Identification of phenolic compounds from the aerial parts of Holy basil ( <i>Ocimum tenuiflorum</i> ) cultivar ‘Himalayan Sunset Blue’, their anti-oxidant activity, and anthocyanin contribution to colour stability

Two anthocyanins, eight flavones, and four phenolic compounds were isolated from the aerial parts of Holy basil (<i>Ocimum tenuiflorum</i>) cultivar 'Himalayan Sunset Blue'. They were identified as cyanidin 3-<i>O</i>-[(6''″-<i>E</i>-<i>p</i>-coumaroylglucopyranosyl)-(1→4)-(6″-<i>E</i>-<i>p</i>-coumaroylglucopyranoside)]-5-<i>O</i>-(6″'-malonylglucopyranoside) and cyanidin 3-<i>O</i>-[glucopyranosyl-(1→4)-(6″-<i>E</i>-<i>p</i>-coumaroylglucopyranoside]-5-<i>O</i>-(6'″-malonylglucopyranoside) for anthocyanins, apigenin, luteolin, chrysoeriol and their 7-<i>O</i>-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 <i>p</i>-coumaric acid and glucose in anthocyanins contributes to stable colour expression.