Antioxidant Capacities, Phenolic Compounds, Carotenoids, and Vitamin C Contents of Nectarine, Peach, and Plum Cultivars from California MARI ÄA I. GIL, ² FRANCISCO A. TOMA Ä S-BARBERA Ä N, ² BETTY HESS-PIERCE, ‡ AND ADEL A. KADER* ,‡ Department of Pomology, University of California, Davis, California 95616, and Department of Food Science and Technology, CEBAS (CSIC), P.O. Box 4195, Murcia 30080, Spain Genotypic variation in composition and antioxidant activity was evaluated using 25 cultivars, 5 each of white-flesh nectarines, yellow-flesh nectarines, white-flesh peaches, yellow-flesh peaches, and plums, at the ripe (ready-to-eat) stage. The ranges of total ascorbic acid (vitamin C) (in mg/100 g of fresh weight) were 5-14 (white-flesh nectarines), 6-8 (yellow-flesh nectarines), 6-9 (white-flesh peaches), 4-13 (yellow-flesh peaches), and 3-10 (plums). Total carotenoids concentrations (in µg/100 g of fresh weight) were 7-14 (white-flesh nectarines), 80-186 (yellow-flesh nectarines), 7-20 (white-flesh peaches), 71-210 (yellow-flesh peaches), and 70-260 (plums). Total phenolics (in mg/100 g of fresh weight) were 14-102 (white-flesh nectarines), 18-54 (yellow-flesh nectarines), 28-111 (white-flesh peaches), 21-61 (yellow-flesh peaches), and 42-109 (plums). The contributions of phenolic compounds to antioxidant activity were much greater than those of vitamin C and carotenoids. There was a strong correlation (0.93-0.96) between total phenolics and antioxidant activity of nectarines, peaches, and plums. KEYWORDS: Stone fruit; Prunus persica; Prunus salicina; Rosaceae; phenolics; ascorbic acid; -carotene; free radical scavenging activity INTRODUCTION Epidemiological studies have shown that consumption of fruit, vegetables, and derived food products have health benefits against chronic diseases including cardiovascular disease and certain types of cancer (1-4). The health-promoting properties of fruits and vegetables are due to the presence of some vitamins (A, C, E, and folates), dietary fiber, and nonessential phy- tochemicals in these food products. Among phytochemicals, polyphenols deserve a special mention due to their free radical scavenging activities and in vivo biological activities that are being investigated by many researchers (4-8). In the past few years there has been a renewed interest in studying and quantifying the phenolic metabolites of fruits and vegetables due to their health-promoting properties. Fruit polyphenols include a wide range of compounds with antioxi- dant activity, that is, hydroxycinnamates, flavan-3-ols (con- densed tannins), gallic acid derivatives (hydrolyzable tannins), flavonols, and anthocyanins. The phenolic composition of fruits varies greatly among cultivars. In a previous paper (9) we identified and quantified individual phenolic constituents of 25 California-grown cultivars of peaches, nectarines, and plums using a high-performance liquid chromatograph with a photo- diode detector (HPLC-DAD) and high-performance liquid chromatography-electronspray ioniziation-mass spectrometry (HPLC-ESI-MS) methods. Peel tissues contain larger amounts of phenolics, anthocyanins, and flavonols than flesh tissues. Similar phenolic profiles were detected for both nectarines and peaches, and no differences were found between white-flesh and yellow-flesh cultivars. The evaluation of fruit antioxidant capacity is not an easy task, as many methods can be used to determine this activity, and substrates, conditions, analytical methods, and concentra- tions can affect the estimated activity (10). We used two simple methods to evaluate the free radical scavenging capacity (DPPH method) (11) and the iron-reducing capacity (FRAP method) (12) of the fruit extracts, although we understand that these simple methods have some limitations (10). The aim of the present work was to determine the phenolic, carotenoid, and vitamin C contents plus the antioxidant capacity of ripe fruits of stone fruit cultivars. Both peel (skin) and flesh tissues were studied to estimate the relative contribution of these tissues to the nutritional value of nectarines peaches, and plums. MATERIALS AND METHODS Fruits. All fruits used were harvested at the “California mature” stage based on skin color and obtained from packinghouses in the Fresno area of California between June 2 and September 7, 1999, and * Corresponding author [telephone (530) 752-0909; fax (530) 752-8502; e-mail aakader@ucdavis.edu]. ² Department of Food Science and Technology, CEBAS (CSIC). ‡ Department of Pomology, University of California, Davis. 4976 J. Agric. Food Chem. 2002, 50, 4976-4982 10.1021/jf020136b CCC: $22.00 © 2002 American Chemical Society Published on Web 07/17/2002