Standardized root extract of Withania somnifera and Withanolide A exert moderate vasorelaxant effect in the rat aortic rings by enhancing nitric oxide generation.

ETHNO-PHARMACOLOGICAL RELEVANCE: Withania somnifera (L.) Dunal, commonly known as Ashwagandha, belongs to the family Solanaceae. In Ayurveda, Ashwagandha has been defined as one of the most important herb and is considered to be the best adaptogen. It is also an excellent rejuvenator, a general health tonic and cure for various disorders such as cerebrovascular, insomnia, asthma, ulcers, etc. Steroidal lactones (Withanolides: Withanolide A, Withaferin A, Withanolide D, Withanone, etc) isolated from this plant, possess promising medicinal properties such as anti-inflammatory, immune-stimulatory etc. Standardized root extract of the plant NMITLI-118R (NM) was prepared at CSIR-CIMAP, and was investigated for various biological activities at CSIR-CDRI. Among the notable medicinal properties, NM exhibited excellent neuroprotective activity in the middle cerebral artery occlusion (MCAO) rat model. AIM OF THE STUDY: Endothelial dysfunction is the primary event in the cerebrovascular or cardiovascular disorders, present study was thus undertaken to evaluate vasoprotective potential of NM and its biomarker compound Withanolide A (WA) using rat aortic rings and EA.hy926 endothelial cells. MATERIAL AND METHODS: Transverse aortic rings of 10 weeks old Wistar rats were used to evaluate effect of NM and WA on the vasoreactivity. While, mechanism of NM and WA mediated vasorelaxant was investigated in Ea.hy926 cell line by measuring NO generation, nitrite content, Serine 1177 phosphorylation of eNOS, reduced/oxidized biopterin levels and expression of endothelial nitric oxide synthase (eNOS) mRNA and protein. RESULTS: Fingerprinting of NM using HPLC identified presence of WA in the extract. NM as well as WA exerted moderate vasorelaxant effect in the endothelium intact rat aortic rings which was lesser than acetylcholine (ACh). NM and WA augmented ACh induced relaxation in the rat aortic rings. NM and WA dependent vasorelaxation was blocked by N-nitro-L-arginine methyl ester (L-NAME) or 1H-[1,2,4] oxadiazolo [4,3,-a]quinoxalin-1-one (ODQ), indicating role of NO/cGMP. Further Ea.hy926 cells treated with NM and WA showed accumulation of nitrite content, enhanced NO levels, eNOS expression and eNOS phosphorylation (Serine 1177). CONCLUSION: Altogether NM and WA dependent improvement in the NO availability seems to be mediated by the enhanced eNOS phosphorylation. WA, seems to be one of the active constituent of NM, and presence of other vasoactive substances cannot be ruled out. The data obtained imply that the vasorelaxant property of NM is beneficial for its neuroprotective potential.

Standardized fraction of Xylocarpus moluccensis fruits improve vascular relaxation and plaque stability in dyslipidemic models of atherosclerosis.

ETHNOPHARMACOLOGICAL RELEVANCE: Xylocarpus moluccensis (Lamk.) M. Roem of family Meliaceae has triterpenoids rich fruits. Triterpenoids have been known to possess cardioprotection and anti-atherosclerotic activities (Han and Bakovic, 2015; Wu et al., 2009). Standardized fraction of these fruits exhibited anti-dyslipidemic (Srivastava et al., 2015), anti-inflammatory (Ravangpai et al., 2011) and CNS depressant activity (Sarker et al., 2007). However, there is no report in the literature on its cardiovascular effects. AIM OF THE STUDY: The present study was undertaken to assess vasoprotective, anti-atherosclerotic and further examine the anti-dyslipidemic effect of the standardized fraction of Xylocarpus moluccensis (F018) fruits in the mechanical injury and high fat diet (HFD) induced dyslipidemic/ atherosclerosis models. MATERIALS AND METHODS: Guinea pigs were fed 0.08% cholesterol + 15% fat diet for 3 weeks, while ApoE KO mice were fed high fat diet for 18 weeks to induce dyslipidemia and atherosclerosis. A combination of balloon injury and high fat diet (1% cholesterol, 6% peanut oil) for 5 weeks was used to accelerate atherosclerosis in NZW rabbits. F018 was administered once daily by oral route in guinea pigs (10, 25 or 50mg/kg/day for 3 weeks), ApoE KO mice (50mg/kg/day for 6 weeks) and in NZW rabbit (25mg/kg/day for 5 weeks) to monitor its effect on dyslipidemia, vasoreactivity and plaque composition by using standard methodologies. RESULTS: F018 treatment in guinea pigs (25 and 50mg/kg/day), ApoE mice (50mg/kg/day) and rabbits (25mg/kg/day) significantly reduced plasma lipids and improved ACh induced vasorelaxation. Anti-dyslipidemic effect of F018 seems to be due to the modulation of enterohepatic genes involved in the cholesterol absorption and excretion. Moreover, significant improvement in the acetylcholine (ACh) induced vasorelaxation was accompanied with reduced inflammatory burden and enhanced activation of eNOS in ApoE mice aortic tissue. Similarly inflammatory cytokines, immunolabeling of macrophage marker (CD68) and MMP-9 were reduced along with augmentation in vascular smooth muscle cells and collagen type I and III in the mechanically injured iliac artery segment in the rabbits. CONCLUSIONS: Altogether, F018 preserved vasoreactivity, reduced atherosclerotic plaque progression and enhanced plaque stability by reducing lipids, inflammatory cytokines, improving endothelial function and collagen content.