Antiprotozoal and Antibacterial Activity of Ravenelin, a Xanthone Isolated from the Endophytic Fungus Exserohilum rostratum.

The natural compound ravenelin was isolated from the biomass extracts of Exserohilum rostratum fungus, and its antimicrobial, antiplasmodial, and trypanocidal activities were evaluated. Ravenelin was isolated by column chromatography and HPLC and identified by NMR and MS. The susceptibility of Gram-positive and Gram-negative bacteria strains to ravenelin was determined by microbroth dilution assay. Cytotoxicity was evaluated in hepatocarcinoma cells (HepG2) and BALB/c peritoneal macrophages by using MTT. SYBR Green I-based assay was used in the asexual stages of Plasmodium falciparum. Trypanocidal activity was tested against the epimastigote and intracellular amastigote forms of Trypanosoma cruzi. Ravenelin was active against Gram-positive bacteria strains, with emphasis on Bacillus subtilis (MIC value of 7.5 µM). Ravenelin's antiparasitic activities were assessed against both the epimastigote (IC50 value of 5 ± 1 µM) and the intracellular amastigote forms of T. cruzi (IC50 value of 9 ± 2 µM), as well as against P. falciparum (IC50 value of 3.4 ± 0.4 µM). Ravenelin showed low cytotoxic effects on both HepG2 (CC50 > 50 µM) and peritoneal macrophage (CC50 = 185 ± 1 µM) cells with attractive selectivity for the parasites (SI values > 15). These findings indicate that ravenelin is a natural compound with both antibacterial and antiparasitic activities, and considerable selectivity indexes. Therefore, ravenelin is an attractive candidate for hit-to-lead development.

Phytosterols isolated from endophytic fungus Colletotrichum gloeosporioides (Melanconiaceae) / Fotoesteróis isolados do fungo endofítico Colletotrichum gloeosporioides (Melanconiaceae)

Endophytic fungi are fungi that colonize internal tissues of plants. There are few studies of compounds isolated from endophytic fungi of Amazon plants. Thus, the aim this study was the isolation and structural identification of sitosterol (1), stigmasterol (2), sitostenone (3), squalene (4), ergosterol (5) and ergosterol peroxide (6) from fungus Colletotrichum gloeosporioidesisolated as endophytic from Virola michelli, a typical Amazon plant, used in folk medicine against skin infection. Compounds were isolated by chromatography column on silica and identified by 1H and 13C NMR and MS. The presence of phytosterols in fungi is rare and this is the first report of the isolation of the phytosterols sitosterol, stigmasterol and sitostenone from the genus Colletotrichum.

Fungos endofíticos são fungos que colonizam os tecidos internos das plantas. Existem poucos estudos de compostos isolados de fungos endofíticos de plantas da Amazônia. Assim, o objetivo deste estudo foi o isolamento e identificação estrutural de sitosterol (1), estigmasterol (2), sitostenona (3), esqualeno (4), ergosterol (5) e peroxido de ergosterol (6) do fungo Colletotrichum gloeosporioidesisolado como endofítico de Virola michelli, uma planta típica da Amazônia, usada na medicina popular no combate a infecções de pele. Os compostos foram isolados por cromatografia em coluna de sílica e identificados por RMN 1H e 13C e EM. A presença de fitoesteróis em fungos é rara e este é o primeiro relato do isolamento dos fitoesteróides sitosterol, estigmasterol e sitostenona do gêreno Colletotrichum.

Antibacterial activity of alkaloids produced by endophytic fungus Aspergillus sp. EJC08 isolated from medical plant Bauhinia guianensis.

Bauhinia guianensis is a typical plant in the Amazon region belonging to the family Leguminosea, used by local populations for the treatment of infectious and renal diseases. Previous work on the plant B. guianensis led to the isolation of substances with anti-inflammatory and analgesic activities. Thus, compounds isolated from B. guianensis with antimicrobial activities had not been identified. Given that there is a possibility of biological activity reported for a given plant being found in the endophytic fungi, we decided to isolate endophytic fungi from B. guianensis and test their antimicrobial activities. The alkaloids known as fumigaclavine C and pseurotin A were isolated by column chromatography and identified by 1D and 2D NMR techniques and mass spectrometry. The alkaloids are first reported as broad-spectrum antibacterial agents with good activity.