DA-9801, a standardized Dioscorea extract, improves memory function via the activation of nerve growth factor-mediated signaling.

OBJECTIVES: Nerve growth factor (NGF) is a neurotrophin that plays a critical role in mammalian learning and memory functions. NGF also regulates neuronal cell differentiation and neurite outgrowth by activating ERK/CREB signaling. This present study examined the effects of a standardized Dioscorea extract (DA-9801), which is composed of Dioscorea japonica Thunb and Dioscorea nipponica Makino on memory function via its NGF-potentiating activities using an in vitro and in vivo paradigm. METHODS: Cells were incubated with or without different concentrations of DA-9801 (10, 25, and 50 µg/ml) extract for 24 h. The cultured conditioned medium from C6 glioma cells was used for NGF production assay, and neurite length in N2a cells was measured after every 2 h. Mice were orally treated with DA-9801 (10 and 100 mg/kg/day) once daily for 7 days. They were subjected to passive avoidance test to evaluate memory functions. The question of whether DA-9801 induced NGF synthesis was assessed by measuring the levels of NGF in the mouse cortical and hippocampal tissues. Hippocampal cell differentiation and NGF-mediated ERK/CREB signaling were evaluated by performing immunohistochemical analysis using BrdU, ki67, DCX, phosphorylated ERK and CREB in the mouse hippocampus. RESULTS: DA-9801 treatment increased the NGF contents and neurite length, respectively. Mice with DA-9801 administration showed memory enhancement in the passive avoidance test. DA-9801 also increased newborn cell differentiation, neurite length, NGF secretion, and ERK/CREB phosphorylation in the mouse hippocampus. DISCUSSION: These results suggest that DA-9801 treatment could improve memory function by inducing hippocampal NGF synthesis and ERK/CREB signaling.

Novel Botanical Therapeutic NB-02 Effectively Treats Alzheimer's Neuropathophysiology in an APP/PS1 Mouse Model.

Alzheimer's disease (AD) is an incurable neurodegenerative disorder and a major cause of dementia. Some of the hallmarks of AD include presence of amyloid plaques in brain parenchyma, calcium dysregulation within individual neurons, and neuroinflammation. A promising therapeutic would reverse or stymie these pathophysiologies in an animal model of AD. We tested the effect of NB-02, previously known as DA-9803, a novel multimodal therapeutic, on amyloid deposition, neuronal calcium regulation and neuroinflammation in 8- to 10-month-old APP/PS1 mice, an animal model of AD. In vivo multiphoton microscopy revealed that two-month-long administration of NB-02 halted amyloid plaque deposition and cleared amyloid in the cortex. Postmortem analysis verified NB-02-dependent decrease in plaque deposition in the cortex as well as hippocampus. Furthermore, drug treatment reversed neuronal calcium elevations, thus restoring neuronal function. Finally, NB-02 restored spine density and transformed the morphology of astrocytes as well as microglia to a more phagocytic state, affecting neuroinflammation. NB-02 was effective at reversing AD neuropathophysiology in an animal model. Therefore, in addition to serving as a promising preventative agent, NB-02 holds potential as a treatment for AD in the clinic.

Anti-Neurodegenerative Biflavonoid Glycosides from Impatiens balsamina.

Four biflavonoid glycosides, balsamisides A-D (1-4), and nine known compounds (5-13) were obtained from the white petals of Impatiens balsamina. The 2D structures of the purified phytochemicals were established using conventional NMR techniques in addition to the new long-range HSQMBC NMR experiment. Acid hydrolysis followed by experimental and quantum-mechanics-based ECD data analysis permitted full configurational assignment of the purified metabolites. Compounds 1-13 were assessed for their potential to impede the generation of nitric oxide in lipopolysaccharide-stimulated BV2 cells. They were also investigated for potential neuroprotective activity using C6 cells and cytotoxicity against some human tumor cell lines, but were inactive (IC50 > 10 µM) against all the cell lines.

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.

Odisolane, a Novel Oxolane Derivative, and Antiangiogenic Constituents from the Fruits of Mulberry (Morus alba L.).

Mulberry, the fruit of Morus alba L., is known as an edible fruit and commonly used in Chinese medicines as a warming agent and as a sedative, tonic, laxative, odontalgic, expectorant, anthelmintic, and emetic. Systemic investigation of the chemical constituents of M. alba fruits led to the identification of a novel oxolane derivative, (R*)-2-((2S*,3R*)-tetrahydro-2-hydroxy-2-methylfuran-3-yl)propanoic acid (1), namely, odisolane, along with five known heterocyclic compounds (2-6). The structure of the new compound was elucidated on the basis of HR-MS, 1D and 2D NMR ((1)H-(1)H COSY, HSQC, HMBC, and NOESY) data analysis. Compound 1 has a novel skeleton that consists of 8 carbon units with an oxolane ring, which until now has never been identified in natural products. The isolated compounds were subjected to several activity tests to verify their biological function. Among them, compounds 1, 3, and 5 significantly inhibited cord formation in HUVECs. The action mechanism of compound 3, which had the strongest antiangiogenic activity, was mediated by decreasing VEGF, p-Akt, and p-ERK protein expression. These results suggest that compounds isolated from M. alba fruits might be beneficial in antiangiogenesis therapy for cancer treatment.

DA-9801 promotes neurite outgrowth via ERK1/2-CREB pathway in PC12 cells.

In the present study, we examined the mechanisms underlying the effect of DA-9801 on neurite outgrowth. We found that DA-9801 elicits its effects via the mitogen-activated protein kinase (MEK) extracellular signal-regulated kinase (ERK)1/2-cAMP response element-binding protein (CREB) pathway. DA-9801, an extract from a mixture of Dioscorea japonica and Dioscorea nipponica, was reported to promote neurite outgrowth in PC12 cells. The effects of DA-9801 on cell viability and expression of neuronal markers were evaluated in PC12 cells. To investigate DA-9801 action, specific inhibitors targeting the ERK signaling cascade were used. No cytotoxicity was observed in PC12 cells at DA-9801 concentrations of less than 30 µg/mL. In the presence of nerve growth factor (NGF, 2 ng/mL), DA-9801 promoted neurite outgrowth and increased the relative mRNA levels of neurofilament-L (NF-L), a marker of neuronal differentiation. The Raf-1 inhibitor GW5074 and MEK inhibitor PD98059 significantly attenuated DA-9801-induced neurite outgrowth. Additionally, the MEK1 and MEK2 inhibitor SL327 significantly attenuated the increase in the percentage of neurite-bearing PC12 cells induced by DA-9801 treatment. Conversely, the selective p38 mitogen-activated protein kinase inhibitor SB203580 did not attenuate the DA-9801 treatment-induced increase in the percentage of neurite-bearing PC12 cells. DA-9801 enhanced the phosphorylation of ERK1/2 and CREB in PC12 cells incubated with and without NGF. Pretreatment with PD98059 blocked the DA-9801-induced phosphorylation of ERK1/2 and CREB. In conclusion, DA-9801 induces neurite outgrowth by affecting the ERK1/2-CREB signaling pathway. Insights into the mechanism underlying this effect of DA-9801 may suggest novel potential strategies for the treatment of peripheral neuropathy.

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

The purpose of this study was to investigate the therapeutic effects of DA-9801, an optimized extract of Dioscorea species, on diabetic peripheral neuropathy in a type 2 diabetic animal model. In this study, db/db mice were treated with DA-9801 (30 and 100 mg/kg, daily, p.o.) for 12 weeks. DA-9801 reduced the blood glucose levels and increased the withdrawal latencies in hot plate tests. Moreover, it prevented nerve damage based on increased nerve conduction velocity and ultrastructural changes. Decrease of nerve growth factor (NGF) may have a detrimental effect on diabetic neuropathy. We previously reported NGF regulatory properties of the Dioscorea genus. In this study, DA-9801 induced NGF production in rat primary astrocytes. In addition, it increased NGF levels in the sciatic nerve and the plasma of type 2 diabetic animals. DA-9801 also increased neurite outgrowth and mRNA expression of Tieg1/Klf10, an NGF target gene, in PC12 cells. These results demonstrated the attenuation of diabetic peripheral neuropathy by oral treatment with DA-9801 via NGF regulation. DA-9801 is currently being evaluated in a phase II clinical study.

Identification of antitumor lignans from the seeds of morning glory (Pharbitis nil).

In the search for antitumor compounds from Korean natural resources, activity-guided fractionation and purification processes were used on seeds of morning glory (Pharbitis nil). Air-dried P. nil seeds were extracted with ethanol and separated into n-hexane, chloroform, ethyl acetate, and n-butanol. Four new lignans, pharbilignans A-D (1-4) were isolated from the most active ethyl acetate fraction of the ethanol extract. Their structures were characterized on the basis of spectroscopic methods, including one- and two-dimensional nuclear magnetic resonance (NMR) techniques, high resolution mass spectrometry (HRMS), and circular dichroism (CD) spectroscopy. The cytotoxic activities of the isolates (1-4) were evaluated by determining their inhibitory effects on four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15) using a sulforhodamine B (SRB) bioassay. Pharbilignan C (3) showed potent cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines with IC50 values of 1.42, 0.16, 0.20, and 0.14 µM, respectively. On the basis of the expanded understanding that inflammation is a crucial cause in tumor progress, we also evaluated anti-inflammatory activity of the isolates (1-4). Pharbilignan C (3) strongly inhibited nitric oxide (NO) production in the lipopolysaccharide (LPS)-activated BV-2 microglia cell line with an IC50 value of 12.8 µM.

Evaluation of the transporter-mediated herb-drug interaction potential of DA-9801, a standardized dioscorea extract for diabetic neuropathy, in human in vitro and rat in vivo.

BACKGROUND: Drug transporters play important roles in the absorption, distribution, and elimination of drugs and thereby, modulate drug efficacy and toxicity. With a growing use of poly pharmacy, concurrent administration of herbal extracts that modulate transporter activities with drugs can cause serious adverse reactions. Therefore, prediction and evaluation of drug-drug interaction potential is important in the clinic and in the drug development process. DA-9801, comprising a mixed extract of Dioscoreae rhizoma and Dioscorea nipponica Makino, is a new standardized extract currently being evaluated for diabetic peripheral neuropathy in a phase II clinical study. METHOD: The inhibitory effects of DA-9801 on the transport functions of organic cation transporter (OCT)1, OCT2, organic anion transporter (OAT)1, OAT3, organic anion transporting polypeptide (OATP)1B1, OATP1B3, P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP) were investigated in HEK293 or LLC-PK1 cells. The effects of DA-9801 on the pharmacokinetics of relevant substrate drugs of these transporters were also examined in vivo in rats. RESULTS: DA-9801 inhibited the in vitro transport activities of OCT1, OCT2, OAT3, and OATP1B1, with IC50 values of 106, 174, 48.1, and 273 µg/mL, respectively, while the other transporters were not inhibited by 300 µg/mL DA-9801. To investigate whether this inhibitory effect of DA-9801 on OCT1, OCT2, and OAT3 could change the pharmacokinetics of their substrates in vivo, we measured the pharmacokinetics of cimetidine, a substrate for OCT1, OCT2, and OAT3, and of furosemide, a substrate for OAT1 and OAT3, by co-administration of DA-9801 at a single oral dose of 1,000 mg/kg. Pre-dose of DA-9801 5 min or 2 h prior to cimetidine administration decreased the Cmax of cimetidine in rats. However, DA-9801 did not affect the elimination parameters such as half-life, clearance, or amount excreted in the urine, suggesting that it did not inhibit elimination process of cimetidine, which is governed by OCT1, OCT2, and OAT3. Moreover, DA-9801 did not affect the pharmacokinetic characteristics of furosemide, as evidenced by its unchanged pharmacokinetic parameters. CONCLUSION: Inhibitory effects of DA-9801 on OCT1, OCT2, and OAT3 observed in vitro may not necessarily translate into in vivo herb-drug interactions in rats even at its maximum effective dose.

Phenolic derivatives from the rhizomes of Dioscorea nipponica and their anti-neuroinflammatory and neuroprotective activities.

ETHNOPHARMACOLOGICAL RELEVANCE: Dioscorea nipponica (Dioscoreaceae) have been used as traditional medicines for diabetes, inflammatory and neurodegenerative diseases in Korea. The aim of the study was to isolate the bioactive components from the rhizomes of Dioscorea nipponica and to evaluate their anti-neuroinfalmmatory and neuroprotective activities. MATERIAL AND METHODS: The phytochemical investigation of 50% EtOH extract of Dioscorea nipponica using successive column chromatography over silica gel, Sephadex LH-20, and preparative high performance liquid chromatography (HPLC) resulted in the isolation and identification of 17 phenolic derivatives, including four new phenolic compounds (1-4). The structural elucidation of these compounds was based on spectroscopic methods, including 1D and 2D nuclear magnetic resonance (NMR) spectroscopy techniques, mass spectrometry, and optical rotation. All isolated compounds were evaluated for their effects on nerve growth factor (NGF) secretion in a C6 rat glioma cell line and nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV2 cells. The neurite outgrowth of compound 16 was further evaluated by using mouse neuroblastoma N2a cell lines. RESULTS: Three new stilbene derivatives, diosniponol C (1), D (2) and diosniposide A (3) and one new phenanthrene glycoside, diosniposide B (4), together with 13 known compounds were isolated from the rhizomes of Dioscorea nipponica. Of the tested compounds (1-17), phenanthrene, 3,7-dihydroxy-2,4,6-trimethoxy-phenanthrene (16) was the most potent NGF inducer, with 162.35±16.18% stimulation, and strongly reduced NO levels with an IC50 value of 19.56 µM in BV2 microglial cells. Also, it significantly increased neurite outgrowth in N2a cells. CONCLUSIONS: This study supports the ethnopharmacological use of Dioscorea nipponica rhizomes as traditional medicine.

Bioactive sesquiterpenes from the essential oil of Thuja orientalis.

A phytochemical investigation on the essential oil of Thuja orientalis resulted in the isolation and identification of three new sesquiterpenes, 3α-methoxy-4α-epoxythujopsane (1), Δ³,¹5-4ß-epoxythujopsene (2), and Δ³,4-thujopsen-2,15-diol (3), together with eight known sesquiterpenoids (4-11). The structures of these new compounds were elucidated based on spectroscopic data analyses including extensive 2D-NMR data and HR-ESIMS. The full assignments of ¹H and ¹³C NMR chemical shifts for thujopsadiene (4) were obtained by 2D-NMR for the first time. All compounds (1-11) showed antiproliferative activities against the SK-OV-3 and SK-MEL-2 cell lines with IC50 values of 5.85-28.64 µM. In addition, compounds 1, 3, 4, 7, 8, and 9 significantly inhibited nitric oxide production in lipopolysaccharide-activated BV-2 cells with IC50 values of 3.93-17.85 µM without cell toxicity.

Pharbinilic acid, an allogibberic acid from morning glory (Pharbitis nil).

Pharbinilic acid (1), the first naturally occurring allogibberic acid, was isolated from ethanol extracts of morning glory (Pharbitis nil) seeds. Its absolute configuration was determined by NOESY NMR and ECD experiments. Compound 1 showed weak cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cells and weakly inhibited nitric oxide production in lipopolysaccharide-activated BV-2 microglia cells.

Anti-neuroinflammatory diarylheptanoids from the rhizomes of Dioscorea nipponica.

In a continuing search for bioactive constituents from Dioscoreaceae medicinal plants, two new cyclic diarylheptanoids, diosniponol A (1) and B (2), together with 10 known compounds (3-12) were isolated from the rhizomes of Dioscorea nipponica. The structures of these new compounds were determined by spectroscopic analyses, including extensive two-dimensional nuclear magnetic resonance, high-resolution mass spectrometry, and optical rotation. All isolated compounds 1-12 were evaluated for their effects on nitric oxide (NO) production in murine microglia cell line BV-2. Compounds 8 and 11 showed potent inhibitory activities on NO production (IC50 13.36 and 14.36 µM, respectively) without cell toxicity in lipopolysaccharide-activated BV-2 cells.

Evaluation of DA-9801, a new herbal drug for diabetic neuropathy, on metabolism-mediated interaction.

DA-9801, the mixture extract of Dioscoreae rhizoma and Dioscorea nipponica Makino, is a new herbal drug currently being evaluated in a phase II clinical study for the treatment of diabetic peripheral neuropathy in Korea. The inhibitory potentials of DA-9801, D. rhizoma extract, D. nipponica Makino extract, and dioscin, an active component of DA-9801, on eight human cytochrome P450 (CYP) enzymes and four UDP-glucuronosyltransferase (UGT) enzymes were investigated in human liver microsomes using liquid chromatography-tandem mass spectrometry. DA-9801 showed slight inhibition of CYP1A2, CYP2C8, UGT1A1, and UGT1A9 enzyme activities with IC(50) values of 396.4, 449.9, 226.0, and 408.8 µg/mL, respectively. D. rhizoma extract showed negligible inhibition of CYP and UGT activities, but D. nipponica extract slightly inhibited CYP1A2, CYP2C8, CYP2C9, UGT1A1, and UGT1A9 activities with IC(50) values of 264.2, 237.1, 206.8, 302.4, and 383.1 µg/mL, respectively. DA-9801 showed volume per dose index values of 0.44-0.88 L for a 200-mg dose, suggesting that they may not cause the inhibition of the metabolism of CYP1A2, CYP2C8, UGT1A1, and UGT1A9-catalyzed drugs in humans. These results suggest that the administration of DA-9801 in human may not cause clinically relevant inhibition of these enzymes.

Diosgenin from Dioscorea nipponica ameliorates diabetic neuropathy by inducing nerve growth factor.

Diabetic neuropathy is characterized by axonal degeneration, demyelination, and atrophy in association with failed axonal regeneration, remyelination, and synaptogenesis. Recent reports suggest that reduced levels of nerve growth factor (NGF) may play a significant role in the pathogenesis of diabetic polyneuropathy. In this study, we investigated the regulation of NGF by steroid diosgenin (DG) in a diabetic neuropathy rodent model. We found that DG, the primary spirostane-type steroid in several Dioscorea species, increased NGF levels in the sciatic nerve of diabetic rats. Additionally, DG increased neurite outgrowth in PC12 cells and enhanced nerve conduction velocities in the diabetic neuropathy mouse model. DG-treated diabetic mice showed reduced disarrangement of the myelin sheath and increased area of myelinated axons by electron microscope studies and exhibited improvement in the damaged axons. Our data further suggest that DG increased the nerve conduction velocity through induction of NGF. Thus, our findings indicate that DG, a major sapogenin obtained from Dioscorea nipponica, reverses functional and ultrastructural changes and induces neural regeneration in a diabetic neuropathy model.

Neurotrophic activity of DA-9801, a mixture extract of Dioscorea japonica Thunb. and Dioscorea nipponica Makino, in vitro.

ETHNOPHARMACOLOGICAL RELEVANCE: Dioscorea japonica Thunb. has been traditionally used to treat polyuria and diabetes in Korea. AIM OF THE STUDY: We previously report the effects of Dioscorea japonica Thunb. extract on glucose control, NGF induction, and neuroprotection in a rodent diabetic model. Since the most potent fraction, DA-9801, was identified from a mixture of Dioscorea japonica Thunb. (DJ) and Dioscorea nipponica Makino (DN) following bioactivity-guided fractionation, here, we investigated the potential mechanism of the extract activity against diabetic peripheral neuropathy (DPN). MATERIALS AND METHODS: A 1:3 mixture of DJ and DN was extracted with ethanol (DA-9801) and further fractionated into an ethylacetate-soluble fraction (DA-9801E). Effects of these extracts on neurite outgrowth were measured in PC-12 cells and DRG neurons. Effects on cell viability and TrkA phosphorylation were evaluated in PC-12 cells. NGF induction effect was determined in primary Schwann cells as well as IMS32 cells (immortalized Schwann cells). RESULTS: No cytotoxicity was observed in PC-12 cells at the concentration below 500 µg/ml of either DA-9801 or DA-9801E. DA-9801 and DA-9801E at 100 µg/ml and 10 µg/ml, respectively, showed a significant effect on neurite outgrowth in PC-12 cells and DRG neurons in the presence of or absence a low concentration of NGF (2 ng/ml). The Trk-A phosphorylation effect of DA9801 was confirmed in PC-12 cells. An NGF induction effect of these extracts was not detected in either IMS-32 cells, or primary Schwann cells. CONCLUSIONS: The NGF agonistic activity of DA-9801 and DA-9801E was demonstrated, which may contribute to their neuroprotective effect against DPN. Studies of the detailed mechanism of these extracts as well as identification of the active components are warranted for the development of an anti-DPN drug from DJ and DN.

Novel botanical drug for the treatment of diabetic neuropathy.

Diabetic neuropathy has multiple aspects of pathophysiology including metabolic derangements and alterations of microvessel with hyperglycemia. Currently, there is no effective long-term treatment based on the pathologic mechanisms. Nerve regeneration with nerve growth factor (NGF) has been on clinical trials as a treatment option. This article reviews an action of a herbal medicine, DA 9801, whose mechanism of action is related to NGF in treating diabetic neuropathy.

Withanolides from the rhizomes of Dioscorea japonica and their cytotoxicity.

Edible yams are tropical crops that serve as important staple foods in many parts of the world. The rhizome of Dioscorea japonica , well-known as "Japanese yam", is a food and medicinal source known as "San Yak" in Korea. Bioassay-guided fractionation and chemical investigation of the extract of this yam resulted in the identification of two new withanolides, named dioscorolide A (1) and dioscorolide B (2). The structures of these new compounds were determined by spectroscopic methods, including 1D and 2D nuclear magnetic resonance (NMR) techniques, high-resolution mass spectrometry (HRMS), and chemical methods. The cytotoxic activities of the isolates (1 and 2) were evaluated by determining their inhibitory effects on four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15) and a human normal cell line (HUVEC) using a sulforhodamine B (SRB) bioassay. Compounds 1 and 2 showed cytotoxicity against tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15) with IC(50) values ranging from 6.3 to 26.9 µM and exhibited lower activity against the normal cell line (HUVEC) with IC(50) values ranging from 27.1 to 28.8 µM, suggesting selective toxicity among tumor and normal cells.

Furostanol saponins from the rhizomes of Dioscorea japonica and their effects on NGF induction.

The rhizome of Dioscorea japonica is a food and medicinal source known as 'San Yak' in Korea. Two new furostanol saponins, coreajaponins A (1) and B (2), together with 10 known compounds (3-12) were isolated from the rhizomes of D. japonica. Their structures were determined by spectroscopic methods, including 1D and 2D NMR techniques, HRMS, and chemical methods. Nerve growth factor (NGF), a crucial factor for neuronal survival and differentiation, can potentially improve neurodegenerative diseases and diabetic polyneuropathy. We evaluated the effects of isolates (1-12) on NGF induction in a C6 rat glioma cell line. Coreajaponin B (2) upregulated NGF content without significant cell toxicity, as did 6, 8, 9, and 11.