Polygodial, the fungitoxic component from the Brazilian medicinal plant Polygonum punctatum

Abstract

Polygonum punctatum (Polygonaceae) is an herb known in some regions of Brazil as "erva-debicho" and is used Several plant species of the genus Polygonum (Polygonaceae) are used in the folk medicine at different parts of the world to treat many diseases including skin infections, dysentery, snake-bite, hemorrhoids, insomnia and heart diseases and is also used for liver protection (WHO 1989a(WHO ,b, 1998a. According to the NAPRALERT database, in Latin America and North America Polygonum punctatum Elliot is used in some areas to treat a diversity of ailments including hemorrhoids, diarrhoea, colds and influenza. In Brazil, P. punctatum (syn. Persicaria punctata and P. acre) is popularly known as "erva-de-bicho", "capiçoba", "pimenta-d'água", "pimenta-do-brejo" and "cataia" (Corrêa 1984). It is used to treat hemorrhoids and rheumatism, as an abortive, a diuretic and a hemenagogue (Martins et al. 1995). Previous pharmacological studies with the ethanol/water extract of the entire plant disclosed antihistaminic, anti-inflammatory, antipyretic and hypotensive activities (Oliveira-Simões et al. 1989). Toxicity assays of the methanolic and aqueous extracts in the rat model indicated an LC 50 > 1g/kg (Bhakuni et al. 1969).In our search for bioactive compounds from the Brazilian flora, we screened hundreds of plant extracts, including those from medicinal plants, for fungitoxic activity against Cladosporium sphaerospermum (Alves et al. 2000) using a bioautographic assay based on the protocol described by Homans and Fuchs (1970). The crude dichloromethane extract of aerial parts of P. punctatum was one of the most active. Aiming to isolate and identify the fungitoxic compound(s) we investigated this extract using a bioassay-guided chemical fractionation protocol. MATERIALS AND METHODSPlant collection -The aerial parts of the plant were collected at Governador Valadares, State of Minas Gerais, Brazil. A voucher specimen was deposited in the Department of Botany Herbarium, Universidade Federal de Minas Gerais, under the code BHCB 41475.Extraction -The plant was dried at 45°C in a convection oven and powdered in a knife mill. The powder (85 g) was macerated at room temperature for 24 h in dichloromethane. After filtration, the solvent was removed by rotary evaporation under reduced pressure and at temperatures below 45°C affording 2 g of crude extract.Isolation and identification of pure compound -The crude extract (500 mg) was submitted to centrifugal circular chromatography using hexane/ ethanol/water (10:9:1). Thirty fractions were collected. The fungitoxic fractions 11 to 13 were grouped (31 mg) and chromatographed on a silicagel column eluted with dichloromethane. A white solid (5 mg, 0.23% yield from dry plant) was obtained as the active compound.Bioautographic assay with C. sphaerospermum-The procedure of Homans and Fuchs (1970) was adapted. Briefly, the extract, fractions 832 Fungitoxic Component from P. punctatum Tânia Maria de Almeida Alves et al.and pure compound (100 µg) were spotted on TLC plates using the app...

Preventing ascidian fouling in aquaculture: screening selected allelochemicals for anti-metamorphic properties in ascidian larvae

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GC-MS analysis of Tasmannia lanceolata Extracts which Inhibit the Growth of the Pathogenic Bacterium Clostridium perfringens

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