Dioscorea Extract (DA-9801) Modulates Markers of Peripheral Neuropathy in Type 2 Diabetic db/db Mice

The genus Dioscorea L. (Dioscoreaceae), a review of traditional uses, phytochemistry, pharmacology, and toxicity

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Dioscorea, a member of the Dioscoreaceae family, comprises approximately 600 species and is widely distributed across temperate and tropical regions such as Asia, South Africa, and North America. The traditional medicinal uses of Dioscorea have been documented in Asian and African pharmacological systems. In Asia, this genus is traditionally used to treat respiratory illnesses, rheumatism, diabetes, diarrhea, dysentery, and other conditions. In Africa, this genus has been used to treat human immunodeficiency virus and ring worms. However, the traditional medicinal practices in North America rarely mention the use of this genus.

AIM OF THE STUDY

The aim of this review is to comprehensively review the genus Dioscorea, focusing on its traditional uses, phytochemical constituents, pharmacological activities, and potential toxicities. The research also aims to highlight the valuable bioactive compounds within Dioscorea and emphasize the need for further investigations into acute and chronic toxicity, activity mechanisms, molecular markers, and other relevant factors to contribute to the discovery of novel pharmaceuticals.

MATERIALS AND METHODS

A search for available information on Dioscorea was conducted using scientific databases, including PubMed, ISI-WOS, Scopus, and Google Scholar, as well as recent academic publications from reputable publishers and other literature sources. The search was not limited by language and spanned the literature published between 1950 and 2022.

RESULTS

This article provides a comprehensive review of the Dioscorea genus, focusing on its traditional uses, phytochemical constituents, pharmacological activities, and potential toxicities. Extensive research has been conducted on this genus, resulting in the isolation and examination of over 1000 compounds, including steroids, terpenoids, and flavonoids, to determine their biological activities. These activities include anti-tumor, anti-inflammatory, immunomodulatory, neuroprotective, hypoglycemic, and hypolipidemic effects. However, some studies have indicated the potential toxicity of high doses of Dioscorea, highlighting the need for further investigations to assess the safety of this genus. Additionally, this review explores potential avenues for future research and discusses the challenges associated with a comprehensive understanding of the Dioscorea genus.

CONCLUSIONS

Based on the existing literature, it can be concluded that Dioscorea is a valuable source of bioactive compounds that have the potential to treat various disorders. Future research should prioritize the investigation of acute and chronic toxicity, activity mechanisms, molecular markers, and other relevant factors. This review provides a comprehensive analysis of the Dioscorea genus, emphasizing its potential to enable a deeper exploration of the biological activity mechanisms of these plants and contribute to the discovery of novel pharmaceuticals.

Dioscin: Therapeutic potential for diabetes and complications

Diabetes mellitus is a widespread metabolic disorder with increasing incidence worldwide, posing a considerable threat to human health because of its complications. Therefore, cost-effective antidiabetic drugs with minimal side effects are urgently needed. Dioscin, a naturally occurring compound, helps to reduce the complications of diabetes mellitus by regulating glucose and lipid metabolism, protecting islet β cells, improving insulin resistance, and inhibiting oxidative stress and inflammatory response. Plant-derived dioscin reduces the risk of toxicity and side effects associated with chemically synthesized drugs. It is a promising option for treating diabetes mellitus because of its preventive and therapeutic effects, which may be attributed to a variety of underlying mechanisms. However, data compiled by current studies are preliminary. Information about the molecular mechanism of dioscin remains limited, and no high-quality human experiments and clinical trials for testing its safety and efficacy have been conducted. As a resource for research in this area, this review is expected to provide a systematic framework for the application of dioscin in the treatment of diabetes mellitus and its complications.

A Thickening Agent Using Dioscorea japonica Powder Exhibits Suitable Properties for People with Dysphagia

In an aging society, the novel concept of added food functionality in a dysphagia diet is necessary for preventing diseases and maintain nutrition intake. The present study evaluated the utilization of Dioscorea japonica as a thickened liquid for people with dysphagia due to its unique physical properties and beneficial effects on chronic inflammation. The viscosity of the prepared thickened liquid using freeze-dried Dioscorea japonica powder was compared with those of xanthan gum and commercially available thickened liquids in selected conditions resembling to cooking. Dioscorea japonica powder showed high versatility, because the viscosity of its thickened liquid could be easily adjusted by modifying its blending amount and temperature. The thickened liquid of Dioscorea japonica had the most stable viscosity among the thickened liquids when NaCl was added and exhibited excellent resistance to α-amylase, similar to that of the other thickened liquids. The viscosity of the thickened liquid of Dioscorea japonica was relatively stable on changing the pH, but it was slightly unstable when the temperature changed. Overall, the thickened liquid of Dioscorea japonica powder has excellent viscosity stability, comparable to or better than commercially available thickened liquids, and is expected to be used as a new thickened liquid with added food functionality.

Screening and identification of lipase inhibitors extracted from Dioscorea nipponica Makino by UV-vis and HPLC coupled to UPLC-Q-TOF-MS/MS

Dioscoreae nipponica Makino (D. nipponica) as the rhizome of dioscoreaceae rich in steroidal saponins, has been reported to have the hypolipidemic effects etc. However, it is still unclear which exact active components are primary responsible for the beneficial effects. This study was conducted to fish out the lipase inhibitors from D. nipponica, and evaluate the inhibitory activity on porcine pancreatic lipase (PPL) through in vitro kinetic assay using p-nitrophenyl palmitate as substrate. Accordingly, the ethanolic extract was subjected to D101 macroporous resin purification for spectrophotometric screening, high performance liquid chromatography (HPLC) separation and structural characterization by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Through orlistat validation, the PPL inhibitory activity and IC₅₀ value of the extract were respectively 68.34 ± 1.47 % and 107.05 μg/mL under the optimized inhibition conditions. From 6 steroidal saponins identified, the inhibitory components named the protodioscin, protogracillin, dioscin and gracillin were fished out by grouping separation and HPLC analysis. Furthermore, dioscin and gracillin with the parent structure of diogenin were confirmed as the major inhibitors by virtue of stability tests based on transformation of protodioscin and protogracillin. Finally, the inhibitory mechanism of the major inhibitors toward PPL was further clarified by kinetic analysis and molecular docking analysis. The proposed method not only revealed the PPL inhibitory components in D. nipponica, but also provided an effective approach to hierarchical screening of PPL inhibitors from natural plants.

Could consumption of yam (Dioscorea) or its extract be beneficial in controlling glycaemia: a systematic review

Yam (Dioscorea spp.) and its associated extracts have been shown to possess a variety of biological activities and identified as beneficial in the control of glycaemia in patients with type II diabetes mellitus (T2DM). The objective was to conduct a systematic search of the literature to investigate whether yam and its extract can improve glycaemia and whether the consumption of yam could be beneficial for managing T2DM. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and the Population, Invention, Comparison and Outcome framework, three databases (PubMed, Scopus and Web of Science) were searched using a key term strategy. Strict inclusion criteria were employed to identify all relevant and available studies. The quality of these studies was assessed using SYRCLE's Risk of Bias tool. Ten studies were included, and all studies consisted of findings from rodent models of diabetes, including animals consuming high fat diets or genetic models of diabetes. All ten studies showed that the consumption of yam and/or its extracts (containing dioscin, dioscorin, diosgenin, DA-9801/02 or Chinese yam polysaccharides) improved glycaemia. These included improvements in fasting blood glucose and reductions in glucose and increase in insulin levels following a glucose tolerance test. Furthermore, significant changes in body weight and adiposity were observed in nine studies, these included improvements in lipid biomarkers in four and reductions in inflammatory markers in one. The current work indicates that the consumption of yam or its extracts can be beneficial for improving blood glucose; however, the molecular mechanism for these effects remains largely unknown. Future trials on human subjects are warranted.

Therapeutic Potential of Ursolic Acid in Cancer and Diabetic Neuropathy Diseases

Ursolic acid (UA) is a pentacyclic triterpenoid frequently found in medicinal herbs and plants, having numerous pharmacological effects. UA and its analogs treat multiple diseases, including cancer, diabetic neuropathy, and inflammatory diseases. UA inhibits cancer proliferation, metastasis, angiogenesis, and induced cell death, scavenging free radicals and triggering numerous anti- and pro-apoptotic proteins. The biochemistry of UA has been examined broadly based on the literature, with alterations frequently having been prepared on positions C-3 (hydroxyl), C12-C13 (double bonds), and C-28 (carboxylic acid), leading to several UA derivatives with increased potency, bioavailability and water solubility. UA could be used as a protective agent to counter neural dysfunction via anti-oxidant and anti-inflammatory effects. It is a potential therapeutic drug implicated in the treatment of cancer and diabetic complications diseases provide novel machinery to the anti-inflammatory properties of UA. The pharmacological efficiency of UA is exhibited by the therapeutic theory of one-drug → several targets → one/multiple diseases. Hence, UA shows promising therapeutic potential for cancer and diabetic neuropathy diseases. This review aims to discuss mechanistic insights into promising beneficial effects of UA. We further explained the pharmacological aspects, clinical trials, and potential limitations of UA for the management of cancer and diabetic neuropathy diseases.

Dioscin and diosgenin: Insights into their potential protective effects in cardiac diseases

BACKGROUND AND ETHNOPHARMACOLOGICAL RELEVANCE

Dioscin and diosgenin derived from plants of the genus Dioscoreaceae such as D. nipponica and D. panthaica Prain et Burk. Were utilized as the main active ingredients of traditional herbal medicinal products for coronary heart disease in the former Soviet Union and China since 1960s. A growing number of research showed that dioscin and diosgenin have a wide range of pharmacological activities in heart diseases.

AIM OF THE STUDY

To summarize the evidence of the effectiveness of dioscin and diosgenin in cardiac diseases, and to provide a basis and reference for future research into their clinical applications and drug development in the field of cardiac disease.

METHODS

Literatures in this review were searched in PubMed, ScienceDirect, Google Scholar, China National Knowledge Infrastructure (CNKI) and Web of Science. All eligible studies are analyzed and summarized in this review.

RESULTS

The pharmacological activities and therapeutic potentials of dioscin and diosgenin in cardiac diseases are similar, can effectively improve hypertrophic cardiomyopathy, arrhythmia, myocardial I/R injury and cardiotoxicity caused by doxorubicin. But the bioavailability of dioscin and diosgenin may be too low as a result of poor absorption and slow metabolism, which hinders their development and utilization.

CONCLUSION

Dioscin and diosgenin need further in-depth experimental research, clinical transformation and structural modification or research of new preparations before they can be expected to be developed into new therapeutic drugs in the field of cardiac disease.

Effects of DA-9801 on the inflammation and apoptosis induced by angiotensin II in human dermal microvascular endothelial cells

DA-9801, a plant-based drug used for the treatment of diabetic neuropathy, is known to improve angiotensin II (Ang II)-induced vascular endothelial cell dysfunction. However, the underlying mechanism is not fully understood. We aimed to determine whether the protective effect of DA-9801 against Ang II-induced endothelial cell dysfunction was mediated via inhibition of endothelial cell inflammation and apoptosis. Ang II-induced oxidative stress was attenuated by pretreatment of human dermal microvascular endothelial cells (HDMECs) with DA-9801. This prevented the Ang II-induced upregulation of NAD(P)H oxidase (the NOX4 and p22phox subunits) and reactive oxygen species. Further, pretreatment of HDMECs with DA-9801 ameliorated Ang II-mediated nuclear factor kappa B activity via prevention of the upregulation of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase. It also decreased the Ang II-stimulated increase in inducible nitric oxide synthase (NOS) and decreased endothelial NOS protein expression. DA-9801 decreased Ang II-induced upregulation of intercellular adhesion molecule 1, vascular adhesion molecule, and E-selectin in HDMECs. Moreover, TUNEL and annexin V-FITC fluorescence staining for apoptosis and the activities of caspases 9, 7, and 3 decreased in HDMECs pretreated with DA-9801, indicating that the drug enhanced anti-apoptotic pathways. Thus, DA-9801 modulated Ang II-induced endothelial cell dysfunction via inflammatory and apoptotic pathways.

The Dioscorea Genus (Yam)-An Appraisal of Nutritional and Therapeutic Potentials

The quest for a food secure and safe world has led to continuous effort toward improvements of global food and health systems. While the developed countries seem to have these systems stabilized, some parts of the world still face enormous challenges. Yam (Dioscorea species) is an orphan crop, widely distributed globally; and has contributed enormously to food security especially in sub-Saharan Africa because of its role in providing nutritional benefits and income. Additionally, yam has non-nutritional components called bioactive compounds, which offer numerous health benefits ranging from prevention to treatment of degenerative diseases. Pharmaceutical application of diosgenin and dioscorin, among other compounds isolated from yam, has shown more prospects recently. Despite the benefits embedded in yam, reports on the nutritional and therapeutic potentials of yam have been fragmented and the diversity within the genus has led to much confusion. An overview of the nutritional and health importance of yam will harness the crop to meet its potential towards combating hunger and malnutrition, while improving global health. This review makes a conscious attempt to provide an overview regarding the nutritional, bioactive compositions and therapeutic potentials of yam diversity. Insights on how to increase its utilization for a greater impact are elucidated.

Preventive effect of Dioscorea japonica on squamous cell carcinoma of mouse skin involving down-regulation of prostaglandin E2 synthetic pathway

Hyperproduced prostaglandin E₂ by cyclooxygenase-2 and microsomal prostaglandin E synthase-1 evokes several pathophysiological responses such as inflammation and carcinogenesis. Our recent study demonstrated that Dioscorea japonica extract suppressed the expression of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 and induced apoptosis in lung carcinoma A549 cells. In the present study, we investigated the effects of Dioscorea japonica on squamous cell carcinoma of mouse skin. Dioscorea japonica feeding and Dioscorea japonica extract topical application suppressed the expression of cyclooxygenase-2, microsomal prostaglandin E synthase-1, interleukin-1β and interleukin-6 and inhibited tumor formation, hyperplasia and inflammatory cell infiltration. Immunohistochemical analyses showed the immunoreactivities of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 in tumor keratinocytes and stronger immunoreactivities of cyclooxygenase-2 and hematopoietic prostaglandin D synthase in epidermal dendritic cells (Langerhans cells). Treatment with Dioscorea japonica decreased the immunoreactivity of cyclooxygenase-2 and microsomal prostaglandin E synthase-1. These results indicate that Dioscorea japonica may have inhibitory effects on inflammation and carcinogenesis via suppression of the prostaglandin E₂ synthetic pathway.

Trigonelline promotes auditory function through nerve growth factor signaling on diabetic animal models

BACKGROUND

Protection of cochlear function and reconstruction of neuronal networks in damaged auditory sensory structures is crucial for therapeutic treatment of diabetic hearing loss. Nerve growth factor (NGF) has been used as a novel therapeutic target to protect against the neurodegenerative effects of Diabetes Mellitus (DM).

PURPOSE

We aimed to evaluate the potential effect of trigonelline (TRG) on reducing auditory damage produced by DM using NGF as a potential marker.

METHOD

Docking simulations were carried out using Autodock Vina software and visualized using Discovery Studio. Morphological analysis of hair cells and neuromasts was performed on alloxan-induced diabetic zebrafish by fluorescence and scanning electron microscopy. Blockage of NGF receptor phosphorylation with K-252a was used to evaluate TRG and NGF action. Further assessment of NGF by ELISA on a primary culture of spiral ganglion cells was performed as a marker of neuronal function on the hearing system. Finally, auditory function was assessed in LepR(^db/db) mice using auditory brainstem response (ABR) and transient evoked otoacoustic emission (TEOAE) during 8 weeks.

RESULTS

Docking simulations showed that TRG binds to the active site of NGF through molecular interactions with Lysine88 (Lys88) and Tyrosine52 (Tyr52). TRG treatment significantly reduced hair cell loss and neuromast damage in diabetic zebrafish (P < .05). Further evaluation revealed a significant increase in the number of neuromasts after NGF administration (P < .001). TRG and NGF action was suppressed during blockage of NGF receptor phosphorylation. Moreover, spiral ganglion cells revealed significant elevation on NGF values after TRG treatment (P < .05). In vivo evaluation of LepR(^db/db) mice revealed a significant reduction in the auditory damage produced under diabetic progression, characterized by reduced ABR hearing threshold shifts and increased signal-to-noise ratio in TEOAE (P < .05).

CONCLUSIONS

This study suggests that the enhanced hearing function produced by TRG may be mediated by NGF, providing a potential therapeutic strategy for diabetic hearing loss.

Combined Application of UHPLC-QTOF/MS, HPLC-ELSD and 1 H-NMR Spectroscopy for Quality Assessment of DA-9801, A Standardised Dioscorea Extract

INTRODUCTION

DA-9801, a standardised 50% aqueous ethanolic extract of a mixture of Dioscorea japonica and D. nipponica, is a botanical drug candidate for the treatment of diabetic neuropathy, which finished its US phase II clinical trials recently. An advanced quality control method is needed for further development of DA-9801, considering its high contents of both primary and secondary metabolites.

OBJECTIVE

Development of a quality assessment strategy for DA-9801, based on the combination of UHPLC-QTOF/MS, HPLC-ELSD, and ¹ H-NMR spectroscopy.

METHODS

The method was developed and tested with 15 batch products of DA-9801. The steroidal saponins of DA-9801 were tentatively identified by UHPLC-QTOF/MS and were quantified with the validated HPLC-ELSD method. Primary metabolites of DA-9801 were identified and profiled using ¹ H-NMR spectrometry. The batch-to-batch equivalence of DA-9801 was tested with the ¹ H-NMR spectra using spectral binning, correlation analysis, and principal component analysis.

RESULTS

Six major saponins of DA-9801 were tentatively identified by UHPLC-QTOF/MS. Among them, protodioscin and dioscin were quantified by the validated HPLC-ELSD method. Twenty-six metabolites were identified in ¹ H-NMR spectra. The similarity between DA-9801 batches could be evaluated with the NMR spectra of DA-9801. The ¹ H-NMR method also revealed that two Dioscorea species contributed distinct amino acids to the contents of DA-9801.

CONCLUSION

This study validates the effectiveness of UHPLC-QTOF/MS, HPLC-ELSD, and ¹ H NMR-combined method for quality control of DA-9801 and its crude materials. Copyright © 2016 John Wiley & Sons, Ltd.

P2X1 Receptor-Mediated Ca2+ Influx Triggered by DA-9801 Potentiates Nerve Growth Factor-Induced Neurite Outgrowth

Nerve growth factor (NGF)-induced neuronal regeneration has emerged as a strategy to treat neuronal degeneration-associated disorders. However, direct NGF administration is limited by the occurrence of adverse effects at high doses of NGF. Therefore, development of a therapeutic strategy to promote the NGF trophic effect is required. In view of the lack of understanding of the mechanism for potentiating the NGF effect, this study investigated molecular targets of DA-9801, a well-standardized Dioscorea rhizome extract, which has a promoting effect on NGF. An increase in intracellular calcium ion level was induced by DA-9801, and chelation of extracellular calcium ions with ethylene-bis(oxyethylenenitrilo)tetraacetic acid (EGTA) suppressed the potentiating effect of DA-9801 on NGF-induced neurite outgrowth. In addition, EGTA treatment reduced the DA-9801-induced phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2), the major mediators of neurite outgrowth. To find which calcium ion-permeable channel contributes to the calcium ion influx induced by DA-9801, we treated PC12 cells with various inhibitors of calcium ion-permeable channels. NF449, a P2X1 receptor selective antagonist, significantly abolished the potentiating effect of DA-9801 on NGF-induced neurite outgrowth and abrogated the DA-9801-induced ERK1/2 phosphorylation. In addition, transfection with siRNA of P2X1 receptor significantly reduced the DA-9801-enhanced neurite outgrowth. In conclusion, calcium ion influx through P2X1 receptor mediated the promoting effect of DA-9801 on NGF-induced neurite outgrowth via ERK1/2 phosphorylation.

Evaluating Pharmacological Effects of Two Major Components of Shuangdan Oral Liquid: Role of Danshensu and Paeonol in Diabetic Nephropathy Rat

Shuangdan oral liquid (SDO) containing radix Salviae miltiorrhizae (Chinese name Danshen) and cortex moutan (Chinese name Mudanpi) is a traditional Chinese medicine using for treating vascular diseases. Danshensu (DSS) is a main effective monomer composition derived from radix Salviae miltiorrhizae and paeonol (Pae) from cortex moutan. Although the two herbs are widely used in traditional Chinese medicine, the pharmacological functions of their active compositions were not reported. Therefore, the research of DSS and Pae in mechanisms and pharmacodynamics interaction can provide scientific evidence to support clinical application. The diabetic nephropathy (DN) rats which were induced by streptozotocin (STZ) were treated with SDO, DSS, Pae, and DSS+Pae for eight weeks. The positive effects on DN animal models were investigated by detection of physiological and biochemical indexes and oxidative stress markers, within five treatments: SDO, DSS, Pae, DSS+Pae and insulin group. Compared with the model group, the DSS+Pae group improved the renal function, blood lipid metabolism and blood viscosity, increased the vitality of T-SOD or T-AOC and decreased the level of MDA or NO after the treatment. The study was successfully showed that the DSS+Pae group could delay the process of DN, especially in the renal injury part of histopathology changes. Our results suggest that the co-administration of DSS and Pae significantly may play a protective role in DN rats through decreasing the oxidative stress and improving the blood lipid metabolism mechanisms.

Lactucopicrin ameliorates oxidative stress mediated by scopolamine-induced neurotoxicity through activation of the NRF2 pathway

Cholinergic activity plays a vital role in cognitive function, and is reduced in individuals with neurodegenerative diseases. Scopolamine, a muscarinic cholinergic antagonist, has been employed in many studies to understand, identify, and characterize therapeutic targets for Alzheimer's disease (AD). Scopolamine-induced dementia is associated with impairments in memory and cognitive function, as seen in patients with AD. The current study aimed to investigate the molecular mechanisms underlying scopolamine-induced cholinergic neuronal dysfunction and the neuroprotective effect of lactucopicrin, an inhibitor of acetylcholine esterase (AChE). We investigated apoptotic cell death, caspase activation, generation of reactive oxygen species (ROS), mitochondrial dysfunction, and the expression levels of anti- and pro-apoptotic proteins in scopolamine-treated C6 cells. We also analyzed the expression levels of antioxidant enzymes and nuclear factor (erythroid-derived 2)-like 2 (NRF2) in C6 cells and neurite outgrowth in N2a neuroblastoma cells. Our results revealed that 1 h scopolamine pre-treatment induced cytotoxicity by increasing apoptotic cell death via oxidative stress-mediated caspase 3 activation and mitochondrial dysfunction. Scopolamine also downregulated the expression the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase, and the transcription factor NRF2. Lactucopicrin treatment protected C6 cells from scopolamine-induced toxicity by reversing the effects of scopolamine on those markers of toxicity. In addition, scopolamine attenuated the secretion of neurotrophic nerve growth factor (NGF) in C6 cells and neurite outgrowth in N2a cells. As expected, lactucopicrin treatment enhanced NGF secretion and neurite outgrowth. Our study is the first to show that lactucopicrin, a potential neuroprotective agent, ameliorates scopolamine-induced cholinergic dysfunction via NRF2 activation and subsequent expression of antioxidant enzymes.

Phytochemicals that regulate neurodegenerative disease by targeting neurotrophins: a comprehensive review

Alzheimer's disease (AD), characterized by progressive dementia and deterioration of cognitive function, is an unsolved social and medical problem. Age, nutrition, and toxins are the most common causes of AD. However, currently no credible treatment is available for AD. Traditional herbs and phytochemicals may delay its onset and slow its progression and also allow recovery by targeting multiple pathological causes by antioxidative, anti-inflammatory, and antiamyloidogenic properties. They also regulate mitochondrial stress, apoptotic factors, free radical scavenging system, and neurotrophic factors. Neurotrophins such as BDNF, NGF, NT3, and NT4/5 play a vital role in neuronal and nonneuronal responses to AD. Neurotrophins depletion accelerates the progression of AD and therefore, replacing such neurotrophins may be a potential treatment for neurodegenerative disease. Here, we review the phytochemicals that mediate the signaling pathways involved in neuroprotection specifically neurotrophin-mediated activation of Trk receptors and members of p75(NTR) superfamily. We focus on representative phenolic derivatives, iridoid glycosides, terpenoids, alkaloids, and steroidal saponins as regulators of neurotrophin-mediated neuroprotection. Although these phytochemicals have attracted attention owing to their in vitro neurotrophin potentiating activity, their in vivo and clinical efficacy trials has yet to be established. Therefore, further research is necessary to prove the neuroprotective effects in preclinical models and in humans.