The determination of phenolic and flavonoid contents in Thunbergia laurifolia extracts and their DPPH radical scavenging activities

Phenolic and flavonoid contents as well as 1,1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging effects of Thunbergia laurifolia leaf extracts obtained from different extraction conditions were determined. The leaves were extracted using decoction with various temperatures and extraction period. Total phenolic and total flavonoid contents of the extracts were quantitatively analyzed using UV Folin-Ciocalteu and aluminium chloride spectrophotometric methods, respectively. The extracts were investigated for free-radical-scavenging activity using the DPPH scavenging assay. Total phenolic and flavonoid contents of the extracts ranged from 1.80 to 2.85g. gallic acid equivalent per 100g. dried powder and from 0.76 to 0.96g. rutin equivalent per 100g. dried powder, respectively. The leaves extracted at 100°C for 4 hrs. showed the strongest free radical scavenging activity with the highest contents of phenolic and flavonoid. Phytochemical analysis of the extracts by thin-layer chromatography revealed some phenolic compounds with the major constituent corresponding to caffeic acid.