Phytochemical investigation and evaluation of antibacterial and antioxidant activities of leaf-bud exudate of Tarenna asiatica (L.) Kuntze ex K. Schum.

Abstract

Tarenna asiatica (L.) Kuntze ex K. Schum. (Magnoliophyta: Rubiaceae) is traditionally used as anthelmintic, antiseptic, antiulcer and to promote suppuration. The leaf-bud exudates collected from the local forests was extracted with benzene by maceration. Preliminary chemical tests were conducted for select secondary metabolites aside isolating the known flavone, corymbosin. Employing the cup-plate method, different concentrations of benzene extract and corymbosin were screened against Bacillus sphaericus, Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus, using streptomycin as the standard drug. The extract evinced a weak to moderate activity against all the strains tested while corymbosin was inactive. The antioxidant activity of the benzene extract was studied by nitric oxide scavenging activity, reduction of DPPH free radical, iron-induced lipid peroxidation and superoxide scavenging activity, with ascorbic acid as the standard drug. The extract was found to be IC50 in the range of 20-60 g/mL in the assays performed.