In Vitro Sensitivity of Some Mycolic Acid-containing Actinomycetes to Nigella Sativa Extracts

Nigella sativa L. (black seed or cumin) is an herbaceous plant, used for centuries for the treatment of various ailments, including infectious diseases. This study investigates the in vitro effect of extract of N. sativa against representative of mycolic acid containing actinomycetes notably members of the genera Gordonia, Mycobacterium, Nocardia and Rhodococcus. Methanolic and petroleum ether extracts of N. sativa at different concentrations (0.3 mg/ mL, 0.6 mg/ mL, 1.25 mg/ mL, 2.5 mg/ mL and 5 mg/ mL) were used to impregnate filter paper disks. The disks were incorporated onto Diagnostic Sensitivity Test agar, plates inoculated with test strains and incubated aerobically for up to seven days at 37 ℃. Inhibition zones around discs were measured in millimetres. At 0.6 mg/ mL all test strains showed inhibition zones of 1.5 cm except Mycobacterium phlei and R. rhodochrous. Petroleum ether extract was found to be more effective than the methanolic extracts since relatively higher concentrations from the latter were needed to achieve similar inhibitions zones produced by petroleum ether extracts. It be concluded that extracts of N. sativa is a promising candidate for the in vivo application since it is a natural food additive with no reported harmful effect.