Six new chromones, named pestalotiopsones A-F (1-6), and the known derivative 7-hydroxy-2-(2-hydroxypropyl)-5-methylchromone (7) were obtained from the mycelia and culture filtrate of the mangrove endophytic fungus Pestalotiopsis sp., which was isolated from leaves of the Chinese Mangrove plant Rhizophora mucronata. Their structures were elucidated on the basis of spectroscopic data. Pestalotiopsones A-F are chromones having both an alkyl side chain substituted at C-2 and a free or substituted carboxyl group at C-5. Compound 6 exhibited moderate cytotoxicity against the murine cancer cell line L5178Y, whereas the other investigated compounds proved to be inactive.
Combretum mucronatum Schumach. & Thonn. is a medicinal plant widely used in West African traditional medicine for wound healing and the treatment of helminth infections. The present study aimed at a phytochemical characterization of a hydroalcoholic leaf extract of this plant and the identification of the anthelmintic compounds by bioassay-guided fractionation. An EtOH-H2O (1:1) extract from defatted leaves was partitioned between EtOAc and H2O. Further fractionation was performed by fast centrifugal partition chromatography, RP18-MPLC and HPLC. Epicatechin (1), oligomeric proanthocyanidins (OPC) 2 to 10 (mainly procyanidins) and flavonoids 11 to 13 were identified as main components of the extract. The hydroalcoholic extract, fractions and purified compounds were tested in vitro for their anthelmintic activity using the model nematode Caenorhabditis elegans. The bioassay-guided fractionation led to the identification of OPCs as the active compounds with a dose-dependent anthelmintic activity ranging from 1 to 1000 μM. Using OPC-clusters with a defined degree of polymerization (DP) revealed that a DP ≥ 3 is necessary for an anthelmintic activity, whereas a DP > 4 does not lead to a further increased inhibitory effect against the helminths. In summary, the findings rationalize the traditional use of C. mucronatum and provide further insight into the anthelmintic activity of condensed tannins.
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