Nutritionally Important Pro-Health Active Ingredients and Antioxidant Properties of Fruits and Fruit Juice of Selected Biennial Fruiting Rubus idaeus L. Cultivars

Abstract

Raspberry fruits are an important source of many biologically active chemical compounds exerting nutritional and pro-health effects. The study presents a comparative analysis of nutritionally important bioactive chemical compounds—polyphenols; flavonoids, including anthocyanins; vitamin C; amino acids; fatty acids; and primary metabolites—contained in the fruits of three biennial fruiting cultivars, R. idaeus ‘Glen Ample’, ‘Laszka’, and ‘Radziejowa’, i.e., common cultivars in Poland and Europe. The antioxidant activity of fresh fruits and juice was determined with five methods. The analyses revealed the strong free radical scavenging potential of the fruits and juice, confirmed by the high concentration of nutrients, e.g., polyphenols, anthocyanins, vitamin C, amino acids, and fatty acids. The antioxidant activity of the juice determined with the ferric reducing antioxidant power (FRAP) and OH radical methods was from 2.5 to 4.0 times higher than that of the fruits. The following orders of total polyphenol contents were established in the analyzed cultivars: ‘Glen Ample’ < ‘Laszka’ < ‘Radziejowa’ in the fruits and ‘Glen Ample’ < ‘Radziejowa’ < ‘Laszka’ in the juice. The highest antioxidant activity was exhibited by the ‘Radziejowa’ fruits. Given their high content of dietary fiber, the fruits of the analyzed raspberry cultivars can be consumed by dieting subjects. The concentrations of vitamin C (28–34 mg/100 g) and anthocyanins (20–34 mg/100 g) indicate the biological and pharmacological activity of these fruits. The main unsaturated fatty acids in the fruits were gamma-linoleic acid (C18:2n6c) and alpha-linolenic acid (C18:3n3), which neutralize excess free radicals. The amino acids nutritionally essential to humans were dominated by leucine, arginine, and phenylalanine. This is the first comparative analysis of the antioxidant activity of fruits and juice and the contents of selected active compounds in the fruits of biennial fruiting cultivars of R. idaeus, i.e., a highly commercialized crop in Europe.