RESUMEN
Aims: To establish and optimize the in vitro antioxidant activity of methanolic extract of flower of C. guianensis at different developmental stages. Place and Duration of Study: Plant Physiology and Pharmacognosy Research Laboratory, Department of Botany, University of North Bengal, Siliguri, between December 2010 and November 2011. Methodology: The antioxidant activities of methanolic extracts of C. guianensis flower of different developmental stages were investigated spectrophotometrically against DPPH, ABTS, H2O2, NO, superoxide, hydroxyl radical and lipid peroxidation, along with ferric reducing power, metal chelating and β-carotene bleaching assay were performed. Total phenols, flavonoids and ortho-dihydric phenols were also determined by folin-ciocalteu, aluminium chloride and Arnow's reagent based standard methods respectively. Results: The methanolic extract of floral stage-I was found to possess higher level of phenolic content, flavonoids as well as ortho-dihydric phenol content. The younger floral stages, stage-I and stage-II were observed with highly potential free radical scavenging activity, while stage-III showed highest degradation rate for β-carotene bleaching assay and stage-IV showed highest anti-lipid per oxidation activity against thiobarbituric acid. Conclusion: The results demonstrated that the early floral stage showed the highest polyphenolic content and best antioxidant activity, therefore the early stages of this flower is suggested as the best harvest stage for medicinal purposes. Further studies are required for the isolation of active principles responsible for its antioxidant activity.