Antioxidant and antimicrobial activity of flowers of Wendlandia thyrsoidea, Olea dioica, Lagerstroemia speciosa and Bombax malabaricum

Flowers of higher plants have been used for centuries for several purposes such as medicine, food and garnishing food in many parts of the world. In the present study, we have determined the antioxidant and antimicrobial activity of methanol extract of flowers of Wendlandia thyrsoidea (Roemer & Schultes) Steudel (Rubiaceae), Olea dioica Roxb. (Oleaceae), Lagerstroemia speciosa L. (Lythraceae) and Bombax malabaricum DC. (Bombacaceae). Antioxidant efficacy of various concentrations of flower extracts was evaluated by DPPH free radical scavenging assay and Ferric reducing assay. Antimicrobial activity was determined against four bacteria and two fungi by agar well diffusion method. Total phenolic and flavonoid contents were determined by Folin-Ciocalteau reagent and Aluminium chloride colorimetric estimation methods respectively. The DPPH free radical scavenging effect of flower extracts was concentration dependent and was higher in case of extract of L. speciosa followed by W. thyrsoidea, B. malabaricum and O. dioica. In ferric reducing assay, it was shown that the absorbance of reaction mixture at 700nm increased on increasing the concentrations of flower extracts indicating reducing power of extracts. The reducing ability was also highest in L. speciosa extract. Extract of L. speciosa displayed marked inhibitory activity against bacteria and fungi than other flower extracts. Gram positive bacteria have shown more susceptibility than Gram negative bacteria. Among fungi, C. neoformans was more inhibited than C. albicans. Extracts of B. malabaricum and O. dioica were not effective against C. albicans. The phenolic and flavonoid contents were higher in L. speciosa and O. dioica respectively. A positive correlation has been observed between total phenolic content of flower extracts and antioxidant and antimicrobial activity. The flowers can be employed as a remedy for treatment of infectious diseases and oxidative damage. Further, isolation of active components from flower extracts and their biological activity determinations are under progress.