Antimicrobial Activities of the Henna Extract and Some Synthetic Naphthoquinones Derivatives

Abstract

Naphthoquinones are compounds widely distributed in the environment, both as natural products and as pharmaceutical agents. They have been the subject of much research due to their pharmacological activities. In this study, methanol extract of henna and a series of synthesized structural analogue of lawsone have been assessed for their antimicrobial activities. Methanol extract of henna and eight naphthoquinones derivatives were tested as potential antimicrobial agents against twelve bacteria and three Candida species using the agar disc diffusion and broth microdilution methods according to guidelines recommended by the Clinical and Laboratory Standards Institute. Besides 2b and 3b, methanol extract and all the synthesized compounds 1a, 2a, 1b and 1c, 2c and 3c showed weakto-strong activity against at least one tested strain. However, the compounds 1c and 1b were found to have the most effective activity against pathogenic bacteria and displayed an activity 8 to 64 fold higher than that othe structural analogue, lawsone. Their MICs ranged from 8-64 µg ml -1. Henna extract was found to have an interesting activity. Our results indicate an effective in vitro activity of 1,4-naphthoquinone derivatives and suggest the benefits of further studies for its application in antibiotherapy