Cyclooxygenase inhibitory and antioxidant compounds from crabapple fruits

Crabapple trees belong to the Malus genus (Rosaceae) and bear fruits that are sparingly consumed and used in the preparation of fruit beverages. Cyclooxygenase (COX) enzyme inhibitory and antioxidant bioassay-guided fractionation of the aqueous and methanol extracts of Malus x kornicensis and Malus x Indian Summer yielded (+)-catechin (1), (-)-epicatechin (2), cyanidin-3-O-beta-galactopyranoside (3), and amygdalin (4). Pure compounds 1-4 were obtained by HPLC, identified by LC-ES/MS, CD, and NMR spectroscopic methods and evaluated for their COX enzyme inhibitory and antioxidant activities. In COX-1 and -2 enzyme inhibitory assays, compounds 1-3 (all at 80 microM) showed activities of 20.4, 46.3%; 57.6, 47.9%; and 8.2, 13.7%, respectively, compared to naproxen (54.3, 41.3%; 10 microM), ibuprofen (47.5, 39.8%; 10 microM), Celebrex (46.2, 66.3%; 1.67 ppm), and Vioxx (23.8, 88.1%, 1.67 ppm). In the antioxidant assay, the catechins (1-2) and anthocyanin (3) (all at 40 microM) showed activities of 61.3, 62.5, and 60.1%, respectively. The synthetic antioxidants, tert-butylhydroquinone (TBHQ), butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and vitamin E (all tested at 10 microM), gave 75.2, 80.1, 70.0, and 10.2% activities, respectively. The cyanogenic glycoside, amygdalin (4), and its hydrolysis products, mandelonitrile (5) and benzaldehyde (6), were not active in the antioxidant or COX enzyme inhibitory assays at 80 microM concentrations.