Antibacterial and antiviral naphthazarins from Maharanga bicolor

Abstract

Maharanga bicolor, Boraginaceae, is used in the Nepalese ethnomedicine for the treatment of several diseases. In the course of screening investigations the dichloromethane extract of the roots of Maharanga bicolor was found to inhibit the growth of gram positive bacteria. Bio-assay directed fractionation led to the isolation of five active naphthazarins, deoxyalkannin (1), alkannin (2), acetylalkannin (3), alkannin beta-hydroxyisovalerate (4) and alkannin beta-acetoxyisovalerate (5). Compounds 2-5 showed antibacterial activity against multi resistant human pathogenic Staphylococcus and Enterococcus species and 1, 4 and 5 showed antiviral activity against herpes simplex virus type-1.