摘要：Antioxidant characteristics of ginger roots, guava leaves, guava seeds, orange peel, sesame coat, rice bran and wheat germ as affected by ethanol, ethyl acetate, chloroform, hexane and petroleum ether were evaluated. Petroleum ether extract of ginger roots, ethanol extracts of guava leaves, guava seeds, orange peel and sesame coat and ethyl acetate extracts of rice bran and wheat germ appeared to possess higher antioxidant activity than those from other solvents. Ginger roots, orange peel and guava leaves exhibited higher antioxidant activity than that of α-tocopherol, while guava seeds, sesame coat, rice bran and wheat germ had lower antioxidant activity than that of α-tocopherol. Guava leaves extract had the highest total phenolics content among the other plant material extracts followed by ginger roots, sesame coat and orange peel extracts. However, total flavonoids content was the highest in ginger roots extract followed by guava leaves extract. Ferulic was the highest phenolic compounds in guava leaves and sesame coat extracts. However, chlorogenic acid was the highest phenolic compounds in ginger roots extract. Antioxidants in ginger roots, guava leaves and sesame coat extracts as well as α-tocopherol were heat stable with 73.1, 73.8, 66.7 and 71.6% activity, respectively, after heating at 100°C for 180 min. Induction periods of sunflower oil containing 2% guava leaves and 2% ginger roots extracts were increased by 230.6% and 226.7%, respectively. However, induction period of sunflower oil containing sesame coat was increased by 174.1%, at 0.5% concentration. Similar increment was found for the protection factor. Ginger roots, guava leaves and sesame coat might be promising sources of natural antioxidant to be used in food products.
