The essential oil and methanol extract of northwestern Argentina medicinal plant Xenophyllum poposum, collected in Catamarca province, were investigated. GC and GC-MS analyses of the essential oil identified 56 compounds accounting for 92.9%. The main components of the oil were -cadinene (16.5%), 6-hydroxytremetone (14.7%), epi--cadinol (12.0%), -cadinol (8.8%), -cadinene (7.5%), 1-epi-cubenol (4.2%) and -muurolene (3.0%). The essential oil exhibited antibacterial activities against five pathogenic strains as well as antifungal activities against two pathogenic fungi. The methanol extract showed antibacterial activity against two strains of Staphylococcus aureus and two pathogenic fungal strains. The main components isolated from the methanol extract were the antifungal 4-hydroxy-3-(isopenten-2-yl)-acetophenone, 6-hydroxytremetone, and tremetone. 6-Hydroxytremetone showed activity against all the fungal strains and one of the S. aureus strains assayed. Antioxidant and radical-scavenging properties of the methanol extract and essential oil were determined using the 2,2'-diphenyl-1-picrylhydrazyl assay and β-carotene bleaching (BCB) test. The methanol extract and the essential oil showed, respectively, moderate and weak antioxidant activity when compared to butylated hydroxytoluene.

A new phenolic derivative, 2,8-dihydroxy-7H-furo[2,3-f]chromen-7-one (1), together with isoquercitrin (2), was isolated from the aerial parts of Tibouchina paratropica. Compound structures were elucidated by spectroscopic methods. Both compounds show antimicrobial activity towards a panel of bacterial and fungal pathogens, and compound 1 displayed potent anti-parasitic activity against Leishmania donovani (IC50  = 0.809 µg/mL). In addition, an 85% reduction in the secretion of the pro-inflammatory cytokine IL-6 was recorded when macrophages challenged with lipopolysaccharide were exposed to compound 1, but no effect on the anti-inflammatory IL-10 was observed. Compound 2 showed neither anti-parasitic nor anti-inflammatory properties. In addition, no cytotoxic activities were observed against the human-derived macrophage THP-1 cells.

High resolution X-ray powder diffraction has been used to obtain the crystal structure of sideroxylin ( 4H-1-Benzopyran-4-one,5-hydroxy-2-(4-hydroxyphenyl)-7-methoxy-6,8-dimethyl) monohydrate, (C18H16O5).H2O, isolated from the bioactive ethyl acetate extract of Miconia ioneura Griseb (Melastomataceae) leaves. The crystal structure was determined using direct space methodology based on the simulated annealing algorithm. Thermogravimetric analysis shows that the material dehydrates while heated from room temperature to ~150°C.