Chemical characterisation of Piper amalago (Piperaceae) essential oil by comprehensive two-dimensional gas chromatography coupled with rapid-scanning quadrupole mass spectrometry (GC×GC/qMS) and their antilithiasic activity and acute toxicity.

IntroductionPiper amalago has a distribution from Mexico to Brazil; their aerial parts have been used in folk medicine to treat diuretic and kidney diseases. ObjectiveThe purpose of this study was to obtain a deeper understanding of the chemical composition of essential oils (EOs) extracted from both the leaves and stems of P. amalago, compare them, and evaluate their antilithiasic activity and acute toxicity. MethodologyExtraction was performed by hydrodistillation, whereas chemical characterisation by two-dimensional gas chromatography coupled with rapid-scanning quadrupole mass spectrometry (GCxGC/qMS). The antilithiasic activity was evaluated by the effect of the EOs on calcium oxalate crystallisation in vitro. The turbidity index and the number of crystals formed were determined and used as an estimative of the activity. In the acute toxicity assay, the effects of a single oral dose of the EOs in Wistar rats were determined. General behaviour, adverse effects, and mortality were determined. ResultsA total of 322 compounds were identified in the EOs. The sesquiterpenes displayed the highest contribution in leaves EOs among which included bicyclogermacrene and -cadinene. Sesquiterpenes and oxygenated sesquiterpenes displayed the highest contribution in EOs from stems, among which included bicyclogermacrene and -cadinol. The EOs demonstrated an excellent action on the crystals growth inhibition, and the oral dose tested did not induce significant changes in the parameters for acute toxicity. ConclusionThe oils have a high chemical complexity, and there are differences between their compositions, which could explain the observed differences in antilithiasic activity. The findings support the use of this plant in folk medicine to treat kidney diseases. For the first time essential oils from Piper amalago leaves and stems were studied for their chemical composition by GCxGC/qMS, and their in vitro antilithiasic activity and in vivo acute oral toxicity were evaluated. A total of 322 different volatiles compounds were identified in the oils. Both essential oils showed an excellent action on the crystals growth inhibition, which could contribute to the antilithiasic activity. The oral dose tested did not induce acute toxicity in rats.