Comparison of chemical composition and antibacterial activity of Nigella sativa seed essential oils obtained by different extraction methods.
Nigella sativa L. seed essential oils obtained by hydrodistillation (HD), dry steam distillation (SD), steam distillation of crude oils obtained by solvent extraction (SE-SD), and supercritical fluid extraction (SFE-SD) were tested for their antibacterial activities, using the broth microdilution method and subsequently analyzed by gas chromatography and gas chromatography-mass spectrometry. The results showed that the essential oils tested differed markedly in their chemical compositions and antimicrobial activities. The oils obtained by HD and SD were dominated by p-cymene, whereas the major constituent identified in both volatile fractions obtained by SD of extracted oils was thymoquinone (ranging between 0.36 and 0.38 g/ml, whereas in oils obtained by HD and SD, it constituted only 0.03 and 0.05 g/ml, respectively). Both oils distilled directly from seeds showed lower antimicrobial activity (MICs > or = 256 and 32 microg/ml for HD and SD, respectively) than those obtained by SE-SD and SFE-SD (MICs > or = 4 microg/ml). All oil samples were significantly more active against gram-positive than against gram-negative bacteria. Thymoquinone exhibited potent growth-inhibiting activity against gram-positive bacteria, with MICs ranging from 8 to 64 microg/ml.
Kokoska
L
L
Department of Crop Sciences and Agroforestry, Institute of Tropics and Subtropics, Czech University of Life Sciences Prague, Kamycka 129, 165 21 Prague 6-Suchdol, Czech Republic. kokoska@its.czu.cz
Havlik
J
J
Valterova
I
I
Sovova
H
H
Sajfrtova
M
M
Jankovska
I
I
D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D002849:Chromatography, Gas; D015169:Colony Count, Microbial; D019652:Extraction and Processing Industry / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D008826:Microbial Sensitivity Tests; D031881:Nigella sativa / Q000737:chemistry*; D009822:Oils, Volatile / Q000737:chemistry / Q000494:pharmacology; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D012639:Seeds / Q000737:chemistry
D000900:Anti-Bacterial Agents; D009822:Oils, Volatile; D010936:Plant Extracts