Estudo químico e potencial antioxidante de extratos de Lasiodiplodia sp.

Abstract

Endophytic fungi are organisms that produce a wide variety of metabolites with complex and diverse structures. These metabolites may exhibit antioxidant activity, making them a promising source of natural products against oxidative stress. The objective of this study was to evaluate the antioxidant potential and identify major compounds present in ethyl acetate extracts obtained from the optimization process of static culture at different times of Lasiodiplodia sp. fungus, isolated from the Handroanthus impetiginosus tree. Flavonoids and phenols content and antioxidant capacity were evaluated using the following methodologies: aluminum chloride, Folin-Ciocalteu, DPPH, FRAP, and ABTS+●, respectively. The extracts obtained from the sixth (POLd-6) and the eleventh (POLd-11) day of cultivation showed the best antioxidant activities as determined by the assays. According to the DPPH, FRAP, and ABTS+● tests, it was possible to classify and group the extracts using Principal Component Analysis (PCA). The results indicated the existence of two distinct groups among the extracts, corresponding to the early and late stages of fungal growth. The 14 fungal extracts were subjected to 1H-NMR analysis and treated for similarities between individual spectra, allowing the comparison of chemical profile. This approach revealed both similarities and differences among the metabolites biosynthesized during the fungal cultivation period. Through 1D and 2D NMR analysis of POLd-14 extract, two known compounds were identified: 3-carboxy-2-methylene-4-heptanolide and decumbic acid. Furthermore, the use of the GNPS platform allowed for the assignment of chemical classes of the compounds in the extracts, including carboxylic acids and derivatives, alkaloids, substituted benzenes and flavonoids. The toxicity of POLd-11 was evaluated through the survival rate of Galleria mellonella larvae. After a 72-hour treatment period with concentrations ranging from 12.5 to 200 μg.mL-1

, all tested larvae remained alive, resulting in a survival rate of 100%. It is concluded that, under the conditions of this study, the endophyte Lasiodiplodia sp. was capable of synthesizing substances with promising antioxidant activity.