Volatile constituents of Acorus calamus and their antimicrobial activity

The use of Acorus calamus (common name sweet flag) has a long history in traditional and folk medicine in Lithuania, where for example, the leaves are still used in baking bread. In this study, the composition of essential oils in leaves and rhizomes for different accessions of A. calamus was analysed using GC and GC-MS. In the leaf oils, phenolic compounds [(Z)-asarone (15.7-25.5%) and (Z)-methyl isoeugenol (2.0-4.9%)] dominated. The rhizome oils were characterized primarily by the oxygenated sesquiterpenes [shyobunone isomers (14.8-27.8%) and acorenones (9.6-21.4%)]. (Z)asarone was also detected in the rhizomes, but in considerably lower amounts (4.3-9.6%) than in the leaf oils. Multivariate analysis of the quantitative composition of essential oils indicated considerable variation among accessions in oil composition. In our samples, the P-asarone content of A. calamus indicated that triploids prevail in Lithuania, similar to other European countries. Antimicrobial activity of the essential oils was evaluated in vitro against three bacteria, four yeasts and ten fungal species obtained from the culture collection Institute of Botany, Lithuania. Leaf oils were more active against all microorganisms than rhizome oils. The strongest inhibitory effect was obtained when testing the oils against Mycobacterium sp., Bacillus subtilis, Fusarium avenacium and Rhizomucor pusillus. Antibiotic substances, used as a control, proved to have a higher antimicrobial activity than the essential oils.