chemical compositions and antimicrobial activities of ocimum sanctum l. essential oils at different harvest stages

background essential oils (eos) possess antibacterial properties and represent a natural source to treat infections and prevent food spoilage. their chemical composition might be affected by the environmental condition and the developmental growth stages of the plant. objectives the current study aimed to determine the variations in chemical compositions and antimicrobial activities of the eos of ocimum sanctum l. at different stages of harvesting. materials and methods the oils constituents were analyzed by gas chromatography/mass spectrometry (gc/ms). the effects of three different harvest stages of o. sanctum eos against most common causes of food-borne were evaluated by broth micro-dilution method as recommended by the clinical and laboratory standards institute (clsi). results the analysis of the eos indicated that eugenol was the major compound of the eos at all developmental stages which reached its maximum level at the second stage. the results showed that the tested eos exhibited antimicrobial activities against all of the examined pathogens at concentrations of 0.125-32 µl/ml, except pseudomonas aeruginosa which was only inhibited by high concentrations of the floral budding and full flowering eos. eo distilled from the second developmental growth stage (floral budding) of o. sanctum exhibited the strongest antibacterial activities against the food borne bacteria. conclusions considering the wide range of antimicrobial activities of the examined eos, they might have the potential to be used to manage infectious diseases or extend the shelf life of food products.