Calycopterin, a major flavonoid from Marcetia latifolia, modulates virulence-related traits in Pseudomonas aeruginosa.

Although bacterial resistance is a worldwide growing concern, the development of bacteriostatic and bactericidal drugs has been decreasing in the last decade. Compounds that modulate the microorganism virulence, without killing it, have been considered promising alternatives to combat bacterial infections. However, most signaling pathways that regulate virulence are complex and not completely understood. The rich chemical diversity of natural products offers a good starting point to identify key compounds that shed some light on this matter. Therefore, we investigated the role of Marcetia latifolia ethanolic extract, as well as its major constituent, calycopterin (5,4'-dihydroxy-3,6,7,8-tetramethoxylflavone), in the regulation of virulence-related phenotypes of Pseudomonas aeruginosa. Our results show that calycopterin inhibits pyocyanin production (EC50 = 32 µM), reduces motility and increases biofilm formation in a dose-dependent manner. Such biological profile suggests that calycopterin modulates targets that may act upstream the quorum sensing regulators and points to its utility as a chemical probe to further investigate P. aeruginosa transition from planktonic to sessile lifestyle.

In vitro acaricide activity of Ocotea aciphylla (Nees) Mez. (Lauraceae) extracts and identification of the compounds from the active fractions.

The in vitro acaricide activity of hexane, ethyl acetate and ethanol extracts of Ocotea aciphylla leaves was investigated by means of an immersion tests using Rhipicephalus (Boophilus) microplus engorged females and larvae. All extracts were shown effective against the different stages of the parasite, and the ethanol extract (50mg/mL concentration) was the most active (more than 90% efficacy in both assays). The ethanolic extract was fractionated using column chromatography with silica gel as stationary phase to furnish several fractions that were tested against larvae of R. (B.) microplus. Three fractions showed high acaricidal activity (50mg/mL), causing between 84.2% and 100% mortality of the larvae. The anticholinesterase effect of these fractions was determined spectrophotometrically using a microtiter assay. The chemical investigation of the active fractions led to the characterization of terpenoids (cadalene 1 and squalene 2), a phenylpropanoid (dillapiole 3) and a phenolic mixture containing five proanthocyanidins (4-8) and a flavonoid(vitexin-2"-O-rhamnoside 9). Our findings suggest that the O. aciphylla has potent acaricidal activity in vitro against R. (B.) microplus, and that different secondary metabolites are responsible for this effect.