The essential oils of Piper cernuum and Piper regnellii leaves were analyzed by gas chromatography-mass spectrometry (GC-MS) and the results were compared to that obtained by means of a program designed to analyse (13)C-NMR data of complex mixtures. Bicyclogermacrene (21.88 %)/beta-caryophyllene (20.69 %) and myrcene (52.60 %)/linalool (15.89 %) were the major constituents in essential oil from leaves of P. cernuum and P. regnellii, respectively. Both essential oils presented growth inhibitory activities against Staphylococcus aureus and Candida albicans.

Os principais metabólitos secundários das folhas de Piper cernuum são derivados de ácidos cinâmico e di-hidrocinâmicos, além da lignana cubebina. No caso de P. crassinervium, há um predomínio de flavonóides, ácidos benzóicos e hidroquinonas preniladas. As culturas celulares de P. cernuum produziram as feniletilaminas dopamina e tiramina enquanto que, no caso de P. crassinervium, foram isoladas quatro alcamidas, incluindo as novas 2,3,4-trimetoxi-N-metilaristolactama e 3-hidroxi-2-metoxi-N-metil-aristolactama.The secondary metabolism in the leaves of P. cernuum produces cinnamic and dihydrocinnamic acid derivatives and the lignan cubebin. In case of P. crassinervium flavonoids and prenylated hydroquinones were characterized as major compounds. The cell cultures showed the production of the phenylethylamines dopamine and tyramine in P. cernuum, while in case of P. crassinervium four alkamides were isolated as major compounds, including the new 2,3,4-trimethoxy-N-methyl-aristolactam and 3-hydroxy-2-methoxy-N-methyl-aristolactam.

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A procedure is presented that utilizes 1 H NMR for prediction of the skeleton of iridoids. A new program was developed, named H1MACH, that presents a database with 800 data points from the 1 H NMR spectra of iridoids. This program was widely tested for the prediction of the skeleton of 40 compounds and compared with other programs in the expert system SISTEMAT. The results obtained show that H1MACH is very useful for the prediction of the skeleton of iridoids, especially for the iridane skeleton.