Larvicidal, Antimycobacterial and Antifungal Compounds from the Bark of the Peruvian Plant Swartzia polyphylla DC

Abstract

Perú is a country with a large number of medicinal plants, many of which are used for the treatment of infectious diseases, 1) although only few studies have been conducted to prove their efficacy and safety. 2,3) Due to the emergence of micro-organism resistance to the common antibiotics 4) and its worldwide impact on health, our research aims to identify new natural products that may lead to the discovery of new antibacterial agents with higher efficiency and lower toxicity.As part of our continuing work on bioactive compounds from Peruvian medicinal plants, [5][6][7] the in vitro antimycobacterial activity of 102 ethanol extracts from 84 plants-used traditionally in Perú for the treatment of inflammatory or infectious disorders-was screened using a tetrazolium microplate assay (TEMA).8) In a separate screening, the antifungal and larvicidal activities of over 100 plants, including those previously tested for antimycobacterial activity, were bio-assayed.As a result of these screenings, Swartzia polyphylla DC (Fabaceae) was found to exhibit powerful antimycobacterial action against the sensitive H 37 Rv and multidrug-resistant Mycobacterium tuberculosis. It also inhibited the in vitro growth of the dermatophyte Trichophyton mentagrophytes, and was active against the larvae of the mosquito Culex quinquefasciatus. We are now pleased to report the isolation of the larvicidal, antimycobacterial and antifungal principles present in the crude extract of S. polyphylla.A solvent-partition of the 95% ethanol extract showed that the larvicidal and antimycobacterial activities were concentrated in the hexane fraction, while the 90% methanol fraction was active only in the antifungal assay. The hexane fraction (28 g) was chromatographed on a silica gel column using a hexane-chloroform-methanol gradient. Each fraction (F1-F7) was evaluated for larvicidal and antimycobacterial activity in vitro. The most active fraction (F6, 8.7 g) was purified by column chromatography using a hexanedichloromethane-ethanol gradient and then by MPLC (Lobar Lichroprep silica gel RP-8, 40-63 mm, 310ϫ25 mm, Merck) with acetonitrile-methanol-water (3 : 2 : 2) yielding the most active fraction F-6-4-2 (51.4 mg). This fraction was finally purified by HPLC (Waters Nova-pak H R silica 6 mm, 3.9ϫ300 mm, Waters Model 600E with Waters 2996 PDA detector) using hexane-chloroform gradient (0 to 70%) to obtain T-cadinol (1, 9 mg) (Fig. 1). 9,10) The 90% methanol fraction (25.5 g) was subjected to column chromatography (silica gel, 0.063-0.200 mm) using a hexane-chloroform-methanol gradient. Each fraction (F1-F9) was tested for antifungal activity in vitro. The most active fraction (F3) yielded fraction F3-7-5 (756 mg) after repeated column chromatography using hexane-ethylacetatemethanol as eluent. This fraction was finally purified by MPLC with methanol-water (6 : 4) to afford biochanin A (2, 15 mg) and dihydrobiochanin A (3, 59 mg) (Fig. 1). 11)The bark of S. polyphylla contains various flavonoids and isoflavones, some of them with strong activity against...

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