Composition of essential oil of sweet flag (Acorus calamus L.) leaves at different growing phases

The essential oil composition of Acorus calamus (sweet flag) leaves collected in Lithuania at different growing phases was examined by GC and GC/MS. Rhizome oils of A. calamus, having been more thoroughly investigated, were used for comparison purposes. The content of the oil in dried sweet flag rhizomes was 1.20+/-0.12% and in the leaves, depending on the vegetation phase, was from 0.56-1.01%. Ninety-one constituents were positively or tentatively identified in the oils-66 in the leaves and 55 in the rhizomes. Possible formation of calacorene hydrates is suggested for the first time on the basis of mass spectral data. P-Asarone [(Z)-asarone] was the major constituent in the leaves (27.4-45.5%), whereas acorenone was dominant in the rhizomes (20.86%) followed by isocalamendiol (12.75%). A higher content of some aliphatic and oxygenated monoterpenes was found in oils of the leaves at their earliest growth phase (May), while the beta-asarone content was at its lowest level.