Antioxidant properties of cold-pressed black caraway, carrot, cranberry, and hemp seed oils

Abstract

Cold-pressed black caraway, carrot, cranberry, and hemp seed oils were extracted with methanol and evaluated for radical-scavenging activities against ABTS⁺ and DPPH, chelating activity, oxygen radical absorbing capacity (ORAC), and total phenolic contents (TPC). All the oil extracts had significant antioxidant activities. The ORAC value ranged from 28 to 220 μmol TE/g oil for the cold-pressed hemp, carrot, and black caraway seed oils, whereas the ABTS⁺ – scavenging capacity ranged 8.9–30.8 μmol TE/g oil for the four cold-pressed edible seed oils. The greatest TPC, 3.53 mg gallic acid equivalent (GE) per gramme of oil, was detected in the cold-pressed black caraway seed oil extract, while the lowest TPC, 0.44 mg GE/g, was observed in the cold-pressed hemp seed oil extract. In addition, methanol extracts of the cold-pressed black caraway and cranberry seed oils were evaluated for their inhibitory capacities on human LDL oxidation by measuring the reduction of the thiobarbituric acid-reactive substance production (TBARS). Both oil extracts significantly suppressed the lipid peroxidation in human LDL, with TBARS reductions of 2.84 and 3.77 mg/g for cranberry and black caraway seed oil extracts, respectively. These results suggest that cold-pressed black caraway, cranberry, carrot and hemp seed oils may serve as dietary sources of natural antioxidants for health promotion and disease prevention, and the cold-pressed black caraway seed oil may be used as a natural antioxidative food additive for improving food quality and stability.

Introduction

The pathology of numerous chronic diseases, including cancer and heart disease, involves oxidative damage to cellular components. Reactive oxygen species (ROS), capable of causing damage to DNA, have been associated with carcinogenesis, coronary heart disease, and many other health problems related to advancing age (Cadenas and Davies, 2000, Marnett, 2000, Uchida, 2000). Minimizing oxidative damage may well be one of the most important approaches to the primary prevention of these aging-associated diseases and health problems, since antioxidants terminate direct ROS attacks and radical-mediated oxidative reactions, and appear to be of primary importance in the prevention of these diseases and health problems. Antioxidants have been detected in a number of food and agricultural products, including cereal grains, vegetables, fruits, and oil seeds (Burits and Bucar, 2000, Kalt et al., 1999, Yu et al., 2002a, Yu et al., 2002d). Recently, cold-pressed edible seed oils, including black caraway, carrot, hemp, and cranberry seed oils, have become commercially available. Cold-pressed seed oils may retain more natural beneficial components of the seeds, including natural antioxidants, and are free of chemical contamination. The cold-pressing procedure, involves neither heat nor chemical treatments, and is becoming a more interesting substitute for conventional practices because of consumers’ desire for natural and safe food products.

Cold-pressed black caraway, carrot, hemp, cranberry, and black raspberry seed oils have been investigated for their fatty acid composition, oxidative stability and colour characteristics (Parker et al., 2003, Parry and Yu, 2004). α-Linolenic acid accounts for 35%, 22.3% and 19.3% of total fatty acids in the cold-pressed black raspberry, cranberry, and hemp seed oils, respectively, whereas the cold-pressed carrot seed oil contains about 80% oleic acid and is low in total saturated fatty acids (Parker et al., 2003, Parry and Yu, 2004). These facts show the potential health benefits from consuming cold-pressed edible seed oils. Fifty percent acetone extracts of the black raspberry oils exhibit radical-scavenging activities against stable DPPH and cation radical ABTS⁺, and contain 35–93 ppm total phenolic components on a weight basis (Parry & Yu, 2004). In addition, the cold-pressed black caraway seed oil shows excellent oxidative stability compared to commercial soybean and corn oils, suggesting the possible presence of natural antioxidants in the cold-pressed seed oils (Parker et al., 2003). Antioxidants are well recognized for their potential in health promotion and prevention of aging-related diseases, including cancer and heart disease (Yu et al., 2002a). Novel dietary sources of natural antioxidants are desired by consumers and food manufacturers to benefit human health through improving nutrition. Therefore, the present study was conducted to evaluate the antioxidant properties of cold-pressed black caraway, cranberry, carrot, and hemp seed oils to determine their potential application in health promotion and disease prevention against radical mediated oxidative damages.