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An essential oil from Senecio atacamensis Phil. (Asteraceae) was obtained by hydrodistillation of its aerial parts (leaves and stems) and its composition was determined by GC and GC/MS analysis. The identification by GC of the essential oil components, in both leaves and stems respectively, showed α-terpinene (36.05% and 20.57%); α-phellandrene (27.79% and 25.37%), and p-cymene (11.85% and 22.55%) as the most abundant monoterpenes. Furthermore, the oil was tested for its antimicrobial activity using paper disc diffusion and the dilution broth method, exhibiting moderate inhibition of human pathogenic bacteria.

Parastrephia lepidophylla, family Asteraceae, has ancient use in traditional medicine in the region of Tarapacá, Chile. Bioguided fractionation of extracts of this plant was undertaken in the search for compounds with analgesic and antioxidant activity. Two benzofuran derivatives were isolated as the major components of this plant, identified as tremetone 1 and methoxytremetone 6. Remarkably, neither of these showed antioxidant activity, but tremetone 1 exhibited a morphine-like analgesic property. Reduction of this analgesic effect by naloxone suggests a direct effect on opiate receptors as a possible signaling pathway. However, both the low diffusion across lipid membranes (PAMPA assay) and the lipophilicity (Log P) shown by tremetone 1 make elusive the mechanism explaining its induced analgesia.

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