Lemon (Citrus limon L.): Antioxidative Activity and Its Marker Compound

Abstract

This study aimed to investigate the antioxidative activity of the lemon peel and flesh, analyze the relationship of total phenolic content (TPC) and total flavonoid content (TFC) also their correlation with the antioxidative activity, along with the identification and quantification of the marker. The TPC and TFC were evaluated by the colorimetric method. The antioxidative activity was determined using DPPH (2,2-diphenyl-1picrylhydrazil) and CUPRAC (Cupric ion Reducing Antioxidant Capacity). The correlation between TPC and TFC with antioxidative activity and a correlation between two measures was analyzed using Pearson's method. HPLC performed the identification and quantification of the marker (high-performance liquid chromatography). The AAI (Antioxidant activity index) in the DPPH method had a range of 1.388–14.923 and the CUPRAC method 0.112-0.784. The highest TPC and TFC were given by the peel’s ethanolic extract (1.52 ± 0.02 g GAE/100 g) and n-hexane extract oh the flesh (3.02 ± 0.20 g QE/100 g), respectively. A positive and significant correlation was found between the TPC in lemon peel extract and the AAI using DPPH. The DPPH and CUPRAC methods did not give linear results to the antioxidative activity of lemon peel and flesh. Luteolin 7-O-glucoside was confirmed as a marker compound, and its content was 0.0238% in ethanolic extract of lemon flesh.