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A central hypothesis in the study of Alzheimer's disease (AD) is the accumulation and aggregation of beta-amyloid peptide (A beta). Recent epidemiological studies suggest that patients with elevated cholesterol and decreased estrogen levels are more susceptible to AD through A beta accumulation. To test the above hypothesis, we used ovariectomized with diet-induced hypercholesterolemia (OVX) and hypercholesterolemia (HCL) diet alone mouse models. HPLC analysis reveals the presence of beta amyloid in the OVX and HCL mice brain. Congo red staining analysis revealed the extent of amyloid deposition in OVX and hypercholesterolemia mice brain. Overall, A beta levels were higher in OVX mice than in HCL. Secondly, estrogen receptors alpha (ER alpha) were assessed by immunohistochemistry and this suggested that there was a decreased expression of ER alpha in OVX animals when compared to hypercholesterolemic animals. A beta was quantified by Western blot and ELISA analysis. Overall, A beta levels were higher in OVX mice than in HCL mice. Our experimental results suggested that OVX animals were more susceptible to AD with significant increase in A beta peptide.

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Standardization of induction of oxidative stress with Fenton mixture (FM) in isolated perfused rat kidney and the antioxidant effect of Terminalia arjuna bark in the isolated oxidatively stressed rat kidney has been evaluated. Six groups each containing eight isolated perfused rat kidneys were used for the present study and the oxidative stress was induced by perfusing the isolated kidneys with FM. The antioxidant effect of Terminalia arjuna at the dose of 250 and 500 mg/kg was evaluated in oxidative stress induced isolated kidneys. A significant (P<0.05) increase in lipid peroxidation, gluatamate pyruvate transaminase, glutamate oxaloacetate transaminase were observed in oxidative stress induced isolated kidney. On perfusion with extract, the oxidative stress was decreased with increasing in antioxidants while the marker enzymes were found to maintain the normal level. It was concluded from the present study that hydroalcholic extract of Terminalia arjuna bark at the dose of 250 and 500 mg/kg showed significant antioxidant potential in isolated perfused rat kidneys.

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ETHNOPHARMACOLOGICAL RELEVANCE: Shilajit is a multi-component natural occurring mineral substance used in Ayurveda and Siddha systems of medicine which originated in India. Its source can be traced to the mountainous regions, where the hilly tribes first identified its beneficial use. Shilajit is aptly referred to as 'rasayana'/'rasayanam' in Ayurveda and Siddha literature which means rejuvenator because it prevents ailment and enhances the quality of life. MATERIALS AND METHODS: An attempt has been put forth to review shilajit pertaining to its origin, synonyms, varieties, physical properties, chemical constituents, therapeutic properties and important biological properties to affirm its rasayana property. All relevant information on shilajit was collected from classical texts including pharmacopoeias, formularies, etc. Moreover, select doctoral thesis from Banaras Hindu University, Varanasi and Gujarat Ayurved University, Jamnagar were also scanned. Published papers on shilajit were collected from important databases for biomedical sciences. Amongst, the various biological properties of shilajit, antioxidant activity and immuno-modulatory activity were focused as it is closely related to its rasayana potential. RESULTS: This review finds that shilajit is used in twenty Sastric formulations and twenty-four proprietary drugs for extraneous indications. Even-though, there is a long history of use of shilajit in traditional Indian materia medica, shilajit unfortunately lacks scientific evaluation and systematic documentation. In vivo antioxidant activity of shilajit has been studied at an irrelevant dose and without using a positive control. The immuno-modulatory activity does not stand the test of critical assessment and currently may be considered as unproven. CONCLUSION: Based on the earlier studies, the bioactivity of shilajit lacks substantial evidence. Nevertheless, further studies are imperative to overcome the lacuna in establishing the antioxidant property of shilajit and more specific assays are needed to vouch shilajit as an immuno-modulator which may be of use to establish its rasayana potential.

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Isoproterenol is a synthetic catecholamine found to cause toxicity leading to severe stress in the myocardium of experimental animals. The aim of the present study is to evaluate the cardioprotective effect of Cymbopogon citratus, which is used as a culinary item and commonly known as lemon grass (LG), in isoproterenol-induced cardiotoxicity. Male Wistar albino rats were segregated into five different groups as follows. Groups I and II rats were treated with vehicle. Groups III and IV rats were treated with 100 and 200 mg/kg b.wt. of LG. Group V with 100 mg/kg b.wt. of vitamin E. Myocardial necrosis was induced in Groups II, III, IV and V on 58(th) and 59(th) day using isoproterenol at a dose of 85 mg/kg twice at 24-hour interval. Animals were sacrificed on the 60( th) day. LG pretreatment exhibited cardioprotective activity as evidenced by decreased activity of cardiac markers in serum and increased the same in heart homogenate (p < 0.05). LG administration decreased the toxic events of lipid peroxidation (TBARS) in both serum and heart tissue, by increasing the level of enzymatic antioxidants and non-enzymatic antioxidants significantly in both heart homogenate and serum sample (p < 0.05). The histopathological observations also revealed that the cardioprotective effect of LG extract was observed at a dose of 200 mg/kg b.wt. The results of the present study reveal that LG is cardioprotective and antilipid peroxidative by increasing various antioxidants at a dose of 200 mg/kg b.wt., which is comparable with that of vitamin E.

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