Chiang Mai Journal of Science

Peanut skin is by-product of peanut processing, which have extremely low commercial value. Interestingly, they contain phytochemicals that are beneficial to health. In this study, phenolic content and antioxidant capacity of peanut skins from 15 genotypes belonging to 3 peanut types (Spanish, Valencia and Virginia) were determined comparatively. Average values for total phenolics, flavonoids and flavanols of all peanut skins tested were 154.56 ± 29.39, 75.77 ± 14.33 and 37.76 ± 10.44 mg (±)-catechin equivalent per g dry weight, respectively. Virginia peanut skins appeared to have greater phenolic content than others. The greater phenolic content of Virginia peanut skins was associated their greater antioxidant capacity determined by DPPH, ABTS and FRAP assays. Virginia peanut skin extracts also exhibited greater hydrogen peroxide scavenging activity in Human Embryonic Kidney 293 cells. Five phenolic acids, 

p-hydroxybenzoic, vanillic, p-coumaric, ferulic and sinapinic acids, were identified and quantified in peanut skin extracts by HPLC analysis. p-Coumaric acid was the most abundant phenolic acid in all peanut skins tested with the average value of 120.14 ± 51.97 mg per g dry weight.