Antioxidant Capacity of Tea and Common Vegetables

TLDR

Previous studies have shown that certain fruits possess high antioxidant activities. This study reports the antioxidant activities of 22 common vegetables, green tea, and black tea using the automated oxygen radical absorbance capacity assay with peroxyl, hydroxyl, and Cu²⁺ reactive species. The antioxidant activities were measured by the automated oxygen radical absorbance capacity assay employing peroxyl, hydroxyl, and Cu²⁺ reactive species. Garlic exhibited the highest peroxyl radical antioxidant activity (19.4 µmol Trolox/g), followed by kale, spinach, and others, while kale had the highest hydroxyl radical activity; green and black teas surpassed all vegetables in peroxyl activity but displayed prooxidant activity in the presence of Cu²⁺, unlike the vegetables. Keywords: antioxidant, free radical, tea, vegetable.

Abstract

Previously, some fruits were shown to contain high antioxidant activities. In this paper, we report the antioxidant activities of 22 common vegetables, one green tea, and one black tea measured using the automated oxygen radical absorbance capacity assay with three different reactive species: a peroxyl radical generator, a hydroxyl radical generator, and Cu2+, a transition metal. Based on the fresh weight of the vegetable, garlic had the highest antioxidant activity (μmol of Trolox equiv/g) against peroxyl radicals (19.4) followed by kale (17.7), spinach (12.6), Brussels sprouts, alfalfa sprouts, broccoli flowers, beets, red bell pepper, onion, corn, eggplant (9.8−3.9), cauliflower, potato, sweet potato, cabbage, leaf lettuce, string bean, carrot, yellow squash, iceberg lettuce, celery, and cucumber (3.8−0.5); kale had the highest antioxidant activity against hydroxyl radicals followed by Brussels sprouts, alfalfa sprouts, beets, spinach, broccoli flowers, and the others. The green and black teas had much higher antioxidant activities against peroxyl radicals than all these vegetables. However, the tea also showed a prooxidant activity in the presence of Cu2+, which was not found with any of the vegetables studied. Keywords: Antioxidant; free radical; tea; vegetable