Cognitive Improving and Cerebral Protective Effects of Acylated Oligosaccharides in Polygala tenuifolia

Polygalins D-G, four new flavonol glycosides from the aerial parts of Polygala sibirica L. (Polygalaceae)

Four new flavonol glycosides (1-4), polygalins D-G, together with 12 known flavonoids (5-16) were isolated from the aerial parts of Polygala sibirica L. The chemical structures of these compounds were characterised by NMR and ESI-MS spectroscopic data and acid hydrolysis results. This report is a continuous research work on the systematic chemical investigations of plants of the genus Polygala in our laboratory.

Promising therapeutics with natural bioactive compounds for improving learning and memory--a review of randomized trials

Cognitive disorders can be associated with brain trauma, neurodegenerative disease or as a part of physiological aging. Aging in humans is generally associated with deterioration of cognitive performance and, in particular, learning and memory. Different therapeutic approaches are available to treat cognitive impairment during physiological aging and neurodegenerative or psychiatric disorders. Traditional herbal medicine and numerous plants, either directly as supplements or indirectly in the form of food, improve brain functions including memory and attention. More than a hundred herbal medicinal plants have been traditionally used for learning and memory improvement, but only a few have been tested in randomized clinical trials. Here, we will enumerate those medicinal plants that show positive effects on various cognitive functions in learning and memory clinical trials. Moreover, besides natural products that show promising effects in clinical trials, we briefly discuss medicinal plants that have promising experimental data or initial clinical data and might have potential to reach a clinical trial in the near future.

Anti-inflammatory effects of Polygala tenuifolia root through inhibition of NF-κB activation in lipopolysaccharide-induced BV2 microglial cells

ETHNOPHARMACOLOGICAL RELEVANCE

The root of Polygala tenuifolia Willd is a well-known traditional Oriental medicine and has been prescribed for treatment of dysfunction in memorial systems and various brain inflammatory diseases. The present study was designed to validate the anti-inflammatory effects of the water extract of Polygala tenuifolia root (WEPT).

MATERIALS AND METHODS

The anti-inflammatory properties of WEPT were studied using lipopolysaccharide (LPS)-stimulated murine BV2 microglia model. As inflammatory parameters, the production of nitric oxide (NO), inducible NO synthase (iNOS), cyclooxygenase (COX)-2, prostaglandin E(2) (PGE(2)), tumor necrosis factor (TNF)-α, and interleukin (IL)-1β were evaluated. We also examined the extract's effect on the activity of nuclear factor-kappaB (NF-κB), and toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (Myd-88) expression.

RESULTS

WEPT suppressed LPS-induced production of NO, PGE(2), and expression of iNOS and COX-2 in a dose-dependent manner, without causing cytotoxicity. It also significantly reduced generation of proinflammatory cytokines, including IL-1β and TNF-α. In addition, WEPT suppressed NF-κB translocation by blockade of IkappaB-α (IκB-α) degradation and inhibited TLR4 and Myd-88 expression in LPS-stimulated BV2 cells.

CONCLUSIONS

These results indicate that the inhibitory effects of WEPT on LPS-stimulated inflammatory mediator production in BV2 microglia are associated with suppression of the NF-κB and toll-like receptor signaling pathways. Therefore, Polygala tenuifolia extracts may be useful in treatment of neurodegenerative diseases by inhibition of inflammatory mediator production in activated microglia.

Antifungal activity of five species of Polygala

Crude extracts and fractions of five species of Polygala - P. campestris, P. cyparissias, P. paniculata, P. pulchella and P. sabulosa - were investigated for their in vitro antifungal activity against opportunistic Candida species, Cryptococcus gattii and Sporothrix schenckii with bioautographic and microdilution assays. In the bioautographic assays, the major extracts were active against the fungi tested. In the minimal concentration inhibitory (MIC) assay, the hexane extract of P. paniculata and EtOAc fraction of P. sabulosa showed the best antifungal activity, with MIC values of 60 and 30 μg/mL, respectively, against C. tropicalis, C. gattii and S. schenckii. The compounds isolated from P. sabulosa prenyloxycoumarin and 1,2,3,4,5,6-hexanehexol displayed antifungal activity against S. schenckii (with MICs of 125 μg/mL and 250 μg/mL, respectively) and C. gattii (both with MICs of 250 μg/mL). Rutin and aurapten isolated from P. paniculata showed antifungal activity against C. gattii with MIC values of 60 and 250 μg/mL, respectively. In the antifungal screening, few of the isolated compounds showed good antifungal inhibition. The compound α-spinasterol showed broad activity against the species tested, while rutin had the best activity with the lowest MIC values for the microorganisms tested. These two compounds may be chemically modified by the introduction of a substitute group that would alter several physico-chemical properties of the molecule, such as hydrophobicity, electronic density and steric strain.

Traditional chinese medicine for senile dementia

Traditional Chinese Medicine (TCM) has a 3000 years' history of human use. A literature survey addressing traditional evidence from human studies was done, with key result that top 10 TCM herb ingredients including Poria cocos, Radix polygalae, Radix glycyrrhizae, Radix angelica sinensis, and Radix rehmanniae were prioritized for highest potential benefit to dementia intervention, related to the highest frequency of use in 236 formulae collected from 29 ancient Pharmacopoeias, ancient formula books, or historical archives on ancient renowned TCM doctors, over the past 10 centuries. Based on the history of use, there was strong clinical support that Radix polygalae is memory improving. Pharmacological investigation also indicated that all the five ingredients mentioned above can elicit memory-improving effects in vivo and in vitro via multiple mechanisms of action, covering estrogen-like, cholinergic, antioxidant, anti-inflammatory, antiapoptotic, neurogenetic, and anti-Aβ activities. Furthermore, 11 active principles were identified, including sinapic acid, tenuifolin, isoliquiritigenin, liquiritigenin, glabridin, ferulic acid, Z-ligustilide, N-methyl-beta-carboline-3-carboxamide, coniferyl ferulate and 11-angeloylsenkyunolide F, and catalpol. It can be concluded that TCM has a potential for complementary and alternative role in treating senile dementia. The scientific evidence is being continuously mined to back up the traditional medical wisdom.

Absorbable phenylpropenoyl sucroses from Polygala tenuifolia

Three phenylpropenoyl sucroses--sibiricose A5, A6 and 3',6-disinapoyl sucrose--were isolated from the 30% EtOH extract of Polygala tenuifolia, which displayed antidepressant-like action. HPLC analysis indicated that the three phenylpropenoyl sucroses could be absorbed into serum. From the serum pharmacochemistry point of view, these three phenylpropenoyl sucroses might prevent or relieve depression.

Cognitive-enhancing effects of polygalasaponin hydrolysate in aβ(25-35)-induced amnesic mice

Polygalasaponins are the major active constituents of Polygala tenuifolia exhibiting antiamnesic activity, but their applications are limited due to their toxicities. Evidence showed that the toxicities can be attenuated by hydrolysis. Herein, effects of a hydrolysate of polygalasaponins (HPS) on cognitive impairment induced by Aβ₂₅₋₃₅ were assessed by Morris water maze and step-through passive avoidance tests. The impaired spatial reference memory was improved by HPS (50 and 100 mg/kg). In the acquisition trial of step-through test, HPS (50 and 100 mg/kg) increased the latency into the dark chamber and decreased the error frequency significantly (P < .05). However, no significant change was observed during the retention trial. Additionally, HPS increased the corresponding SOD activities (62.34%, 22.09%) and decreased MDA levels (28.21%, 32.35%) in both cortex and hippocampus as compared to model animals. These results show that HPS may be a useful treatment against amnesia probably via its antioxidant properties.

Potential antidepressant properties of Radix Polygalae (Yuan Zhi)

Radix Polygalae ("Yuan Zhi", the roots of Polygala tenuifolia Willd., YZ) is an important herb used in traditional Chinese medicine to mediate depression. The present study was designed to verify the antidepressant effects of the standardized YZ ethanol extract (YZE) and its four fractions YZ-30, YZ-50, YZ-70 and YZ-90 on the tail suspension (TST) and forced swimming test (FST). Furthermore, the standardization of the fractions obtained from the separation procedures was carried out by high-performance liquid chromatography (HPLC)-fingerprint. The YZ-50 fraction (Oligosaccharide esters--enriched, oral (200 mg/kg) showed a significant anti-immobility like effects. The data of YZ-50 on the corticosterone-induced injure of SH-SY5Y human neuroblastoma cell indicated that YZ-50 may have biological effects on neuroprotection. Proliferation of cell lines was assessed by dimethylthiazoldiphenyltetrazoliumbromide (MTT) and 5-bromo-2'-deoxyuridine (BrdU) incorporation assays. It was found that YZ-50 and its two bioactive compounds, 3,6'-di-o-sinapoyl-sucrose (DISS) and tenuifoliside A(TEA) showed protection activities in SY5Y cells from the lesion. By using bioassay-screening methods, our results indicate that the presence of oligosaccharide esters such as DISS and TEA in this herb may be responsible for the cytoprotective activity effects.

Antidepressant effects of the extract YZ-50 from Polygala tenuifolia in chronic mild stress treated rats and its possible mechanisms

YZ-50 is an active fraction obtained from the root of Polygala tenuifolia Willd. (Polygalaceae) extract and it has been reported previously to exert beneficial effects on mental health in depressed sufferers, however, its mechanism of action remains unresolved. This study utilized the chronic mild stress (CMS) model of depression in Sprague-Dawley rats to evaluate the effects of YZ-50 on depressive behaviors. Furthermore, we tested the hypothesis that the capacity of YZ-50 to reverse the harmful effects of CMS is relative to the hypothalamo-pituitary-adrenal (HPA) system and brain-derived neurotrophic factor (BDNF) in the hippocampus. Repeated administration of YZ-50 for 28 days at the doses of 140 and 280 mg/kg in CMS, YZ-50 reversed the CMS-induced changes in sucrose consumption, plasma corticosterone levels and open field activity. In addition, CMS significantly decreased hippocampal BDNF mRNA levels. However, YZ-50 counteracted a decrease in hippocampal BDNF mRNA caused by CMS. In conclusion, YZ-50 reversed the harmful effects of CMS on mood and behaviors in rats and it possesses an antidepressant property that is at least in part mediated by the neuroendocrine and neuropropective systems, and it is likely that the HPA system plays an important role in this process.

Polygalasaponin XXXII from Polygala tenuifolia root improves hippocampal-dependent learning and memory

AIM

The aim of this study was to investigate the cognition-enhancing activity and underlying mechanisms of a triterpenoid saponin (polygalasaponin XXXII, PGS32) isolated from the roots of Polygala tenuifolia Willd.

METHODS

The Morris water maze was used to evaluate the spatial learning and memory of mice. To detect the basic properties of synaptic transmission and long-term potentiation (LTP) in the dentate gyrus of rats, electrophysiological recordings were made of evoked potentials. Western blotting analysis and immunofluorescence assays were used to determine the phosphorylation of extracellular signal-regulated kinase (ERK), cAMP response element-binding protein (CREB), synapsin I and the expression of brain derived neurotrophic factor (BDNF).

RESULTS

When administered at 0.125, 0.5, or 2 mg/kg, PGS32 could significantly prevent scopolamine-induced cognitive impairments in mice. Intracerebroventricular (icv) administration of PGS32 greatly enhanced basic synaptic transmission in the dentate gyrus of rats and induced LTP. In primary hippocampal neurons, as well as in the hippocampus of maze-trained mice, PGS32 activated the mitogen-activated protein (MAP) kinase cascade by promoting phosphorylation of ERK, CREB and synapsin I. The expression of BDNF was also greatly enhanced in the hippocampus.

CONCLUSION

Our findings suggest that PGS32 can improve hippocampus-dependent learning and memory, possibly through improvement of synaptic transmission, activation of the MAP kinase cascade and enhancement of the level of BDNF. Therefore, PGS32 shows promise as a potential cognition-enhancing therapeutic drug.

Tenuifolin, an extract derived from tenuigenin, inhibits amyloid-beta secretion in vitro

AIM

Previous studies have shown that tenuigenin, a crude extract of Polygala tenuifolia Willd. that is commonly used in traditional Chinese herbal medicine for memory loss, can reduce the secretion of Abeta from cultured cells. However, the mechanism underlying this effect and the active compound derived from tenuigenin is unknown. In this study, a purified component of tenuigenin, tenuifolin, was examined and revealed to be an effective compound in vitro.

METHODS

Abeta secretion from three sets of COS-7 cells, each carrying a plasmid expressing a different form of APP was examined following the treatment with tenuifolin. Initially, tenuifolin was determined to have no inherent toxicity to either the transfected or wild type cells at the effective concentrations. Cells were then treated with 0.5-2.0 microg mL(-1) tenuifolin for 12 h and their media were examined via an ELISA for Abeta1-40 and Abeta-42.

RESULTS

We found that treatment with 2.0 microg mL(-1) tenuifolin significantly decreased Abeta secretion from COS-7 cells without altering the ratio of Abeta1-40 and Abeta-42. This effect is most probably due to inhibition of the beta-site APP cleaving enzyme as Abeta secretion was not inhibited from cells expressing the C99 fragment.

CONCLUSION

Tenuifolin is an effective compound from tenuigenin. We believe that this finding should lead the way for future experiments to determine the exact mechanism for tenuifolin's effect on Abeta secretion.

Oligosaccharide polyester and triterpenoid saponins from the roots of Polygala japonica

An oligosaccharide polyester, 1-O-(E)-p-coumaroyl-(3-O-benzoyl)-beta-D-fructofuranosyl-(2-->1)-[6-O-(E)-feruloyl-beta-D-glucopyranosyl-(1-->2)]-[6-O-acetyl-beta-D-glucopyranosyl-(1-->3)-(4-O-acetyl)-beta-D-glucopyranosyl-(1-->3)]-4-O-[4-O-alpha-L-rhamnopyranosyl-(E)-p-coumaroyl]-alpha-D-glucopyranoside (polygalajaponicose I), and four triterpenoid saponins, 3beta, 23, 27-trihydroxy-29-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-olean-12-en-28-oic acid (polygalasaponin XLVII), 3-O-beta-D-glucopyranosyl presenegenin 28-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranosyl ester (polygalasaponin XLVIII), 3-O-beta-D-glucopyranosyl presenegenin 28-O-beta-D-galactopyranosyl-(1-->5)-beta-D-apiofuranosyl-(1-->4)-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl ester (polygalasaponin XLIX) and 2beta, 27-dihydroxy-3-O-beta-D-glucopyranosyl 11-oxo-olean-12-en-23, 28-dioic acid 28-O-beta-D-galactopyranosyl-(1-->5)-beta-D-apiofuranosyl-(1-->4)-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranosyl ester (polygalasaponin L), in addition to five known compounds have been isolated from the roots of Polygala japonica.

Effect of Polygala tenuifolia root extract on scopolamine-induced impairment of rat spatial cognition in an eight-arm radial maze task

The effects of Polygala tenuifolia root fractions and the acyl groups of its constituents on the retrieval process of spatial cognition in rats were studied using an eight-arm radial maze task. Oral administration of a precipitate fraction (PTB) obtained by concentration of the n-BuOH-soluble portion from the extract of the roots significantly decreased the number of total errors (TEs) and that of working memory errors (WMEs) at doses of 100 mg/kg and 200 mg/kg. However, it caused no significant decrease in the number of reference memory errors (RMEs). In addition, the saponin-rich fraction (PTBM) obtained by purification of PTB also showed significant decreases in TEs and WMEs at a dose of 100 mg/kg. Among the cinnamic acid derivatives present as the acyl groups in the P. tenuifolia constituents, sinapic acid (SNPA) significantly decreased TEs and WMEs at doses of 10 to 100 mg/kg. These results indicated that P. tenuifolia extracts, PTB and PTBM, and SNPA had a beneficial effect on the memory impairment induced by dysfunction of the cholinergic system in the brain. The memory improvement in the scopolamine-induced memory impairment seen in the radial maze performance was due to improvement in the short-term memory. A contribution of some constituents other than SNPA to the memory improvement was also suggested.

Simultaneous determination of phenols in Radix Polygalae by high performance liquid chromatography: Quality assurance of herbs from different regions and seasons

Radix Polygalae, roots of Polygala tenuifolia or of Polygala sibirica, is a Chinese herbal medicine commonly used to prevent dementia. Reliable chemical markers for quality assurance of this herb are missing. Here, a high performance liquid chromatography method coupled with diode array detection was developed to simultaneously determine nine different phenols in Radix Polygalae, including sibiricose A(5), sibiricose A(6), glomeratose A, tenuifoliside A, glomeratose D, 3',6-di-O-sinapoyl sucrose ester, mangiferin, polygalaxanthone III, and polygalaxanthone XI. By using two different detection wavelengths in the HPLC analysis, the developed method was able to determine the phenols with excellent resolution, precision, and recovery. This established method was therefore applied to determine the amounts of phenols in thirty-two samples from different cultivation regions and harvest seasons in China, and significant variations were revealed. The amounts of phenols in the roots of P. tenuifolia collected in Shanxi and Shannxi Provinces were markedly higher than in roots collected from other Provinces. Moreover, the samples harvested in the spring contained higher contents of phenols than those collected in other seasons.

Cerebral protective and cognition-improving effects of sinapic acid in rodents

We previously demonstrated that tenuifoliside B and 3,6'-disinapoylsucrose in Polygalae Radix, the root of Polygala tenuifolia WILLDENOW, inhibited potassium cyanide (KCN)-induced hypoxia and scopolamine-induced memory impairment in mice. Because both ingredients have a common sinapoyl moiety in their structure, we inferred that the sinapoyl moiety could inhibit hypoxia and memory impairment. In the present study to clarify the hypothesis, sinapic acid inhibited KCN-induced hypoxia and scopolamine-induced memory impairment as well as tenuifoliside B and 3,6'-disinapoylsucrose did. In addition, sinapic acid inhibited decompression- or bilateral carotid artery ligation-induced hypoxia (or mortality) and CO2-induced impairment in mice, and basal forebrain lesion-induced cerebral cholinergic dysfunction (decreases in acetylcholine concentration and choline acetyltransferase activity) in rats. These results, taken together, suggest the possibilities that sinapic acid is not only a very important moiety in the pharmacological activities of tenuifoliside B and 3,6'-disinapoylsucrose but also a candidate for a cerebral protective and cognition-improving medicine.

Characterizing the neuroprotective effects of alkaline extract of Lycium barbarum on β-amyloid peptide neurotoxicity

Lycium barbarum is an oriental medicinal herb that has long been used for its anti-aging and cell-protective properties. Previous studies have shown that aqueous extracts from L. barbarum exhibit neuroprotection via inhibiting pro-apoptotic signaling pathways. Other active components can also be accomplished by novel alkaline extraction method, which may give different profiles of water-soluble components. We hypothesize that another active component obtained by alkaline extraction method exerts different biological mechanisms to protect neurons. In this study, we aim to examine the neuroprotective effects from the alkaline extract of L. barbarum, namely LBB, to attenuate beta-amyloid (Abeta) peptide neurotoxicity. Primary cortical neurons were exposed to Abeta-peptides inducing apoptosis and neuronal cell death. Pretreatment of LBB significantly reduced the level of lactate dehydrogenase (LDH) release and the activity of caspase-3 triggered by Abeta. "Wash-out" procedures did not reduce its neuroprotective effects, suggesting that LBB may not bind directly to Abeta. We have further isolated three subfractions from LBB, namely LBB-0, LBB-I and LBB-II. LBB-I and LBB-II showed differential neuroprotective effects. Western blot analysis demonstrated that LBB-I and LBB-II markedly enhanced the phosphorylation of Akt. Taken together, our results suggested that the glycoconjugate isolated from novel alkaline extraction method can open up a new avenue for drug discovery in neurodegenerative diseases.

Effect of Tremella fuciformis on the neurite outgrowth of PC12h cells and the improvement of memory in rats

We investigated the neuritogenic effects of Tremella fuciformis (TF), which has been valued in traditional Chinese medicine as a remedy with nutritive and tonic actions, on PC12h cells. The cognitive improving effects of TF on scopolamine-induced (2 mg/kg, s.c.) amnesia in rats were also evaluated with using the Morris water maze task and by performing choline acetyltransferase (ChAT) immunohistochemistry. The water extract of TF (0.01-1 microg/ml) promoted neurite outgrowth of the PC12h cells in a dose dependent manner. TF was highly efficient at the concentration range of 0.1-1 microg/ml. Oral daily treatment with TF (100 or 400 mg/kg) for 14 consecutive days significantly reversed the scopolamine-induced deficit in learning and memory, and it alleviated decrease in cholinergic immunoreactivity induced by scopolamine in the medial septum and hippocampus. The results demonstrate that the promotion of neuritogenesis in neuronal culture cells by TF water extract is related with its activity for improving the performance of rats on a spatial learning and memory task. Moreover, the impairments of spatial learning and memory may be attributable to the decrease in activation of the septohippocampal cholinergic system and that TF ameliorated learning and memory deficits partly through its increasing the central cholinergic activity. Therefore, TF could represent a potentially useful agent that is able to improve the function of impaired cognitive processes.

Characterization of Anti-neurodegenerative Effects of Polygala tenuifolia in A.BETA.(25-35)-Treated Cortical Neurons

Although Polygala tenuifolia WILLD (PT) was classically mentioned as an anti-dementia drug in Chinese and Japanese traditional medicine, basic research showed only enhancement of the cholinergic function. In Alzheimer's disease, neuritic atrophy and synaptic loss occur prior to neuronal death event, and may be the first trigger of the memory impairment. Therefore, we studied effects of Polygala tenuifolia WILLD (PT) on Abeta(25-35)-induced neuronal damage using rat cortical neurons for characterization of activities of PT under Abeta-induced neuronal damage. Treatment with the water extract of PT enhanced axonal length dose-dependently after Abeta(25-35)-induced axonal atrophy. However, dendritic atrophy and synaptic loss induced by Abeta(25-35) were not recovered by treatment with PT extract. In contrast, Abeta(25-35)-induced cell damage was completely inhibited by PT extract. By characterization of PT effects on neuronal morphological plasticity and cell damage, usefulness as well as an insufficiency of PT as an anti-dementia drug was clarified.