Microwave-Assisted Hydrodistillation of Essential Oil from Plectranthus amboinicus : Evaluation of Its Antifungal Effect and Chemical Composition.

Fusarium wilt, a vascular syndrome in a wide range of plants, is caused by the pathogen Fusarium Oxysporum . The objective of this investigation was to evaluate the antifungal effect of four essential oils (EOs) ( Plectranthus amboinicus , Syzygium aromaticum , Lippia alba , and Rosmarinus officinalis ), which were obtained by using microwave-assisted hydrodistillation (MAH), against F. oxysporum . The yield obtained from P. amboinicus with the use of MAH was 0.2%, which was higher than that of a conventional extraction; its extraction time was also shorter. For concentrations of 100 and 300 μL/L, P. amboinicus caused an inhibition rate of 27.2 and 55.7%, respectively, while S. aromaticum caused an inhibition rate of 23.1 and 87.3%, respectively. It was observed that increasing the concentration also increased the % inhibition rate. The extracts of L. alba and R. officinalis caused an inhibition rate of 14.5 and 14.7% at 500 µL/L, respectively, at 10 days of incubation, while at this concentration, P. amboinicus and S. aromaticum achieved 100%. The major chemical compounds of P. amboinicus were carvacrol (41.20%), o-cymene (11.61%), caryophyllene (11.45%), α-bergamotene (7.71%), and caryophyllene oxide (4.62%), and these monoterpene hydrocarbons were responsible for the biological activity. The essential oil of P. amboinicus in appropriate concentrations is a potent antifungal agent that could be used for the control of F. oxysporum .