Helenalin- und 11,13-Dihydrohelenalinester aus Blüten vonArnica montana*

Abstract
From the flowers of Arnica montana L. 13 helenanolides were isolated and identified. They are shown to be 11,13-dihydrohelenalin (1), helenalin (2) and their ester derivatives 3-13 (see figure). The natural occurence of 6-O-isobutyryl-, 6-O-tigloyl-, 6-O-isovaleryl- and 6-O-(2-methyl)-butyrylhelenalin (compounds 9, 11, 12, 13) is reported for the first time. The qualitative sesquiterpene lactone composition in flowers of A. montana from different regions was found to be variable.