Macrofilaricidal activity of the plant Plumbago indica/rosea in vitro

The macrofilaricidal property of the plant, Plumbago indica/rosea, was investigated in vitro against Setaria digitata, a filarial parasite of cattle. Adult worms were incubated in a medium containing crude extract at concentrations 0.05, 0.04, 0.02, and 0.01 mg mL−1 for various incubation periods of 30 min, 1 h, 2 h, and 6 h, respectively, at 37°C and the worm motility was compared with that of solvent control worms kept in drug-free medium. Complete inhibition of motility was observed for concentrations ranging from 0.02 to 0.05 mg mL−1, whereas in the control all the worms were active. Bioassay-guided fractionation of the crude extract by silica gel column chromatography resulted in the identification of a very active fraction. The activity of this fraction against adult worms was further confirmed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide–formazan colorimetric assay, which gave >50% inhibition for the active fraction at concentrations 0.05, 0.002, 0.005, and 0.0006 mg mL−1 at 30 min, 1 h, 2 h, and 6 h incubation periods, respectively. The physical and chemical data obtained from melting point determination, thin-layer chromatography and high-performance liquid chromatography analysis and IR, 1HNMR, 13CNMR, and gas chromatography-mass spectrometry spectral analysis have indicated the chemical structure of the active molecule as 5-hydroxy-2-methyl-1,4-naphthalenedione (plumbagin). Drug Dev. Res. 56:33–39, 2002. © 2002 Wiley-Liss, Inc.