Comparative Investigation of the Antimicrobial Properties of the Root, Leaf, and Seed Oils of Carrot Plant Growing in Sierra Leone

Abstract

Abstract Daucus carota L. (Carrot) is a biennial herbaceous plant which has various nutritional, cosmetic, and medicinal benefits. This study determined the antimicrobial activity of the oil extract from the leaves, roots, and seeds of carrot plants against four selected bacterial isolates. The leaves, roots, and seeds of the carrot plant were weighed and the oils were extracted by hydrodistillation using the Clevenger apparatus. The antimicrobial susceptibility testing was performed by disc and well diffusion methods against Streptococcus pneumoniae, Staphylococcus aureus, Salmonella typhi, and Pseudomonas aeruginosa. Nigella sativa oil was used as the positive control. The extraction process of essential oils from the part of the carrot plants yielded varying quantities of oil, spanning from the roots (0.3%), the leaves (0.4%) and the seeds (0.8%). The results of the study showed that all the extracted essential oils had some activity against the selected bacterial isolates, with varying degrees of inhibition. The root oil showed the highest antimicrobial activity (14mm) against Streptococcus Pneumoniae, matching the control oil using the well diffusion method and a higher activity (17mm) than the control when the disc diffusion method was used. The seed oil had the highest activity (15mm) against Pseudomonas aeruginosa, which is slightly less than the control oil using the disc diffusion method. The zones of inhibition were generally higher by the disc diffusion method than the well diffusion method for most of the isolates. The essential oils extracted from Daucus carota L. oils had antimicrobial activity against the four bacterial isolates used, with higher activity against gram-positive bacteria than gram-negative. The antimicrobial activity varied according to the extracted plant parts, the bacterial isolate and the susceptibility test methods used.