Abstract
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.
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