Characterization of antioxidants from Detarium microcarpum Guill. et Perr. leaves using HPLC-DAD coupled with pre-column DPPH assay

Detarium microcarpum is an African tree which is widely used as a folk medicine and food. A methanol extract from the leaves as well as its hexane, dichloromethane, ethyl acetate and n-butanol fractions were evaluated for their total phenolic content and radical scavenging activities. Additionally, a pre-column DPPH-HPLC assay was performed to screen and identify the compounds responsible for the antioxidant properties of the extract. Results indicated that the methanol extract contained a substantial amount of phenolic compounds with a value of 51.7 +/- 0.2 mg gallic acid equivalent/g. It also exerted potent radical scavenging activities in both DPPH and ORAC assays, with respective values of 937 +/- 16 and 2247 +/- 63 mu mol trolox equivalent/g. Its ethyl acetate and n-butanol fractions were shown to possess the highest TPC and radical scavenging activities. Pre-column DPPH-HPLC experiments led to the direct detection of five potential radical scavenging compounds which were identified as gallic acid, quercetin 3,7-O-dirhamnoside, myricetin 3-O-rhamnoside, quercetin 3-O-glucoside and quercetin 3-O-rhamnoside. All of them were confirmed to exert potent radical scavenging activities using common DPPH spectrophotometric assay. These findings revealed that D. microcarpum leaves possess potent antioxidant activity and could be recommended as a nutraceutical resource. Additionally, the identified bioactive compounds can be considered as appropriate markers for quality control.