During an investigation of the sesquiterpene phases and contents in leaves of several Rosa rugosa hybrids (hybrid rugosas), Martin Frobisher and Vanguard were found to accumulate a large amount of (+)-4-epi-alphabisabolol (1) as a single constituent. Although glandular trichomes of Martin Frobisher on the leaves are dense, this R. rugosa hybrid produces none of the carota-1,4dienaldehyde (2) or bisaborosaol A (3) that are both found as representative sesquiterpenes of the carotane and bisabolane classes, respectively, in a glandular trichome exudate of wild-type R. rugosa. Compound 1 was also apparent as a nearly single constituent detectable by GC in the leaf constituents of Vanguard possesses sparse glandular trichomes on the leaf. Martin Frobisher and Vanguard had likely lost their capability to form carotane-type sesquiterpenes and had also lost their activity to oxygenate the C-7 allyl methyl carbon of compound 1 to convert 3. The presence of (+)-4-epi-alphabisabolol-accumulating R. rugosa hybrids is significant when considering the sesquiterpene biogenesis of Rosa rugosa
