Comparison of free radical scavenging activity of Siamese neem tree (Azadirachta indica A. Juss var. siamensis Valeton) leaf extracts prepared by different methods of extraction.

OBJECTIVE The aim of this study was to investigate the antioxidant activity of the aqueous extracts of leaves of Siamese neem tree (Azadirachta indica A. Juss var. siamensis Valeton) from several extracting and drying methods using 2,2-diphenyl-1-picrylhydrazyl (DPPH)-scavenging assay. MATERIALS AND METHODS The leaves of Siamese neem tree were extracted using percolation, decoction, maceration, soxhlet extraction, freeze drying or spray drying methods. The extract was tested for antioxidant activity using DPPH-scavenging assay. Thin-layer chromatography of the extract from decoction was also investigated. RESULTS The freeze drying method gave the highest yield (51.50%, w/w) of crude extract, while decoction gave the most effective DPPH-scavenging activity (EC(50): 31.4 microg/ml). Thin-layer chromatography analysis was used to screen the leaf extract obtained using decoction, and the chromatogram showed spots corresponding to quercetin and rutin flavonoids which exhibited antioxidant activities (EC(50): 2.29 and 34.67 microg/ml, respectively). CONCLUSION Siamese neem tree leaf extracts possessed free radical scavenging activity against the DPPH radical. The most active extract was obtained with the leaf decoction method. It showed antioxidant activity with EC(50) of 31.4 microg/ml.