Total Phenolic and Flavonoid Contents and Antioxidant Activities of Two Raphanus sativus L. cultivars (Cherry Belle and Valentine)

Raphanus sativus L., a small-sized red radish, is an important root vegetable crop found worldwide and is commonly used in salads. The objective of this study was to measure the total phenolic and flavonoid content as well as to evaluate the antioxidant activity of the ethanol extract of Raphanus sativus L. cv. Cherry Belle and Raphanus sativus L. cv. Valentine. The total phenolic content and the flavonoid and anthocyanin contents were measured using the Folin-Ciocalteu reagent and aluminum chloride methods, respectively. The total phenolic content in the ethanol extracts of R. sativus L. cv. Cherry Belle was more (160.38 ± 5.0 mg GA/g) than that in R. sativus L. cv. Valentine (124.46 ± 6.13 mg GA/g), while the concentration of total flavonoids in R. sativus L. cv. Valentine was higher than that in R. sativus L. cv. Cherry Belle (42.93 ± 1.58 mg rutin/g and 16.26 ± 1.84 mg rutin/g, respectively). We also evaluated the antioxidant activity of the ethanol extracts of the two cultivars using the (1,1-diphenyl-2-picrylhydrazyl) (DPPH) and superoxide dismutase (SOD) assays; R. sativus L. cv. (Valentine) showed 18.71 ± 0.58% DPPH activity at 800 μg/mL of ethanol extract, and Cherry Belle showed a lower, but significant activity of 15.43 ± 1.25%. No SOD activity was found in either of the cultivars. Our findings indicate that the antioxidant activities of the phenolic and flavonoid contents in the ethanol extracts of the two cultivars depend on the concentration of these compounds in the extracts. Moreover, the flavonoids showed higher antioxidant activity than the phenols, suggesting that the Valentine radish cultivar showed higher antioxidant activity than Cherry Belle owing to its high content of flavonoids.