Wee Sim Choo and Wee Khing Yong
The antioxidant properties of fruits (peels and pulps) and pulps of two species of Hylocereus, Hylocereus polyrhizus (red dragon fruit) and Hylocereus undatus (white dragon fruit) were investigated. The ascorbic acid and total phenolic contents of pulps were higher than those of fruits (peels and pulps) of the two species of Hylocereus. The anti-radical power measured using 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activity ranked in the following order: pulp of H. undatus » pulp of H. polyrhizus > fruit (peel and pulp) of H. polyrhizus > fruit (peel and pulp) of H. undatus. The ferrous ion chelating activity ranked in the following order: pulp of H. undatus > fruit (peel and pulp) of H. polyrhizus > fruit (peel and pulp) of H. undatus > pulp of H. polyrhizus. Both phenolics and ascorbic acids contributed to the anti-radical power of the two species of Hylocereus fruits but the latter contributed more. By taking into account the free radical scavenging activity and ferrous ion chelating activity, pulp of H. undatus had the highest antioxidant properties.
