Antifungal amides from Piper hispidum and Piper tuberculatum
Introduction
Various amides bearing isobutyl, pyrrolidine, dihydropyridone and piperidine moieties have been isolated from Piperaceae species (Parmar, 1997). These amides have generated interest as a result of their potent insecticidal properties (Miyako et al., 1989). In a previous paper, we described the structure of the antifungal amide N-[7-(3′,4′-methylenedioxyphenyl)-2(Z),4(Z)-heptadienoyl]pyrrolidine isolated from the leaves of Piper hispidum H.B.K. (Alécio et al., 1998).
In this paper, we describe the isolation, structure elucidation and evaluation of the antifungal activity of two new amides, (3Z,5Z)-N-isobutyl-8-(3′,4′-methylenedioxyphenyl)-heptadienamide (1), 8(Z)-N-(12,13,14-trimethoxycinnamoyl)-Δ3-pyridin-2-one (2) and also of eight known antifungal amides N-[3-(6′-methoxy-3′,4′-methylenedioxyphenyl)-2(Z)-propenoyl]pyrrolidine (3), piperamine (4), N-(12,13,14-trimethoxydihydrocinnamoyl)-Δ3-pyridin-2-one (5), piplartine (6), piperine (7), Δα,β-dihydropiperine (8), 5,6-dihydropiperlonguminine (9) and pellitorine (10). The amides isolated from stems of Piper hispidum (1, 3 and 4) and from seeds of Piper tuberculatum (2, 5–10) were active against the fungus Cladosporium sphaerospermun as evaluated by direct bioautography (Homans and Fuchs, 1970).
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Results and discussion
A CH2Cl2:MeOH (2:1) extract of the stems of P. hispidum was subjected to silica gel column chromatography, followed by HPLC purification to afford the compounds 1, 3 and 4.
Compound 1, has a molecular formula C18H23NO3 as determined by analysis of electrospray mass spectrum (ES–MS) and of the 13C NMR spectral data. The IR spectrum exhibited bands at 1640 (conjugated carbonyl group), 1620 (conjugated double bond), and 925 (methylenedioxyphenyl group) cm−1. Its 1H NMR spectrum (Table 1) revealed
Instrumentation and chromatography materials
Silica gel (Merck 230–400 mesh) was used for all column chromatography unless otherwise stated and solvents were redistilled prior to use. 1H and 13C NMR spectra were recorded at 200 and 50 MHz, respectively, using CDCl3 as a solvent and TMS as reference. IR spectra were obtained on a Nicolet spectrometer. ES–MS were recorded on a VG Platform II spectrometer. HPLC separations were performed on a Shimadzu LC-10AS using a reverse phase column (Waters Nova Pack, C18; 3.9 × 150 mm) eluted with
Acknowledgements
This work was funded by grants provided by FAPESP and CNPq/PADCT. M.F., M.J.K., M.C.M.Y. and V.S.B. are grateful to CNPq for research fellowships. H.M.D.N. thanks FAPESP for providing a scholarship.
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