Abstract
Betalains are plant pigments, consisting of red betacyanins and yellow betaxanthins. Distribution of betalains is limited in Caryophyllales except for Caryophyllaceae and Molluginaceae, and betalains and anthocyanins are mutually exclusive. It has been reported that flavonoids including anthocyanins have antioxidant functions in plant. However, the physiological role of betalains in plant is not clear. Here we examined betalains as antioxidant agents to elucidate their functionality.
Two major betalains, beet betaxanthin(BBx) and beet betacyanin(BBc), were isolated from red beet(Beta vulgaris L.). Both BBx and BBc were rapidly bleached by the addition of peroxynitrite(ONOO-). This bleaching reaction was dependent on concentration of ONOO-, while suppressed by glutathione, a well-known ONOO- scavenger. These results indicated that betalains have an ability to quench ONOO-. In this present study, we also discuss antioxidant activity of betalains against reactive oxygen species.
