Investigation of total phenolic contents, antioxidant activities and analyses of active compounds in some sweet peppers (Capsicum annuum L.)

Abstract

This work focused on the investigation of total phenolic contents, antioxidant activities and analyses of active compounds in red, yellow and green sweet peppers (Capsicum annuum L.). All crude extracts were extracted from dried samples preparing from two different methods; an oven-dried technique (at 70??C) and a freeze-dried technique. Antioxidant activities of all crude extracts were investigated using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method, while total phenolic compounds were determined via the Folin-Ciocalteu Colorimetric method. It was found that antioxidant activities and total phenolic contents of all crude extracts from freeze-dried samples were better or higher than those from oven baked samples. Yellow sweet pepper crude extracts showed the best antioxidant activity (IC₅₀ = 304.44 ppm) and highest contents of total phenolic compounds (74.58 mg/g of crude extract). Analyses of active compounds such as phenolic and flavonoid compounds in all crude extracts were carried out via a high performance liquid chromatography (HPLC) technique. ??The results showed that five active compounds including caffeic acid, p-coumaric acid, feruilc acid, luteolin and quercetin were present in all crude extracts preparing from freeze dried samples. In the case of crude extracts preparing from oven baked samples, four active compounds including p-coumaric acid, feruic acid, luteolin and quercetin were detected in yellow sweet pepper crude extracts, while quercetin was not detected in red and green sweet pepper crude extracts.