Changes in the composition of the leaf oil from Baccharis punctulata D.C. specimens from Argentina depend on the different stages of the plant through the year

ABSTRACT The leaf oil from Baccharis punctulata D.C. specimens from Argentina, analyzed by GC and GC/MS during a one-year phenological cycle, showed important changes. In spring and summer, during the stem and floral bud development, the percentages of amorpha-4,7(11)-diene, amorpha-4-en-7-ol, amorpha-4,7-diene-11-ol and amorpha-4,7(11)-dien-8-one increased, while the percentage of verboccidentafuran decreased (c.a. 50% to 10%). The percentage of the guaiane alismol, which was negligible in other months, also increased (19.1–24.8 %). Alismol structure was spectroscopically established. Interesting, when buds opened, alismol percentage fell, so pre- and full-flowering oil composition resulted very different. Germacra-1(10),5-dien-4α-ol (16.7–23.0 %), verboccidentafuran (16.1–18.4%) and elemane-type sesquiterpenes were main components at flowering. Germacra-1(10),5-dien-4α-ol may have the adequate configuration and conformation to be biosynthetically related to alismol. Finally, germacra-1(10),5-dien-4α-ol and elemene derivative percentages decreased. Verboccidentafuran (27.6–52.4%) was the main compound in winter. These cyclic changes appear to be associated with the phenological stages of the plant during the year.