Abstract
The aim of this study was to identify pigments present in the red dragon fruit ( Hylocereus polyrhizus ) and to further investigate the antioxidant properties in this fruit. Pigment was identified using the High Performance Liquid Chromatography (HPLC) and results confirmed the presence of betanin in sample at a retention time of 11.5 min which corresponded to the retention time of the betanin standard used. In the antioxidant properties determination, there were 86.10 mg of total polyphenolic compound in 0.50 g of dried dragon fruit extract using the total polyphenol assay which expresses gallic acid as equivalent. The reducing power assay further confirmed the antioxidant activity present in dragon fruit where the reducing capability increased from 0.18 to 2.37 with the increase of dry weight sample from 0.03 to 0.5 g. The Vanillin-HCl assay which measures the amount of condensed tannin showed that the dried dragon fruit sample had an equivalent of 2.30 mg catechin/g. The DPPH• radical scavenging activity determination showed that the effective concentration (EC50) for dragon fruit was 2.90 mM vitamin C equivalents/g dried extract.
Highlights
Hylocereus polyrhizus which originated from Latin America is a member in the Cactaceae family (Stintzing et al, 2002)
Cai et al (2003) reported that the structureactivity relationships of various betacyanins and betaxanthins exhibited free radical scavenging capacities which further contribute to the elevation of interest in H. polyrhizus to be a source of antioxidant
Results obtained from this study identified the presence of betanin in H. polyrhizus and as the main contributing pigment in the deep purple coloured pulp
Summary
Hylocereus polyrhizus which originated from Latin America is a member in the Cactaceae family (Stintzing et al, 2002). The deep purple colour of the pulp is contributed by a set of pigments known as the betalains which are nitrogen-containing pigments (Wyler and Dreiding, 1957; Harivaindaran et al, 2008), made up of the red-violet. According to Stintzing et al (2002) and Wybraniec and Mizrahi (2002), dragon fruits are totally devoid of betaxanthins and there are at least seven identified betacyanins in the Hylocereus genus namely: betanin, isobetanin, lhyllocactin, isophyllocactin, betanidin, isobetanidin and bougainvillein-R-I where all have identical absorption spectra that contribute to the deep purple coloured pulp. The objectives of this study are to identify the pigment present in the dragon fruit and to determine the antioxidant capabilities using selected antioxidant assays
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