Comparison of antioxidant activity and tyrosinase inhibition in fresh and processed white radish, garlic and ginger

Abstract

In Thailand, there is a diversity of vegetables and fruits due to the country’s tropical rain forest ecological system. White radish (Raphanus sativus), garlic (Allium sativum) and ginger (Zingiber officinale) are consumed on a daily basis, in both raw and processed forms. They are popular for cooking and preservation, e.g., pickling. The objectives of this study are to compare antioxidant activities, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), total flavonoid and phenolic contents, as well as tyrosinase inhibition in fresh and processed vegetables. Data were collected in three representative markets in Bangkok. The results showed that DPPH in fresh ginger was 80.90 ± 5.70 % and white radish was 84.99 ± 11.39 % in processed form. The highest value of ABTS test was 48.30 ± 8.38 % in fresh garlic and 109.39 ± 4.34 % in processed ginger. The highest value for total flavonoid contents in garlic was 8.85 ± 1.08 and 2.26 ± 0.88 mg/100g in fresh and processed samples respectively, while the total phenolic contents of garlic were 1.76 ± 0.33 and 19.48 ± 5.51 mg/100g for the fresh and processed samples respectively. The highest tyrosinase inhibitory activity was 363.71 ± 58.75 % in fresh ginger and 151.42 ± 15.12 % in processed garlic. Thus, the studied vegetables have shown some advantages for a daily diet, as they are a rich source of phytochemicals.