RESUMO
Five alkaloids, in addition to hydroxytyrosol and uridine, were isolated from aerial parts of Alternanthera littoralis P. Beauv. Among the isolated compounds, alternamide A was an unusual tricyclic alkaloid with a bridged benzoazepine core. All isolated alkaloids have a catechol moiety, indicating a possible common biosynthetic route. Their structures were established by 1D and 2D NMR spectroscopy in combination with extensive tandem MS experiments by collisional induced dissociation (CID). The antiprotozoal activity of the isolated compounds was assayed against trypomastigote forms of Trypanosoma cruzi and amastigotes of Leishmania amazonensis. Alternamine A was the most active compound, reducing markedly the viability of both parasites. Antioxidant capacities evaluated by ORACFL assay showed that the isolated alkaloids (mainly alternamide B) contributed to the high activity recorded for the ethanolic crude extract; possibly, the catechol moiety present in all structures plays a central role in this result.
Assuntos
Alcaloides/isolamento & purificação , Alcaloides/farmacologia , Amaranthaceae/química , Antioxidantes/isolamento & purificação , Antioxidantes/farmacologia , Antiprotozoários/isolamento & purificação , Antiprotozoários/farmacologia , Alcaloides/química , Antioxidantes/química , Antiprotozoários/química , Brasil , Catecóis/química , Leishmania/efeitos dos fármacos , Ressonância Magnética Nuclear Biomolecular , Trypanosoma cruzi/efeitos dos fármacosRESUMO
The essential oils from leaves, twigs and trunk bark of Onychopetalum amazonicum R.E. Fr. (Annonaceae), obtained by hydrodistillation, were analysed by GC and GC-MS, and also were evaluated for in vitro antimicrobial activity. Forty-one compounds, which correspond to 75.0-92.2% of the oil components, were identified. Major compounds were sesquiterpenes, including (E)-caryophyllene, caryophyllene oxide, spathulenol, α-gurjunene, allo-aromadendrene and α-epi-cadinol. The oils were evaluated for antimicrobial activities against four bacteria strains and five pathogenic fungi. The oil of the trunk bark exhibited good activity against Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 10538 and Kocuria rhizophila ATCC 9341, with a minimal inhibitory concentration of 62.5 µg/mL. The essential oil composition and the antimicrobial evaluation are reported for the first time for the genus Onychopetalum.