Influência das variáveis climáticas sobre a composição química e a atividade antimicrobiana dos óleos essenciais das folhas de Piper macedoi e Piper fuligineum

Abstract

The genus Piper is distinguished by its wide diversity of secondary metabolites and the biological potential of its essential oils, whose chemical composition can be influenced by environmental factors, making seasonal studies important for understanding the dynamics of plant secondary metabolism. In this context, the present study aimed to evaluate the influence of seasonality on the chemical composition of the essential oils from the leaves of Piper macedoi and Piper fuligineum, as well as to investigate their antimicrobial activity against yeasts of the genus Candida and the bacterium Helicobacter pylori. Leaves were collected during six distinct periods between September 2024 and July 2025, encompassing different climatic conditions. Essential oils were obtained by hydrodistillation and characterized by gas chromatography coupled to mass spectrometry (GC-MS), gas chromatography with flame ionization detection (GC-FID), and nuclear magnetic resonance (NMR). A total of 36 constituents were annotated in P. macedoi and 40 in P. fuligineum, with a predominance of hydrocarbon and oxygenated sesquiterpenes. Germacreno D was the major constituent in both species, while the chromene 2,2-dimetil-2H-cromeno-6-carboxilato de metila stood out as one of the major metabolites in P. macedoi, with its structure being confirmed by NMR. The results demonstrated that P. macedoi exhibited a relatively stable chemical profile throughout the collection periods, whereas P. fuligineum showed greater chemical plasticity and stronger influence of climatic variables on its composition. Correlation analyses indicated associations between precipitation, atmospheric pressure, and temperature with the relative abundance of specific constituents and chemical classes. Regarding biological activity, the essential oils did not show activity against H. pylori at the concentrations evaluated. In contrast, selective antifungal activity was observed against Candida glabrata, particularly for certain collections of P. fuligineum, whose minimum inhibitory concentration values reached 23.48 μg mL⁻¹. Overall, the results expand the chemical and biological knowledge of both species and highlight the influence of seasonality on the modulation of secondary metabolism and the biological properties of their essential oils.