl palmitate, trimethylsilyl palmitate, stearic acid, ethyl stearate, ethyl tetracosanoate, pentadecanoic acid, ethyl ester, ethyl laurate, ethyl myristate, elaidic acid trimethylsilyl, and a lactone fatty acid ester 2H-pyran-2-one, tetrahydro-4-hydroxy-6-pentyl (Supplementary Figure S5 ).

Various studies reported the presence of alkaloids in A. laxiflora using phytochemical screening, but only a few compounds have been isolated (Table 2; Supplementary Figure S6). An unusual prenylguanidinyl-epicatechin derivative alchornealaxine was separated from A. laxiflora leaves by Tapondjou et al. (2016). In another report, one pyrrolidine alkaloid, namely, 4-fluoro-2-nitroaniline, 5-[4-(pyrrolidin-1-yl) carbonylmethylpiperazin1-yl]-, was isolated from the extract of A. laxiflora leaves (Morah and Uduagwu, 2017). In two distinct studies by Okokon et al. (2017b, 2017a), two capsaicinoid alkaloids (capsaicin and dihydrocapsaicin) and one purine alkaloid called 1,3,7,9-tetramethyluric acid were isolated from the leaves and roots of A. laxiflora. Bafor et al. (2018) captured the porphine derivative pheophorbide A from the methanol A. laxiflora extract.

Notable compounds isolated from A. laxiflora include megastigmane glycoside (byzantionoside B, leeaoside), carbohydrates (2-methylerythritol, 4-amino-4-deoxyarabinose, 3-deoxy-arabino-hept-2-ulosonic acid), amino acids (2-amino-4,5-dihydroxy-3,4-dimethylpentanoic acid), alkanes (octadecane, 3-ethyl-5-(2-ethylbutyl)-), and 2-methyl-3,5-dinitrobenzyl alcohol (Tapondjou et al., 2016; Morah and Uduagwu, 2017). Two distinct studies by Okokon et al. (2017b, 2017a) reported the GC and GC-MS analysis of ethyl acetate fraction from A. laxiflora leaves and roots. They discovered that the ethyl acetate fraction was dominated by multifarious bioactive compounds: 1-hexadecene, 1-octadecene, 1-tetradecene, D-galactitol,3,6-anhydro-1,2,4,5-tetra-O-methyl-; 10,11-dihydro-10-hydroxy-2,3-dimethoxydibenz(b,f)oxepin; hydroxy-4,4-dimethyldihydro-2(3H)-furanone; 2-coumaranone, 2-cyclopenten-1-one, 2-methyl-; (Z),(Z)-2,5-dimethyl-2,4-hexadienedioic acid; 1-octadecene, propanoic acid, 3-(trimethylsilyl)-, ethyl ester; 2-furancarboxylic acid, trimethylsilyl ester; cyclopropenoic acid,1-trimethylsilyl,-2-(2-methylpropen-1-yl), methyl ester; 2H-pyran-2-one, 5,6-dihydro-6-pentyl-, (R)-; 1,2,4-cyclopentanetrione, 3-butyl-; octadecane, 1-bromo-; 2-butenoic acid, 2-methoxy-3-methyl-, methyl ester; benzoic acid, 3-acetyloxy-, trimethylsilyl ester; cyclopropanecarboxylic acid, 2,2-dimethyl-3-cis-(2-methyl-3-buten-2-yl)-; 3-{[tert-butyl (dimethyl)silyl]oxy}butanal; benzeneacetic acid, alpha-[(trimethylsilyl)oxy]-; 2-hydroxy-3-methoxybenzaldehyde, trimethylsilyl ether and benzene, and (2-ethyl-4-methyl-1,3-pentadienyl)-, (E) (Table 2; Supplementary Figure S7).

This literature review reveals that A. laxiflora is rich in flavonoids, phenolic compounds, terpenoids, fatty acids, steroids, and alkaloids. To date, 132 compounds have been identified and structurally elucidated from the extracts of A. laxiflora, including 13 flavonoids, 19 phenolics, 22 terpenoids, 43 fatty acids, 6 alkaloids, and other secondary metabolites. Nonetheless, most of these compounds have been identified from the leaves, stems, and roots of this plant. Consequently, it is suggested to utilize inflorescence, flowers, and fruits to identify and isolate chemical constituents. Moreover, further research is required to establish the therapeutic applications of isolated compounds of this plant.

The most common ethnomedicinal use of A. laxiflora includes the treatment of various infectious diseases such as typhoid, diarrhea, urinary tract infections, and venereal diseases. Hence, the application of A. laxiflora as an anti-infective agent prompted (Ogundipe et al., 2001b) to carry out bioactivity-guided isolation of the active constituent of A. laxiflora. Ogundipe et al. (2001b) evaluated six flavonoids associated with ethyl acetate fraction of methanolic A. laxiflora leave extract, namely, quercetin-7,4′-disulphate, quercetin, quercetin-3′,4′-disulphate, quercetin-3,4′-diacetate, rutin, and quercitrin against Escherichia coli (E. coli) NCTC 7001, Pseudomonas aeruginosa (P. aeruginosa) NCTC 6750, Staphylococcus aureus (S. aureus) NCTC 6571, Bacillus cereus (B. cereus) LSCV, Bacillus subtilis (B. subtilis) LSCV, Candida albicans (C. albicans) LSCV, and Aspergillus flavus (A. flavus) LSCV using the broth dilution method for determining the MIC and MBC of isolates with gentamicin 2.5 μg/ml, ampicillin 2.5 μg/ml, and tioconazole 10 μg/ml as reference compounds. The sulfated quercetin derivates quercetin-7,4′-disulphate (MIC range 3.13–12.50 μg/ml) and quercetin-3′,4′-disulphate (MIC range 6.25–15.63 μg/ml) showed preferred antimicrobial activity against all microorganism species than quercetin (MIC range 62.5–120.2 μg/ml) and comparable activity with standard drug ampicillin and tioconazole. Unfortunately, rutin and quercitrin did not exhibit any activity in this study (Table 3; Figure 4).

Different extracts (hexane, ethyl acetate, and butanol) of A. laxiflora leaves were screened against S. aureus, E. coli NCIB 86, B. subtilis NCIB 3610, and P. aeruginosa NCIB 950 using the agar well-diffusion method with streptomycin as a control. The mean zone of inhibition (ZOI) ranged between 10.1 and 17.1 mm, equivalent to the solvents (hexane, ethyl acetate, and butanol) used in the study (Oloyede et al., 2010), thereby getting negative results. Similar findings were reported (Essiett and Ajibesin, 2010) for antimicrobial evaluation of ethanolic extract of leaves against six human pathogenic bacteria—S. aureus NCIB 8588, B. subtilis NCIB 3610, E. coli NCIB 86, Proteus vulgaris (P. vulgaris) NCIB 67, P. aeruginosa NCIB 950, and Klebsiella pneumoniae (K. pneumoniae) NCIB 418—and two clinical fungal isolates, C. albicans and A. flavus. The obtained results revealed that the extract exhibits moderate inhibition against P. aeruginosa NCIB 950, P. vulgaris NCIB 67, and A. flavus with ZOI of 15 ± 3.6 mm, 11 mm, and 9 mm, respectively. The highest MIC value of 250 µg/ml was observed against P. aeruginosa NCIB 950 and A. flavus. However, no activity was observed with other tested strains (four bacterial and one fungal) (Table 3).

Akinpelu et al. (2015) reported a broad-spectrum antimicrobial activity of hydroalcoholic extract from A. laxiflora leaves. The antibacterial and antifungal activity of the A. laxiflora extract was evaluated against a panel of bacterial (39) and fungal (17) isolates. The extract at a concentration of 25 mg/ml inhibited all the bacterial isolates, with the ZOI ranging between 12 and 24 mm and MIC ranging between 0.78 and 25 mg/ml. Similarly, at the concentration of 35 mg/ml, the A. laxiflora extract inhibited 15 isolates out of 17 fungal isolates, with ZOI ranging between 11 and 23 mm and MIC ranging between 8.75 and 35.00 mg/ml. The highest antibacterial, antifungal activity of A. laxiflora was observed against Shigella species (24 ± 0.50 mm; MIC 3.13 mg/ml) and Trichophyton tonsurans (T. tonsurans) (23 ± 0.50 mm; MIC 2.19 mg/ml), respectively.

Another investigation of the antibacterial activity of A. laxiflora was conducted by Mbaveng et al. (2015). The antibacterial activity of a novel flavonoid, 3,4,3′-tri-O-methylellagic acid, isolated from the stem bark of A. laxiflora was evaluated against a panel of 14 g negative multi-drug resistant (MDR) bacteria, including strains of E. coli (ATCC 8739, AG102, AG100 A_tet), Enterobacter aerogenes (E. aerogenes) (ATCC 13048, CM64, EA27), K. pneumoniae (ATCC 11296, KP55), Providencia stuartii (P. stuartii) (ATCC29916, PS299645), Enterobacter cloacae (E. cloacae) (BM47, BM67), and P. aeruginosa (PA01, PA124) using chloramphenicol as a standard antibiotic. Compound 3,4,3′-tri-O-methylellagic acid exhibited weak antibacterial activity with MIC values ranging from 64 to 256 µg/ml on 4/14 (29%) and more than 256 µg/ml on 8/14 (57%), with no activity on the 2/14 (14%) tested bacteria. The lowest MIC value of 64 µg/ml was obtained against P. stuartii ATCC29916. Likewise, the methanolic extract from the leaves and stem bark of A. laxiflora was tested for their antibacterial activity against sensitive and resistant strains of bacteria, namely, P. aeruginosa (PA01, PA124), K. pneumoniae (ATCC11296, KP55, KP63), E. aerogenes (ATCC13048, CM64, EA 27, EA 289), E. coli (ATCC8739, ATCC10536, AG100ATet, AG102), and P. stuartii (ATCC29916, NEA 16) using rapid INT colorimetric assay. The result showed that except for E. coli AG100ATet and P. aeruginosa PA124, all other test strains (13/15, 86.7%) exerted sensitivity to methanolic leaves and stem bark extract of A. laxiflora with a MIC value range of 64–1,024 µg/ml. The A. laxiflora bark extract exhibited the highest antibacterial activity with a MIC value of 64 µg/ml against E. aerogenes EA 289 (Tchinda et al., 2017).

The different extracts (aqueous, ethyl acetate, and ethanol) of A. laxiflora leaves were tested against the clinical strains of Salmonella typhi (S. typhi) and Salmonella paratyphi (S. paratyphi) isolated from human stool. The extract showed dose-dependent inhibition in both the tested strains in different concentrations, likely 20, 40, and 60 mg/ml. However, ethyl acetate extract at the concentration of 60 mg/ml showed the highest antibacterial activity against S. typhi and S. paratyphi with ZOI of 24 and 19 mm, respectively (Osuntokun and Olajubu, 2015). Similar results were reported in another study by Wansi et al. (2017), in which the extract of methanol leaves exhibited preferred activity against S. typhi and Shigella flexneri (S. flexneri) with MIC values of 512 μg/ml and 1024 μg/ml, respectively.

Osabiya et al. (2017) demonstrated that aqueous and ethanol extracts from the leaves of A. laxiflora inhibited six bacterial strains, namely, B. subtilis, S. aureus, E. coli, Enterococcus faecalis (E. faecalis), K. pneumoniae, and S. typhi. The MIC ranged between 2.5 and 40 mg/ml. However, it was a noteworthy result that the ethanol extract exhibited more potent inhibitory activity at a concentration of 60 mg/ml against S. aureus (19.33 ± 0.58 mm) and K. pneumoniae (18.33 ± 0.58 mm) compared with the antibiotic chloramphenicol (11.67 ± 0.57 mm and 10.01 ± 0.00 mm). Furthermore, in vitro antibacterial activity of essential oils from leaves of A. laxiflora was carried out against B. cereus ATCC 10872, B. subtilis ATCC 6633, S. aureus ATCC 25923, P. aeruginosa ATCC 9027, and E. coli ATCC 25922. The mean ZOI ranged between 7 and 9 mm in contrast to the standard antibiotic ampicillin, with ZOI ranging between 6 and 8 mm (Otuechere et al., 2019).

On account of the traditional use of A. laxiflora leave decoction and infusion for the treatment of digestive and gastric disorders, Ngnameko et al. (2019) investigated the anti-Helicobacter pylori (H. pylori) activity of A. laxiflora leave extract. The extract was active against H. pylori at a MIC of 20 mg/ml. Lately, in vitro antibacterial activity of hexane, chloroform, ethyl acetate, methanol, ethanol, and aqueous extracts of the leaves, roots, and stem bark of A. laxiflora on the skin, gastrointestinal, respiratory, and urinary pathogens was also conducted. The extracts were tested against four Gram-positive bacteria, namely, B. cereus ATCC 11778, E. faecalis ATCC 29212, S. aureus ATCC 25923, and Staphylococcus saprophyticus (S. saprophyticus) ATCC 15305, and four Gram-negative bacterial strains, namely, E. coli ATCC 25922, K. pneumoniae ATCC 13883, Moraxella catarrhalis (M. catarrhalis) ATCC 23246, and Proteus mirabilis (P. mirabilis) ATCC 43071 using ciprofloxacin as a standard antibacterial agent. All the extracts were effective against most of the tested Gram-positive strains, with MIC ranging between 50 and 63 μg/ml. In addition, bioactivity-guided fractionation of methanolic extract of the A. laxiflora stem results in the isolation of ellagic acid, 3-O-methylellagic acid, 3-O-β-D-glucopyranosyl-β-sitosterol, 3-O-acetyl-oleanolic acid, and 3-O-acetyl-ursolic acid. All the compounds displayed antibacterial activity against tested strains with MIC values as low as 4 μg/ml (Siwe-Noundou et al., 2019) (Table 3).

Based on the literature survey, certain gaps were identified in the reported studies. For example, Osabiya et al. (2017) did not mention the strain collection numbers of investigated bacterial strains, which makes it difficult to establish a comparison with other studies. Similarly, limitations were observed in the studies reported by Ngnameko et al. (2019), Osuntokun and Olajubu (2015), and Wansi et al. (2017). For the purpose of quality control, the European Committee on Antimicrobial Susceptibility Testing (EUCAST) has recommended strain collection numbers from the distributors such as ATCC (American Type Culture Collection, United States), NCTC (National Collection of Type Cultures, United Kingdom), CIP (Collection de Institut Pasteur, France), CECT (Coleccion Espanola de Cultivos Tipo, Spain), CCUG (The Culture Collection University of Gothenburg, Sweden), and DSM (Deutsche Stammsammlung fur Mikroorganismen und Zellkulturen, Germany) (Matuschek et al., 2014). Furthermore, the assessment of anti-microbial activity using only the disc diffusion method is a preliminary approach because it did not ascertain the exact concentration-causing antimicrobial effect. Oloyede et al. (2010) reported the ZOI of different extracts determined by the disc diffusion method only. Unfortunately, they did not use agar or broth dilution tests to determine the MIC values. Moreover, the use of the agar diffusion method to determine the antimicrobial activity of plant extracts is considered inadequate owing to the lack of diffusion of non-polar molecules into the aqueous agar matrix, insensitivity, and non-reproducibility of the results in different laboratories. Therefore, serial microplate dilution methods using INT or rezurasin as indicators of growth are the preferred methods to determine realistic and reproducible MIC values (Eloff, 2019). Only a few studies reported the outcomes of rapid INT colorimetric assay. Plant extracts displaying MIC value ≤100 μg/ml are considered to possess noteworthy antimicrobial activity (Bueno, 2012). Nonetheless, multiple studies included in this review have reported MIC values higher than the accepted limit of ≤100 μg/ml. It is often not determined whether the antimicrobial activity is caused by general toxicity to all cells or a selective activity against the microorganisms.

Moundipa et al. (2005) investigated the in vitro amoebicidal activity of methanolic leave extract of A. laxiflora against clinical isolates of Entamoeba histolytica (E. histolytica). The extract, at a concentration of 100 μg/ml, showed 60.43% and 52.17% mortality on day 2 and day 4, respectively, indicating anti-amoebic activity.

Okokon et al. (2017b) investigated the in vitro antiplasmodial activity of A. laxiflora leaves, crude ethanol, petroleum ether, chloroform, ethyl acetate, and butanol extracts against two Plasmodium falciparum (P. falciparum) strains: CQ sensitive Pf-3D7 and CQ resistant Pf INDO SYBR green assay method. The crude ethanol, petroleum ether, chloroform, ethyl acetate, butanol, and aqueous leave extract of A. laxiflora were found to be active in vitro with CQ-sensitive IC₅₀ values of 31.57 ± 0.94, 27.85 ± 0.36, 26.06 ± 0.19, 9.92 ± 0.28, >100, >100 μg/ml, respectively, and had CQ-resistant IC₅₀ values of 16.38 ± 0.94, 23.47 ± 0.15, 14.47 ± 0.35, 7.51 ± 0.24, 52.63 ± 0.22, and >100 μg/ml, respectively. However, the ethyl acetate fraction exhibited the most promising activity against both strains of P. falciparum. Further, the fractionation of ethyl acetate extract led to the isolation of 34 phytoconstituents, including polyunsaturated fatty acids (PUFA), phenolics, and flavonoids. Likewise, prophylactic, suppressive, and curative effects of ethanol A. laxiflora leave extract (200–600 mg/kg, p. o.) were tested in vivo using Plasmodium berghei (P. berghei) infected mice. The extract showed promising antimalarial activity (Table 4; Figure 5). Similar results were reported by Okokon et al. (2017a) with the A. laxiflora root extract. The root extract and fractions also exerted moderate activity against CQ-sensitive (Pf 3D7) and CQ-resistant (Pf INDO) strains of P. falciparum, with ethyl acetate fraction exerting the highest activity with an IC₅₀ value of 38.44 ± 0.89 and 40.17 ± 0.78 μg/ml in Pf 3D7 and Pf INDO strains, respectively. Recently, an in vivo antiplasmodial activity of methanol and chloroform leave extract of A. laxiflora was reported (Table 4; Figure 5). Briefly, the extract was administered orally (200–600 mg/kg) to P. berghei-infected mice. After 5 days of the treatment study, methanol extract exhibited significantly higher prophylactic, suppressive, and curative activity than the chloroform extract. These studies confirmed the ethnopharmacological use of A. laxiflora as a promising indigenous antimalarial drug (Oluyemi and Blessing, 2019) (Table 4).

Morah and Uduagwu (2017) investigated the larvicidal activity of ethanol and petroleum ether extracts from the leaves of A. laxiflora against the third and fourth instar Anopheles mosquito larvae. Larva mortality was observed for both petroleum ether and ethanol extract at all concentrations assayed (0.08, 0.1, 0.15, 0.2 mg/ml), with the lowest activity at 0.08 mg/ml and the highest mortality rate observed at 0.2 mg/ml. Moreover, petroleum ether extract exhibited the highest 78% mortality compared to 68%, by ethanol extract at a similar dose of 0.2 mg/ml. In contrast, the larvicidal activity was attributed to the presence of methyl palmitate, icosyl oleate, and diisooctyl phthalate (Table 4; Figure 5).

Various extracts of A. laxiflora leaves, stem, and roots were evaluated for their Anti-HIV activity using HIV-1 integrase strand transfer assay. HIV-1 integrase inhibitory activity dwelt in most of the root extracts of A. laxiflora. The methanolic extract of A. laxiflora root exhibited noteworthy HIV-1 integrase inhibitory activity at an IC₅₀ value of 0.21 ng/ml compared to chicoric acid taken as a reference (IC₅₀ = 6.82 μM) without any significant cytotoxicity against HeLa cells. The ethanolic root extract and ethyl acetate root extract also exhibited marked HIV-1 integrase inhibitory activity with IC₅₀ values of 67.07 and 6.034 μg/ml, respectively. Moreover, the inhibitory activity of five compounds (ellagic acid, 3-O-methylellagic acid, 3-O-β-D-glucopyranosyl-β-sitosterol, 3-O-acetyl-oleanolic acid, and 3-O-acetyl-ursolic acid) isolated from the methanolic stem extract of A. laxiflora was also investigated on HIV-1 integrase, although all the isolated compounds were non-cytotoxic. However, they did not exhibit significant anti-HIV-1 integrase activity. Only ellagic acid laid out the best HIV-1 integrase inhibitory activity with an IC₅₀ value of 90.23 μM. The IC₅₀ values of other isolated compounds (3-O-methylellagic acid, 3-O-β-D-glucopyranosyl-β-sitosterol, 3-O-acetyl-oleanolic acid, and 3-O-acetyl-ursolic acid) were either >100 μM or could not be determined (Siwe-Noundou et al., 2019) (Table 4; Figure 5).

The use of A. laxiflora leave decoction for treating diabetes is common among the Badagry people of Nigeria. This practice was validated through in vitro and in vivo studies. Ogbole et al. (2016) showed that methanolic extract obtained from A. laxiflora leaves inhibits α-amylase moderately with an IC₅₀ value of 295.60 μg/ml. The anti-diabetic properties of A. laxiflora have recently been studied using an in vivo alloxan-induced diabetic rat model. When methanolic extract of A. laxiflora leaves was administered orally at a dose of 500 mg/kg, it showed a significant (p < 0.05) anti-hyperglycemic effect by lowering blood glycemic levels in diabetic rats (Nimenibo-uadia, 2018) (Table 4).

In order to substantiate the folklore medicinal use of A. laxiflora roots infusion or decoction as treatment of malaria and associated pain-related symptoms, Okokon et al. (2017a) investigated the analgesic activity of the crude ethanol extract and other solvent fractions of A. laxiflora using mice against the standard drug acetylsalicylic acid (ASA; 100 mg/kg) by acetic acid-induced writhing, hot plate, and formalin-induced hind paw licking methods. The administration of A. laxiflora root extract ((75, 150, and 225 mg/kg, p.o.) and extract fractions (150 mg/kg, p.o.) demonstrated a significant (p < 0.05–0.001) and dose-dependent analgesic activity in all used pain models. The ethyl acetate fraction exerted the highest analgesic activity compared with the standard drug ASA. The aqueous and methanol extracts from A. laxiflora leaves were appraised for analgesic effect in mice. The hot plate and tail immersion tests were used to evaluate the central analgesic effects, whereas the acetic acid-induced abdominal writhing assay was used to evaluate peripheral analgesic activity. The extract increased the mean reaction time to pain significantly in the hot plate and tail immersion tests. Additionally, the number of abdominal writhes also decreased substantially, endorsing the folklore use of this plant (Nwonu et al., 2018a).

The anti-inflammatory activity of acetone extract from A. laxiflora leaves was investigated in vitro. In the study, A. laxiflora extracts exerted dose-dependent inhibition of NO production by LPS-activated malignant macrophage cell line RAW264.7 at doses 6.25, 12.5, 25, and 50 μg/ml. At the concentration of 25 μg/ml, the extract exhibited the highest percent inhibition (96.53%). Simultaneously, the A. laxiflora extract significantly inhibited 15-LOX activity with an IC₅₀ value of 46.03 μg/ml compared to quercetin used as a reference drug (35.85 μg/ml) (Dzoyem and Eloff, 2015). Furthermore, Ngoungoure et al. (2019) reported that methylene chloride/methanol (1:1; v/v) extract obtained from leaves of A. laxiflora demonstrated similar results. The A. laxiflora extract exerted 68.10% NO inhibition (IC₅₀ = 66.57 μg/ml) and 54.58% 15-LOX inhibitory activity (IC₅₀ = 90.42 μg/ml) (Table 4).

To substantiate the ethnomedicinal use of A. laxiflora leaves in Cameroon to treat some gastrointestinal disorders, Wansi et al. (2017) conducted an in vivo study to appraise the antidiarrheal activity of methanolic and aqueous extracts of A. laxiflora (125, 250, and 500 mg/kg) using S. flexneri-induced infectious, castor oil-induced secretory, and magnesium sulphate-induced osmotic diarrhea in rats. The methanolic extract showed promising antidiarrheal activity in all animal models. The A. laxiflora methanolic extract significantly prolonged the latency period at all doses in the model of osmotic diarrhea, with the 250 mg/kg dose giving the highest 71.6% prolongation in latency time (Table 4).

In the Bamun folk medicine (Cameroon), A. laxiflora is reported to treat hepatitis and other liver-related disorders. As toxic hepatitis is often associated with the oxidative destruction of lipids and proteins, Njayou et al. (2008) carried out ex vivo rat liver microsomal lipid peroxidation (enzymatic and non-enzymatic) and protein oxidation inhibitory potential of methanol-methylene chloride extract of A. laxiflora leaves. On the whole, the A. laxiflora extract inhibited the biochemical process in a dose-dependent manner (10, 100, and 200 μg/ml) with the significant inhibition of microsomal lipid peroxidation (95.90 ± 0.57% and 79.17 ± 1.57%; enzymatic and non-enzymatic, respectively) and protein oxidation (95.60 ± 0.59%) at 200 μg/ml concentration.

The ethyl acetate extract of A. laxiflora was studied for its possible hepatoprotective effect against CCl₄-induced hepatotoxicity in rats to rationalize some folklore use. The ethyl acetate extract of A. laxiflora at 100 mg/kg body weight significantly counteracted the CCl₄-induced liver damage by lowering the elevated marker enzymes, namely, ALT, AST, ALP, and LDH levels in the blood to 18.872, 7.054, 22.864, and 180.321, respectively, compared to CCl₄ elevated levels of 35.712, 12.513, 27.509, and 480.312 for ALT, AST, ALP, and LDH, respectively. Further, histopathological analysis of the liver showed that the ethyl acetate extract may protect the liver from centrilobular necrosis, vacuolization, and macrovesicular fatty change set up by CCl_4. The hepatoprotective activity was ascribed to four isolated flavonoids, namely, quercetin, quercetin-3,7.3′,4′-tetrasulphate, quercetin-3-O-β-D-glucopyranoside, and quercitrin (Oloyede et al., 2011) (Table 4; Figure 6). In a separate study, A. laxiflora was tested for its ability to alleviate sodium arsenate-induced liver damage in Wistar rats. The hexane extract of the A. laxiflora leaves could significantly reverse the liver damage caused by sodium arsenate (Esosa et al., 2013). Similarly, the methanolic extract of A. laxiflora leaves significantly modulated the levels of liver biochemical parameters GGT, GST, ALT, and AST (Uhunmwangho et al., 2016). The hepatoprotective activity of A. laxiflora roots has recently been investigated using sodium arsenate-induced hepatotoxicity as a model. The hexane root extract could significantly lower the liver enzymes (ALT, AST, and ALP), liver metabolizing enzymes (NAD, GST, and Cytochrome b5), and other biochemical parameters (total protein, albumin level, and globulin) (Uhunmwangho et al., 2018). These findings backed up the folklore’s claim that this botanical drug can help with liver problems. (Table 4).

Oladiji et al. (2014) investigated the anti-anemic potential of aqueous leave extract of A. laxiflora at doses 100, 200, and 300 mg/kg, p.o. on hematological indices (PCV, Hb, RBC, MCV, MCH, and MCHC) of iron-deficient rats. The extract could significantly increase the hematological indices at all doses, compared with the reference drug ferrous sulfate and iron-sufficient rats, attesting to its folklore medicinal use in the treatment of anemia. Similar results were reported by Bada et al. (2017) with an ethanolic extract of A. laxiflora leaves. Another study was conducted on the anti-sickle cell anemic activity of A. laxiflora. The Anti-sickling activity of methanolic extract from A. laxiflora leaves was reported by Bamimore and Elujoba (2018). The extract had 98.8% sickling inhibitory action when given at a level of 8 mg/ml (Table 4; Figure 5).

Traditional African medicine uses the leaf of A. laxiflora to treat various reproductive system diseases, including preterm labor, miscarriage, menstrual disorders, postpartum discomfort, fibroids, and infertility. To appraise the ethnomedicinal use of A. laxiflora leaves to prevent preterm labor or miscarriage, Bafor et al. (2015) investigated the effect of methanolic extract of A. laxiflora leaves on female reproductive structures. Briefly, non-pregnant female mice were orally administered methanolic leave extract (100 and 1,000 mg/kg) for 6 days, using progesterone (10 mg/kg s.c.) as a positive control. The results revealed that the A. laxiflora extract at a lower dose (100 mg/kg) exerted progesterone-like activity on the ovaries, uterus, and cervical glands asserting its folklore use in maintaining pregnancy. In another investigation, ex vivo uterine contraction modulatory activity of methanolic extract of A. laxiflora was conducted using uterine tissue preparation isolated from female albino mice. The extract significantly inhibited spontaneous, oxytocin, and potassium chloride-induced uterine contractions, possibly via calcium and potassium ions channel interaction. Furthermore, the authors also isolated three important bio-constituents, namely, 3-deoxy-arabino-hept-2-ulosonic acid, 17-hydroxyingenol, and pheophorbide A, possibly contributing to the methanolic A. laxiflora extract activity (Bafor et al., 2018).

Uhunmwangho et al. (2016) studied the effect of the methanolic A. laxiflora leave extract on CCl₄-induced reproductive toxicity. The oral administration of the extract at a graded dose (0.1, 0.5, 1.0, 10.0, and 50 mg/kg body weight) in male Wistar rats for 7 days, significantly reversed the toxic effects of CCl₄ and aided in male fertility by significantly increasing the percentage motility of sperm and inhibiting sperm morphological aberrations compared with positive control (normal saline) (Table 4).

The leaves of A. laxiflora are traditionally used in the form of decoction or maceration to treat epilepsy and sleeplessness. Hence, the in vivo anti-convulsant and sedative activity of A. laxiflora was evaluated by Bum et al. (2009). The aqueous extract of the leaves of A. laxiflora was investigated for anticonvulsant and sedative activity in male Swiss mice using MES, PTZ, NMDA, INH, PIC, and STR-induced convulsions or turning behavior and diazepam sleep-induced animal models. The aqueous extract at a dose of 60 mg/kg protected 100% of mice against NMDA-induced turning behavior, and at a dose of 120 mg/kg, it protected 75% of mice against STR-induced seizures. The A. laxiflora extract failed to provide any significant protection against MES, PTZ, INH, and PIC-induced seizures. Moreover, in the diazepam-induced sleep test, A. laxiflora was insignificant in modifying the sleep duration of the control group, indicating the non-sedative activity of A. laxiflora. However, a recent study by Nwonu et al. (2018b) demonstrated the anxiolytic and sedative effects of aqueous and methanol extracts of A. laxiflora leaves using a staircase climbing test in mice. The results showed that both the methanol and the aqueous extracts of A. laxiflora leaves had significant sedative activity at a high dose (800 mg/kg) by significantly decreasing staircase climbing (Table 4).

The cholinergic deficit is implicated in the pathogenesis of neurodegenerative disorders such as Alzheimer’s disease and associated progressive memory loss and cognitive function impairments. The cholinergic deficit is the result of a reduction in central nervous system ACh activity due to the AChE-related breakdown of ACh. The extracts from different parts of A. laxiflora have been screened for AChE and BuChE inhibitory activity. The first report is that of Dzoyem and Eloff (2015), reporting the AChE inhibition activity of the acetone extract of A. laxiflora leaves using the modified Ellman method. The extract exhibited significant but weak inhibitory activity with an IC₅₀ value of 364.12 ± 2.39 μg/ml compared to eserine with an IC₅₀ value of 4.94 ± 0.015 μg/ml. Similarly, the methylene chloride: methanol (1:1; v/v) extract at a single concentration of 200 μg/ml exhibited 36.02 ± 0.18% AChE inhibitory activity with >200 μg/ml, IC₅₀ value compared to galantamine (100 μg/ml; IC₅₀ value 24.65 ± 2.12 μg/ml); a standard drug (Ndam Ngoungoure et al., 2019). Elufioye (2017) investigated the effects of various extracts (hexane, ethyl acetate, and aqueous) obtained from A. laxiflora leaves, stem bark, and root bark in inhibiting both AChE and BuChE. The results reported that the A. laxiflora stem bark and root bark extracts showed selective AChE inhibitory activity with percent inhibition ranging from 10.69% to 34.20% (Table 4).

In vivo antipsychotic effects of aqueous and methanol extracts of A. laxiflora leaves were evaluated by Nwonu et al. (2018c). According to their findings, oral administration of the aqueous and methanol extracts in mice at graded doses (100, 200, 400, 800, and 1,600 mg/kg, p.o.) significantly reduced apomorphine-induced climbing and stereotypic behavior in mice at all tested doses, compared with chlorpromazine, a psycholeptic agent (Table 4).

Ngoungoure et al. (2019) assessed whether A. laxiflora methylene chloride: methanol (1:1; v/v) leave extract with antioxidant and anti-inflammatory activities could serve as a protective agent against aminochrome-induced toxicity in human astrocytoma cells (U373MG and U373MGsiGT6 cell lines). The results indicated that A. laxiflora extracts at doses 0.1 and 1.0 μg/ml significantly altered the aminochrome-induced (75 μM) cell death and mitochondrial membrane potential reduction in both cell lines, implicating the potential usefulness of A. laxiflora in Parkinson’s disease. However, further studies are warranted in isolating the active constituents and detailed elucidation of the mechanism of the action for safe and effective utility in Parkinson’s disease (Table 4).

The anti-anxiety efficacy of aqueous and methanol extracts of A. laxiflora in mice was tested using the elevated plus-maze and the staircase behavioral paradigms to indicate the ethnomedicinal usage of A. laxiflora as an anxiolytic drug (Nwonu et al., 2018b). A. laxiflora exerted a significant anxiolytic effect on the elevated plus maze and staircase animal model against the standard drug diazepam (0.1 mg/kg, p.o.). Albino mice were divided into seven groups of six animals each. The control group (I) received 10% Tween-80 (10 ml/kg, p.o.), whereas the test groups (II–VI) received A. laxiflora aqueous or methanol leave extract in graded doses (100, 200, 400, 800, 1,600 mg/kg, p.o.) and standard drug group (VII) received standard drug diazepam (1 mg/kg i.p.) 30 or 60 min before the experiments. In the elevated plus maze model, the A. laxiflora methanol extract significantly increased the percent entry and percent time spent in open arms at lower and higher doses (100, 200, 800, and 1,600 mg/kg). In contrast, almost all doses significantly decreased the index of open-arm avoidance, attesting to anxiolytic activity. Similar results were observed for the aqueous extract of A. laxiflora leaves at doses 400 and 1,600 mg/kg, p.o., validating its anti-anxiety effect. In the staircase paradigm also, the methanol and the aqueous extracts of A. laxiflora leaves exhibited anti-anxiety activity by decreasing staircase rearing (aqueous extract: all doses; methanol extract: 400, 800, and 1,600 mg/kg, p.o.) and increasing staircase step-climbing (aqueous extract: 200 and 800 mg/kg p.o.; methanol extract: 100 and 200 mg/kg, p.o.) behaviors significantly (Table 4).

In the Ugba region of Nigeria, the leaves of A. laxiflora are traditionally used to wrap food items for preservation. Farombi et al. (2003) were the first to report the antioxidant activity of hexane and methanol extracts from A. laxiflora leaves and roots using the ferric thiocyanate method, horseradish peroxidase catalyzed oxidation of ABTS, β-carotene linoleate model system, and rat liver microsomal lipid peroxidation assay. The antioxidant activity was observed in the following order: hexane root extract (76.4%) > methanol root extract (63%) > methanol leave extract (40%) > hexane leave extract (38%) at 0.05% concentration. The hexane root extract’s antioxidant activity was compared with that of BHA (80%), a standard antioxidant. Another report indicated the antioxidant activity of hydroethanolic extract and solvent fractions of A. laxiflora leaves by the DPPH spectrophotometric assay method. All the test samples showed less scavenging activity (EC₅₀ 12.97, 24.34, and 106.74 μg/ml for ethyl acetate, n-butanol, and crude ethanol extract, respectively) relative to the reference standard ascorbic acid (EC₅₀ 4.78 μg/ml). Moreover, bioassay-guided fractionation of n-butanol fraction led to the isolation of two flavonoids, namely, taxifolin glycoside and quercitrin, suggesting their involvement in observed antioxidant activity (Adeloye et al., 2005).

According to Oloyede et al. (2010), the H₂O₂ scavenging activity of the butanol extract of A. laxiflora through the FTC method was compared favorably with standard reference α-tocopherol at 500 μg/ml concentration. The scavenging activity was observed for the various extracts (hexane, ethyl acetate, butanol, and aqueous) of leaves at various concentrations (50, 100, 250, and 500 μg/ml) assayed in a concentration dependant manner. Similarly, the acetone leave extract showed significant (p < 0.05) antioxidant activity in DPPH, ABTS, and FRAP assays with IC₅₀ values of 17.19 ± 1.02, 18.53 ± 1.42, and 438.42 ± 15.55 μg/ml, respectively. Trolox was used as a standard antioxidant with IC₅₀ values of 3.14 ± 0.10 and 6.05 ± 0.24 μg/ml in DPPH and ABTS assay, respectively (Dzoyem and Eloff, 2015). The in vivo antioxidant assay of methanolic extract was investigated by determining the effects on serum CAT, SOD, and GSH enzymes in experimental animals. The extract at different concentrations (0.5, 1.0, and10.50 mg/kg body weight, p.o.) significantly (p < 0.05) raised the GSH, SOD, and CAT activity (Uhunmwangho et al., 2017). Lately, Morah and Uduagwu (2017) assessed the radical scavenging activity of petroleum ether and ethanol extract of A. laxiflora using a DPPH spectrophotometric assay. Both extracts at all concentrations (40, 80, 100, 150, and 200 μg/ml) exhibited a dose-dependent anti-DPPH activity. The petroleum ether and ethanol extract at 200 μg/ml concentration exhibited greater percent DPPH radical scavenging ability (50.50% and 42.95%, respectively) than ascorbic acid at the same concentration (35.22%). The antioxidant activity of extracts was attributed to the isolated compounds, namely, 3-acetoxy-7,8-epoxylanostan-11-one, rhodopin, ethyl iso-allocholate, hexadecanoic acid, 9-octadecenyl hexanoate, eicosyl oleate, and astaxanthin. The results laid the credence for the ethnobotanical food preservative and natural oxidant use of A. laxiflora (Table 4).

Although A. laxiflora plant parts are traditionally used as an alternative medicine for cancer treatment, there is a paucity of experimental and clinical data on the anticancer activity of A. laxiflora (Dzoyem and Eloff, 2015). In the brine shrimp bioassay against Artemia salina, the aqueous, ethanol, and methanol extract of A. laxiflora was found toxic with LC₅₀ values of 41.01, 8.91, and 142.40 μg/ml, respectively, indicating potential anti-cancer properties (Ogbole et al., 2016; Osabiya et al., 2017) (Figure 5). The methanolic extract of A. laxiflora root, stem, and leaves had significant anticancer activity against drug-sensitive leukemia CCRF-CEM cell line with IC₅₀ values of >80, 49.21 ± 11.16, and 43.67 ± 4.06 μg/ml, respectively (Kuete et al., 2016). In two separate studies, Okokon et al. (2017a, 2017b) investigated the cytotoxicity activity of ethanol extract and solvent fractions (petroleum ether, dichloromethane, ethyl acetate, butanol, and aqueous) of A. laxiflora leaves and root against HeLa and HEK cell lines using MTT assay. The A. laxiflora root crude ethanolic extracts and fractions were non-toxic in the HeLa cell line with an IC₅₀ value greater than 100 μg/ml, whereas the A. laxiflora root extracts and fractions were cytotoxic to the tested HeLa and HEK cell lines with potency order of ethyl acetate > chloroform > petroleum ether > crude extract. The ethyl acetate fraction was highly toxic to both cell lines with TC₅₀ values of 8.83 and 1.41 μg/ml, respectively, suggesting ethyl acetate fraction could be a potential source of anticancer agents. In contrast, Siwe-Noundou et al. (2019) reported that various extracts (hexane, chloroform, ethyl acetate, methanol, ethanol, and aqueous, 25 μg/ml) of A. laxiflora root, stem, and leaves and five isolated compounds from methanolic A. laxiflora stem bark, namely, ellagic acid, 3-O-methylellagic acid, 3-O-β-D-glucopyranosyl-β-sitosterol, 3-O-acetyl-oleanolic acid, and 3-O-acetyl-ursolic acid (20 μM), were non-toxic against HeLa cell lines (cell viability >100%). Sandjo et al. (2011) tested the cytotoxicity of six isolated compounds, namely, (10Z)-tetradec-10-enoic acid-(2S)-2-carboxy-2-hydroxyethyl ester; (2R)-2-hydroxy-N-[(2S,3S,4R,15Z)-1,3,4-trihydroxy-15-triaconten-2-yl]octacosamide; 3-acetyloleanolic acid; 3-acetoxyursolic acid; 3-O-methylellagic acid; and 3-O-methylellagic acid-3′-O-α-rhamnopyranoside, against the HL60 cell line. Compounds 3-acetyloleanolic acid and 3-acetoxyursolic acid exhibited potent cytotoxic effects with IC₅₀ values of 6.6 and 6.8 μM, respectively (Table 4).

Though multiple studies have focused on the pharmacological role of A. laxiflora, some parts of A. laxiflora, such as stem branchlets, fruits, and seeds, have not yet been studied. Indeed, fruits of this plant are used in traditional medicine for curing infertility and fibroid treatment in women. Hence, it is highly recommended to conduct further research in this domain. Moreover, most of the research focuses on in vitro pharmacology of A. laxiflora. Thus, researchers are strongly recommended to conduct in vivo pharmacological and clinical studies to understand the molecular mechanism of action of this botanical drug.