Revision of the structure of an aristolane sesquiterpene aldehyde isolated from the root of Plectranthus hereroensis and Aristolochia debilis

Abstract From the acetone extract of the root of Plectranthus hereroensis an aristolane sesquiterpene aldehyde has been isolated. This substance was identical to a compound previously isolated from the root of Aristolochia debilis to which the structure of 1(10)-aristolen-12-al was attributed. Now, extensive NMR spectroscopic studies have established that the structure of this substance must be amended to 1(10)-aristolen-13-al. This sesquiterpene showed moderate antimicrobial activity.