Structure Elucidation, Antimicrobial and Cytotoxic Activities of a Halimane Isolated from Vellozia kolbekii Alves (Velloziaceae).

A new halimane diterpene was isolated from Vellozia kolbekii Alves (Velloziaceae) and identified as (5R,8R,9S,13R)-halim-1,10-ene-15,16-diol (1). It showed cytotoxicity against three human cancer cell lines, SF-295 (glioblastoma), MDA-MB-435 (melanoma), and HCT-8 (colon adenocarcinoma). In the mechanism of cytotoxic action, halimane 1 interferes in two major phases of the cell cycle: in S phase, in which DNA synthesis occurs and where it is very sensitive to damage, and G2M phase which is the phase of preparation for mitosis and mitosis itself, showing apoptosis-inducing properties. Antimicrobial activity towards Gram-positive and Gram-negative bacteria was studied and, against Bacillus cereus, B. subtilis, Escherichia coli, and Pseudomonas aeruginosa, a MIC value of 0.025 µM was observed for halimane 1, which is more active than the positive control chloramphenicol.

Aureonitol, a Fungi-Derived Tetrahydrofuran, Inhibits Influenza Replication by Targeting Its Surface Glycoprotein Hemagglutinin.

The influenza virus causes acute respiratory infections, leading to high morbidity and mortality in groups of patients at higher risk. Antiviral drugs represent the first line of defense against influenza, both for seasonal infections and pandemic outbreaks. Two main classes of drugs against influenza are in clinical use: M2-channel blockers and neuraminidase inhibitors. Nevertheless, because influenza strains that are resistant to these antivirals have been described, the search for novel compounds with different mechanisms of action is necessary. Here, we investigated the anti-influenza activity of a fungi-derived natural product, aureonitol. This compound inhibited influenza A and B virus replication. This compound was more effective against influenza A(H3N2), with an EC50 of 100 nM. Aureonitol cytoxicity was also very low, with a CC50 value of 1426 µM. Aureonitol inhibited influenza hemagglutination and, consequently, significantly impaired virus adsorption. Molecular modeling studies revealed that aureonitol docked in the sialic acid binding site of hemagglutinin, forming hydrogen bonds with highly conserved residues. Altogether, our results indicate that the chemical structure of aureonitol is promising for future anti-influenza drug design.

New hemiketal steroid from the introduced soft coral Chromonephthea braziliensis is a chemical defense against predatory fishes.

Recent studies show that chemical defenses in the exotic soft coral Chromonephthea braziliensis Ofwegen (Nephtheidae, Alcyonacea) can be one of the reasons for the success of this introduced species. We report for the first time the detailed composition of the monohydroxylated sterol fraction and a new hemiketal steroid, 23-keto-cladiellin-A, isolated from the unpalatable hexane extract from C. braziliensis. Bioassay-guided fractionation of this extract revealed that this hemiketal steroid exhibits potent feeding deterrent properties against a natural assemblage of fishes at the natural concentration. The major sterol fraction, containing the monohydroxylated sterols, was inactive in the bioassay. The results suggest that this active molecule may be driving the observed success of the invasion of this soft coral along the Brazilian Atlantic coast.