Identification of phenolic compounds from the aerial parts of Holy basil (Ocimum tenuiflorum) cultivar 'Himalayan Sunset Blue', their anti-oxidant activity, and anthocyanin contribution to colour stability.

Abstract

Two anthocyanins, eight flavones, and four phenolic compounds were isolated from the aerial parts of Holy basil (Ocimum tenuiflorum) cultivar 'Himalayan Sunset Blue'. They were identified as cyanidin 3-O-[(6''″-E-p-coumaroylglucopyranosyl)-(1→4)-(6″-E-p-coumaroylglucopyranoside)]-5-O-(6″'-malonylglucopyranoside) and cyanidin 3-O-[glucopyranosyl-(1→4)-(6″-E-p-coumaroylglucopyranoside]-5-O-(6'″-malonylglucopyranoside) for anthocyanins, apigenin, luteolin, chrysoeriol and their 7-O-glycosides for flavones, and rosmarinic acid, globoidnans A and B, and rabdosiin for phenolic compounds. In this survey, antioxidant activity of selected six compounds was measured. Moreover, two anthocyanins which are main pigments in the sky-blue herb tea 'Tulsi', were dissolved the buffer solutions and were measured their absorption spectra under interval measurement over 8 h. It was suggested that the chain structure of p-coumaric acid and glucose in anthocyanins contributes to stable colour expression.