Identification of pigment and its antioxidant activity of several species of Indonesian dragon fruit

Abstract

Dragon fruit has been known as source of betalain pigment. The aims of this study were to identify pigment compound through spectral and TLC analyses and to evaluate its antioxidant activity by DPPH IC50 and FRAP methods on peel and flesh extracts of four Indonesian dragon fruit species or varieties. The identified pigment in new variety of dragon fruit (the orange and yellow peels) was not reported yet. Dragon fruit extract pigments showed a good stability in pH range of 3-10. Spectral and TLC analyses showed that two dragon fruits varieties (the red peels) contained betalains and the other varieties (the orange and yellow peels) consisted anthocyanins. They were characterized by the spectra peaks ranged from λmax 480-490 nm (betaxantin), 530-540 nm (betacyanin) and 580-582 nm (anthocyanin). TLC analysis yielded Rf values ranged from 0.43-0.52 with red-spot chromatogram identical to the betacyanin pigment, while Rf values ranged from 0.51-0.69 and 0.85 with orange, yellow and pink-spot chromatograms were identified as anthocyanins. Betaxantin in dragon fruit extract was in the range of 12.44-92.64 mg indicaxantin Eq/g and betacyanin ranged from 37.50-204.55 mg betanin Eq/g. Dragon fruit extracts had antioxidant activity by DPPH method with IC50 concentration ranged from 0.95-1.97 mg/g extract and could reduce Fe3+ at concentration of 0.02-0.05 mgAAE/g extract. The ratio of pigment (betaxanthin: betacyanin) values ranged from 0.33-0.53 indicated that the proportion of betacyanin was more dominant in influencing the antioxidant activity of dragon fruit extract while evaluated using correlation analysis with DPPH IC50 and FRAP antioxidant activity values.