No abstract

The present study aimed to evaluate possible variations in the chemical composition and antimicrobial activity of essential oils extracted from Piper marginatum leaves obtained by hydrodistillation at pH4, pH7, and pH10. When compared, the chemical profiles of the three oils were different. A reduction of major phenylpropanoids Z-asarone, dillapiole, and E-asarone was observed for samples pH4-EO and pH10-EO as compared to sample pH7- EO. Sesquiterpenes macrocarpene (10.8%), viridiflorene (9.1%), caryophyllene (7.7%), and E-nerolidol (6.5%) were the major compounds identified in the pH10-EO sample. Compound α-santonin (36.1%) was identified as a major constituent of the essential oil obtained at pH4. The antimicrobial activity of the essential oils also showed variations in their minimum inhibitory concentration values (MIC). The oil obtained at pH4 exhibited strong activity with an MIC of 78.1 µg/ml for both Escherichia coli and Candida utilis microorganisms. We evidenced the influence of water pH on the chemical composition of essential oils obtained by hydrodistillation, as well as its importance as a parameter in studies using the hydrodistillation method.