In vitro antimicrobial activity of Alpinia zerumbet and A. purpurata nonpolar fraction of leaf extract

This study aimed to evaluate the in vitro antimicrobial activity of fractions of leaf hydroalcoholic crude extracts: hexane, dichloromethane, ethyl acetate and butanolic of Alpinia zerumbet and A. purpurata by the agar drop diffusion method in order to screen the main compounds involved in antimicrobial activity. Leaves of A. zerumbet (Pers.) B.L. Burtt et R.M. Sm. and A. purpurata (Vieill) K. Schum adult plants were collected and then dried and macerated in 70% ethanol. Leaf extracts were further partitioned using solvents in increasing polarity. Dichloromethane fractions were analyzed by gas chromatography/mass spectrometry (GC/MS). The major compound in the dichloromethane fraction of both species was the hexadecanoic acid (palmitic acid). By drop diffusion assay, the antimicrobial activity of crude extract, as well as fractions of hexane, dichloromethane, ethyl acetate and butanolic, was evaluated against pathogenic bacteria and fungi. No bacteria were inhibited. However, the dichloromethane fraction exhibited promising antifungal activity against the following fungi tested: Cryptococcus neoformans, Fonsecaea pedrosoi, Trichophytoon rubrum, Microsporium canis and M. gypseum.