Estudo químico sazonal do óleo essencial e de neolignanas de Piper rivinoides Kunth da Mata Atlântica do Estado do Rio de Janeiro

Abstract

The World Health Organization has stated that it is essential to carry out investigations of plants used for medicinal purposes and their active principles to elucidate their effects in order to ensure their efficacy and safety. It also highlighted the importance of popular knowledge and the need for scientific involvement for better applicability of plant use and biodiversity. Piper rivinoides Kunth is a species belonging to the Piperaceae family, with popular medicinal uses, shrubby and native to the Atlantic Forest. Previous studies conducted by our group have demonstrated excellent leishmanicidal and antifungal activities for extracts, fractions and neolignans isolated from this plant. Based on these considerations, this work aims to conduct a seasonal study of neolignan content and volatile chemical composition of P. rivinoides leaves. For this purpose, leaves of the species have been collected from native specimens from two different locations in the Atlantic Forest (Tijuca Forest/ RJ and Serra da Tiririca, Niterói/ RJ). Leaves were submitted to drying, fragmentation and extraction processes to measure the neolignan content with different extractive solvents. The extracts were quantified according to the developed and validated analytical method by High-Performance Liquid Chromatography coupled to Diode-array UV Detector. Fresh leaf essential oil (EO) were obtained by hydrodistillation in a modified Clevenger-type apparatus and analyzed by Mass Spectrometry Coupled to Gas Chromatography, and the compounds identification were performed by comparing mass spectra and retention indices with data from the literature. The yield of the extracts ranged from 0.92 to 6.90%. The percentages of conocarpan (CNC) varied from 0.04 to 0.13%, of eupomatenoid-6 (EUP-6) from 0.34 to 1.03% and of eupomatenoid-5 (EUP-5) from 2.73 to 4.44%. Therefore, the most abundant neolignan in the extract was EUP-5. The specimen from Niterói/ RJ recorded lower percentage levels of neolignans for the months of December, January, February and March (0.09-0.70% CNC; 0.78-1.41% EUP-6 and 2.29- 3.30% EUP-5) which corresponds to summer and higher levels in May, July, August, September and October (0.79-1.43% CNC; 1.73-2.45% EUP-6 and 4.06-6.13% EUP-5), which corresponds to winter and spring. The three compounds registered higher percentage levels in July (winter). The speciemenfrom Floresta da Tijuca/ RJ showed a different chemical profile, registering the lowest values for June (0.06% CNC; 0.49% EUP-6 and 1.67% EUP-5) and more homogeneous percentage levels for the other months. The yield of EO extracted from fresh leaves of P. rivinoides collected in the Atlantic Forest of Rio de Janeiro was quite significant, varying from 0.16 to 1.36% (w / w) and demonstrated a similar and relatively stable chemical composition for both sites, over a year of analysis. It was possible to identify 97 different compounds, being the non-oxygenated monoterpenes -pinene (34.78 to 53.87%) and β-pinene (15.24 to 47.71%) the major constituents, which are substances with great biological potential. The biosynthetic variations found in P. rivinoides over the year suggest that its phenological cycle has a greater influence on the biosynthesis of special metabolites (both neolignans and volatile components) than the abiotic factors.The results suggest that for P. rivinoides there is a chemical phenotypic stability in the two sites of study. This is excellent in terms of the development of new phytomedicines, since the greater chemical phenotypic diversity requires greater investment in the domestication of the plant