Antimicrobial and Toxic Effects of Boswellia serrata Roxb. and Mentha piperita Linn. Essential Oils on Vaginal Inhabitants

Commercial essential oils (EOs) of incense, Boswellia serrata Roxb, and mint, Mentha piperita L., were investigated against vaginal bacterial and Candida albicans isolates for antimicrobial potential and safety use. The antimicrobial activity of EOs was investigated through a double-dilution micro-plate assay. A brine shrimp assay was used for the determination of toxicity, while the determination of the chemical composition of EOs was carried out using GS–MS. Obtained minimal inhibitory (MIC) and minimal bactericidal concentration (MBC) point to the activity of mint essential oil (EO) against the multi-resistant P. aeruginosa isolate (MIC/MBC at 6.25 µL/mL), while MIC and MBC values for other isolates were reached at higher concentrations (25–50 µL/mL). According to the toxicity assay, the incense EO reached the LC(50) value at 3.07 µL/mL, while mint EO showed higher toxicity at lower concentrations (0.5 µL/mL) and the LC(50) could not be determined. The highest antimicrobial potential was obtained for incense against P. aeruginosa. Although the toxicity assay showed high toxicity of mint EO to the eggs of aquatic crustaceans Artemia salina, further testing of EO toxicity is proposed, for example on healthy cell-lines. According to the GC/MS spectrometry, the most represented components of mint EO were the oxygenated hydrocarbons L-menthone (20.86%) and menthol (31.86%), and they could be proposed for further antimicrobial and toxicity investigation.