Chemical constituents and antimicrobial activity of a traditional herbal medicine containing garlic and black cumin

Abstract

A combination of crushed garlic (Allium sativum) and black cumin seeds (Nigelia sativum) has been used as a traditional remedy for urinary tract infections. In-vitro antimicrobial testing suggested that the mixture of two spices in the ratio of 1:1 has antimicrobial effects on both Staphylococcus aureus and Escherichia coli species. Analyses of the extract of garlic and black cumin by GC-MS as well as LC–MS & MSP2P confirmed that the main components of garlic were allicin, γ-glutamyl-S-allylcysteine and allicin transformed products such as diallyldisulfide and vinyldithiins. Components of black cumin were thymoquinone, p-cymene, p-tert-butylcatechol, and pinene. Isolated samples of allicin by preparative HPLC from garlic extract and reference samples of diallyldisulfide and thymoquinone were tested individually and in combination for their antimicrobial activities against S. aureus and E. coli. All of these compounds showed modest antimicrobial effects individually (except diallyldisulfide against E. coli) and in combination.