Triterpenoid saponins have anti-inflammatory, antioxidant, and neuroprotective effects (Chen et al., 2022). Currently, the triterpenoid saponins isolated from Achyranthes aspera are mainly saponins derivatives with oleanolic acid (OA) as the aglycone. A total of 39 compounds (1–39) have been identified, and their core structures are illustrated in Figure 2 (Luo et al., 2020).

Triterpenes and their saponins, particularly OA and its derivatives, have been widely studied in the field of neuroprotection. These compounds can treat neurological diseases by alleviating excitotoxicity, Ca²⁺ overload, mitochondrial dysfunction, and blood-brain barrier permeability, as well as regulating immunity, anti-inflammatory, antioxidant, anti-apoptosis, and promoting angiogenesis and neurogenesis (Chen et al., 2022). The studies reported that OA (100 mg/kg) protects dopamine neurons by attenuating striatal microglial activation in a PD rat model induced by 6-hydroxydopamine (6-OHDA) (Mabandla et al., 2015; Msibi and Mabandla, 2019). The pretreatement with OA (20 μM) can exhibited antioxidative, anti-inflammatory and anti-apoptosis activities via decreasing GSH, raising the activity of SOD and catalase, reducing the release of IL-6 and TNF-α in PC12 cells (Tsai and Yin, 2008).

A significant pathological feature of AD is Aβ plaque deposition. OA (10 mg/kg) has been shown to inhibit Aβ25-35-induced cellular and synaptic toxicity (Wang et al., 2018), Aβ levels, and neuronal apoptosis, and reduce ROS levels by regulating uncoupling protein-2 (UCP2) expression through stanniocalcin-1 (STC-1), which can alleviate oxidative stress damage and play a role in the treatment of AD (Guo et al., 2020). Astrocytes and microglia are the primary immune cells in AD. In Aβ-activated astrocytes, OA (40 μM) pretreatment inhibits the transcription and release of inflammatory cytokines IL-6, TNF-α, and IL-1β, as well as inhibits neuroinflammation and neurotoxicity triggered by Ca²⁺ overload in co-cultured neurons (Zhang et al., 2018). OA (1 μM, 5 μM, and 10 μM) also inhibits inflammatory responses triggered by microglia overactivation (Castellano et al., 2019). In addition, OA (10 mg/kg) can promote the proliferation and differentiation of neural stem cells to enhance hippocampal neurogenesis, improve cell survival, thereby achieving neuroprotection and repair. These help ameliorate Aβ-induced cognitive and memory impairment (Lin et al., 2021). The oleanolic acid derivative, oleanolic acid saponin, increases acetylcholine levels and improves cognitive function by inhibiting the activity of acetylcholinesterase (AChE) (Puri et al., 2024).

Ketosteroid compounds are also the main active ingredients of Achyranthes aspera. Currently, there are seven ketosteroid compounds isolated from Achyranthes aspera, primarily including 25R-inokosterone (Figure 3A), 25S-inokosterone (Figure 3B), and β-ecdysterone (Figure 3C) (Meng, 2004).

Inokosterone, especially β-ecdysterone, have demonstrated potential and research value in the treatment of neurological disorders. Ecdysterone exhibits neuroprotective effects including antioxidant, anti-inflammatory, neurotransmitter modulation, inhibition of neuronal apoptosis, and promotion of neuronal regeneration and repair. Various factors, such as oxidative stress and neuronal loss, have been associated with neurodegenerative diseases like PD. β-Ecd (0.8 μM) has a protective effect on rotenone-induced neurotoxicity in PC12 cells, which can enhance the viability of PC12 cells through the Akt/Nrf2 pathway and reduce rotenone-induced apoptosis by decreasing Bax expression, caspase-9 activity, and caspase-3 activity (Liu et al., 2016).

β-Ecd also has a good therapeutic effect on AD. Ecd (5 mg/kg) administrated for 4 weeks in micehas been shown to scavenge oxygen free radicals as well as improve cognitive function, restore hippocampal SOD, CAT, and GRx activities, and inhibit neuronal loss in the cerebral cortex and hippocampus (Gholipour et al., 2022a; Gholipour et al., 2022b; Xing et al., 2024). BACE1 is an aspartic protease that cleaves amyloid precursor protein (APP) to generate neurotoxic Aβ (Mullard, 2017). β-Ecd strongly binds to the active site of BACE1, inducing a conformational change from an open to a closed form, thereby blocking substrate binding. Even 500 nM of the compound completely blocks the enzyme activity. Furthermore, β-Ecd strongly inhibits the formation and aggregation of Aβ fibrils and promotes the degradation of Aβ fibrils. (Chakraborty and Basu, 2017; Yang et al., 2010).

Neuronal hyperexcitability is a common phenomenon in neurodegenerative diseases. Ecd prevents glutamatergic excitotoxicity by enhancing mTOR/Akt/PI3K signaling activity to significantly reduce cortical cell death and exerts cortical neuron protectant for the prevention and treatment of dementia, mental and behavioral disorders (Wu et al., 2017). In the brain, dysfunction of the GABAergic system also disrupts t the balance between excitation and inhibition, resulting in neurodegeneration (Piot et al., 2023). Factors such as Aβ, BACE1, ApoE4, TREM2 mutations, and overactivated glial cells can all contribute to GABAergic system dysfunction (Bi et al., 2025; Cheng et al., 2023; Kaarniranta et al., 2023). Therefore, abnormalities in GABAergic system may serve as a common target for multiple aberrant signaling pathways in AD. Dysfunction of the GABAergic system, in turn, promotes the spread of Aβ and tau pathology, further exacerbating cognitive impairment in AD patients (Rossano et al., 2024). Ecd can act on the regulatory sites of GABAergic receptors to enhance GABAergic inhibition in cortical neurons, thereby reducing excitotoxicity and reducing neuronal cell death (Tsujiyama et al., 1995).

Ecd also possesses the ability to promote neuronal growth and repair. 200 mg/L ecd significantly increased the neurogenesis and differentiation of hippocampal neural stem cells, which is highly beneficial for stem cell transplantation in the treatment and injury repair of central nervous system disorders (Chu, 2008), β-ecd has been studied for its potential to improve symptoms of cerebral ischemia, alleviate cerebrovascular spasms, and enhance learning and memory capabilities, all of which hold significant importance for AD patients (Hindle et al., 2017).

Flavonoids are effective components of antioxidant and scavenging oxygen free radicals, as well as immunomodulatory, anti-inflammatory, anti-tumor, antibacterial, vascular-nourishing, and cardiovascular disease-preventing effects (Guan and Liu, 2016; Wang et al., 2023). Flavonoids are a class of yellow pigments derived from the flavone (2-phenylchromogen, as shown in Figure 4A) (Wen et al., 2010). The two main flavonoids found in Achyranthes aspera are hyperoside (HYP) (Figure 4B) and 5,2′-dimethoxy-6-(methoxymethyl)-7-hydroxy-isoflavonol (Figure 4C).

In the field of neuroprotection, HYP is the most extensively studied flavonoid, while other flavonoid components in Achyranthes aspera have not been reported in related studies. HYP, also known as quercetin-3-O-β-D-Nitrophenyl β-D-fucopyranoside, is alternatively referred to as hyperin or quercetin-3-galactoside. It is an important natural product belonging to the flavonol glycoside class, with a structure of quercetin-3-galactoside (Li, 2008). Clinically, HYP is used in many drugs, primarily for treating cardiovascular diseases. In addition, HYP exhibits a variety of effects, including anti-tumor, anti-aging, antidepressant, and anti-inflammatory properties. It also regulates the circulatory system, immune, digestive, and nervous system (Wang Q. et al., 2022).

In animal and cellular models of AD, HYP inhibits endoplasmic reticulum-related apoptotic pathways and attenuates Aβ-induced brain endothelial cell damage and blood-brain barrier (BBB) disruption, thus exerting a protective effect against AD (Liu et al., 2018; Liu et al., 2017). HYP (2.5, 5, 10, and 20 μM) also reversed Aβ-induced mitochondrial dysfunction, including elevation of mitochondrial membrane potential, reduction of reactive oxygen species (ROS) production and release of mitochondrial cytochrome c, and inhibition of caspase-9 and caspase-3, thereby inhibiting apoptosis (Zeng et al., 2011). Pretreatment with hyperoside for 30 min significantly increases cell viability, and morphological assessments of axonal damage supported that HYP pretreatment effectively reverses the toxic effects induced by Aβ and improves learning and memory deficits (Yi et al., 2022; Zeng et al., 2011). Aβ peptides can spontaneously aggregate into β-sheet-containing oligomers and fibrils, and the activation of this amyloid pathway alters the Ca²⁺ signaling, leading to neurotoxicity, which in turn leads to neuronal apoptosis (Angelova and Abramov, 2014). HYP (20, 40, 80 mg/kg) has been shown to exert neuroprotective effects in cellular or APP/PSEN1 double transgenic AD mouse models by anti-Aβ aggregation, BACE1 inhibition, reduction of Aβ plaques and GFAP levels in cortex and hippocampus. It also modulates Aβ-induced cell death by regulating Ca²⁺ signaling cascades and mitochondrial membrane potential, thereby providing neuroprotection (Song et al., 2023). Pharmacokinetic data confirmed that intranasal administration of HYP increased bioavailability in the mouse brain. Further in vivo studies demonstrated that it improved motor deficits, spatial memory, and learning ability in APP/PSEN1 mice (Song et al., 2023).

PD is characterized by the pathological loss of DA neurons in the nigrostriatal pathway, leading to insufficient DA release and resulting in both motor and nonmotor symptoms. HYP (100 μg/mL) reduced 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-mediated cytotoxicity in SH-SY5Y cells in vitro, while HYP (25 mg/kg) alleviated MPTP-induced motor symptoms in vivo, reduced levels of nitric oxide (NO), H₂O₂, and malondialdehyde (MDA), and mitochondrial damage in dopaminergic neurons (Xu et al., 2023). Additionally, HYP treatment elevated the levels of neurotrophic factors such as glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), and cerebral dopamine neurotrophic factor (CDNF) in vivo (Xu et al., 2023). HYP (2 μM) also inhibits oxidative stress-induced neuronal death by activating Nrf2-dependent heme oxygenase-1 (HO-1), significantly ameliorating 6-hydroxydopamine (6-OHDA)-induced neurotoxicity and providing protective effects against PD and related disorders (Kwon et al., 2019). HYP effectively inhibit microglia overactivation and inflammation. Studies have found that hyperoside significantly inhibits LPS-induced production of NO, IL-1β and TNF-α in BV2 microglia by suppressing the activation of p38 and NF-κB, as well as reducing iNOS expression, thereby exerting neuroprotective effects (Fan et al., 2017). Furthermore, HYP inhibits the NLRP3 inflammasome activation by upregulating pituitary adenylate cyclase-activating peptide (PACAP), thus effectively suppressing neuroinflammation to protect dopaminergic neurons and treat PD (Wang K. et al., 2022).

HYP was able to significantly inhibit corticosterone-induced Ca²⁺ overload in PC12 cells, suggesting its ability to protect neuronal cells by preventing intracellular Ca²⁺ overload (Zheng et al., 2012). Additionally, HYP enhances the body’s immunity by promoting the activity and function of immune cells. For example, it stimulates lymphocyte proliferation, enhances the phagocytic function of monocytes and macrophages, and increases the production of antibodies (Gao et al., 2010; Huang et al., 2009). These effects provide a theoretical basis for the role of HYP in other neurodegenerative diseases.

Alkaloids are another important active components in Achyranthes aspera, exhibiting a variety of pharmacological activities. Alkaloids compounds, primarily including N-trans-feruloyltyramine (NTF) (Figure 5A), indole-3-carboxaldehyde (I3A) (Figure 5B), and betaine (Figure 5C), exert neuroactive effects on the nervous system, such as sedation and anti-depression (Bhosale et al., 2011).

NTF has been demonstrated to be a potent antioxidant (Gao et al., 2019). In the human neuroblastoma cell line SK-N-SH, NTF (320 μM) pretreatment significantly reduced H₂O₂-induced ROS generation and attenuated H₂O₂-mediated cytotoxicity. It reversed H₂O₂-mediated increases in the expression of Bax and activated caspase-3 as well as the decrease in Bcl-2, suggesting that NTF ameliorates H₂O₂-induced intracellular ROS generation and reduces apoptosis. These protective effects of NTF may be beneficial for neurodegenerative diseases associated with oxidative stress (Gao et al., 2019; Tu et al., 2016). NTF also inhibits BACE1, Monoamine oxidase-B (MAO-B), tau hyperphosphorylation, and Aβ aggregation, thereby inhibiting neurodegenerative diseases, especially AD (Othman et al., 2022). The alkaloid I3A also inhibits Aβ and tau protein aggregation (Purgatorio et al., 2020).

Betaine exhibits a wide range of pharmacological effects and has shown therapeutic potential for cardiovascular disease, liver disease, kidney disease, and neuroprotection. It can be used in the prevention and treatment of neurodegenerative diseases such as AD and PD (Rosas-Rodríguez and Valenzuela-Soto, 2021). Betaine metabolism provides methyl for methionine synthesis, which regulates homocysteine (Hcy) levels, and blood Hcy is a biomarker of human health status, and high levels of Hcy are associated with a variety of diseases (Azzini et al., 2020; Hainsworth et al., 2016). Betaine can attenuate high Hcy-induced memory impairment, chronic stress, and oxidative stress by reducing matrix metalloproteinases (MMP) in the frontal cortex of the brain (Kunisawa et al., 2015; Xie et al., 2016) and reversing tau hyperphosphorylation, Aβ aggregation, and levels of the inflammatory factors IL-1β and TNFα (Sun et al., 2017). Betaine inhibited Aβ-induced neuroinflammation in microglia by inhibiting the activation of the NLRP3 inflammasome and NF-κB (Zhang and Jia, 2023). Betaine interacts with GABA receptors to activate the GABAergic system, thereby reducing memory impairment (Kunisawa et al., 2017). It also regulates inhibitory neurotransmission, such as glycine and glutamine (Knight et al., 2017). These mechanisms highlight the significant potential of alkaloids in the prevention and treatment of neurodegenerative diseases.

Additionally, polysaccharides in Achyranthes aspera exhibit immunomodulatory effects, which help enhance the body’s immune function and reduce inflammatory damage to the nervous system. Achyranthes aspera extract is beneficial to improve the immunity of dogs by stimulating B cells and inducing anti-inflammatory response (Lee et al., 2020). Achyranthes polysaccharides(ABPS)selectively enhance the Th1 immune response, control the proliferation of plasmodium, and prolong the survival of mice in subsequent plasmodium infection (Zhu et al., 2012). ABPS significantly enhanced humoral response and B lymphocyte proliferation and antagonized the immunosuppressive effects (Li, 2000). Studies have shown that ABPS can markedly enhance the immunomodulatory functions of macrophages (Wang et al., 2021), increase the activity of natural killer cells (NK cells) in immunocompromised mice, and elevate the expression of CD40, CD80, and CD86 on the cell surface, stimulate the activation of T lymphocytes, and thus enhance the humoral immunity and non-specific immunity of the body. Therefore, Achyranthes aspera can improve neurodegenerative diseases by stimulating the immune system and increasing the body’s immune function.