Protective effect of stilbenes containing extract-fraction from Cajanus cajan L. on Abeta(25-35)-induced cognitive deficits in mice

Stilbenes: Source plants, chemistry, biosynthesis, pharmacology, application and problems related to their clinical Application-A comprehensive review

Stilbenes are some of the important phenolic compounds originating from plant families like Vitaceae, Leguminaceae, Gnetaceae, and Dipterocarpaceae. Structurally, they have a C6-C2-C6 skeleton, usually with two isomeric forms. Stilbenes are biosynthesized due to biotic and abiotic stresses such as microbial infections, high temperatures, and oxidation. This review aims to provide a comprehensive overview of stilbenes' botanical sources, chemistry, biosynthetic pathways, pharmacology, and clinical applications and challenges based on up-to-date data. All included studies were collected from PubMed, ScienceDirect, Google Scholar, and CNKI, and the presented data from these indexed studies were analyzed and summarized. A total of 459 natural stilbene compounds from 45 plant families and 196 plant species were identified. Pharmacological studies also show that stilbenes have various activities such as anticancer, antimicrobial, antioxidant, anti-inflammatory, anti-degenerative diseases, anti-diabetic, neuroprotective, anti-aging, and cardioprotective effects. Stilbene synthase (STS) is the key enzyme involved in stilbene biosynthetic pathways. Studies on the therapeutic application of stilbenes pinpoint that challenges such as low bioavailability and isomerization are the major bottlenecks for their development as therapeutic drugs. Although the medicinal uses of several stilbenes have been demonstrated in vivo and in vitro, studies on the development of stilbenes deserve more attention in the future.

BACE1 and cholinesterase inhibitory activities of compounds from Cajanus cajan and Citrus reticulata: an in silico study

Alzheimer's disease (AD) is one of the major neurodegenerative diseases whose underlying risk factors are yet to be fully understood. However, reduced cellular level of cholinesterase, as well as formation and deposition of amyloid plaques (Aβ) are thought to play critical roles in the pathogenesis of AD. Therefore, increases in cholinergic transmitter levels via cholinesterase (ChE) inhibitors as well as inhibition of amyloid plaques formation and aggregation via beta secretase-1 (BACE1) inhibitors have been proposed as treatment for this disease. This study was aimed at investigating the BACE1 and ChE inhibitory properties of compounds from Cajanus cajan and Citrus reticulata based on their traditional connection with the management of neurodegenerative diseases, coupled with their protective effects on chemical-induced cognitive impairment. Using in silico methods, one hundred and nineteen compounds from C. cajan and C. reticulata were docked with acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and BACE1 using Vina. Molecular interactions of the top-ranked compounds for the 3 protein targets were viewed with Discovery Studio, followed by characterization of their ADME properties using the Swiss online ADME web tool. Among the one hundred and ninety nine compounds screened, 3 compounds, genistin (76), naphthalen-2-yl-acetic acid, 6-hydroxy-6-methyl-cyclodecyl ester (94) and vitexin (119) have remarkable binding affinity for the three protein targets and passed the oral drugability test, while only naphthalen-2-yl-acetic acid, 6-hydroxy-6-methyl-cyclodecyl ester (94) exhibited BBB permeation property. Genistin and vitexin from C. cajan and naphthalen-2-yl-acetic acid, 6-hydroxy-6-methyl-cyclodecyl ester from C. reticulata possibly contributed, at least in part, to the neurotherapeutic potentials of these plants.

Cajaninstilbene Acid Ameliorates Cognitive Impairment Induced by Intrahippocampal Injection of Amyloid-β1-42 Oligomers

Amyloid-β_1-42 (Aβ_1-42) oligomers play an important role at the early stage of Alzheimer's disease (AD) and have been a vital target in the development of therapeutic drugs for AD. Cajaninstilbene acid (CSA), a major bioactive stilbene isolated from pigeon pea (Cajanus cajan) leaves, exerted the neuroprotective property in our previous studies. The present study utilized a validated mouse model of early-stage AD induced by bilateral injection of Aβ_1-42 oligomers into hippocampal CA1 regions (100 pmol/mouse) to investigate the cognitive enhancing effects of CSA and the underlying mechanism, by a combination of animal behavioral tests, immunohistochemistry, liquid chromatography-tandem mass spectrometry analysis, and Western blot methods. Intragastric administration of CSA (7.5, 15, and 30 mg/kg) attenuated the impairment of learning and memory induced by Aβ_1-42 oligomers. CSA stimulated Aβ clearance and prevented microglial activation and astrocyte reactivity in the hippocampus of model mice. It also decreased the high levels of Glu but increased the low levels of GABA. In addition, CSA inhibited excessive expression of GluN2B-containing NMDARs and upregulated the downstream PKA/CREB/BDNF/TrkB signaling pathway. These results suggest that CSA could be a potential therapeutic agent at the early stage of AD.

Natural products and their derivatives as multifunctional ligands against Alzheimer's disease

Alzheimer's disease (AD), a complex neurodegenerative disorder causing multiple cellular changes including impaired cholinergic system, beta-amyloid (βA) aggregation, tau hyperphosphorylation, metal dyshomeostasis, neuroinflammation, and many other pathways are involved in the pathogenesis of the disease. However, the exact cause of the disease is not known. Natural products such as flavonoids, alkaloids, resveratrol, and curcumin have multifunctional properties, and have drawn the attention of the researchers because these molecules are capable of interacting concurrently with the multiple targets of AD. Therefore, natural products and their derivatives with proven efficacy could be used in the management of the neurodegenerative disorders. This review focuses on the natural product based multitarget directed ligands like tacrine-coumarin, tacrine-huperzine A, harmine-isoxazoline, berberine-thiophenyl, galantamine-indole, pyridoxine-resveratrol, donepezil-curcumin and their mode of action.

Natural products against Alzheimer's disease: Pharmaco-therapeutics and biotechnological interventions

Alzheimer's disease (AD) is a severe, chronic and progressive neurodegenerative disease associated with memory and cognition impairment ultimately leading to death. It is the commonest reason of dementia in elderly populations mostly affecting beyond the age of 65. The pathogenesis is indicated by accumulation of the amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFT) in brain tissues and hyperphosphorylation of tau protein in neurons. The main cause is considered to be the formation of reactive oxygen species (ROS) due to oxidative stress. The current treatment provides only symptomatic relief by offering temporary palliative therapy which declines the rate of cognitive impairment associated with AD. Inhibition of the enzyme acetylcholinesterase (AChE) is considered as one of the major therapeutic strategies offering only symptomatic relief and moderate disease-modifying effect. Other non-cholinergic therapeutic approaches include antioxidant and vitamin therapy, stem cell therapy, hormonal therapy, use of antihypertensive or lipid-lowering medications and selective phosphodiesterase (PDE) inhibitors, inhibition of β-secretase and γ-secretase and Aβ aggregation, inhibition of tau hyperphosphorylation and intracellular NFT, use of nonsteroidal anti-inflammatory drugs (NSAIDs), transition metal chelators, insulin resistance drugs, etanercept, brain-derived neurotrophic factor (BDNF) etc. Medicinal plants have been reported for possible anti-AD activity in a number of preclinical and clinical trials. Ethnobotany, being popular in China and in the Far East and possibly less emphasized in Europe, plays a substantial role in the discovery of anti-AD agents from botanicals. Chinese Material Medica (CMM) involving Chinese medicinal plants has been used traditionally in China in the treatment of AD. Ayurveda has already provided numerous lead compounds in drug discovery and many of these are also undergoing clinical investigations. A number of medicinal plants either in their crude forms or as isolated compounds have exhibited to reduce the pathological features associated with AD. In this present review, an attempt has been made to elucidate the molecular mode of action of various plant extracts, phytochemicals and traditional herbal formulations investigated against AD as reported in various preclinical and clinical tests. Herbal synergism often found in polyherbal formulations were found effective to combat disease heterogeneity as found in complex pathogenesis of AD. Finally a note has been added to describe biotechnological improvement, genetic and genomic resources and mathematical and statistical techniques for empirical model building associated with anti-AD plant secondary metabolites and their source botanicals.

A novel acetylcholinesterase inhibitor and calcium channel blocker SCR-1693 improves Aβ25-35-impaired mouse cognitive function

RATIONALE

The mechanism involved in AD is complex, which has prompted to develop compounds that could simultaneously interact with several potential targets. Here, we report a new synthesized compound SCR-1693 which is designed to target both AChE and calcium channels that are potential for AD therapy.

OBJECTIVES

We investigated the effects of SCR-1693 on AChE and calcium channels, the effects of neuroprotection and anti-amnesia in icv-Aβ25-35-injected mice, and the potential mechanisms.

METHODS

AChE activity assay, intracellular Ca(2+) content and calcium currents measurement, and Aβ25-35-induced cellular death determine were performed for validation of designed targets and neuroprotection of SCR-1693. Mice were orally administrated with SCR-1693 once daily after an Aβ25-35 injection. The Morris water maze and Y-maze test, and hippocampal protein detection were conducted on days 5-10, day 11, and day 8. The pyramidal neuron number, hippocampal AChE activity, and synaptic transmission were measured on day 12.

RESULTS

SCR-1693 acted as a selective, reversible, and noncompetitive inhibitor of AChE, and a nonselective voltage-gated calcium channel blocker. SCR-1693 also inhibited the increase of AChE activity in the mouse hippocampus. SCR-1693 was more effective than donepezil and memantine in preventing Aβ25-35-induced long-term and short-term memory impairment, maintaining the basal transmission of Schaffer collateral-CA1 synapses, and sustaining LTP in mouse hippocampus. SCR-1693 attenuated Aβ25-35-induced death of SH-SY5Y cell and the loss of hippocampal pyramidal neurons, and regulated Aβ25-35-induced signal cascade in neurons.

CONCLUSIONS

All these findings indicated that SCR-1693, as a double-target-direction agent, is a considerable candidate for AD therapy.

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.

Synthesis and cytotoxicity of longistylin C derivatives

The present study was designed to identify potent anti-tumor compounds from a series of new longistylin C derivatives. Ten longistylin C derivatives were synthesized and their structures were confirmed by (1)H NMR, MS, and elemental analyses. Their cytotoxicity in vitro against three human cancer cell lines (A549, HepG2, and MCF-7) were evaluated by the MTT assay. Among these compounds, DT-6 and DT-9 displayed much better cytotoxicity against A549, HepG2, and MCF-7 cells, DT-1 exhibited selective cytotoxicity against HepG2, and the structure-activity relationships were investigated. In conclusion, Compounds DT-6 and DT-9 may serve as potential lead compounds for the discovery of new anti-cancer drugs.

Cajaninstilbene acid protects corticosterone-induced injury in PC12 cells by inhibiting oxidative and endoplasmic reticulum stress-mediated apoptosis

It has been reported that high corticosterone level could damage the normal hippocampal neurons both in vitro and in vivo. Furthermore, high concentration of corticosterone induced impair in PC12 cells has been widely used as in vitro model to screen neuroprotective agents. Cajaninstilbene acid (CSA), a natural stilbene isolated from Cajanus cajan leaves, has various activities. In present study, we investigated the effect of CSA on corticosterone-induced cell apoptosis and explored its possible signaling pathways in PC12 cells. We demonstrated that pretreatment with CSA at the concentrations of 1-8 μmol/L remarkably reduced the cytotoxicity induced by 200 μmol/L of corticosterone in PC12 cells by MTT, and further confirmed the neuroprotection by Hoechst 33342 and PI double staining and lactate dehydrogenase release (LDH) assay at the concentration of 8 μmol/L. Moreover, the cytoprotection of CSA was proved to be associated with the homeostasis of intracellular Ca(2+), relieving corticosterone-induced oxidative stress by decreasing the contents of ROS and malondialdehyde (MDA), increasing the activities of superoxide dismutase (SOD) and catalase (CAT), and the stabilization of ER stress via down-regulating the expression of ER chaperone protein glucose-regulated protein 78 (GRP78), ER stress associated transcription factor C/EBP homologous protein (CHOP/GADD153), and the X box-binding protein-1 (XBP-1), as well as the expression of ER stress-specific protein caspase-12 and its downstream protein caspase-9. Considering all the findings, it is suggested that the neuroprotective activity of CSA against the impairment induced by corticosterone in PC12 cells was through the inhibition of oxidative stress and ER stress-mediated pathway.

(+)- and (-)-Cajanusine, a pair of new enantiomeric stilbene dimers with a new skeleton from the leaves of Cajanus cajan

A pair of new enantiomeric stilbene dimers, (+)- and (-)-cajanusine [(+)-1 and (-)-1], with a unique coupling pattern were isolated from the leaves of Cajanus cajan . Their structures including absolute configurations were elucidated on the basis of comprehensive spectroscopic and single-crystal X-ray diffraction analyses, as well as CD calculations. The plausible biogenetic pathway of 1 was also proposed. Additionally, (±)-1, (+)-1, and (-)-1 exhibited inhibitory activities on the growth of human hepatocellular carcinoma cells.

Variation in contents of main active components and antioxidant activity in leaves of different pigeon pea cultivars during growth

Pigeon pea is an important and multiuse grain legume crop, and its leaves are a very valuable natural resource. To obtain a high-quality biological resource, it is necessary to choose the excellent cultivar and determine the appropriate harvest time. In this study, the variation in contents of main active components and antioxidant activity in leaves of six pigeon pea cultivars during growth were investigated. The level of each individual active component significantly varied during growth, but with a different pattern, and this variation was different among cultivars. Flavonoid glycosides orientin, vitexin, and apigenin-6,8-di-C-α-L-arabinopyranoside showed two peak values at mid-late and final stages of growth in most cases. Pinostrobin chalcone, longistyline C, and cajaninstilbene acid showed remarkablely higher values at the mid-late stage of growth than at other stages. Pinostrobin had an extremely different variation pattern compared to other active components. Its content was the highest at the earlier stage of growth. Principal component analysis (PCA) revealed that vitexin and apigenin-6,8-di-C-α-L-arabinopyranoside were mainly responsible for distinguishing cultivars analyzed. In a comprehensive consideration, the leaves should preferentially be harvested at the 135th day after sowing when the level of active components and antioxidant activity reached higher values. Cultivars ICP 13092, ICPL 87091, and ICPL 96053 were considered to be excellent cultivars with high antioxidant activity. Our findings can provide valuable information for producing a high-quality pigeon pea resource.

Pioglitazone improves cognitive function via increasing insulin sensitivity and strengthening antioxidant defense system in fructose-drinking insulin resistance rats

Insulin resistance (IR) links Alzheimer’s disease (AD) with oxidative damage, cholinergic deficit, and cognitive impairment. Peroxisome proliferator-activated receptor γ (PPARγ) agonist pioglitazone previously used to treat type 2 diabetes mellitus (T2DM) has also been demonstrated to be effective in anti-inflammatory reaction and anti-oxidative stress in the animal models of AD and other neuroinflammatory diseases. Here, we investigated the effect of pioglitazone on learning and memory impairment and the molecular events that may cause it in fructose-drinking insulin resistance rats. We found that long-term fructose-drinking causes insulin resistance, oxidative stress, down-regulated activity of cholinergic system, and cognitive deficit, which could be ameliorated by pioglitazone administration. The results from the present study provide experimental evidence for using pioglitazone in the treatment of brain damage caused by insulin resistance.

(E)-2-Hy-droxy-4-meth-oxy-3-(3-methyl-but-2-en-yl)-6-styryl-benzoic acid

The title compound, C21H22O4, also known as cajanine, features an intra-molecular O-H⋯O hydrogen bond between the adjacent carb-oxy and hy-droxy groups. The benzene rings make an inter-planar angle of 175.4 (2)°. In the crystal, mol-ecules are linked by pairs of O-H⋯O hydrogen bonds, forming inversion dimers.

Cajaninstilbene acid relaxes rat renal arteries: roles of Ca2+ antagonism and protein kinase C-dependent mechanism

Cajaninstilbene acid (CSA) is a major active component present in the leaves of Cajanus cajan (L.) Millsp. The present study explores the underlying cellular mechanisms for CSA-induced relaxation in rat renal arteries. Vascular reactivity was examined in arterial rings that were suspended in a Multi Myograph System and the expression of signaling proteins was assessed by Western blotting method. CSA (0.1–10 µM) produced relaxations in rings pre-contracted by phenylephrine, serotonin, 9, 11-dideoxy-9α, 11α-epoxymethanoprostaglandin F_2α (U46619), and 60 mM KCl. CSA-induced relaxations did not show difference between genders and were unaffected by endothelium denudation, nor by treatment with N^G-nitro-L-arginine methyl ester, indomethacin, ICI-182780, tetraethylammonium ion, BaCl₂, glibenclamide, 4-aminopyridine or propranolol. CSA reduced contraction induced by CaCl₂ (0.01–5 mM) in Ca²⁺-free 60 mM KCl solution and by 30 nM (−)-Bay K8644 in 15 mM KCl solution. CSA inhibited 60 mM KCl-induced Ca²⁺ influx in smooth muscle of renal arteries. In addition, CSA inhibited contraction evoked by phorbol 12-myristate 13-acetate (PMA, protein kinase C agonist) in Ca²⁺-free Krebs solution. Moreover, CSA reduced the U46619- and PMA-induced phosphorylation of myosin light chain (MLC) at Ser19 and myosin phosphatase target subunit 1 (MYPT1) at Thr853 which was associated with vasoconstriction. CSA also lowered the phosphorylation of protein kinase C (PKCδ) at Thr505. In summary, the present results suggest that CSA relaxes renal arteries in vitro via multiple cellular mechanisms involving partial inhibition of calcium entry via nifedipine-sensitive calcium channels, protein kinase C and Rho kinase.

Determination and quantification of active phenolic compounds in pigeon pea leaves and its medicinal product using liquid chromatography–tandem mass spectrometry

A novel method using liquid chromatography coupled to electrospray ionization mass spectrometry (LC-ESI-MS) has been optimized and established for the qualitative and quantitative analysis of ten active phenolic compounds originating from the pigeon pea leaves and a medicinal product thereof (Tongluo Shenggu capsules). In the present study, the chromatographic separation was achieved by means of a HiQ Sil C18V reversed-phase column with a mobile phase consisting of methanol and 0.1% formic acid aqueous solution. Low-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) using the selected reaction monitoring (SRM) analysis was employed for the detection of ten analytes which included six flavonoids, two isoflavonoids and two stilbenes. All calibration curves showed excellent coefficients of determination (r(2) ≥ 0.9937) within the range of tested concentrations. The intra- and inter-day variations were below 5.36% in terms of relative standard deviation (RSD). The recoveries were 95.08-104.98% with RSDs of 2.06-4.26% for spiked samples of pigeon pea leaves. The method developed was a rapid, efficient and accurate LC-MS/MS method for the detection of phenolic compounds, which can be applied for quality control of pigeon pea leaves and related medicinal products.

Semantic Web for data harmonization in Chinese medicine

Scientific studies to investigate Chinese medicine with Western medicine have been generating a large amount of data to be shared preferably under a global data standard. This article provides an overview of Semantic Web and identifies some representative Semantic Web applications in Chinese medicine. Semantic Web is proposed as a standard for representing Chinese medicine data and facilitating their integration with Western medicine data.