C: Food Chemistry Comparative Antioxidant and Antiproliferative Activities of Red and White Pitayas and Their Correlation with Flavonoid and Polyphenol Content HyoenJi Kim, ∗ Hyung-Kyoon Choi, ∗ Jeong Yong Moon, Young Suk Kim, Ashik Mosaddik, and Somi Kim Cho Abstract: Pitaya, commonly known as dragon fruit, has generated considerable consumer interest because of its attractive color and micronutrient content. The present study investigated the total polyphenol and flavonoid content, antioxidant activity against various free radicals, and antiproliferative effect on several cancer cell lines of extracts of flesh and peel of white and red pitayas, collected from Jeju Island, Korea. The total polyphenol and flavonoid contents of 80% methanol extracts of red pitaya peel (RPP) and white pitaya peel (WPP) were approximately 3- and 5-fold higher than those of red pitaya flesh (RPF) and white pitaya flesh (WPF), respectively. Overall, the total flavonoid and polyphenol contents of these extracts were RPP>WPP>RPF>WPF and WPP>RPP>RPF>WPF, respectively. In addition, a study involving nontargeted high-performance liquid chromatography coupled with a photodiode array and electrospray ionization mass spectrometry (HPLC–PDA-ESI-MS) of different pitaya extracts indicated the presence of phenolic, hydroxycinnamic acid derivatives, flavonol glycosides, betacyanin, and its derivatives with a few unknown compounds. Separately, peel extracts of both red and white pitayas showed higher 2,2-diphenyl-1-picrylhydrazyl, hydroxyl, and alkyl radical-scavenging activity than did the corresponding flesh extracts. Both peel extracts also showed stronger antiproliferative activity against AGS and MCF-7 cancer cells than either flesh extract. There was a direct correlation between the phenolic content and antioxidant effect, but no correlation observed between antioxidant activity and antiproliferative activity. These results suggest that the peel of white and red pitaya may be a valuable ingredient in foods and may also be useful in cosmetic, nutraceutical, and pharmaceutical applications. Keywords: antioxidant, antiproliferative activity, flavonoid, pitaya, polyphenol Introduction Consumer concerns about the safety of synthetic antioxidants have increased the demand for natural alternatives (Shahidi 1997). Many experiments have reported the antioxidant properties of fruit juices and pulps from edible fruits (Mokbel and Hashinaga 2006). The antioxidant activity of fruits is noteworthy, since fruits are rich in compounds that have important roles in free radical scavenging. Numerous other studies also have reported that fresh products, including apples (Wolfe and others 2003), grape seeds (Chidambara-Murthy and others 2002), strawberries (Meyers and others 2003), common vegetables (Chu and others 2002), and raspberries (Liu and others 2002), produced antiproliferative ef- fects. However, limited information is available on the medicinal MS 20100484 Submitted 5/5/2010, Accepted 9/27/2010. Authors Kim, Moon, Mosaddik, and Cho are with Faculty of Biotechnology, College of Applied Life Sci- ences, Jeju Natl. Univ., Jeju 690-756, Republic of Korea. Author Choi is with College of Pharmacy, Chung-Ang Univ., Seoul 156-756, Republic of Korea. Author Kim is with Dept. of Food Science and Technology, Ewha Womans Univ., Seoul 120-750, Republic of Korea. Author Cho is with The Research Inst. for Subtropical Agriculture and Biotechnology, Jeju Natl. Univ., Jeju 690-756, Republic of Ko- rea. Authors Mosaddik and Cho are with Subtropical Horticulture Research Inst., Jeju Natl. Univ., Jeju 690-756, Republic of Korea. Direct inquiries to author Cho (E-mail: phd.kim.somi@gmail.com, somikim@jejunu.ac.kr). ∗ These authors equally contributed to this work. and nutritional value of subtropical fruits, especially the more ex- otic species. Pitaya is mentioned in historical documents as being a popular fruit with the Aztecs Native to tropical forest regions of Mex- ico and Central and South America (Mizrahi and others 1997). On the basis of their skin and pulp colors, pitaya species have been classified as white (Hylocereus undatus [Howorth] Britton & Rose), red (H. costaricensis [F.A.C Weber] Britton & Rose), and yellow (Selenicereus megalanthus [F.A.C Weber] Britton & Rose) (Nerd and others 2002; Hoa and others 2006). Pitaya fruits have recently drawn much attention, not only because of their strik- ing color and economic value as food products, but also for their health properties (Li and others 2003; Chen and He 2007). For example, red pitaya was reported to offer many health benefits including chemoprevention of cancer, anti-inflammatory and an- tidiabetic effects, and a reduction in the mortality risk of car- diovascular disease (Stintzing and others 2002; Cos and others 2004), as well as antioxidative properties conferred by its beta- cyanin content (Wybranice and Mizrahi 2002). Asmah and others (2008) reported that the flesh of H. polyrhizus (red pitaya) and H. undatus (white pitaya) are both rich in polyphenols. However, only ethanol extract of red pitaya flesh (RPF) displays promising antioxidant and antiproliferative effects against HeLa cells. In ad- dition, red pitaya has shown cytotoxicity to human oral cancer cell metastases induced by B16F10 melanoma cells (Menon and C  2010 Institute of Food Technologists R  C38 Journal of Food Science  Vol. 76, Nr. 1, 2011 doi: 10.1111/j.1750-3841.2010.01908.x Further reproduction without permission is prohibited