Elsevier

Phytochemistry

Volume 55, Issue 6, November 2000, Pages 621-626
Phytochemistry

Antifungal amides from Piper hispidum and Piper tuberculatum

In honour of Professor Otto R. Gottlieb's 80th birthday
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Abstract

Piper hispidum and Piper tuberculatum accumulate amides bearing isobutyl, pyrrolidine, dihydropyridone and piperidine moieties. The isolation and characterization of several representatives including two hitherto unreported amides were performed by chromatographic techniques and by analysis of spectroscopic data. The antifungal activity of each amide was determined by direct bioautography against Cladosporium sphaerospermum.

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, 510) were active against the fungus Cladosporium sphaerospermun as evaluated by direct bioautography (Homans and Fuchs, 1970).

Section snippets

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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