The Standardized Extract of Centella asiatica and Its Fractions Exert Antioxidative and Anti-Neuroinflammatory Effects on Microglial Cells and Regulate the Nrf2/HO-1 Signaling Pathway

Background

Neuroinflammation and oxidative stress can aggravate the progression of Alzheimer's disease (AD). Centella asiatica has been traditionally consumed for memory and cognition. The triterpenes (asiaticoside, madecassoside, asiatic acid, madecassic acid) have been standardized in the ethanolic extract of Centella asiatica (SECA). The bioactivity of the triterpenes in different solvent polarities of SECA is still unknown.

Objective

In this study, the antioxidative and anti-neuroinflammatory effects of SECA and its fractions were explored on lipopolysaccharides (LPS)-induced microglial cells.

Methods

HPLC measured the four triterpenes in SECA and its fractions. SECA and its fractions were tested for cytotoxicity on microglial cells using MTT assay. NO, pro-inflammatory cytokines (TNF-α, IL-6, IL-1β), ROS, and MDA (lipid peroxidation) produced by LPS-induced microglial cells were measured by colorimetric assays and ELISA. Nrf2 and HO-1 protein expressions were measured using western blotting.

Results

The SECA and its fractions were non-toxic to BV2 microglial cells at tested concentrations. The levels of NO, TNF-α, IL-6, ROS, and lipid peroxidation in LPS-induced BV2 microglial cells were significantly reduced (p < 0.001) by SECA and its fractions. SECA and some of its fractions can activate the Nrf2/HO-1 signaling pathway by significantly enhancing (p < 0.05) the Nrf2 and HO-1 protein expressions.

Conclusions

This study suggests that the inhibitory activity of SECA and its fractions on pro-inflammatory and oxidative stress events may be the result of the activation of antioxidant defense systems. The potential of SECA and its fractions in reducing neuroinflammation and oxidative stress can be further studied as a potential therapeutic strategy for AD.

Nanoemulsion of Ethanolic Extract of Centella asiatica (NanoSECA) Ameliorates Learning and Memory Performance by Enhancing Cholinergic Activities, Increasing Antioxidative Levels, and Attenuating oxidative stress markers in adult rats

BACKGROUND

Centella asiatica (C. asiatica) has long been traditionally used as a memory enhancer. Nanoemulsion of ethanolic extract C. asiatica (NanoSECA) has been developed to improve brain functions. However, the effect of NanoSECA on enhancing memory and cognitive functions remains unexplored.

OBJECTIVES

This research aimed to investigate the potential of NanoSECA on cognitive tasks and memory enhancement pathways in a normal adult rat model.

METHODS

Thirty male Sprague Dawley rats (7-8 weeks old) were randomly subjected to five groups (n=six per group). Treatment groups were supplemented with NanoSECA and ethanolic extract of C. asiatica (SECA) for 28 days by oral gavages. Different brain sections were isolated, homogenized, and tested for acetylcholinesterase, antioxidants (glutathione and malondialdehyde), and anti-inflammatory agents (nitric oxide, tumour necrosis factor-α, and prostaglandin E2).

RESULT

NanoSECA supplementation markedly enhanced the acetylcholine, glutathione levels and reduced a distinct diminution in plasma activities of acetylcholinesterase, malondialdehyde, nitric oxide, prostaglandin E, and tumor necrosis factor-α levels.

CONCLUSION

NanoSECA can be used as a memory enhancer through enhanced cholinergic activity, increased antioxidant level, and reduced oxidative stress.

Ethanol Extract of Centella asiatica Improved Methamphetamine-Induced Neurotoxicity on Mouse Model via Stimulating Superoxide Dismutase II and microRNA-34A Expression

Neurotoxicity induced by a psychostimulant drug, methamphetamine (METH) is associated with devastating and persistent neurotoxicity effects on the central nervous system (CNS). Centella asiatica (CA) is known as an antioxidant and neuroprotective agent. However, there is a limited study on natural-derived therapeutic to attenuate neurotoxicity induced by METH. We aimed to investigate the effects of METH and ethanol extract CA (CAE) on motor performance of animal model and the expression of manganese superoxide dismutase II (SOD2) and microRNA-34a (miR-34a) in the brain tissue. Male Sprague-Dawley rats were administered with METH (50 mg/kg per body weight) twice per day for 4 days, CAE (300 mg/kg & 500 mg/kg per body weight for 21 days and combination of METH and CAE for 21 day(s). Weight of rat was measured and motor performance was evaluated using vertical pole and narrow beam tests. Expression of SOD2 and miR-34a were measured using Quantitative Real-time Polymerase Chain Reaction (RT-qPCR). Group III (300 mg/kg CAE); p<0.001, Group IV (500 mg/kg CAE); p<0.001, Group V (METH+300 mg/kg CAE); p<0.01 and Group VI (METH+500 mg/kg CAE); p<0.01 significantly improved latency in the vertical pole test compared to METH group. Meanwhile, Group III (300 mg/kg CAE); p<0.001 and Group IV (500 mg/kg CAE); p<0.001 significantly decreased latency in the narrow beam test compared to METH. Post-treatment of CAE on METH-treated rats, Group V (METH+300 mg/kg CAE) and Group VI (METH+500 mg/kg CAE) non-significantly upregulated the SOD2 expression by 3.78±1.03 and 4.05±0.19 folds compared to METH, respectively. Post-treatment of CAE on METH-treated rats, Group V (METH+300 mg/kg CAE) and Group VI (METH+500 mg/kg CAE) non-significantly upregulated the miR-34a expression by (7.02±3.73) and (6.75±1.94) folds compared to METH, respectively. CAE could be suggested as a promising natural-derived therapeutic for METH-induced neurotoxicity to ameliorating motor performance and triggering SOD2 and miR-34a expression.

Centella asiatica (L.) Urban. Attenuates Cell Damage in Hydrogen Peroxide-Induced Oxidative Stress in Transgenic Murine Embryonic Stem Cell Line-Derived Neural-Like Cells: A Preliminary Study for Potential Treatment of Alzheimer's Disease

BACKGROUND

Centella asiatica (L.) (C. asiatica) is commonly known in South East and South East Asia communities for its nutritional and medicinal benefits. Besides being traditionally used to enhance memory and accelerate wound healing, its phytochemicals have been extensively documented for their neuroprotective, neuroregenerative, and antioxidant properties.

OBJECTIVE

The present study aims to investigate the effects of a standardized raw extract of C. asiatica (RECA) on hydrogen peroxide (H2O2)-induced oxidative stress and apoptotic death in neural-like cells derived from mouse embryonic stem (ES) cell line.

METHODS

A transgenic mouse ES cell (46C) was differentiated into neural-like cells using 4-/4+ protocol with addition of all-trans retinoic acid. These cells were then exposed to H2O2 for 24 h. The effects of RECA on H2O2-induced neural-like cells were assessed through cell viability, apoptosis, and reactive oxygen species (ROS) assays, as well as neurite length measurement. The gene expression levels of neuronal-specific and antioxidant markers were assessed by RT-qPCR analysis.

RESULTS

Pre-treatment with H2O2 for 24 hours, in a dose-dependent manner, damaged neural-like cells as marked by a decrease in cell viability, substantial increase in intracellular ROS accumulation, and increase in apoptotic rate compared to untreated cells. These cells were used to treat with RECA. Treatment with RECA for 48 h remarkably restored cell survival and promoted neurite outgrowth in the H2O2- damaged neurons by increasing cell viability and decreasing ROS activity. RT-qPCR analysis revealed that RECA upregulated the level of antioxidant genes such as thioredoxin-1 (Trx-1) and heme oxygenase-1 (HO-1) of treated cells, as well as the expression level of neuronal-specific markers such as Tuj1 and MAP2 genes, suggesting their contribution in neuritogenic effect.

CONCLUSION

Our findings indicate that RECA promotes neuroregenerative effects and exhibits antioxidant properties, suggesting a valuable synergistic activity of its phytochemical constituents, thus, making the extract a promising candidate in preventing or treating oxidative stress-associated Alzheimer's disease.

Hypoxia-Induced Neuroinflammation in Alzheimer's Disease: Potential Neuroprotective Effects of Centella asiatica

Alzheimer's disease (AD) is a neurodegenerative disorder that is characterised by the presence of extracellular beta-amyloid fibrillary plaques and intraneuronal neurofibrillary tau tangles in the brain. Recurring failures of drug candidates targeting these pathways have prompted research in AD multifactorial pathogenesis, including the role of neuroinflammation. Triggered by various factors, such as hypoxia, neuroinflammation is strongly linked to AD susceptibility and/or progression to dementia. Chronic hypoxia induces neuroinflammation by activating microglia, the resident immune cells in the brain, along with an increased in reactive oxygen species and pro-inflammatory cytokines, features that are common to many degenerative central nervous system (CNS) disorders. Hence, interests are emerging on therapeutic agents and plant derivatives for AD that target the hypoxia-neuroinflammation pathway. Centella asiatica is one of the natural products reported to show neuroprotective effects in various models of CNS diseases. Here, we review the complex hypoxia-induced neuroinflammation in the pathogenesis of AD and the potential application of Centella asiatica as a therapeutic agent in AD or dementia.

Biocatalytic modifications of ethynodiol diacetate by fungi, anti-proliferative activity, and acetylcholineterase inhibitory of its transformed products

The fungal transformations of ethynodiol diacetate (1) were investigated for the first-time using Botrytis cinerea, Trichothecium roseum, and R3-2 SP 17. The metabolites obtained are as following: 17α-Ethynyl-17β-acetoxyestr-4-en-3-one-15β-ol (2), 19-nor-17a-ethynyltestosterone (3), and 17α-ethynyl-3β-hydroxy-17β-acetoxyestr-4-ene (4). The new metabolite, 2 (IC₅₀ = 104.8 µM), which has ketone group at C-3, and the β-hydroxyl group at C-15, resulted in an almost equipotent strength with the parent compound (IC₅₀ = 103.3 µM) against proliferation of SH-SY5Y cells. The previously reported biotransformed product, 3, showed almost equal strength to 1 against acetylcholinesterase. Molecular modelling studies were carried out to understand the observed experimental activities, and also to obtain more information on the binding mode and the interactions between the biotransformed products, and enzyme.

Medroxyprogesterone derivatives from microbial transformation as anti-proliferative agents and acetylcholineterase inhibitors (combined in vitro and in silico approaches)

The fungal transformations of medroxyrogesterone (1) were investigated for the first time using Cunninghamella elegans, Trichothecium roseum, and Mucor plumbeus. The metabolites obtained are as following: 6β, 20-dihydroxymedroxyprogesterone (2), 12β-hydroxymedroxyprogesterone (3), 6β, 11β-dihydroxymedroxyprogesterone (4), 16β-hydroxymedroxyprogesterone (5), 11α, 17-dihydroxy-6α-methylpregn-4-ene-3, 20-dione (6), 11-oxo-medroxyprogesterone (7), 6α-methyl-17α-hydroxypregn-1,4-diene-3,20-dione (8), and 6β-hydroxymedroxyprogesterone (9), 15β-hydroxymedroxyprogesterone (10), 6α-methyl-17α, 11β-dihydroxy-5α-pregnan-3, 20-dione (11), 11β-hydroxymedroxyprogesterone (12), and 11α, 20-dihydroxymedroxyprogesterone (13). Among all the microbial transformed products, the newly isolated biotransformed product 13 showed the most potent activity against proliferation of SH-SY5Y cells. Compounds 12, 5, 6, 9, 11, and 3 (in descending order of activity) also showed some extent of activity against SH-SY5Y tumour cell line. The never been reported biotransformed product, 2, showed the most potent inhibitory activity against acetylcholinesterase. Molecular modelling studies were carried out to understand the observed experimental activities, and also to obtain more information on the binding mode and the interactions between the biotransformed products, and enzyme.

Synthesis of symmetrical bis-Schiff base-disulfide hybrids as highly effective anti-leishmanial agents

Leishmaniasis has affected a wider part of population around the globe. Most often, the existing regiments to battle against leishmaniasis are inadequate and limited. In our ongoing efforts to develop new leishmanicidal agents, we have synthesized a series of novel and symmetrical bis-Schiff base-disulfide hybrids 1-27. Intermediate disulfide was synthesized from corresponding 2-aminothiol followed by reacting the coupled adduct with various aromatic aldehydes. All these compounds showed outstanding inhibition when compared with standard (Table 1). Out of twenty seven analogues, twenty two analogues i.e. 1-5, 7-13, 17-21, 23-27 analogues showed excellent inhibitory potential with EC₅₀ values ranging from 0.010 ± 0.00 to 0.096 ± 0.01 μM while five compounds i.e. 6, 14-16, and 22 showed good inhibitory potential with EC₅₀ values ranging from 0.10 ± 0.00 to 0.137 ± 0.01 μM when compared with the standard Amphotericin B. Structure-activity relationship has been established while molecular docking studies were performed to pin the binding interaction of active molecules. This study will help to develop new antileishmanial lead compounds.

Mitragynine, an euphoric compound inhibits hERG1a/1b channel current and upregulates the complexation of hERG1a-Hsp90 in HEK293-hERG1a/1b cells

Mitragyna speciosa Korth (M. speciosa) has been widely used as a recreational product, however, there are growing concerns on the abuse potentials and toxicity of the plant. Several poisoning and fatal cases involving kratom and mitragynine have been reported but the underlying causes remain unclear. The human ether-a-go-go-related gene 1 (hERG1) encodes the pore-forming subunit underlying cardiac rapidly delayed rectifier potassium current (I_Kr). Pharmacological blockade of the I_Kr can cause acquired long QT syndrome, leading to lethal cardiac arrhythmias. This study aims to elucidate the mechanisms of mitragynine-induced inhibition on hERG1a/1b current. Electrophysiology experiments were carried out using Port-a-Patch system. Quantitative RT-PCR, Western blot analysis, immunofluorescence and co-immunoprecipitation methods were used to determine the effects of mitragynine on hERG1a/1b expression and hERG1-cytosolic chaperones interaction. Mitragynine was found to inhibit the I_Kr current with an IC₅₀ value of 332.70 nM. It causes a significant reduction of the fully-glycosylated (fg) hERG1a protein expression but upregulates both core-glycosylated (cg) expression and hERG1a-Hsp90 complexes, suggesting possible impaired hERG1a trafficking. In conclusion, mitragynine inhibits hERG1a/1b current through direct channel blockade at lower concentration, but at higher concentration, it upregulates the complexation of hERG1a-Hsp90 which may be inhibitory towards channel trafficking.

Centella asiatica prevents chronic unpredictable mild stress-induced behavioral changes in rats

Background: Depression is a psychological disorder which is associated with mood swings and cognitive deficits, and is ranked third among the leading causes of global health care burden. Chronic unpredictable mild stress (CUMS) has been shown to induce depression-like behaviors in rodents, which exhibit similarities to the human form of depression. Centella asiatica (CA) is an ancient medicinal plant which has neuroprotective potential. This work aimed to assess the protective role of CA on CUMS-induced rats. Methods: Thirty six rats randomly divided into six groups were used for the evaluation. The groups were as follows: 1, Unstressed + normal saline (control); 2, CUMS + normal saline (model); 3, CUMS + fluoxetine (10 mg/kg) standard antidepressant; 4-6, CUMS + CA (200, 400 & 800 mg/kg). Nine different stressors (S) (S1: 24-h food deprivation, S2: 24- h water deprivation, S3: 5-min cold swimming (at 5◦C), S4: 12-h change of cage mate, S5: 1-min tail pinch (1 cm from the tip of the tail), S6: 12-h cage tilt (at 45◦), S7: 12-h overcrowding of cage, S8: 12-h wet bedding with 200 mL of water, and S9: 4-h physical restraint) were administered to the stressed groups with at least 2 stressors per day. The treatments lasted for 8 weeks, and the rats were evaluated through open field test (OFT) and elevated plus maze (EPM) for anxiety-like behavior, forced swimming test (FST) for depression-like behaviour, and T-maze spontaneous alternation for learning and memory. Furthermore, serum cortisol levels were also evaluated. Results: CUMS-induced rats showed anxiety-like behaviors in OFT and EPM tests, depression-like behavior in FST and cognitive deficits in T-maze test, as well as increased serum cortisol levels. Conversely, administration of CA (at 400 and 800 mg/kg doses) and fluoxetine (at 10 mg/kg dose) prevented the aberrant behavioral changes and also the changes in the serum cortisol levels. No significant differences of behaviors were observed between the groups of rats administered with CA (400 and 800 mg/kg) and those administered with fluoxetine (10 mg/kg), suggesting that the therapeutic potential of CA is comparable to that of fluoxetine. Conclusion: The data obtained showed that CA, at doses of 400 and 800 mg/kg, effectively reversed the anxiety and depression-like behaviors, amnesic behaviors, as well as serum cortisol levels in a CUMS-induced rat model of depression. This suggests that CA is a potential candidate for the development of future anti-depressants.  

Centella asiatica Protects d-Galactose/AlCl3 Mediated Alzheimer's Disease-Like Rats via PP2A/GSK-3β Signaling Pathway in Their Hippocampus

Alzheimer's disease (AD) is a progressive neurodegenerative disorder more prevalent among the elderly population. AD is characterised clinically by a progressive decline in cognitive functions and pathologically by the presence of neurofibrillary tangles (NFTs), deposition of beta-amyloid (Aβ) plaque and synaptic dysfunction in the brain. Centella asiatica (CA) is a valuable herb being used widely in African, Ayurvedic, and Chinese traditional medicine to reverse cognitive impairment and to enhance cognitive functions. This study aimed to evaluate the effectiveness of CA in preventing d-galactose/aluminium chloride (d-gal/AlCl3) induced AD-like pathologies and the underlying mechanisms of action were further investigated for the first time. Results showed that co-administration of CA to d-gal/AlCl3 induced AD-like rat models significantly increased the levels of protein phosphatase 2 (PP2A) and decreased the levels of glycogen synthase kinase-3 beta (GSK-3β). It was further observed that, CA increased the expression of mRNA of Bcl-2, while there was minimal effect on the expression of caspase 3 mRNA. The results also showed that, CA prevented morphological aberrations in the connus ammonis 3 (CA 3) sub-region of the rat's hippocampus. The results clearly demonstrated for the first time that CA could alleviate d-gal/AlCl3 induced AD-like pathologies in rats via inhibition of hyperphosphorylated tau (P-tau) bio-synthetic proteins, anti-apoptosis and maintenance of cytoarchitecture.

Protective Effects of Centella asiatica on Cognitive Deficits Induced by D-gal/AlCl₃ via Inhibition of Oxidative Stress and Attenuation of Acetylcholinesterase Level

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with cholinergic dysfunctions and impaired redox homeostasis. The plant Centella asiatica (CA) is renowned for its nutritional benefits and herbal formulas for promoting health, enhancing cognition, and its neuroprotective effects. The present study aims to investigate the protective role of CA on D-gal/AlCl₃-induced cognitive deficits in rats. The rats were divided into six groups and administered with donepezil 1 mg/kg/day, CA (200, 400, and 800 mg/kg/day) and D-gal 60 mg/kg/day + AlCl₃ 200 mg/kg/day for 10 weeks. The ethology of the rats was evaluated by the Morris water maze test. The levels of acetylcholinesterase (AChE), phosphorylated tau (P-tau), malondialdehyde (MDA) and activities of superoxide dismutase (SOD), in the hippocampus and cerebral cortex were estimated by enzyme-linked immunosorbent assay (ELISA). Additionally, the ultrastructure of the prefrontal cortex of the rats’ was observed using transmission electron microscopy (TEM). Rats administered with D-gal/AlCl₃ exhibited cognitive deficits, decreased activities of SOD, and marked increase in AChE and MDA levels. Further, prominent alterations in the ultrastructure of the prefrontal cortex were observed. Conversely, co-administration of CA with D-gal/AlCl₃ improved cognitive impairment, decreased AChE levels, attenuated the oxidative stress in hippocampus and cerebral cortex, and prevented ultrastructural alteration of neurons in the prefrontal cortex. Irrespective of the dose of CA administered, the protective effects were comparable to donepezil. In conclusion, this study suggests that CA attenuated the cognitive deficits in rats by restoring cholinergic function, attenuating oxidative stress, and preventing the morphological aberrations.

Supplementation of 100% Flesh Watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] Juice Improves Swimming Performance in Rats

Nutritional intervention of fruit juice supplementation is able to maximize exercise performance. Watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] contains high L-citrulline content and consumption of watermelon juice may promote ergogenic effects. The aim of the present study was to investigate the role of 100% flesh watermelon juice and 100% rind watermelon juice supplementation for 14 days on swimming performance in rats. Twenty four male Sprague-Dawley rats were randomly divided into four groups: Cx group of rats supplemented with filtered tap water (negative control), L-cit group of rats supplemented with L-citrulline (positive control), FR group of rats supplemented with 100% flesh watermelon juice, and RR group of rats supplemented with 100% rind watermelon juice. Each group was supplemented for 14 days ad libitum prior to swimming exercise protocol. The rats were performed swimming exercise for 3 days and swimming time until exhaustion was measured. Plasma samples were collected to measure lactate concentration, ammonia concentration, and nitric oxide production. Rats supplemented with 100% flesh watermelon juice demonstrated significantly prolonged of swimming time until exhaustion, reduction of lactate and ammonia concentrations, and increased of nitric oxide production compared to Cx and L-cit groups (P<0.05). These findings postulate that supplementation with 100% flesh watermelon juice improves endurance in swimming performance.

Protective effect of Centella asiatica against D-galactose and aluminium chloride induced rats: Behavioral and ultrastructural approaches

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder and the commonest cause of dementia among the aged people. _D-galactose (D-gal) is a senescence agent, while aluminium is a known neurotoxin linked to pathogenesis of AD. The combined administration of rats with d-gal and aluminium chloride (AlCl₃) is considered to be an easy and a cheap method to obtain an animal model of AD. The plant Centella asiatica (CA) is reported to exert neuroprotective effects both in vitro and in vivo. Therefore, this study explored the protective effects of CA on cognition and brain ultrastructure in d-gal and AlCl₃ induced rats.

MATERIALS AND METHODS

Rats were exposed to d-gal 60 mg/kg/b.wt/day + AlCl₃ 200 mg/kg/b.wt/day and CA (200, 400 and 800 mg/kg/b.wt/day) and 1 mg/kg/b.wt/day of donepezil for 70 days. Different cognitive paradigms viz. T maze spontaneous alternation, modified elevated plus maze and novel object recognition test, were used to evaluate full lesions of the hippocampus, spatial learning and memory and non-spatial learning and memory respectively. Nissl's staining was used to determine the survival of hippocampus CA1 pyramidal cells, while transmission electron microscopy was used to check the ultrastructural changes.

RESULTS

The results revealed that d-gal and AlCl₃ could significantly impair behavior and cognitive functions, besides causing damage to the hippocampal CA1 pyramidal neurons in rats. In addition, it also caused ultrastructural morphological alterations in rat hippocampus. Conversely, co-administration o;f CA, irrespective of the dosage used, alleviated the cognitive impairments and pathological changes in the rats comparable to donepezil.

CONCLUSION

In conclusion the results suggest that CA could protect cognitive impairments and morphological alterations caused by d-gal and AlCl₃ toxicity in rats. Biochemical and molecular studies are ongoing to elucidate the probable pharmacodynamics of CA.

Inhibitory effects of (+)-spectaline and iso-6-spectaline from Senna spectabilis on the growth and ultrastructure of human-infective species Trypanosoma brucei rhodesiense bloodstream form

In our ongoing work searching for new trypanocidal lead compounds from Malaysian plants, two known piperidine alkaloids (+)-spectaline (1) and iso-6-spectaline (2) were isolated from the leaves of Senna spectabilis (sin. Cassia spectabilis). Analysis of the ¹H and ¹³C NMR spectra showed that 1 and 2 presented analytical and spectroscopic data in full agreement with those published in the literature. All compounds were screened in vitro against Trypanosoma brucei rhodesiense in comparison to the standard drug pentamidine. Compound 1 and 2 inhibited growth of T. b. rhodesiense with an IC₅₀ value of 0.41 ± 0.01 μM and 0.71 ± 0.01 μM, without toxic effect on L6 cells with associated a selectivity index of 134.92 and 123.74, respectively. These data show that piperidine alkaloids constitute a class of natural products that feature a broad spectrum of biological activities, and are potential templates for the development of new trypanocidal drugs. To our knowledge, the compounds are being reported for the first time to have inhibitory effects on T. b. rhodesiense. The ultrastructural alterations in the trypanosome induced by 1 and 2, leading to programmed cell death were characterized using electron microscopy. These alterations include wrinkling of the trypanosome surface, formation of autophagic vacuoles, disorganization of kinetoplast, and swelling of the mitochondria. These findings evidence a possible autophagic cell death.

The effects of deoxyelephantopin on the cardiac delayed rectifier potassium channel current (IKr) and human ether-a-go-go-related gene (hERG) expression

Elephantopus scaber Linn and its major bioactive component, deoxyelephantopin are known for their medicinal properties and are often reported to have various cytotoxic and antitumor activities. This plant is widely used as folk medicine for a plethora of indications although its safety profile remains unknown. Human ether-a-go-go-related gene (hERG) encodes the cardiac I_Kr current which is a determinant of the duration of ventricular action potentials and QT interval. The hERG potassium channel is an important antitarget in cardiotoxicity evaluation. This study investigated the effects of deoxyelephantopin on the current, mRNA and protein expression of hERG channel in hERG-transfected HEK293 cells. The hERG tail currents following depolarization pulses were insignificantly affected by deoxyelephantopin in the transfected cell line. Current reduction was less than 40% as compared with baseline at the highest concentration of 50 μM. The results were consistent with the molecular docking simulation and hERG surface protein expression. Interestingly, it does not affect the hERG expression at both transcriptional and translational level at most concentrations, although higher concentration at 10 μM caused protein accumulation. In conclusion, deoxyelephantopin is unlikely a clinically significant hERG channel and I_kr blocker.

Synthesis and molecular modelling studies of phenyl linked oxadiazole-phenylhydrazone hybrids as potent antileishmanial agents

Molecular hybridization yielded phenyl linked oxadiazole-benzohydrazones hybrids 6-35 and were evaluated for their antileishmanial potentials. Compound 10, a 3,4-dihydroxy analog with IC₅₀ value of 0.95 ± 0.01 μM, was found to be the most potent antileishmanial agent (7 times more active) than the standard drug pentamidine (IC₅₀ = 7.02 ± 0.09 μM). The current series 6-35 conceded in the identification of thirteen (13) potent antileishmanial compounds with the IC₅₀ values ranging between 0.95 ± 0.01-78.6 ± 1.78 μM. Molecular docking analysis against pteridine reductase (PTR1) were also performed to probe the mode of action. Selectivity index showed that compounds with higher number of hydroxyl groups have low selectivity index. Theoretical stereochemical assignment was also done for certain derivatives by using density functional calculations.

Establishing Natural Nootropics: Recent Molecular Enhancement Influenced by Natural Nootropic

Nootropics or smart drugs are well-known compounds or supplements that enhance the cognitive performance. They work by increasing the mental function such as memory, creativity, motivation, and attention. Recent researches were focused on establishing a new potential nootropic derived from synthetic and natural products. The influence of nootropic in the brain has been studied widely. The nootropic affects the brain performances through number of mechanisms or pathways, for example, dopaminergic pathway. Previous researches have reported the influence of nootropics on treating memory disorders, such as Alzheimer's, Parkinson's, and Huntington's diseases. Those disorders are observed to impair the same pathways of the nootropics. Thus, recent established nootropics are designed sensitively and effectively towards the pathways. Natural nootropics such as Ginkgo biloba have been widely studied to support the beneficial effects of the compounds. Present review is concentrated on the main pathways, namely, dopaminergic and cholinergic system, and the involvement of amyloid precursor protein and secondary messenger in improving the cognitive performance.

(+)-Spectaline, a Piperidine Alkaloid from Senna spectabilis DC. Effective in Reducing the In Vitro Infection of Leishmania major

Senna spectabilisis known to have antimicrobial, laxative, antiulcerogenic, analgesic, and anti-inflammatory properties in folk medicine. Piperidine alkaloids extracted from various parts of this plant have been shown to have anticonvulsant (iso-6-spectaline), antinociceptive [(-)-spectaline] and lipid peroxidation [(+)-3-O-feruloylcassine, (-)-spectaline and (-)-3-O-acetylspectaline] activities. In our study, the ethyl acetate extract fromS. spectabilisexhibited antileishmanial activity via intracellular promastigote assay or leishmanicidal assay and was further fractionated by using bioassay-guided isolation approach. The antiprotozoal principle was isolated from the ethyl acetate portion through solvent fractionation and a few series of chromatographic processes. The isolated active compound 1 was identified as (+)-spectaline on the basis of its spectral analysis (MS, 1D & 2D NMR) with EC50value of 0.063 ± 0.005 µM for antileishmanial activity and selectivity index of 3.76.

Development of resazurin-based assay in 384-well format for high throughput whole cell screening of Trypanosoma brucei rhodesiense strain STIB 900 for the identification of potential anti-trypanosomal agents

To accelerate the discovery of novel leads for the treatment of Human African Trypanosomiasis (HAT), it is necessary to have a simple, robust and cost-effective assay to identify positive hits by high throughput whole cell screening. Most of the fluorescence assay was made in black plate however in this study the HTS assay developed in 384-well format using clear plate and black plate, for comparison. The HTS assay developed is simple, sensitive, reliable and reproducible in both types of plates. Assay robustness and reproducibility were determined under the optimized conditions in 384-well plate was well tolerated in the HTS assay, including percentage of coefficient of variation (% CV) of 4.68% and 4.74% in clear and black 384-well plate, signal-to-background ratio (S/B) of 12.75 in clear 384-well plate and 12.07 in black 384-well plate, Z' factor of 0.79 and 0.82 in clear 384-well plate and black 384-well plate, respectively and final concentration of 0.30% dimethylsulfoxide (DMSO) in both types of plate. Drug sensitivity was found to be comparable to the reported anti-trypanosomal assay in 96-well format. The reproducibility and sensitivity of this assay make it compliant to automated liquid handler use in HTS applications.

Evaluation of the cardiotoxicity of mitragynine and its analogues using human induced pluripotent stem cell-derived cardiomyocytes

Introduction

Mitragynine is a major bioactive compound of Kratom, which is derived from the leave extracts of Mitragyna speciosa Korth or Mitragyna speciosa (M. speciosa), a medicinal plant from South East Asia used legally in many countries as stimulant with opioid-like effects for the treatment of chronic pain and opioid-withdrawal symptoms. Fatal incidents with Mitragynine have been associated with cardiac arrest. In this study, we determined the cardiotoxicity of Mitragynine and other chemical constituents isolated using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).

Methods and Results

The rapid delayed rectifier potassium current (I_Kr), L-type Ca²⁺ current (I_Ca,L) and action potential duration (APD) were measured by whole cell patch-clamp. The expression of KCNH2 and cytotoxicity was determined by real-time PCR and Caspase activity measurements. After significant I_Kr suppression by Mitragynine (10 µM) was confirmed in hERG-HEK cells, we systematically examined the effects of Mitragynine and other chemical constituents in hiPSC-CMs. Mitragynine, Paynantheine, Speciogynine and Speciociliatine, dosage-dependently (0.1∼100 µM) suppressed I_Kr in hiPSC-CMs by 67% ∼84% with IC₅₀ ranged from 0.91 to 2.47 µM. Moreover, Mitragynine (10 µM) significantly prolonged APD at 50 and 90% repolarization (APD50 and APD90) (439.0±11.6 vs. 585.2±45.5 ms and 536.0±22.6 vs. 705.9±46.1 ms, respectively) and induced arrhythmia, without altering the L-type Ca²⁺ current. Neither the expression,and intracellular distribution of KCNH2/Kv11.1, nor the Caspase 3 activity were significantly affected by Mitragynine.

Conclusions

Our study indicates that Mitragynine and its analogues may potentiate Torsade de Pointes through inhibition of I_Kr in human cardiomyocytes.

Mechanisms of action of 17βH-neriifolin on its anticancer effect in SKOV-3 ovarian cancer cell line

AIM

Abnormalities in apoptotic signalling pathways often occur in cancer cells and limit the successful chemotherapy outcomes in cancers. Therefore, there is an urgent need to discover new anticancer agents with novel mechanisms of action to overcome the resistance effect in chemotherapy.

MATERIALS AND METHODS

In the present study, the anticancer effects and the mechanisms of action of 17βH-neriifolin (cardiac glycoside) were evaluated by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and a proteomic approach in treated and non-treated SKOV-3 ovarian cancer cells.

RESULTS

17βH-neriifolin was found to be active with IC50 values of 0.01 ± 0.001 in SKOV-3 ovarian cancer cell line, as evaluated by the sulforhodamine B (SRB) assay. RESULTS from TUNEL assay indicated that 17βH-neriifolin caused apoptosis in SKOV-3 cells in a dose-dependent manner. Based on differential analysis of treated and non-treated SKOV-3 two-dimensional electrophoresis (2-DE) profiles, four proteins, namely vimentin (VIM), pyruvate kinase, muscle (PKM), heterogeneous nuclear ribonucleoprotein A1 (HNRNPA1) and transgelin (TAGLN1) were identified to be involved in apoptosis. Other proteins including piggybac transposable element derived 5 (PGBD5), DENN/MADD domain containing 2D (DENND2D) and formin-like 1(FMNL) have also been identified to be associated in SKOV-3 cell death induced by 17βH-neriifolin.

CONCLUSION

These findings may provide new insights on the potential of 17βH-neriifolin's mechanism of action in killing ovarian cancer cells.

Bioassay-guided isolation of a sesquiterpene lactone of deoxyelephantopin from Elephantopus scaber Linn. active on Trypanosome brucei rhodesience

Methanolic extracts of 70 Malaysia plants were screened for their in vitro antitrypanosomal activity using Trypanosome brucei rhodesience, strain STIB 900 and mouse skeletal cell (L-6) in cytotoxicity activity assay. Results indicated that methanol extract from Elephantopus scaber Linn. (E. scaber) possessed the highest value of antitrypanosomal activity with good selectivity index (antitrypanosomal IC50 of 0.22±0.02 μg/ml, SI value of 204.55). Based on these results, E. scaber was chosen for further study by applying bioassay guided fractionation to isolate its antiprotozoal principle. The antiprotozoal principle was isolated from the ethyl acetate partition through solvent fractionation and crystallization process. The isolated active compound 1 was identified as deoxyelephantopin on the basis of its spectral analysis (FTIR, MS, 1D and 2D NMR).

The effect of mitragynine on cAMP formation and mRNA expression of mu-opioid receptors mediated by chronic morphine treatment in SK-N-SH neuroblastoma cell

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] Mitragynine is an indole alkaloid compound of Mitragyna speciosa (M. speciosa) Korth. (Rubiaceae). This plant is native to the southern regions of Thailand and northern regions of Malaysia and is frequently used to manage the withdrawal symptoms in both countries.

AIM OF STUDY

To investigate the effect of mitragynine after chronic morphine treatment on cyclic AMP (cAMP) level and mRNA expression of mu-opioid receptor (MOR) in human neuroblastoma SK-N-SH cell.

METHOD AND MATERIALS

Mitragynine was isolated from the Mitragyna speciosa plant using the acid-base extraction method. The cAMP level upon forskolin stimulation in the cells was determined using the Calbiochem(®) Direct Immunoassay Kit. The mRNA expression of the MOR was carried out using quantitative RT-PCR.

RESULT

Cotreatment and pretreatment of morphine and mitragynine significantly reduced the production of cAMP level at a lower concentration of mitragynine while the higher concentration of this compound could lead to the development of tolerance and dependence as shown by the increase of the cAMP level production in foskolin stimulation. In MOR mRNA expression study, cotreatment of morphine with mitragynine significantly reduced the down-regulation of MOR mRNA expression as compared to morphine treatment only.

CONCLUSION

These finding suggest that mitragynine could possibly avoid the tolerance and dependence on chronic morphine treatment by reducing the up-regulation of cAMP level as well as reducing the down-regulation of MOR at a lower concentration of mitragynine.

In vitro evaluation of cytochrome P450 induction and the inhibition potential of mitragynine, a stimulant alkaloid

CYP450 enzymes are key determinants in drug toxicities, reduced pharmacological effect and adverse drug reactions. Mitragynine, an euphoric compound was evaluated for its effects on the expression of mRNAs encoding CYP1A2, CYP2D6 and CYP3A4 and protein expression and resultant enzymatic activity. The mRNA and protein expression of CYP450 isoforms were carried out using an optimized multiplex qRT-PCR assay and Western blot analysis. CYP1A2 and CYP3A4 enzyme activities were evaluated using P450-Glo™ assays. The effects of mitragynine on human CYP3A4 protein expression were determined using an optimized hCYP3A4-HepG2 cell-based assay. An in silico computational method to predict the binding conformation of mitragynine to the active site of the CYP3A4 enzyme was performed and further validated using in vitro CYP3A4 inhibition assays. Mitragynine was found to induce mRNA and protein expression of CYP1A2. For the highest concentration of 25 μM, induction of mRNA was approximately 70% that of the positive control and was consistent with the increased CYP1A2 enzymatic activity. Thus, mitragynine is a significant in vitro CYP1A2 inducer. However, it appeared to be a weak CYP3A4 inducer at the transcriptional level and a weak CYP3A4 enzyme inhibitor. It is therefore, unlikely to have any significant clinical effects on CYP3A4 activity.

Aqueous extract of Centella asiatica promotes corneal epithelium wound healing in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Centella asiatica is a traditional herbal medicine that has been shown to have pharmacological effect on skin wound healing, and could be potential therapeutic agent for corneal epithelial wound healing.

AIM OF THE STUDY

This study was done to evaluate the effects of Centella asiatica on the proliferation and migration of rabbit corneal epithelial (RCE) cells in the in vitro wound healing model.

MATERIALS AND METHODS

RCE cells were cultured with or without supplementation of Centella asiatica aqueous extract. Viability and proliferation of the RCE cells was determined by MTT assay and cell cycle was analyzed by flow cytometry. In vitro re-epithelization was studied by scratch assay and migration rate was evaluated quantitatively by image analyzer. Expression of corneal specific differentiation markers, CK12 and connexin 43, were studied via RT-PCR.

RESULTS

It was found that supplementation of Centella asiatica did not show any significant effect on the RCE cells proliferation at the concentration up to 500ppm, while at the concentration of 1000ppm significantly inhibited RCE cells proliferation (p<0.05). However, at the concentration up to 62.5ppm, RCE cells shows significant enhancement of migration rate compared to the control group (p<0.05). It was also found that the supplementation of Centella asiatica aqueous extract did not alter the expression of differentiation markers and cell cycle.

CONCLUSION

In conclusion, supplementation of Centella asiatica aqueous extract at low concentrations could be useful to promote corneal epithelium wound healing.

Mitragynine inhibits the COX-2 mRNA expression and prostaglandin E₂ production induced by lipopolysaccharide in RAW264.7 macrophage cells

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] Mitragyna speciosa Korth (Rubiaceae) is one of the medicinal plants used traditionally to treat various types of diseases especially in Thailand and Malaysia. Its anti-inflammatory and analgesic properties in its crude form are well documented. In this study, the cellular mechanism involved in the anti-inflammatory effects of mitragynine, the major bioactive constituent, was investigated.

MATERIALS AND METHODS

The effects of mitragynine on the mRNA and protein expression of COX-1 and COX-2 and the production of prostaglandin E(2) (PGE(2)) were investigated in LPS-treated RAW264.7 macrophage cells. Quantitative RT-PCR was used to assess the mRNA expression of COX-1 and COX-2. Protein expression of COX-1 and COX-2 were assessed using Western blot analysis and the level of PGE(2) production was quantified using Parameter™ PGE(2) Assay (R&D Systems).

RESULTS

Mitragynine produced a significant inhibition on the mRNA expression of COX-2 induced by LPS, in a dose dependent manner and this was followed by the reduction of PGE(2) production. On the other hand, the effects of mitragynine on COX-1 mRNA expression were found to be insignificant as compared to the control cells. However, the effect of mitragynine on COX-1 protein expression is dependent on concentration, with higher concentration of mitragynine producing a further reduction of COX-1 expression in LPS-treated cells.

CONCLUSIONS

These findings suggest that mitragynine suppressed PGE(2) production by inhibiting COX-2 expression in LPS-stimulated RAW264.7 macrophage cells. Mitragynine may be useful for the treatment of inflammatory conditions.

Natural Antioxidants: Piper sarmentosum (Kadok) and Morinda elliptica (Mengkudu)

The antioxidant activity of two edible medicinal plants commonly used in Malaysian traditional medicine i.e. Piper sarmentosum (kadok) and Morinda elliptica (mengkudu) were tested for antioxidant activity. The methanolic leave extracts of kadok and mengkudu, at 250ug/ml, were tested using the Xanthine/Xanthine Oxidase (X/XOD) Superoxide Scavenging assay. Both extracts showed high superoxide scavenging assay, 88% and 80% respectively compared to superoxide dismutase (SOD) standard. The crude extracts were further fractionated using column chromatography and tested for superoxide scavenging activity, to obtain antioxidant active fractions. Two active fractions were obtained from kadok, PsFr6-71.3%, PsFr7-71.3%, and one active fraction from mengkudu, MeFr3-86.6%. These active fractions were compared against 14 phenolic compound standards. After a series of HPLC analysis of samples and standards, a natural antioxidant compound was identified in kadok and mengkudu i.e. Naringenin (4',5,7-Trihydroxyflavanone) with 75.7% superoxide scavenging activity. Naringenin is a highly potent natural antioxidant that has been reported in the raw materials of larch and grapefruit extracts. Thus, kadok and mengkudu which contain Naringenin, could be used as antioxidant dietary supplements.

A cytotoxic principle of Tamarindus indica, di-n-butyl malate and the structure-activity relationship of its analogues

Bioassay-guided fractionation of the methanolic extract of Tamarindus indica fruits led to the isolation of L-(-)-di-n-butyl malate which exhibited a pronounced cytotoxic activity against sea urchin embryo cells. In order to study structure-activity relationships, close-structure relatives of di-n-butyl malate were synthesized using D-(+)- and L-(-)-malic acid as starting materials, and their cytotoxic activities were examined for the sea urchin embryo assay. L-(-)-Di-n-pentyl malate was the most effective inhibitor to the development of the fertilized eggs. Significant inhibitory activity was not seen in the esters of D-(-)-isomer.

Temporal variation of Malaysian rotavirus electropherotypes

An analysis of rotavirus electropherotypes circulating in Kuala Lumpur, Malaysia, over 7 years showed that all except 1 of the 360 electropherotypes encountered were characteristic of group A rotaviruses. The long electropherotype predominated annually, and there was a rarity of short electropherotypes. Extensive genome variability and cocirculation of different electropherotypes were observed annually. A sequential appearance of the predominant electropherotype was observed in all years of the study, except for 1985 and 1988, when one electropherotype predominated throughout the study periods. There was no shift in the predominant electropherotype over a 6-year period.