Browsing by Author "V. Saravanan"

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A plausible chemical mechanism of the bioactivities of mangiferin
(1996) Shibnath Ghosal; Gangadhara Rao; V. Saravanan; Nira Misra; Dipak Rana
A plausible chemical mechanism of the observed bioactivities of mangiferin, a naturally occurring C-glucosylxanthone (1), is depicted. The mechanism focuses its capacity to provide cellular protection as an antioxidant and a radical captodative agent. Mangiferin performs its antioxidant function at different levels of systemic oxidation sequence. As far as membrane lipid peroxidation and consequent immunomodulations are concerned, it acts by (i) decreasing localized O2 concentration there-by generating, in concert, mangiferin phenoxy radicals (2); (ii) by binding metal ions (Fe2+/3+) in forms 3 and 4 that will not allow the generation of such tissue damaging species as hydroxyl and highly reactive oxo-ferryl radicals; (iii) regulating polymer chain lengthening (membrane lipids) by interacting with the reactive oxygen species; (iv) chain breaking (by 2), i.e. scavanging intermediate radicals (such as lipid peroxy and alkoxy radicals) to prevent continued H abstraction from cellular lipid molecules; and (v) maintaining systemic oxidant-antioxidant balance (by 1 and 2). Chemical evidence in support of the above postulate has been sought and obtained in the form of a complex polymer (5) through the intermediates 2 to 4.
The chemistry and action of 6-alkylsalicylates of Indian Ginkgo biloba
(1997) S. Ghosal; R. Sundaram; A.V. Muruganandam; S.K. Singh; K.S. Satyan; S.K. Bhattacharya; V. Saravanan; N. Mishra
Five 6-alkyl (n-tridecyl-, n-pentadecyl-, n-heptadecyl-, n-pentadecenyl- and n-heptadecenyl-) salicylates 1a-e, in free and conjugated (esters, phospholipids) forms, constituting one of the largest classes of bioactive metabolites have been isolated from the leaves and fruits of ten Ginkgo biloba trees of different ages (3-80 years) and indigenous occurrence. These compounds have been characterized by comprehensive chromatographic-spectroscopic analyses (HPTLC, HPLC, GC-MS, 1H NMR), chemical transformation, and by direct comparison of some of them with authentic markers. Selective anti-oxidative (lipoxygenase modulatory), free radical captodative (0OH, 0SO3- ), and anti-allergic and anti-inflammatory screening of the total IGb extract and of 1a-e have been conducted. Our findings suggest a significant contribution of the 6-alkylsalicylates towards the elixir effect of Ginkgo, contrary to an earlier apprehension that ginkgolic acids (equivalent to 6-alkylsalicylates) might cause allergic manifestations in recipients and, therefore, that they should be removed from Ginkgo formulations.