Review

Naturally occurring saponins: Chemistry and biology

J. S. Negi1*, P. S. Negi2, G. J. Pant2, M. S. M. Rawat2, S. K. Negi3

Abstract

Naturally occurring saponins are glycosides of steroids, alkaloids and triterpenoids. They are widely distributed in nature and reported to be present in 500 genera of plants. A wide variety of plants belonging to family Liliaceae, Dioscoreaceae, Solanaceae, Sapindaceae and Agavaceae are the major source of saponins. They are amorphous substances having high molecular weight and are soluble in water and alcohol to produce foam but organic solvents inhibit their foaming property. Plants saponins are generally extracted into butanol through liquid-liquid partition and separated through column chromatography using silica gel as adsorbent and chloroform: methanol as mobile phase. HPLC, GC, Sephadex LH-20 Chromatography, DCCC, preparative paper chromatography and TLC were also used for the separation and isolation of saponins. The structures of saponins were determined by several spectroscopic techniques, viz., UV, IR, 1H NMR, 13C NMR and Mass spectroscopy. Saponins possess several biological activities such as antioxidant, immunostimulant, antihepatotoxic, antibacterial, anticarcinogenic, antidiarrheal, antiulcerogenic, antioxytoxic, antihypoglycemic, anticytotoxic and antimolluscicidal. Saponins are biologically synthesized by C5 isoprene units through cytosolic mevalonate pathway. 2,3-Oxidosqualene gives -amyrin or triterpenoid skeletons on cyclization through isoprenoid pathway. The triterpenoid backbone then undergoes various modifications to form saponins.

Key words: Saponin, triterpenoid, isoprene, aglycone.

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