The antifungal activity of essential oils as determined by different screening methods

The existing methods for studying the antimicrobial activity of essential oils (e.g. the dilution of the test substances in broth or agar medium) are not adequate to evaluate the effects of the volatile components. Growth inhibition of fungi by various essential oils was determined by direct contact in broth and agar media and compared with the fungistatic action of their vapors using the micro-atmosphere method. Tests were performed on eight cellulolytic mold strains that often contaminate archive and museum reserves. Thirty-seven essential oils were screened to find the most antifungal ones with potential to be employed as atmospheric preservatives. Chenopodium ambrosioides L. var. anthelminticum, Cymbopogon martinii (Roxb.) W. Watson var, martinii, Cymbopogon nardus (L.) W. Watson var. nardus, Syzygium aromaticum (L.) Merr. et L.. M. Ferry and Pimenta racemosa (Mill.) J.W. Moore were the most active essential oils on the eight strains tested according to direct contact methods. C. martinii was inhibitory even after 12 days of incubation. Using the microatmosphere method, C. nardus and C. martinii volatiles were the most fungistatic, but the vapors of Ch. ambrosioides, S. aromaticum and P. racemosa gave moderate results with a specific short effect of P. racemosa.