Antimicrobial with time-kill kinetics, antioxidant, and anticancer properties of Rosmarinus officinalis L. oil extract based on its bioactive components

There is a major clinical problem associated with antimicrobial resistance. Rosmarinus officinalis L. is an effective medicinal source. Its oil has been extracted and tested for its multiple therapeutic capabilities. The oil extract was found to be a broad-spectrum antimicrobial agent against Bacillus subtilis and Staphylococcus aureus as Gram-positive bacteria, Escherichia coli and Klebsiella pneumonia as Gram-negative bacteria, and Candida albicans as the most common pathogenic mold. The minimum inhibitory concentration of the oil extract was found to be 15.6 μg/mL against B. subtilis, S. aureus, and C. albicans, and 62.5 μg/mL and 125 μg/mL against E. coli and K. pneumonia, respectively. The bactericidal activity started at 150 and 180 min against Gram-positive and Gram-negative bacteria, respectively, with clear time-killing kinetics. The oil extract was able to scavenge DPPH free radicals with an IC50 of 4.0 μg/mL. The oil extract was found to have high toxicity on the Caco2 cell line (colon tissue) at high dose 1000 μg/mL with IC50 of 75.39 ± 0.56 μg/mL. The chemical composition of the oil extract was determined employing gas chromatography/mass spectrometry, in which 53 compounds were named at different surface area ratios, retention times, and probability ratios.