Polyphenol Composition of Plum Selections in Relation to Total Antioxidant Capacity Aidilla Mubarak, †,‡,§ Ewald E. Swinny, ∥ Simon Y. L. Ching, ⊥ Steele R. Jacob, # Kevin Lacey, # Jonathan M. Hodgson, ‡ Kevin D. Croft, ‡, * and Michael J. Considine* ,†,# † School of Plant Biology and the Institute of Agriculture, University of Western Australia, Crawley, Western Australia 6009, Australia ‡ School of Medicine and Pharmacology, University of Western Australia, Medical Research Foundation, Perth, Western Australia 6000, Australia § Faculty of Agrotechnology and Food Science, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia ∥ Investigative Chemistry Laboratory, ChemCentre, Curtin University, Bentley, Western Australia 6845, Australia ⊥ PathWest Laboratory Medicine WA, Queen Elizabeth II Medical Centre, Western Australia 6009, Australia # Department of Agriculture and Food Western Australia, South Perth, Western Australia 6151, Australia ABSTRACT: Dietary polyphenols are associated with protection against chronic diseases such as cardiovascular disease. Pharmacological studies show a range of bioactivities and efficacy attributable to specific polyphenols. While many fruits are rich in polyphenols, wide cultivar variation of polyphenol composition is common. Our objective was to determine the composition of major bioactive polyphenols in 29 prevarietal selections of Western Australian plums, and Black Amber as an evaluation in developing breeding tools to develop fruit that may have enhanced health-promoting capacities. Total phenolics were quantified colorimetrically; selected polyphenols were quantified by HPLC; and the total antioxidant capacity (TAC) was measured by the antioxidant inhibition of oxygen radicals (AIOR) assay. Total phenolic concentration was significantly correlated with TAC (R = 0.95, P < 0.01). Neo-chlorogenic acid and quercetin glycosides were found to be the predominant polyphenols (mean 29.9 mg·kg −1 and 50.7 mg·kg −1 , respectively). No significant correlations were found between the composition of predominant polyphenols in plums and the TAC. We argue that the value of in vitro TAC assays to breeding programs may be limited, and future research should focus on the heritability of known bioactive polyphenols. KEYWORDS: fruits, breeding, total phenolics, plum, antioxidant, flavonoid ■ INTRODUCTION It is widely accepted that dietary intake of fruits and vegetables is inversely related to the incidence of chronic disease, including cardiovascular disease, cancers, obesity, and type II diabetes mellitus. 1 Government and intergovernment agencies have widely promoted consumption of fruits and vegetables to improve health outcomes and reduce the medical burden. Horticultural breeders and marketers have also seen the commercial opportunity in crop improvement. Dietary polyphenols are principal candidates to explain the health-protective effects of fruit, vegetables and beverages derived from them. 2,3 However, the nexus between in vitro bio- activity and food polyphenol composition is still under debate. 4−6 Early research focused on the role of polyphenols in attenuating oxidative damage, as they are an abundant form of antioxidant in the human diet. 7,8 Crude antioxidant activity was evaluated from a wide range of foods 9,10 and found to positively correlate to total phenolic concentration. 11−13 Yet, this is recognized as a simpli- fication, as knowledge of the diverse bioactivities of various polyphenols has vastly advanced over the past decade. 4,5,14 Furthermore, antioxidant activity per se may be altered by metabolism and bioavailability. 15 In addition, the activity of quercetin and (−)-epicatechin to enhance nitric oxide production and reduce endothelin-1 in healthy human subjects is not necessarily related to their antioxidant activity. 16 Evidence for roles in mod- ulating gene expression and cell signaling is rapidly accumulating, e.g., the effect of quercetin on the Nrf2/Keap1 pathway 17,18 and of proanthocyanidins on microRNA expression. 19 Increasingly, investigation of cell signaling or other secondary effects of flavonoids is being applied in clinical trials with whole foods such as apple. 20 Plums are a rich dietary source of polyphenols, are widely consumed, 21 widely available, and a lucrative horticultural crop. 22,23 Predominant polyphenols in plum include the hydroxycinnamic acid derivatives, neo-chlorogenic acid and chlorogenic acid, and the quercetin glycoside rutin. 24−27 Evidence for various bio- activities of chlorogenic acids and quercetin glycosides, in addition to flavan-3-ols, is accumulating. 28−33 However, polyphenol com- position is determined by (plant) genetic, environmental, and cultural influences, and hence varies quantitatively and qualitatively among cultivars of plum and other Rosaceae family fruit. 34,35 Thus, in order to manipulate polyphenol content for dietary benefit, it is important to understand the cultivar variation in polyphenols that have potential health promoting activity. Understanding this would aid the agricultural sector in developing and commercializing plum cultivars of high quality, which meets consumer satisfaction and potentially becomes a prospective dietary approach toward pre- vention and treatment of various diseases. Received: July 5, 2012 Revised: August 31, 2012 Accepted: September 12, 2012 Published: September 12, 2012 Article pubs.acs.org/JAFC © 2012 American Chemical Society 10256 dx.doi.org/10.1021/jf302903k | J. Agric. Food Chem. 2012, 60, 10256−10262