Dicoma anomala is a perennial herb that is typically called stomach or fever bush. It is a member of the family Asteraceae. It has an erect stem covered with thin hairs as well as an underground tuber (Balogun and Ashafa, 2017). It is native to sub-Saharan Africa, and, in South Africa, it is widely distributed in the Free State, Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga, Northern Cape, and North West provinces. This plant has been used traditionally in Africa to treat diseases such as colds, coughs, fever, ulcers, and diabetes (Balogun and Ashafa, 2017). It has wide ethnomedical uses and its roots are universally used to treat diseases that affect animals and humans. Among the different species of Dicoma, D. anomala, D. zeyheri, D. capensis and D. schinzii have been utilized for their medicinal properties and were duly classified based on their phytochemical composition. Some of these phytochemicals are acetylenic compounds, flavonoids, phenolic acids, phytosterols, sesquiterpenes and triterpenes. They are non-toxic to normal non-cancerous cells. These compounds occur primarily in the leaves and roots and have been used to treat various cancers such as prostate, kidney, ovarian and breast cancers (Greenwell and Rahman, 2015; Maroyi, 2018). D. anomala Sond roots have shown antiproliferative effects against MCF-7 breast cancer cells wherein sesquiterpene conjugated to silver nanoparticles demonstrated anticancer properties by causing oxidative damage in the cancerous cells (Shafiq et al., 2020). Dicoma capensis aqueous extracts have also shown anticancer properties against breast cancer cell lines such as MCF-12A, MDA-MB-231 and MCF-7 (Asita et al., 2015).

The genus Fagaropsis belongs to the family Rutaceae and is widely distributed in Africa. Fagaropsis are mostly shrubs or deciduous trees with buttress roots. The plant species Fagaropsis angolensis is found in Angola, Ethiopia, Kenya, Namibia, Tanzania, Uganda, and Zimbabwe; F. hildebrandtii is primarily found in Ethiopia, Kenya, Somalia, and Tanzania while F. velutina and F. glabra occur endemically in Madagascar (Sun et al., 2021). F. angolensis whole root methanol extracts have been shown to exhibit antitumor activity against throat cancer cells (Hep2) at an IC₅₀ value of 10.05 ± 2.15 μg/mL. Whole root and root-stem methanol extracts showed high degrees of anticancer effects against CT26 colon cancer cells with IC₅₀ values of 8.33 ± 1.42 μg/mL and 5.25 ± 0.35 ug/mL respectively (Yiaile, 2017). F. angolensis stem bark methanolic extracts demonstrated significant activity against DU-145 prostate cancer cells and HCC 1395 breast cancer cells at IC₅₀ values of 12.8 ± 1.1 μg/mL and 53.9 ± 5.6 μg/mL respectively (Misonge et al., 2019). Anticancer effects of methanol extracts of the bark of F. angolensis against HCC 1395 cells were also reported by (Onyancha et al., 2018). Despite its anticancer activities, F. angolensis has shown high levels of toxicity on Vero cells. Therefore, more research is needed to evaluate the precise dosages of the active anticancer ingredients in this plant to mitigate toxicity issues and validate them for their use in folklore medicine.

Tribulus terrestris is a small, silky and hairy herb which is indigenous to tropical regions, including Africa, and is a member of the Zygophyllaceae family (Hashim et al., 2014). Methanol extracts of T. terrestris showed strong inhibition against SK-OV-3 ovarian carcinoma cells and MCF-7 breast cancer cells with IC₅₀ values of 89.4 μg/mL and 74.1 μg/mL respectively (Abbas et al., 2022). Tribulus terrestris occurs as a perennial herb and is known for its antineoplastic effects against a wide range of human cancers. The high anticancer potential of T. terrestris has been attributed to its high content of steroidal saponins which have been shown to induce programmed cell death in MCF-7s by eliciting both extrinsic and intrinsic apoptotic pathways (Osbourn, 2003; Sun et al., 2003; Sparg et al., 2004; Kim et al., 2011; Angelova et al., 2013; Faizal and Geelen, 2013). (Patel et al., 2021) reported in silico studies implicating the anticancer properties to active saponin compounds such as nuatigenin saponin that could be essential in the treatment of breast cancer. T. terrestris fruit extracts are capable of inhibiting autophagy in TW2.6 and SAS oral cancer cells and can impact cell proliferation, growth, cell migration and invasion of neoplastic/metastatic cancer cells (Shu et al., 2021).

Portulaca oleracea is a common succulent plant that is often referred to as Purslane. It belongs to the genus Portulaca in the family Portulacaceae and is abundant in most regions of Africa such as Botswana (Uddin et al., 2014). The polysaccharides of P. oleracea L., POL-P3b, have shown inhibition of tumors by means of cell cycle arrest, elicitation of DNA damage and induction of apoptosis (Zhao et al., 2013). (Jia et al., 2021) demonstrated that there was a high-level induction of TNF-α, IFN-γ and IL-12 when POL-P3b was co-administered with a dendritic cell vaccine in mouse models, implicating Th1 immune response modulation by POL-P3b. Therefore, POL-P3b serves as an adjuvant that stimulates maturation and augment the antigen presentation capability of the Dendritic Cell (DC) vaccine. Additionally, POL-P3b upregulated the expression levels of MyD88, NF-κB and TLR4 in the DC vaccine and promoted Th1 cytokine secretion. The Ki 67 index is closely associated with the degree of tumor malignancy (Bleckmann et al., 2016; Christensen et al., 2016) and a combination of the DC vaccine and POL-P3b was found to be capable of reducing Ki 67 expression. Also, this combination triggered more significant apoptotic characteristics such as nuclear fragmentation, massive shrinkage of cells and high numbers of TUNEL-positive cells when compared to either the DC vaccine alone or POL-P3b alone. Additionally, higher immunomodulatory properties were observed in immune mice when administered with POL-P3b (Jia et al., 2021). Lymphocyte proliferation elicited by LPS and Con A was augmented, the CD4+/CD8+ ratio increased and the expression of cytokines, including that of TNF-α, IFN-γ, IL-4 and IL-12p70, was also significantly enhanced, suggesting that the POL-P3b adjuvant administered along with the vaccine can upregulate immune response reactions in mice. CD31, CD34 and VEGF expressions were more pronouncedly diminished when a combination of POL-P3b and the DC vaccine was administered and there was a synergistic suppression of angiogenesis. POL-P3b as an adjuvant for the DC vaccine also demonstrated diminished mortality and prolonged survival of tumor-bearing mice, showing the anti-tumor effect of POL-P3b. Therefore, POL-P3b functions as a highly propitious dietary adjuvant for the DC vaccine, inducing DC maturation. POL-P3b, in addition to inhibiting tumor growth by increasing tumor apoptosis, also inhibited lung metastasis, and induced non-toxic side effects in mouse models (Jia et al., 2021). Therefore, POL-P3b holds great promise as an efficient and safe immunomodulatory agent capable of regulating DC maturation and enhancing immune responses of the DC vaccine against breast cancer (Liu et al., 2021). isolated two novel amide glycosides, oleraciamide E and oleraciamide F, containing similar molecular structures from P. oleracea L. wherein oleraciamide E demonstrated anticholinesterase activity with an IC₅₀ value of 52.43 ± 0.33 M and exhibited scavenging activity in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical quenching assays with an IC₅₀ value of 24.64 ± 0.33 M which indicate antioxidant effects.

Withania somnifera is a small, bushy, evergreen shrub widely distributed across the world and abundant in South Africa and Botswana. It is a member of the Solanaceae family (Gaurav et al., 2015). It has been shown that W. somnifera root extracts can inhibit vimentin, a protein normally found in regions of metastasis, thus suggesting its counteracting effects on tumour formation in breast cancer (Yang et al., 2013). The anticancer potential of W. somnifera has been mainly attributed to Withanolide and Withaferin A, which are two principal phytochemicals from this plant. In vivo, in mice, it was reported that W. somnifera, through the activities of Withanolide and Withaferin-A, modulate different signalling pathways such as apoptosis, autophagy and reactive oxygen species (ROS) pathways (Shikder et al., 2020). In male Swiss albino mice, extracts from W. somnifera were shown to inhibit lung adenoma (Senthilnathan et al., 2006a) while the root extracts of this plant were shown to prevent ROS-induced injury in model mice (Senthilnathan et al., 2006b). Ethanol extracts of the roots of W. somnifera were shown to inhibit the proliferation of A549 lung cancer cells through the downregulation of PI3K, which reduced metastasis (Vamsi et al., 2020). In vitro, Withaferin-A has been shown to reduce the proliferation of the human breast cancer cell line MDA-MB-231 by inhibiting the two-pore domain potassium (K2P9) channel TASK-3 (Zúñiga et al., 2020). Withaferin-A has also been shown to inhibit the proliferation of other cancer cell lines such as the cervical cancer cell lines (HeLa, SKGII, ME180) and ovarian cancer cell lines (OKV-18 and SKOV3) (Sari et al., 2020). The activity of Withaferin-A against these cells is said to be brought about by the upregulation of the tumour suppressor p53 coupled with cell growth arrest and DNA damage signalling (Sari et al., 2020). Withanolides have been shown to inhibit the proliferation of MCF-7s by inducing apoptosis, inducing the overexpression of Hsp70 and reducing the expression of ER in MCF-7s (Chen et al., 2008). Withanolides were also found to suppress TGF-b1 and TNF-a induced Epithelial-Mesenchymal Transition (EMT) in the lung cancer cell lines H129 and A549 (Yang et al., 2013). Table 1 shows bioactive compounds of Withania, the plant parts they are derived from, the different types of cancer that they target, and their mechanisms of action during cancer alleviation.

Azanza garckeana is a semi-deciduous tree and a member of the Malvaceae family that is commonly found in East and Southern Africa. According to (Michael et al., 2015), on evaluating phytochemicals of the seeds of this plant, it was discovered that they have tannins, saponins, flavonoids, alkaloids, phenols, glycosides and carotenoids. The benzopyrone ring structure, known for its antioxidant properties, is integral to flavonoids, making flavonoids to have antioxidant behaviour. This antioxidant activity is able to fight and remove free radicals in biological systems and inhibit the development of tumors (Michael et al., 2015). The seeds of A. garckeana are said to be able to reduce cancer development due to their possession flavonoids, which are able to interfere with oestrogen synthase, an enzyme that produces oestrogen (Okwu, 2005). A complex formed between Mansone G and β-Cyclodextrin, which are some of the phytochemicals extracted from A. garckeana, was found to exhibit high levels of cytotoxicity towards A549 lung cancer cells (Bioltif et al., 2020). Figure 1 shows the leaves of Portulaca oleracea, Tribulus terrestris, A. garckeana and Withania somnifera.

Ovarian cancer is the second most prevalent gynecological malignancy and one of the most lethal cancers. The major challenge in the treatment of ovarian cancer is the emergence of multi-drug resistance during chemotherapy. Cajanol is derived from Cajanol cajan roots and has a multitude of pharmacological activities such as anti-tumor properties. Cajanol inhibits NF-κB phosphorylation and nuclear ectopia by interfering with PI3K expression and the phosphorylation of Akt. This diminishes the transcription and translation of the permeability glycoprotein and eventually decreases cancer related multi-drug resistance that is induced by the efflux of paclitaxel (Sui et al., 2021). Cajanus cajan is a medicinal plant that is native to the Southwest of Nigeria. It is grown for food in Nigeria (Ashidi et al., 2010). C. cajan synthesizes cajanin stilbene acid (CSA) which shares structural analogies with estrogen. CSA exerts antiestrogenic and anticancer activities towards estrogen receptor (ERα)-positive breast cancer cells. Particularly, it shows cytotoxicity towards MCF-7 cells resistant to tamoxifen while exhibiting low cytotoxicity towards ERα-negative breast tumor cells (Fu et al., 2015). This cytotoxicity is independent of the cellular p53 status. CSA binds to the same site as tamoxifen and 17β-estradiol on ERα. Thus, CSA displays its anticancer properties against ERα-positive breast cancer cells by interacting with and inhibiting ERα. The cytotoxicity of CSA towards MCF-7s resistant to tamoxifen indicates its promise as a tamoxifen alternative for treatment of breast cancer. When combined with tamoxifen, CSA enables synergistic cytotoxicity and promotes p53 protein expression. Cajanol, scientifically known as 5-hydroxy-3-(4-hydroxy-2-methoxyphenyl)-7-methoxychroman-4-one, is an isoflavone isolated from the roots of C. cajan. In MCF-7s, cajanol causes cell cycle arrest at the G2/M phase while inducing apoptosis through a mitochondrial pathway mediated by ROS (Luo et al., 2010). This leads to the disintegration of the outer membrane of the mitochondria and the release of cytochrome C followed by the elicitation of the caspase-3 and caspase-9 cascade which causes apoptosis. In COR-L23 lung cancer cells, C. cajan was shown to have anticancer activity with an IC₅₀ value of 5–10 μg/mL. It was reported that stilbenes longistylins A and C present in the leaf extracts of the plant were responsible for this anticancer property (Ashidi et al., 2010).

The bark of Combretum caffrum, the African bush willow tree, is a source of natural phenolic stilbene compounds called combrestatins (Pettit et al., 1987). Among these combrestatins, combrestatin A-4 (CA4) is the most efficient as an antitumor agent. CA4 inhibits tubulin polymerization, augments vascular permeability, and abrogates blood flow into tumors (Simoni et al., 2006). A drug candidate, Ecust004, has been developed as an optimized agent derived from the structure-activity investigations of the sulfamate derivatives of CA4 and Erianin. This is a strong inhibitor of steroid sulfatase and tubulin in addition to exhibiting antiproliferative activity against tumor cells at low concentrations. This sulfate modification augments the pharmacokinetic profiles and bioavailability of the parental CA4 and Erianin natural compounds (Raobaikady et al., 2005; Foster et al., 2008; Visagie et al., 2015). Ecust004 inhibits tumor proliferation in vivo and in vitro in addition to diminishing cell viability, migration, and invasion of MCF-7 and MDA-MB -231 cells at low dosages. Combrestatins comprise a category of closely analogous stilbenes including combretastatins A, dihydrostilbenes or combretastatins B, phenanthrenes or combretastatins C and macrocyclic lactones or combretastatins D which are all derived from the bark of C. caffrum. Some of these compounds are the strongest antitubulin agents ever known. Owing to the structural simplicity of these substances, several analogs have been synthesized. Amongst these, Combrestatin A4 phosphate is the most tested substance in preclinical and clinical trials (Karatoprak et al., 2020). This water-soluble prodrug is rapidly metabolized in the body to combrestatin A4 that displays antitumor, antiproliferative, anti-inflammatory and antioxidant activities. Nano-formulations of CA4 phosphate have important advantages such as increased water solubility, drug targeting capabilities, improved efficiency, protracted half-lives in circulation and lesser side effects. Therefore, combrestatins are favorable candidates for novel tumor therapeutics.

Combrestatins have been shown to be active against many human cancer cell lines and combrestatin A-4 is the strongest in terms of potency. Their principal action is their interaction with the colchicine binding site of the tubulin b subunit and the disruption of tubulin polymerization into microtubules (Izuegbuna, 2022). CA4 has been shown to be cytotoxic towards some cancer cell lines such as the leukemia cell line, P-388, which is resistant to daunorubicin (McGown and Fox, 1990). It acts by disrupting cell signaling pathways involved in the maintenance and regulation of the cytoskeleton of the endothelial cells occurring in the tumor vasculature, thus causing the selective disruption of blood flow through the tumors. Thereupon, these tumor cells undergo necrosis. Intriguingly, while enabling disruption of blood supply into the tumor cells, CA4 maintains normal blood flow into adjacent normal tissues (Nihei et al., 1999). CA4 activity is not dependent on temperature. This contrasts with colchicine, which interacts with a similar binding site on the tubulin molecule. The complexation of CA4 tubulin occurs easily even on ice (Nam, 2003). Another CA4 sodium phosphate (CA4P) pro-drug has also been synthesized. The action of CA4P is like that of CA4. It leads to microtubule depolymerization and represses tumor cell angiogenesis (Tozer et al., 2002). CA4P eventually induces apoptosis in tumor cells (Iyer et al., 1998), although it has been reported that it results in cell death through molecular pathways, rather than apoptosis, such as the mitotic catastrophe pathways (Nabha et al., 2001). These pathways, which lead to cell death, make combrestatin a powerful anticancer compound of high efficacy (Jaroch et al., 2016).

Prunus avium (Sweet cherry) is a plant that is widely distributed in the north of Africa (Osafo et al., 2017). Dark sweet cherry is a rich source of phenolics and is characterized by its anti-invasive and anticancer activities. Prunus avium phenolics inhibit MDA-MB-453 breast cancer cells by triggering cell signaling pathways that elicit apoptosis and disrupt cell invasion. Amongst these phenolics, anthocyanins have shown augmented chemopreventative properties (Layosa et al., 2021). Polyphenols, especially anthocyanins, are well known for their anti-inflammatory, cytoprotective and antioxidant properties (Tsuda et al., 2000; Li et al., 2014; Huang et al., 2018; Silva et al., 2020). Table 2 shows examples of anticancer bioactive compounds found in P. avium and outcomes of their experimental uses.

Prunus africana is a widely distributed tree of African origin which is primarily found in Southern and Central Africa (Komakech et al., 2022). In previous ethnomedical studies, the bark decoction of P. Africana was used to treat prostate cancers (Grace et al., 2003; Ochwang’i et al., 2014; Tugume et al., 2016). In vivo studies, mice with transgenic adenocarcinoma in their prostate were fed with P. africana and demonstrated a significant decrease in the incidence of prostate cancer when compared to control mice fed with casein (Shenouda et al., 2007). Likewise, in human in vivo studies, P. africana bark extracts induced 50% inhibition of the growth of human prostate cancer (PC-3). It also elicited notable apoptosis in vitro in the PC-3 cell line (Shenouda et al., 2007). The anticancer property of the P. africana stem bark is attributed to several novel bioactive compounds such as β-amyrin, N-butylbenzene-sulfonamide, β-sitosterol, β-sitosterol-3-O-glucoside, ferulic acid, tartaric acid, oleanolic acid, lauric acid and ursolic acid (Komakech and Kang, 2019). However, P. africana is an endangered species and the supply of the P. africana stem bark does not meet global demand (Cunningham et al., 2016). A micropropagation protocol has been developed for P. africana towards enabling drug development in the future for the treatment of prostate cancer (Komakech et al., 2022). The presence of β-Sitosterol in P. Africana has been attributed to its anti-prostate cancer properties wherein it induces apoptosis in human prostate cancer cells during the development of carcinoma in prostate lymph-nodes (von Holtz et al., 1998; Awad et al., 2000). Also, the 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-one in extracts of P. africana is capable of inactivating NF-kB which could account for its proapoptotic and antiproliferative activities on PC-3 cancer cells. Additionally, the occurrence of benzoic acid in these extracts could be responsible for its activity against cancer as earlier studies showed that derivatives of benzoic acid hinder growth of prostate cancer cells thus precluding oncogene expression by the inhibition of histone deacetylases (Anantharaju et al., 2017).

Securidaca longipedunculata Fresen (violet tree) belongs to the family Polygalaceae, which is called the mother of all medicines in Northern Nigeria. Traditional medical practitioners use extracts of Securidaca longipedunculata to manage cancer in Africa (Saidu et al., 2015). The antiproliferative effects of S. longipedunculata on Ehrlich ascites carcinoma in vivo and in vitro are due to the downregulation of angiogenesis and the elicitation DNA fragmentation (Lawal et al., 2012). Root bark extracts of S. longipedunculata have been reported to repress proliferation and stimulate apoptosis in U87 brain tumor cells through the cleavage of Poly-ADP-Ribose Polymerase (Ngulde et al., 2019). Ethanolic extracts of the plant hindered the proliferation of the U87 cells. The most polar fraction of these extracts accounted for this activity with an IC₅₀ value of 20.535 μg/mL. When administered at 10 mg/kg, the extracts augmented the lifespan of tumor-harboring mice by decreasing tumor cell viability (Ngulde et al., 2019). Several active compounds have been identified in Securidaca longipendunculata including xanthones (muchimangins), methyl-salicylate, benzyl benzoates, bisdesmosidic saponins and triterpene saponins, of which xanthones have been implicated in antitumor and cytotoxic activities (Mitaine-Offer et al., 2010; Dibwe et al., 2014; Zuo et al., 2016; Obasi et al., 2018; Klein-Júnior et al., 2020). Saponins in Securidaca longepedunculata induced apoptosis and inhibited the migration and invasion of cervical cancer cells (Obasi et al., 2018). Xanthones of in S. longipedunculata impeded the proliferation of lung cancer cells and functioned as an elicitor of apoptosis (Zuo et al., 2016).

Annona senegalensis, which is often called wild soursop, is a 2 to 5-m-tall shrub with alternate, oblong, simple, blue to greenish leaves. It is an important plant in Northern Nigeria and all its parts have been found to be useful in medicine. It contains a plethora of phytochemicals including alkaloids, glycosides, flavonoids, saponins, anthocyanins, tannins, and steroids (Potchoo et al., 2008; Johnson et al., 2017; Musa et al., 2017). Extracts from this plant have been shown to have antitumor activity in hepatocellular carcinoma induced by N-diethylnitrosamine in male Wistar rats. A. senegelensis n-hexane extracts have shown anticancer effects by augmenting liver architecture, enhancing antioxidant defense systems, downregulating anti-apoptotic, pro-inflammatory, angiogenic, farnesyl transferase and alpha-fetoprotein mRNA expression and upregulating P21 and P53 tumor suppressor mRNAs (Yakubu et al., 2020).

Annona muricata is a tropical fruit tree that belongs to the family Annonaceae. This plant is widely cultivated in African countries such as Angola and some West African countries where its products such as fruits are consumed as food. Annona muricata is a plant of great applicability in traditional medicine. Ethanol extracts from the leaves of this plant contain several phytochemicals such as alkaloids, tannins, flavonoids, cardiac glycosides, reducing sugars, triterpenoids and saponins (Gavamukulya et al., 2014). Aqueous extracts of the leaves contain terpenoids, alkaloids, coumarin, flavonoids, fatty acids, steroids, phenols, saponins and tannins while ethyl acetate fractions contain saponins, phenols, flavonoids, polyphenols, and tannins (Agu and Okolie, 2017). Annona muricata expresses over 45 acetogenins in its leaves and seeds (Gleye et al., 1998). The ethyl acetate fraction of A. muricata leaves induced cytotoxic and antiproliferative activity against breast cancer cells by significantly decreasing mitochondrial membrane integrity, leading to the elicitation of apoptosis in the cells (Hadisaputri et al., 2021). This apoptotic mechanism was identified by alterations in cell morphology and the expression levels of caspase-3, caspase-9 and Bcl-2 mRNAs that were involved in the cytotoxic activity induced by the ethyl acetate fractions on MCF-7 cells (Jabir et al., 2021). prepared silver nanoparticles (AgNPs) by using A. muricata as a reducing agent and studying its potential as a novel therapeutic strategy against cancer. Specifically, the ability of these nanoparticles to decrease NLRP3 inflammasome activity by inducing autophagy was examined. The AgNPs showed antiproliferative effects against AMJ-13 and THP-1 cells through the stimulation of apoptosis by damaging the mitochondria and inducing the p53 protein pathway (Jabir et al., 2021). This AgNP-elicited autophagy decreased the levels of IL-1β and NLRP3 inflammasome activation. This study showed that A. muricata AgNPs could serve as a robust anticancer agent by inducing apoptosis and autophagy and causing inhibition of tumorigenesis (Eritja et al., 2017; Galluzzi et al., 2017). Annona muricata contains two important phytochemicals; acetogenins and flavonoids which have both been implicated in several pharmacological activities (Fang et al., 1993; Yang et al., 2015; Al-Dabbagh et al., 2018). Annonacin, the main acetogenin in A. muricata, has anticancer activities against skin, breast and endometrial cancers mediated by cell cycle arrest and the inhibition of other cellular signaling pathways (Yap et al., 2017; Yiallouris et al., 2018; Roduan et al., 2019). There is growing evidence that this antitumor activity is enabled by the induction of apoptosis in several breast and colon cancer cell lines (Rady et al., 2018). Additionally, the G1 phase cell cycle arrest has been reported to be involved in the antitumor activity of A. muricata leaf extracts. Both annonacin and ethyl acetate A. muricata bark extracts showed selective and robust cytotoxicity against DU-145 prostate carcinoma cells with respective IC₅₀ values of 0.1 ± 0.07 μM and 55.501 ± 0.55 μg/mL. Normal RWPE-1 prostate cells were not affected. The chemotherapeutic agent, docetaxel, was, however, devoid of such selectivity. Moreover, when docetaxel was administered in combination with A. muricata ethyl acetate bark extracts, its impact against DU-145 cells was enhanced by 50% (Foster et al., 2020). This was attributed to a non-apoptotic mechanism mediating cell death. Annonacin and bark extracts of A. muricata acted as selective cytotoxic compounds with antiangiogenic and antimetastatic potential. Leaf methanolic extracts of A. muricata (LMAM) showed inhibitory effects on the growth of MCF-7s (Naik and Sellappan, 2020) in a dose-dependent fashion and without causing cytotoxic effects against normal breast cancer cells. This was achieved through an apoptotic pathway (Pieme et al., 2014). Caspase-3 was found to be upregulated, serving as a determinant of apoptosis. LMAM arrested cell cycle at the G1 phase and blocked the G1/S transition attributed to the activation of apoptosis and sub-G0/G1 cell cycle arrest. LMAM displayed major inhibitory activity against MCF-7 cancer cells with an IC₅₀ value of 85.55 mg/mL.

Aerva javanica is a shrub that belongs to the Amaranthaceae family of plants. This plant is native to tropical African countries and has been reported to have anticancer properties in Ethiopia (Ayele, 2018). During its use in the treatment of breast cancer, the roots of A. javanica are ground into powder and mixed with blood from bats. This mixture is then consumed by the cancer patient early in the morning before breakfast (Teklehaymanot, 2009). The callus and leaf methanol extracts of A. javanica were tested against MCF-7s (Teklehaymanot, 2009; Abate et al., 2022) and were found to induce DNA fragmentation and cytotoxicity, which are indicators of apoptosis.

Abelmoschus esculentus, also known as Okra, is a native African plant of the family Malvaceae. It has been historically been used to treat different ailments such as constipation, hypoglycaemia, inflammation and microbial infections (de Sousa Ferreira Soares et al., 2012). The seeds of A. esculentus contain flavonoids such as isoquercitrin which have shown cytotoxicity towards carcinoma cell lines; MCF-7 (breast cancer), HepG2 (liver cancer) and HeLa (cervical cancer) (Agregán et al., 2022). Okra flower extracts, which are rich in flavonoids, are capable of inhibiting cell proliferation in colorectal tumors and this inhibitory activity has been found to be due to the dysfunction of the mitochondria which is caused by the activation of p53 and the elicitation of apoptosis and senescence. In mice models, flavonoids in A. esculentus have shown cancer preventative activities which precluded tumor appearance. Okra flower phytochemicals positively impacted liver cancer prognosis while Okra ethyl acetate extracts showed inhibitory activity against HepG2 cells at concentration ranges between 62.5 and 1,000 μg/mL (Solomon et al., 2016). Therefore, Okra flowers were shown to be a valuable source of anticancer molecules which could augment the health of cancer patients. A novel lectin has been found in Okra seeds and it promotes antitumor effects in MCF-7s wherein it inhibits cell growth. It also enhances p21, caspase-3 and caspase-9 expression in the carcinogenic cells (Monte et al., 2014). Cerium oxide (CeO₂) nanoparticles were generated using A. esculentus as a stabilizing and reducing agent. Exposure of HeLa cells to these CeO₂ nanoparticles at 10–125 μg/mL resulted in the loss of cell viability in the cervical cancer cells in a dose-dependent fashion (Ahmed et al., 2021). Abelmoschus esculentus has been shown to exhibit anticancer effects due to its high antioxidant activity against free radicals (Arapitsas, 2008; Ahmed and Kumar, 2016). It is a source of polysaccharides, flavonoids, terpenoids, tannins, alkaloids, enzymes, proteins, and vitamins (Musthafa et al., 2021) demonstrated the apoptotic potential of A. esculentus lectins against human glioblastoma cells by the modulation of the caspase-3 and caspase-7 gene expression and the downregulation of CLOCK and Bma1 circadian genes, implicating a correlation between these circadian genes and apoptotic cell death. Increased cytotoxicity, morphological changes, increased intracellular ROS generation and anti-migratory activity were also observed. Due to these effects, A. esculentus extracts can be considered as adjunct therapy in alleviating human glioblastoma. Furthermore, pulp extracts of A. esculentus were used to synthesize gold nanoparticles which showed enhanced anticancer effects (Devanesan and AlSalhi, 2021). Silver nanoparticles made using A. esculentus flower extracts showed antiproliferative, apoptotic and cytotoxic effects against A-549 and TERT-4 cancer cell lines. Quercetin diglucoside and isoquercitrin identified in A. esculentus were shown to be potently anti-ROS and thus could be used in cancer treatment (Taiwo et al., 2021).

Flueggea virosa is widely distributed is the Southern Africa. Flueggea virosa leaves and twigs were used to isolate flueggines A 1) and B 2) indolizidine alkaloids, the latter of which showed notable inhibitory activities against the growth of breast cancer cells MDA-MB-231s (estrogen-independent) and MCF-7s (estrogen-dependent) with IC₅₀ values of 147 ± 3 and 135 ± 5 nM respectively. This suggested that cell proliferation was inhibited irrespective of estrogen receptor status (Zhao et al., 2011).

Lagenaria siceraria is a native African climbing plant that belongs to the Cucurbitaceae family (Abebe, 2016). (Mondal and Swamy, 2020) identified BGL24, a novel PP2-type lectin in the phloem exudate of this plant, which is also called Bottle gourd. This lectin displayed high specificity for chito-oligosaccharides. BGL24 showed moderate cytotoxicity towards MDA-Mb-231 breast cancer cells but did not impact normal splenocytes. The latex sap of L. siceraria (LSL) markedly elicited lymphocyte proliferation and demonstrated potent cytotoxicity against cancer both in vivo and in vitro (Vigneshwaran et al., 2016). LSL caused tumor regression and drastically impacted tumoral neovasculature. Additionally, LSL stimulated the apoptotic signaling cascade in tumor cells through the activation of caspase-3 and the induction of apoptotic cellular events. Therefore, LSL possesses immunopotentiating properties which negatively impact tumor progression by attacking angiogenesis and inducing programmed cell death, which are major hallmarks of cancer. Bottle gourd juice (BGJ) was examined for its chemopreventive properties against croton oil and 7,12-dimethylbenz(a)anthracene (DMBA) and was found to elicit skin papillomagenesis in murine models (Kumar et al., 2013). BGJ caused drastic reductions in the incidence, latency, number, multiplicity, size, and volume of the papillomas. This chemopreventive effect was mediated by reducing loss of stratification, decreasing the number of epithelial layers, diminishing dermal infiltration and protection from several cytoplasmic changes. Therefore, BGJ consumption could help in the inhibition of skin cancer.

Cytotoxic metabolites have been identified in methanol extracts of X. aethiopica and were found to inhibit the growth of multidrug resistant and drug-sensitive cancer cell lines (Kuete et al., 2015). Among these metabolites, flavone elicited apoptosis in CCRF-CEM leukemia cells through the disruption of the mitochondrial membrane potential and isoquinoline triggered apoptosis via the production of ROS, implicating these compounds as antiproliferative agents against drug-resistant cancers. Essential oils obtained from Xylopia aethiopica sourced from Cameroon and Chad were found to be abundant in monoterpene hydrocarbons such as β-phellandrene, β-pinene, γterpinene and sabinene. Oxygenated monoterpenes were highly prevalent, amongst which terpinen-4-ol was most significant (Bakarnga-Via et al., 2014). Hydroethanolic extracts of X. aethiopica showed antiproliferative activity against HCT116 colon cancer cells as well as KG1a and U937 leukemia cell lines. Xylopia ethiopica extracts also demonstrated antiproliferative effects on human cervical cancer cells. Furthermore, α-cadinol and terpinen-4-ol in essential oils isolated from X. ethiopica were found to be active against laryngeal, lung, ovarian, breast, gastric and colon cancer cell lines (Bakarnga-Via et al., 2014). Additionally, βpinene, a monoterpene found in this oil, showed notable cytotoxic activity against epidermal skin and breast cancer cell lines. Fruit extracts of X. aethiopica caused the activation of caspase-3 and led to the cleavage of cytoskeletal proteins and the elicitation of DNA fragmentation factors, condensation of chromatin, formation of apoptotic bodies and eventually apoptosis as observed through morphological analysis (Fulda and Debatin, 2006; Ribeiro et al., 2021). (Adaramoye et al., 2011) showed that fruit extracts of X. aethiopica caused antiproliferative activity against human cervical carcinoma cells causing cell cycle arrest and elevated levels of p53 and p21 gene transcripts. Caspase-3 activation and apoptotic cell death have been demonstrated in MBA-MD-231 breast cancer cells upon exposure to hydroethanol extracts sourced from the Cameroonian varieties of X. aethiopica fruits (Choumessi et al., 2012).

Nymphaea lotus belongs to the family Nymphaeaceae and is a perennial aquatic flowering plant that is native to Egypt and grown in several regions in Madagascar, West Africa, and Central Africa (Slocum, 2005). Hydroethanolic leaf extracts of N. lotus contain saponins, tannins, flavonoids, phenolics and triterpenoids but are lacking in alkaloids. These extracts have been shown to have anti-inflammatory and cytotoxic activities along with high antioxidant potential against Jurkat and MCF-7s, properties that are attributed to the occurrence of abundant flavonoids and phenolics as well as micro/macro-elements such as sulfur, phosphorus, manganese, magnesium, zinc and copper (Saleem et al., 2001; Elegami et al., 2003; Laszczyk, 2009; Afolayan et al., 2013; Oyeyemi et al., 2015; N’guessan et al., 2021). These properties may account for the use of the leaves of Nymphaea lotus in traditional anticancer treatments.

Zanthoxylum chalybeum is a deciduous shrub with a rounded but open crown. It can grow between 1.5 and 40 cm in diameter, with large woody spines that can grow up to 2 cm long. It is a widely used traditional medicine in East Africa and can be harvested from the wild for local use as tea, medicine, toothbrush, and timber. Zanthoxylum chalybeum is reported to exhibit anti-cervical cancer properties, where part of the plant used is pound before adding water to drink (Tugume et al., 2016; Omara et al., 2020). Significant antiproliferative effects of crude extracts of alkaloids from Zanthoxylum species were observed against human cervical cancer cells (HeLa), human gastric cancer cells (SGC-7901), human hepatocyte carcinoma cells (Hep G2) and human colorectal adenocarcinoma cells (HT29), ranging from 60.71% to 93.63% at 200 μg/mL concentration (Tian et al., 2017). Zanthoxylum contains quaternary alkaloids which have been shown to be potential anti-cancer candidates that can penetrate through the cell membranes of carcinomas (Yung et al., 2016) and can attract the negative charges on DNA (Bai et al., 2006). Based on their structural skeleton, these quaternary alkaloids have been shown to belong to the berberine type, tetrahydroproberberine type, benzophenanthridine type, benzyltetrahydroisoquinoline type and aporphine type (Tian et al., 2017). In Z. chalybeum, the amount of quaternary alkaloids account for 83.4%. Bioactivity tests on Zanthoxylum showed both high inhibitory rates against cancer cells and high quaternary alkaloid content, therefore justifying its use in traditional anticancer medications. The active ingredients responsible for the anticancer activity of this plant include skimmianine, furoquinoline, benzophenanthridine, alkaloids, chelerythrine and nitidine, aporphine alkaloids, tembetarine, N-methylisocorydine, N- methylisocorydine (menisperine) and bernerine, phenylethylamine, candicine, alkamide, fagaramide, dihydrochelerythrine, lupeol and sesamin (Omara et al., 2020).

Ceratonia siliqua is a Mediterranean evergreen plant that is abundantly distributed in North African countries such as Algeria, Morocco, Tunisia, and Egypt (Kaderi et al., 2015). Common ethnomedicinal uses of Ceratonia siliqua include treatment of gastrointestinal diseases, diarrhea, constipation and colon cancer (Benarba and Pandiella, 2018). These medicinal properties may chiefly be due to the presence of fibers and phenolic compounds (Rtibi et al., 2017). (Ghanemi et al., 2017) demonstrated that C. siliqua leaf phenolic extracts inhibited the growth of HTC-116 and CT-26 cell lines, in a dose dependent manner, confirming earlier similar findings by (Custódio et al., 2013).

Moringa oleifera, a member of the Moringaceae family, is a drumstick tree which was first used medically by the ancient Egyptians before its cultivation around the globe which spread its medicinal benefits (Abd-Rabou et al., 2017). Moringa oleifera was found to be effective in treating colon cancer (Al-Asmari et al., 2015). The plant owes its anticancer properties to the presence of quercetin, kaempferol, β–D-glucopyranoside, tetracanoate, β–sitosterol glucoside, isothiocyanate (Kaur, 2015), hexadecenoic acid and eugenol (Al-Asmari et al., 2015). (Suphachai, 2014) reported the growth inhibition of hepatocarcinoma (HepG2), colorectal adenocarcinoma (Caco-2), and breast adenocarcinoma (MCF-7) cell lines by dichloromethane leaf extracts of Moringa oleifera with IC₅₀ values between 112 and 113 μg/mL. Recently, in vitro in vivo anticancer activities of M. oleifera have been reported. In their study (Barhoi et al., 2021), identified quinic acid, octadecanoic acid and hexadecanoicacid (palmitic acid) as the active compounds during the activity of aqueous extracts of M. oleifera on Ehrlich ascites carcinoma (EAC) and Hep2 (Human laryngeal carcinoma) cells. They reported that, in vivo, aqueous extracts of M. oleifera led to a reduction in tumor weight and tumor volume in tumor bearing mice, consequently elongating the life span of the mice. Additionally, in vitro, the extracts of M. oleifera were toxic to both Hep2 and EAC cancer cell lines. Apoptosis was also induced through the alteration of the mitochondrial membrane potential in the EAC cells (Barhoi et al., 2021).

It has also been recently shown that methanolic extracts of M. oleifera leaves led to a reduction in cell growth in cervical cancer cells (Pandey and Khan, 2021). The cervical cancer cells were reported to have undergone apoptosis. The anticancer potential of the M. oleifera leaf extracts was due to the inhibitory activity of the extracts on Jab-1, which is an important biomarker associated with the development of different cancers (Pandey and Khan, 2021). The inhibition of M. oleifera on Jab-1 led to its downregulation. There was also an increase in the expression of the tumor suppressor p27, which led to cell growth arrest at the G0/G1 phase.

Methanol extracts of M. oleifera leaves have also been reported to have apoptotic effects on PC-3 prostate cancer cells (Khan et al., 2020). The anticancer activity of M. oleifera leaf methanolic extracts was due to the induction of ROS-mediated apoptosis and the activation of caspase-3 activity in the prostate cancer cells. Cell cycle arrest at the G0/G1 phase and changes in the expression of genes of the Hedgehog signalling pathway were also observed (Khan et al., 2020).

Moringa oleifera leaf extracts have been shown to have anticancer activity on the human squamous cell carcinoma 15 cell line (SCC15). In their study (Luetragoon et al., 2020), reported that the proliferation of SCC15 cells treated with M. oleifera leaf extracts was inhibited. The extracts were shown to induce cell cycle arrest at the G2/M phase and apoptosis in the cells. Cell migration and colony formation were also inhibited in the cells. Furthermore, there was a downregulation of the anti-apoptotic marker Bcl-2 and an upregulation of both Bax and caspase-3 (Luetragoon et al., 2020).

Through the activity of its bioactive compound 4-[(α-L-Rhamnosyloxy) benzyl] isothiocyanate (MIC-1), which is found in the seeds, M. oleifera has been reported to inhibit the migration and proliferation of renal cancer cells (Xie et al., 2022). This regulatory activity is said to be brought about by the regulation of the PTP1B-dependent Src/Ras/Raf/ERK signalling pathway in 786-O hypertriploid renal cell carcinoma (RCC) cancer cells. MCI-1 from M. oleifera seeds also induced cell cycle arrest and caused the downregulation of the expression of cell cycle-related proteins in the 786-O cells (Xie et al., 2022).

Peganum harmala is a perennial herbaceous plant with a woody underground root stalk. It is a member of the Nitriaceae family and mostly grows in temperate deserts and Mediterranean regions (Alves-Silva et al., 2017). reported the ethnomedicinal uses of P. harmala as a remedy for the treatment of breast, liver, and bone cancer. It is also considered as a treatment for other different types of cancer (Kabbaj et al., 2012). Peganum harmala seeds from Morocco are ground with honey during cancer treatment. Despite the ethnomedicinal uses of P. harmala, the plant is also toxic and may cause hallucinogenic effects because of the presence of β-carbolines such as harmaline, harmine, harmalol, harmol, tetrahydroharmine, and the quinazoline derivatives vasicinone and deoxyvasicinone (Passos and Mironidou-Tzouveleki, 2016). Table 3 gives a summary of some of the in vivo and in vitro studies that has been carried out on plants that have been discussed in the manuscript as well as the identified bioactive compounds in these plants and the effects of these compounds on cancer progression.