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pelagiaresearchlibrary.com Pelagia Research Library Advances in Applied Science Research, 2011,

2 (3): 418-425 ISSN: 0976-8610 CODEN (USA): AASRFC

418 Pelagia Research Library Antioxidant properties of two species of Hylocereus fruits Wee Sim Choo* and Wee Khing Yong School of Science, Monash University Sunway Campus, Jalan Lagoon Selatan,

46150 Bandar Sunway, Selangor, Malaysia. ABSTRACT 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. Keywords: dragon fruit, pitaya fruit, anti-radical power, chelating activity. INTRODUCTION Hylocereus polyrhizus (red dragon fruit) and Hylocereus undatus (white dragon fruit) are fruits belong to the vine cacti from the subfamily Cactoideae of the tribe Cacteae [1,2]. There are about

16 species of Hylocereus in Central America and Mexico [3]. Varieties of Hylocereus guatemalensis, Hylocereus polyrhizus and Hylocereus undatus as well as hybrids of these three species are grown commercially worldwide. H. undatus has white pulp with pink skin, H. polyrhizus has red pulp with pink skin while Selenicereus megalanthus has white pulp with yellow skin [4]. The pulp is delicate and juicy and contains numerous small soft seeds. The fruits are covered with bracts or scales'

, hence the name dragon fruit [5]. These edible fruits are also mostly known as pitaya or pitahaya, which means the the scaly fruit in Latin America [1]. Red dragon fruit weighs up to

1 kg and is a rich source of nutrients and minerals such as vitamin B1, vitamin B2, vitamin B3 and vitamin C, protein, fat, carbohydrate, crude fiber, flavonoid, Wee Sim Choo et al Adv. Appl. Sci. Res., 2011,

2 (3): 418-425

419 Pelagia Research Library thiamin, niacin, pyridoxine, kobalamin, glucose, phenolic, betacyanins, polyphenol, carotene, phosphorus, iron and phytoalbumin [6,7]. It is also rich in phytoalbumins which are highly valued for their antioxidant properties [8]. The most important fruit pigments in red dragon fruit are the betalains such as the betacyanins and betaxanthins [9,10]. Betalains are used as natural food colorants in various areas of the food industry [11]. Dragon fruit plants are grown in the open in tropical areas but must be protected from intense solar radiation and subfreezing temperatures when cultivated under subtropical conditions [12]. This fruit is being cultivated on a large scale in Malaysia [13] and grown commercially in Nicaragua, Columbia, Vietnam, Israel, Australia and U.S. [14]. The pulp of H. polyrhizus is used for the production of red-violet colored ice cream in Israel [1]. In Malaysia, the fruit of H. polyrhizus (peel and pulp) is sometimes used to produce juice but when eaten as a fruit, the consumers usually discard the peel. H. polyrhizus fetches higher price than H. undatus in Malaysia due to consumers'