Antioxidant compounds from four Opuntia cactus pear fruit varieties

Abstract

The antioxidant compounds in extracts from four cactus ( Opuntia species) fruit varieties were investigated. Conjugated flavonoids (quercetin, kaempferol and isorhamnetin), ascorbic acid, and carotenoids were isolated from the extracts. Quercetin was the most abundant in all varieties [ O. ficus-indica (green-skinned), O. lindheimeri (purple-skinned), O. streptacantha (red-skinned), and O. stricta var. stricta (yellow-skinned)] examined. Kaempferol was found in green-skinned, purple-skinned and red-skinned varieties and isorhamnetin in green-skinned and purple-skinned varieties. The red-skinned fruits contained the most ascorbic acid (815 μg/g fw) and the yellow-skinned fruits the most carotenoids (23.7 μg/g fw). The antioxidant activity of the fruit extracts was stronger in the purple-skinned than other varieties. This result was consistent with total flavonoid content of the purple-skinned fruits. Thus, antioxidant capacity of cactus fruits may be attributed to their flavonoid, ascorbic acid and carotenoid contents. The data indicate that cactus fruits are a rich source of natural antioxidants for foods.