Caracterização química e avaliação da influência do tempo de armazenamento da biomassa seca na composição química do óleo essencial de Baccharis microdonta

Abstract

The species Baccharis microdonta belongs to a genus widely distributed in South America, recognized for its medicinal potential and the presence of essential oils rich in bioactive compounds, especially monoterpenes and sesquiterpenes. These bioactive compounds are part of the secondary metabolites of plants. They are associated with various biological activities, such as antioxidant, anti-inflammatory, and antimicrobial properties, which spark interest in the pharmaceutical, cosmetic, and food industries. However, the chemical composition of essential oils can vary significantly depending on factors such as environmental conditions, the phenological stage of the plant, and, above all, post-harvest stages, including drying and storage of the plant material. In this context, standardization of processing conditions becomes essential to guarantee the quality and reproducibility of the essential oils obtained. The interval between drying and extraction can induce relevant chemical changes, resulting from processes such as volatilization of lighter compounds, oxidation, and possible structural transformations. Therefore, understanding the influence of storage time after drying is fundamental to optimizing extraction methods and preserving the desirable characteristics of the essential oil, contributing to its safe and efficient application in different industrial sectors. Given this, the present work aimed to evaluate the influence of drying and storage time on the chemical composition of Baccharis microdonta essential oil, through a comparison between two experimental protocols: the first involving the collection, drying, and immediate extraction of plant material; and the second method involving the collection, drying, and storage of material for four to six months before extraction. The proposal consisted of investigating qualitative and quantitative variations in the profile of volatile compounds, as well as possible alterations in their relative concentrations as a function of storage time. The extraction of essential oils was carried out by hydrodistillation in a Clevenger-type apparatus, under controlled time and temperature conditions, ensuring process standardization and reproducibility of results. After harvesting, the samples were subjected to gas chromatography-mass spectrometry (GC-MS) analysis, allowing the identification of constituents based on the comparison of mass spectra with commercial libraries, such as NIST, in addition to the determination of linear retention indices (LRI), calculated from a homologous series of n-alkanes. The comparative analysis of the chromatographic profiles showed that the storage time after drying has a significant influence on the composition of the essential oil. Greater preservation of more volatile compounds was observed in samples extracted immediately after drying, while prolonged storage resulted in changes in the chemical profile, possibly associated with volatilization, oxidation, and degradation of certain constituents. Furthermore, variations in the relative concentrations of major and minor compounds were identified, indicating modifications in the chemical equilibrium of the system. These results reinforce the importance of rigorous control of post-harvest steps, highlighting the impact of storage time on the quality, stability, and applicability of Baccharis microdonta essential oils.