Aralia cordata Protects Against Amyloid β Protein (25–35)–Induced Neurotoxicity in Cultured Neurons and Has Antidementia Activities in Mice

The Use of Bioactive Compounds in Hyperglycemia- and Amyloid Fibrils-Induced Toxicity in Type 2 Diabetes and Alzheimer’s Disease

It has become increasingly apparent that defective insulin signaling may increase the risk for developing Alzheimer’s disease (AD), influence neurodegeneration through promotion of amyloid formation or by increasing inflammatory responses to intraneuronal β-amyloid. Recent work has demonstrated that hyperglycemia is linked to cognitive decline, with elevated levels of glucose causing oxidative stress in vulnerable tissues such as the brain. The ability of β-amyloid peptide to form β-sheet-rich aggregates and induce apoptosis has made amyloid fibrils a leading target for the development of novel pharmacotherapies used in managing and treatment of neuropathological conditions such as AD-related cognitive decline. Additionally, deposits of β-sheets folded amylin, a glucose homeostasis regulator, are also present in diabetic patients. Thus, therapeutic compounds capable of reducing intracellular protein aggregation in models of neurodegenerative disorders may prove useful in ameliorating type 2 diabetes mellitus symptoms. Furthermore, both diabetes and neurodegenerative conditions, such as AD, are characterized by chronic inflammatory responses accompanied by the presence of dysregulated inflammatory biomarkers. This review presents current evidence describing the role of various small bioactive molecules known to ameliorate amyloidosis and subsequent effects in prevention and development of diabetes and AD. It also highlights the potential efficacy of peptide–drug conjugates capable of targeting intracellular targets.

Oleanolic Acid Exerts a Neuroprotective Effect Against Microglial Cell Activation by Modulating Cytokine Release and Antioxidant Defense Systems

Microglia respond to adverse stimuli in order to restore brain homeostasis and, upon activation, they release a number of inflammatory mediators. Chronic microglial overactivation is related to neuroinflammation in Alzheimer's disease. In this work, we show that oleanolic acid (OA), a natural triterpene present in food and medicinal plants, attenuates the activation of BV2 microglial cells induced by lipopolysaccharide (LPS). Cell pretreatment with OA inhibited the release of IL-1β, IL-6, TNF-α, and NO, which was associated with the downregulation of the expression of genes encoding for these cytokines and inducible nitric oxide synthase (iNOS), and the reinforcement of the endogenous antioxidant cell defense. These findings advocate considering OA as a novel neuroprotective agent to inhibit oxidative stress and inflammatory response in activated microglia associated with Alzheimer's disease.

Effect of alcohol tincture of Aralia elata on the organism of rats and their gut microbiota against the background of excessive fat diet

Pharmacological effects of the medicinal plant Aralia elata (Miq.) Seem. 1868 (Araliaceae) are related to presence of over 150 secondary metabolites, including flavonoids, sterols, polysaccharides, terpenoid saponins and terpenoid acids, though the main biologically active substances of A. elata are saponins and flavonoids. Some clinical tests and experimental studies have proved the influence of A. elata on the organism through increase in physical work capacity, exerting an anti-stress effect against a broad range of harmful factors, including stress from cold, immobilization, ultraviolet radiation and low pressure. The literature also reports the anti-ulcer, anti-secretory, antifungal, anti-tumour, and antimicrobial activity of preparations from this plant. In our laboratory experiment, we determined that ethanolic tincture of A. elata has no effect on the intensity of growth of body weight of young rats against the background of excessive content of fat in their diet. Excessive fat-feeding of male rats leads mostly to disorders in the functioning of the liver and development of steatosis. This was accompanied by reduction in relative mass of the liver, increase in activity of hepatic enzymes, dysproteinemia, increase in the level of bilirubin and decrease in the level of urea. Additional use of 0.1% ethanol led to impaired functioning of the kidneys, reduction of their relative mass, signs of dehydration, increase in the level of creatinine and total calcium in the blood. Use of ethanolic tincture of A. elata mitigates negative excess of fat, is accompanied by normalization of indices of mass of the organs, less notable dysproteinemia, impairment in the level of creatinine, glucose, urea, cholesterol, bilirubin and total calcium. Ethanolic tincture of A. elata has a low immunosuppressive action, against the background of a high fat diet it leads to increase in the amount of typical Escherichia сoli, decrease in Еnterococcus spp. and Enterobacter spp., significant decrease and in high concentrations (0.1% ethanolic tincture of A. elata) elimination of bacteria of Clostridium and Klebsiella genera, and also various yeast fungi in the intestine. In the examined male rats, against the background of excess of fat in the diet, no serious changes in the composition of the normal gut microbiota (Bifidobacterium spp., Lactobacillus spp., Proteus spp., Staphylococcus spp., Candida spp.) was observed, nor were any lactose-negative enterobacteria (Citrobacter genus) found. Perspectives of further research include determining histological, histochemical and immune-histological changes in the organs of laboratory animals under the effect of ethanolic tincture of A. elata following excessive accumulation of fat.

Malva parviflora extract ameliorates the deleterious effects of a high fat diet on the cognitive deficit in a mouse model of Alzheimer's disease by restoring microglial function via a PPAR-γ-dependent mechanism

Background

Alzheimer’s disease (AD) is a neuropathology strongly associated with the activation of inflammatory pathways. Accordingly, inflammation resulting from obesity exacerbates learning and memory deficits in humans and in animal models of AD. Consequently, the long-term use of non-steroidal anti-inflammatory agents diminishes the risk for developing AD, but the side effects produced by these drugs limit their prophylactic use. Thus, plants natural products have become an excellent option for modern therapeutics. Malva parviflora is a plant well known for its anti-inflammatory properties.

Methods

The present study was aimed to determine the anti-inflammatory potential of M. parviflora leaf hydroalcoholic extract (MpHE) on AD pathology in lean and obese transgenic 5XFAD mice, a model of familial AD. The inflammatory response and Amyloid β (Aβ) plaque load in lean and obese 5XFAD mice untreated or treated with MpHE was evaluated by immunolocalization (Iba-1 and GFAP) and RT-qPCR (TNF) assays and thioflavin-S staining, respectively. Spatial learning memory was assessed by the Morris Water Maze behavioral test. Microglia phagocytosis capacity was analyzed in vivo and by ex vivo and in vitro assays, and its activation by morphological changes (phalloidin staining) and expression of CD86, Mgl1, and TREM-2 by RT-qPCR. The mechanism triggered by the MpHE was characterized in microglia primary cultures and ex vivo assays by immunoblot (PPAR-γ) and RT-qPCR (CD36) and in vivo by flow cytometry, using GW9662 (PPAR-γ inhibitor) and pioglitazone (PPAR-γ agonist). The presence of bioactive compounds in the MpHE was determined by HPLC.

Results

MpHE efficiently reduced astrogliosis, the presence of insoluble Aβ peptides in the hippocampus and spatial learning impairments, of both, lean, and obese 5XFAD mice. This was accompanied by microglial cells accumulation around Aβ plaques in the cortex and the hippocampus and decreased expression of M1 inflammatory markers. Consistent with the fact that the MpHE rescued microglia phagocytic capacity via a PPAR-γ/CD36-dependent mechanism, the MpHE possess oleanolic acid and scopoletin as active phytochemicals.

Conclusions

M. parviflora suppresses neuroinflammation by inhibiting microglia pro-inflammatory M1 phenotype and promoting microglia phagocytosis. Therefore, M. parviflora phytochemicals represent an alternative to prevent cognitive impairment associated with a metabolic disorder as well as an effective prophylactic candidate for AD progression.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1515-3) contains supplementary material, which is available to authorized users.

Pharmacokinetic Profile of Kaurenoic Acid after Oral Administration of Araliae Continentalis Radix Extract Powder to Humans

The objective of this study was to characterize pharmacokinetics (PKs) of kaurenoic acid (KAU) after administration of the clinical usual dose of Araliae Continentalis Radix extract powder to Korean subjects for the first time and evaluate the mechanism of its absorption in vitro. A simple, sensitive, and selective analytical method was developed for the detection of KAU in human plasma. Concentrations of KAU were quantified by ultra-performance liquid chromatography tandem mass spectrometry after simple liquid–liquid extraction. This pharmacokinetic model of KAU was best described by a two-compartment model with first-order absorption. To identify efflux transporters involved in the absorption of KAU, a Caco-2 monolayer model was used. Estimated PK parameters were: systemic clearance, 23.89 L/h; inter-compartmental clearance, 15.55 L/h; rate constant for absorption, 1.72 h⁻¹; volume of distribution of the central compartment, 24.44 L; and volume of distribution of the peripheral compartment, 64.05 L. Results from Caco-2 bidirectional transport study suggested that KAU was a potential substrate of efflux transporters. In summary, PKs of KAU were successfully characterized after administration of a usual dose of Araliae continentalis Radix extract powder in human with the newly developed bioanalytical method and the mechanism of absorption of KAU was identified clearly.

Gelidiella acerosa protects against Aβ 25-35-induced toxicity and memory impairment in Swiss Albino mice: an in vivo report

CONTEXT

Alzheimer's disease (AD) is believed to develop due to deposition of β-amyloid (Aβ) peptide. Hence, efforts are being made to develop potent drug that target amyloid hypothesis.

OBJECTIVE

The present study explores the effect of the seaweed Gelidiella acerosa (Forsskål) Feldmann & Hamel (Gelidiellaceae) against Aβ 25-35 peptide in Swiss albino mice.

MATERIALS AND METHODS

The animals were administered through intracerebroventricular (ICV) injection with the Aβ 25-35 peptide (10 μg/10 μL/ICV site) on 21st day of the pretreatment of G. acerosa (whole plant) benzene extract (200 and 400 mg/kg bw). On day 30, animals were sacrificed and brain tissue homogenate was prepared. The activities of AChE, BuChE, b-secretase, MAO-B, and caspase-3 were determined, and Bax expression was assessed by Western blotting.

RESULTS

Gelidiella acerosa benzene extract restored the level of antioxidant enzymes and prevented lipid and protein oxidation significantly (p < 0.05). The extract protected the mice from cholinergic deficit significantly (p < 0.05) by inhibiting the activities of AChE and BuChE, which was about 0.116 ± 0.0088 U/mg of protein and 0.011 ± 0.0014 U/mg of protein respectively, which was otherwise increased in peptide-treated group (0.155 ± 0.007 U/mg of protein and 0.015 ± 0.0012 U/mg of protein respectively). Interestingly, G. acerosa benzene extract inhibited β-secretase and MAO-B activity. Reduction (p < 0.05) in level of caspase-3 activity and Bax expression suggests that G. acerosa protects the cells from apoptosis.

DISCUSSION AND CONCLUSION

The results suggest that G. acerosa possesses excellent neuroprotective potential against peptide mediated toxicity under in vivo conditions.

Oleanolic Acid Promotes Neuronal Differentiation and Histone Deacetylase 5 Phosphorylation in Rat Hippocampal Neurons

Oleanolic acid (OA) has neurotrophic effects on neurons, although its use as a neurological drug requires further research. In the present study, we investigated the effects of OA and OA derivatives on the neuronal differentiation of rat hippocampal neural progenitor cells. In addition, we investigated whether the class II histone deacetylase (HDAC) 5 mediates the gene expression induced by OA. We found that OA and OA derivatives induced the formation of neurite spines and the expression of synapse-related molecules. OA and OA derivatives stimulated HDAC5 phosphorylation, and concurrently the nuclear export of HDCA5 and the expression of HDAC5 target genes, indicating that OA and OA derivatives induce neural differentiation and synapse formation via a pathway that involves HDAC5 phosphorylation.

Phytoceramide ameliorates ß-amyloid protein-induced memory impairment and neuronal death in mice

The present study was performed to investigate the protective effect of phytoceramide against ß-amyloid protein (Aβ) (25-35)-induced memory impairment and its underlying mechanisms in mice. Memory impairment in mice was induced by intracerebroventricular injection of 15 nmol Aβ (25-35) and measured by the passive avoidance test and Morris water maze test. Chronic administration of phytoceramide (10, 25 and 50 mg/kg, p.o.) resulted in significantly less Aβ (25-35)-induced memory loss and hippocampal neuronal death in treated mice compared to controls. The decrease of glutathione level and increase of lipid peroxidation in brain tissue following injection of Aβ (25-35) was reduced by phytoceramide. Alteration of apoptosis-related proteins, increase of inflammatory factors, and phosphorylation of mitogen activated proteins kinases (MAPKs) in Aβ (25-35)-administered mice hippocampus were inhibited by phytoceramide. Phosphatidylinositol 3'-kinase (PI3K)/Akt pathway and phosphorylation of cyclic AMP response element-binding protein (CREB) were suppressed, while phosphorylation of tau (p-tau) was increased in Aß (25-35)-treated mice brain; these effects were significantly inhibited by administration of phytoceramide. These results suggest that phytoceramide has a possible therapeutic role in managing cognitive impairment associated with Alzheimer's disease. The underlying mechanism might involve inhibition of p-tau formation via anti-apoptosis and anti-inflammation activity and promotion of PI3K/Akt/CREB signaling process.

Cognitive-enhancing and antioxidant activities of the aqueous extract from Markhamia tomentosa (Benth.) K. Schum. stem bark in a rat model of scopolamine

BACKGROUND

Plants of the genus Markhamia have been traditionally used by different tribes in various parts of West African countries, including Cameroun. Markhamia tomentosa (Benth.) K. Schum. (Bignoniaceae) is used as an antimalarial, anti-inflammatory, analgesic, antioxidant and anti-Alzheimer agent. The current study was undertaken in order to investigate its anti-amnesic and antioxidant potential on scopolamine-induced cognitive impairment and to determine its possible mechanism of action.

METHODS

Rats were pretreated with the aqueous extract (50 and 200 mg/kg, p.o.), for 10 days, and received a single injection of scopolamine (0.7 mg/kg, i.p.) before training in Y-maze and radial arm-maze tests. The biochemical parameters in the rat hippocampus were also assessed to explore oxidative status. Statistical analyses were performed using two-way ANOVA followed by Tukey's post hoc test. F values for which p < 0.05 were regarded as statistically significant.

RESULTS

In the scopolamine-treated rats, the aqueous extract improved memory in behavioral tests and decreased the oxidative stress in the rat hippocampus. Also, the aqueous extract exhibited anti-acetylcholinesterase activity.

CONCLUSIONS

These results suggest that the aqueous extract ameliorates scopolamine-induced spatial memory impairment by attenuation of the oxidative stress in the rat hippocampus.

Ilex latifolia Prevents Amyloid β Protein (25-35)-Induced Memory Impairment by Inhibiting Apoptosis and Tau Phosphorylation in Mice

Ilex latifolia Thunb. (Aquifoliaceae), a Chinese bitter tea called "kudingcha," has been widely consumed as a health beverage and found to possess antioxidant, antidiabetic, antihypertensive, anti-inflammatory, and anti-ischemic activities. The aim of the present study was to investigate the neuroprotective effects of an ethanol extract of I. latifolia against amyloid β protein (Aβ)-induced memory impairment in mice and neurotoxicity in cultured rat cortical neurons. Memory impairment in mice was induced by intracerebroventricular injection of 15 nmol Aβ (25-35) and measured by the passive avoidance test and Morris water maze test. Chronic administration of I. latifolia (25-100 mg/kg, p.o.) significantly prevented Aβ (25-35)-induced memory loss. I. latifolia also prevented the decrease of glutathione concentrations, increased lipid peroxidation, expression of phosphorylated tau (p-tau), and changes in apoptosis-associated proteins in the memory-impaired mouse brain. Exposure of cultured cortical neurons to 10 μM Aβ (25-35) for 36 h induced neuronal apoptotic death. The neuronal cell death, elevation of intracellular Ca(2+) concentration, generation of reactive oxygen species, and expression of proapoptotic proteins caused by Aβ (25-35) in the cultured neurons were inhibited by treatment with I. latifolia (1-50 μg/mL). These results suggest that I. latifolia may have a possible therapeutic role in managing cognitive impairment associated with Alzheimer's disease. The underlying mechanism might involve the antiapoptotic effects mediated by antioxidant activity and inhibition of p-tau formation.

Identification of 5-Methoxyflavone as a Novel DNA Polymerase-Beta Inhibitor and Neuroprotective Agent against Beta-Amyloid Toxicity

Cell-cycle reactivation is a core feature of degenerating neurons in Alzheimer's disease (AD) and Parkinson's disease (PD). A variety of stressors, including β-amyloid (Aβ) in the case of AD, can force neurons to leave quiescence and to initiate an ectopic DNA replication process, leading to neuronal death rather than division. As the primary polymerase (pol) involved in neuronal DNA replication, DNA pol-β contributes to neuronal death, and DNA pol-β inhibitors may prove to be effective neuroprotective agents. Currently, specific and highly active DNA pol-β inhibitors are lacking. Nine putative DNA pol-β inhibitors were identified in silico by querying the ZINC database, containing more than 35 million purchasable compounds. Following pharmacological evaluation, only 5-methoxyflavone (1) was validated as an inhibitor of DNA pol-β activity. Cultured primary neurons are a useful model to investigate the neuroprotective effects of potential DNA pol-β inhibitors, since these neurons undergo DNA replication and death when treated with Aβ. Consistent with the inhibition of DNA pol-β, 5-methoxyflavone (1) reduced the number of S-phase neurons and the ensuing apoptotic death triggered by Aβ. 5-Methoxyflavone (1) is the first flavonoid compound able to halt neurodegeneration via a definite molecular mechanism rather than through general antioxidant and anti-inflammatory properties.

Phytomedicines as potential inhibitors of β amyloid aggregation: significance to Alzheimer's disease

Throughout the history of drug development, plants have been an important source for the discovery of novel therapeutically active compounds for many diseases. The ethnopharmacological approach has provided several leads to identify potential new drugs from plant sources, including those for memory disorders. For the treatment of Alzheimer's disease the drug discovery focus shifted from cholinesterase inhibitors, to other targets primarily based on two key neuropathological hallmarks, namely the hyperphosphorylation of the tau protein resulting in the formation of neurofibrillary tangles (NFTs), and the increased formation and aggregation of amyloid-beta peptide (Aβ) derived from amyloid precursor protein (APP). The present article aims to provide a comprehensive literature survey of plants and their constituents that have been tested for Aβ aggregation, thus possibly relieving several features of Alzheimer's disease (AD).

Early use of oleanolic acid provides protection against 6-hydroxydopamine induced dopamine neurodegeneration

Oleanolic acid is a triterpenoid that has been shown to possess antioxidant properties. In this study we investigated the effects of oleanolic acid in a parkinsonian rat model. Unilateral 6-hydroxydopamine (6-OHDA) lesions were carried out on postnatal day (PND) 60 in 4 groups viz. (1) Rats that started oleanolic acid treatment 7 days prior to lesion. (2) Rats not treated with oleanolic acid. (3) Rats that started oleanolic acid treatment 1 day post-lesion. (4) Rats treated with oleanolic acid 7 days post-lesion. The degree of forelimb impairment was assessed using limb use asymmetry and forelimb akinesia tests. Neurochemical changes were assessed using a Dopamine ELISA kit and mitochondrial apoptosis was measured using a mitochondrial apoptosis detection kit. In this study, animals injected with 6-OHDA displayed forelimb use asymmetry that was ameliorated by treatment with oleanolic acid 7 days pre- and 1 day post-lesion. In the cylinder test, rats injected with 6-OHDA favored using the forelimb ipsilateral (unimpaired) to the lesioned hemisphere while rats treated with oleanolic acid used the forelimb contralateral (impaired) to the lesioned hemisphere significantly more. Rats treated with oleanolic acid 7 days pre- and 1 day post-lesion had more dopamine in the striatum than the non-treated or the 7 days after lesion rats. Similarly, 6-OHDA-induced membrane depolarization was decreased in rats that received oleanolic acid treatment pre- or immediately post-lesion. This suggests that early treatment with oleanolic acid protects dopamine neurons from the toxic effects of 6-OHDA.

Effects of ginsenoside Rg1 on the expression of toll-like receptor 3, 4 and their signalling transduction factors in the NG108-15 murine neuroglial cell line

As one of the most important components of Panax ginseng, ginsenoside Rg1 has certain anti-aging effects, improving the activity of learning and memory. Studies have showed that ginsenoside Rg1 improves the memory impairment associated with Alzheimer’s disease (AD). In this study, the effects of ginsenoside Rg1 were investigated through the activity of toll-like receptor (TLR) 3, TLR4 and their signaling transduction pathways in amyloid β peptide 25–35 (Aβ_25–35) induced AD cell model. Thus we investigated several critical components of the TLR pathway. The neuroglial cell line NG108-15 was stimulated with or without Aβ_25–35, while different concentrations of ginsenoside Rg1 were administered. After 24 h, tumor necrosis factor-α (TNF-α), interferon-β (IFN-β) in cell supernatant and inducible nitric oxide synthase (iNOS) in cell lysate supernatant were measured with enzyme-linked immunosorbent assays (ELISAs). The mRNA and protein expression of TLR3, TLR4, nuclear factor kappa B (NF-κB) and tumor necrosis factor receptor-associated factor-6 (TRAF-6) were detected by real-time PCR and western blot methods, respectively. The experimental results showed that Aβ_25–35 could markedly raise the level of TNF-α, IFN-β and iNOS, and increase the expressions of mRNA and TLR3, TLR4, NF-κB and TRAF-6 protein in the NG108-15 cells. At the same time, the ginsenoside Rg1 significantly reduced the expressions of proteins and mRNA of TLR3, TLR4, NF-κB and TRAF-6, and down-regulated the levels of TNF-α, IFN-β of cell supernatant and iNOS of cell lysate supernatant in a concentration-dependent manner. In conclusion, ginsenoside Rg1 has good activity for suppressing the signaling transduction pathway of TLR3 and TLR4, and decreasing the inflammation factors induced by Aβ_25–35 in NG108-15 cells, and this may be the mechanism of ginsenoside Rg1 action in AD treatment, but more studies are needed to identify its specificity.

Metabolic alteration of neuroactive steroids and protective effect of progesterone in Alzheimer's disease-like rats

A correlation between metabolic alterations of neuroactive steroids and Alzheimer's disease remains unknown. In the present study, amyloid beta (Aβ) 25–35 (Aβ_25–35) injected into the bilateral hippocampus CA1 region significantly reduced learning and memory. At the biochemical level, hippocampal levels of pregnenolone were significantly reduced with Aβ_25–35 treatment. Furthermore, progesterone was considerably decreased in the prefrontal cortex and hippocampus, and 17β-estradiol was significantly elevated. To our knowledge, this is the first report showing that Aβ_25–35, a main etiological factor of Alzheimer's disease, can alter the level and metabolism of neuroactive steroids in the prefrontal cortex and hippocampus, which are brain regions significantly involved in learning and memory. Aβ_25–35 exposure also increased the expression of inflammatory mediators, tumor necrosis factor-α and interleukin-1β. However, subcutaneous injection of progesterone reversed the upregulation of tumor necrosis factor-α and interleukin-1β in a dose-dependent manner. Concomitant with improved cognitive abilities, progesterone blocked Aβ-mediated inflammation and increased the survival rate of hippocampal pyramidal cells. We thus hypothesize that Aβ-mediated cognitive deficits may occur via changes in neuroactive steroids. Moreover, our findings provide a possible therapeutic strategy for Alzheimer's disease via neuroactive steroids, particularly progesterone.

In vitro acetylcholinesterase inhibitory activity and the antioxidant properties of Aegle marmelos leaf extract: implications for the treatment of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder clinically characterized by loss of memory and cognition. The effective therapeutic options for AD are limited and thus there is a demand for new drugs. Aegle marmelos (Linn.) (A. marmelos) leaves have been used in traditional medicine to promote intellect and enhance memory. In this study, we evaluated A. marmelos for its acetylcholinesterase (AChE) inhibitory activity and antioxidant property in vitro in the treatment of AD.

METHODS

A crude methanol extract and four fractions (petroleum ether, chloroform, ethyl acetate and aqueous) were prepared from the leaves of A. marmelos. The preparations were assessed for AChE inhibitory activity by the Ellman method, and their antioxidant properties were assessed by several assays: reducing power, scavenging of 1,1-diphenyl-2-picrylhydrazyl free radical and hydroxyl radical, and inhibition of lipid peroxidation. Qualitative and quantitative analyses of endogenous substances in A. marmelos were performed by the standard phytochemical methods.

RESULTS

Among the different extracts tested, the ethyl acetate fraction exhibited the highest inhibition of AChE activity. In the same way, ethyl acetate fraction showed the highest reducing activity and radical scavenging ability towards the 1,1-diphenyl-2-picrylhydrazyl (half maximal inhibitory concentration = 3.84 μg/mL) and hydroxyl free radicals (half maximal inhibitory concentration = 5.68 μg/mL). The antiradical activity of the ethyl acetate fraction appeared to be similar to that of the reference standard butylated hydroxytoluene and catechin used in this study. In addition, the ethyl acetate fraction displayed higher inhibition of brain lipid peroxidation. Phytochemical screening of different extractives of A. marmelos showed the presence of phenols and flavonoids, alkaloid, saponin, glycoside, tannin and steroids. Quantitative analysis revealed higher contents of phenolics (58.79-mg gallic acid equivalent/g dried extract) and flavonoids (375.73-mg gallic acid equivalent/g dried extract) in the ethyl acetate fraction.

CONCLUSION

The results suggest that the ethyl acetate fraction of A. marmelos is a significant source of polyphenolic compounds with potential AChE inhibitory property and antioxidant activity and, thus, may be useful in the treatment of AD.

Aralia cordata inhibits triacylglycerol biosynthesis in HepG2 cells

Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the first committed step in triacylglycerol (TAG) and phospholipid biosynthesis, and has been considered as one of the drug targets for treating hepatic steatosis, insulin resistance, and other metabolic disorders. The aim of this study was to investigate the GPAT inhibitors from natural products and to evaluate their effects. The methanol extract of Aralia cordata roots showed a strong inhibitory effect on the human GPAT1 activity. A further bioactivity-guided approach led to the isolation of ent-pimara-8(14),15-dien-19-oic acid, (PA), one of the major compounds of A. cordata, which suppressed the GPAT1 activity with IC50 value of 60.5 μM. PA markedly reduced de novo lysophosphatidic acid synthesis through inhibition of GPAT activity and therefore significantly decreased synthesis of TAG in the HepG2 cells. These results suggest that PA as well as A. cordata root extract could be beneficial in controlling lipid metabolism.

Pimaric acid from Aralia cordata has an inhibitory effect on TNF-α-induced MMP-9 production and HASMC migration via down-regulated NF-κB and AP-1

Many studies have indicated that activation of matrix metalloproteinase (MMP)-9 and smooth muscle cell (SMC) migration are involved in neointimal formation and atherosclerosis. In this study, we revealed that pimaric acid (PiMA) purified from Aralia cordata had an inhibitory effect on MMP-9 production and migration of human aortic smooth muscle cells (HASMCs) induced by tumor necrosis factor (TNF)-α. Down-regulated MMP-9 mRNA transcription was detected in PiMA-treated cells using RT-PCR and the luciferase-tagged MMP-9 promoter assay. Results of an electrophoretic mobility shift assay indicated that PiMA-treated HASMCs showed decreased binding activity of nuclear factor (NF)-κB and activator protein-1 transcription factors. A Western-blot analysis using nuclear extract demonstrated that PiMA reduced the levels of NF-κB p65, c-Fos, p-c-Jun, Jun-D, and p-ATF2 proteins in the nucleus. In addition, TNF-α stimulated mitogen activated protein kinase (MAPK) containing extracellular signal regulated kinase 1 and 2, p38, and c-Jun N-terminal kinase was inhibited by PiMA. Using the Transwell system, we found that PiMA inhibited TNF-α stimulated HASMC migration/invasion in a dose-dependent manner. To confirm whether MAPK mediated MMP-9 expression, we used MAPK inhibitors including U0126, SB253580, and SP600125 and found that those inhibitors reduced MMP-9 expression and HASMC migration/invasion. These results suggest that PiMA has potent anti-atherosclerotic activity with inhibitory action on MMP-9 production and cell migration in TNF-α-induced HASMCs.

Terpenoids as potential anti-Alzheimer's disease therapeutics

Alzheimer's disease (AD) is one of the most well-known neurodegenerative diseases and explains 50-60% of dementia in patients. The prevalence rate of AD is positively correlated with age and AD affects ≥ 40% of those over 85 years old. The major AD therapeutics available on the market are acetylcholinesterase inhibitors, such as tacrine and donepezil. New therapeutic agents that can block the disease-inducing mechanisms are essential. Diverse efforts have been made to discover anti-AD agents from natural sources. In this review article, we describe some representative terpenoids such as ginsenosides, gingkolides, and canabinoids as potential anti-AD agents. These compounds exhibit promising in vitro and in vivo biological activities, but are still waiting clinical trials. Additionally, we also discuss some terpenoids including cornel iridoid glycoside, oleanolic acid, tenuifolin, cryptotanshinone, and ursolic acid, which are under investigation for their in vitro and in vivo animal studies.

Experimental inhibition of fibrillogenesis and neurotoxicity by amyloid-beta (Aβ) and other disease-related peptides/proteins by plant extracts and herbal compounds

Amyloid-β (Aβ) fibrillogenesis and associated cyto/neurotoxicity are major pathological events and hallmarks in diseases such as Alzheimer's disease (AD). The understanding of Aβ molecular pathogenesis is currently a pharmacological target for rational drug design and discovery based on reduction of Aβ generation, inhibition of Aβ fibrillogenesis and aggregation, enhancement of Aβ clearance and amelioration of associated cytotoxicity. Molecular mechanisms for other amyloidoses, such as transthyretin amyloidosis, AL-amyloidosis, as well as α-synuclein and prion protein are also pharmacological targets for current drug therapy, design and discovery. We report on natural herbal compounds and extracts that are capable binding to and inhibiting different targets associated with AD and other amyloid-associated diseases, providing a basis for future therapeutic strategies. Many herbal compounds, including curcumin, galantamine, quercetin and other polyphenols, are under active investigation and hold considerable potential for future prophylactic and therapeutic treatment against AD and other neurodegenerative diseases, as well as systemic amyloid diseases. A common emerging theme throughout many studies is the anti-oxidant and anti-inflammatory properties of the compounds or herbal extracts under investigation, within the context of the inhibition of cyto/neurotoxicity and anti-amyloid activity.

A strong protective action of guttiferone-A, a naturally occurring prenylated benzophenone, against iron-induced neuronal cell damage

Guttiferone-A (GA) is a natural occurring polyisoprenylated benzophenone with several reported pharmacological actions. We have assessed the protective action of GA on iron-induced neuronal cell damage by employing the PC12 cell line and primary culture of rat cortical neurons (PCRCN). A strong protection by GA, assessed by the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carbox-anilide (XTT) assay, was revealed, with IC(50) values <1 µM. GA also inhibited Fe(3+)-ascorbate reduction, iron-induced oxidative degradation of 2-deoxiribose, and iron-induced lipid peroxidation in rat brain homogenate, as well as stimulated oxygen consumption by Fe(2+) autoxidation. Absorption spectra and cyclic voltammograms of GA-Fe(2+)/Fe(3+) complexes suggest the formation of a transient charge transfer complex between Fe(2+) and GA, accelerating Fe(2+) oxidation. The more stable Fe(3+) complex with GA would be unable to participate in Fenton-Haber Weiss-type reactions and the propagation phase of lipid peroxidation. The results show a potential of GA against neuronal diseases associated with iron-induced oxidative stress.