The chemistry and action of 6-alkylsalicylates of Indian Ginkgo biloba

Abstract

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.