Anatomical and histochemical investigations of Sphagneticola trilobata (L.) Pruski, Asteraceae, secretory structures in leaves and stems and the seasonal variation of essential oils were carried out. Histochemical techniques enabled the specific location of the essential oil accumulation in the internal (canals) and external structures (trichomes). Histochemical analysis showed that the secretory trichomes produced steroids. The highest yield was obtained from plants collected in winter, when it was registered low temperature and precipitation. The essential oil was characterized by high percentage of hydrocarbon sesquiterpenes, hydrocarbon monoterpenes and low levels of oxygenated sesquiterpenes. The major components were germacrene D (11.9-35.8%), α-phellandrene (1.4-28.5%), α-pinene (7.3-23.8%), E-caryophyllene (4.6-19.0%), bicyclogermacrene (6.0-17.0%), limonene (1.8-15.1%) and α-humulene (4.0-11.6%). The percentage of most of the individual constituents present in S. trilobata essential oil changed significantly during the months.

Volatile oils from the leaves of Verbenaceae species Aloysia virgata, Lantana camara, Lantana trifolia, Lantana montevidensis, Lippia brasiliensis and Lippia sericea were investigated for its chemical composition and antibacterial activity. The volatile oils were characterized by a high content of sesquiterpenes of which (E)-caryophyllene (10-35%), germacrene-D (5-46%) and bicyclogermacrene (7-17%) were the major components for all studied species. For the flowers, a higher concentration of monoterpenes was observed for the species L. camara, L. trifolia and L. brasiliensis. These compounds probably act as attractive to specific pollinators. The volatile oils from A. virgata was the most active, exhibiting moderate antimicrobial activity against the bacteria Staphylococcus aureus, Bacillus cereus and Escherichia coli.

The essential oils of seven Myrtaceae species were investigated for its chemical composition and antibacterial activity. The volatile oils were characterized by a high content of monoterpenoids of which 1,8-cineole (88.0, 65.0 and 77.0% for Melaleuca hypericifolia, Callistemon viminalis and Callistemon citrinus respectively), terpinen-4-ol (47.0 and 49.8% for Melaleuca thymifolia and Callistemon polandii respectively) and α-pinene (54.5% for Kunzea ericoides) were the major components. The oil from M. linariifolia was characterized by a high concentration of methyleugenol (87.2%). The oil from Melaleuca thymifolia was the most active, exhibiting high antimicrobial activity against all tested bacteria.

Considering the broad spectrum of biological activity of gamma-butyrolactone derivatives, we presented the synthesis of 3,4-dihalo-5-arylidenefuran-2(5H)-ones (17-21) and analogues (24-28) of the natural product nostoclide (7,8). Furanones 17-21 were synthesized from the condensation of aromatic aldehydes with lactones 14 and 15, that were obtained from mucobromic and mucochloric acids. Lactone 15 was converted into the intermediate 23 in 36% overall yield. Compound 23 was then transformed into the nostoclide analogues 24-28. Some of the compounds prepared showed antimicrobial activities against Escherichia coli, Staphylococcus aureus and Bacillus cereus comparable to commercial antibiotics.