Avaliação química e biológica dos fungos endofíticos de Palicourea prancei (Rubiaceae)

Abstract

Endophytic fungi isolated from plants of the genus Palicourea are sources of bioactive molecules with biotechnological applications. With the emergence of new pathologies and the issue of microbial resistance to conventional drugs, there is a need for the development of new medicines. In view of this context, this study analyzed the chemical composition as well as the antibacterial and toxicity activities against Artemia salina of endophytic fungi isolated from Palicourea prancei leaves, aiming at obtaining active substances. The endophytic fungi of P. prancei were cultivated in Sabouraud broth (0.2% yeast extract) in a shaker incubator (30 °C, 120 rpm) for 20 days to obtain the mycelial mass. The metabolites of the mycelia were extracted in methanol (MeOH) solvent and concentrated in a rotary evaporator to obtain the crude extracts. The chemical profile of the crude extracts was analyzed by comparative thin layer chromatography (TLC). The bacterial inhibition activity of the fungal extracts was evaluated by the microdilution method and the toxicity level against A. salina. The selected fungus was cultivated on a large scale and its mycelia were extracted in MeOH, which was partitioned using EtOAc, obtaining the EtOAc phase and the hydromethanolic phase. The extract and the phases obtained had their chemical profile analyzed by comparative TLC. Only the MeOH extract and its EtOAc phase were analyzed by 1H NMR and subjected to antibacterial and toxicity tests against A. salina. Comparative TLC analysis of crude extracts from endophytic fungi of P. prancei indicated the presence of substances with double bonds, terpenes, phenolic compounds, and nitrogenous compounds. The MeOH extracts of the fungi G1 PP8 and G2 PP5 tested at 1000 μg/mL showed bacteriostatic activity above 35% against the bacteria Aeromonas hydrophila and Staphylococcus aureus, and the MeOH extract of G1 PP8 exhibited high toxicity against A. salina, with LC50 = 2.76 μg/mL. The fungus G1 PP8 stood out in the analyses and was selected for large-scale cultivation and molecular identification, being identified as Xylaria cubensis G1 PP8. The EtOAc phase of the MeOH extract of X. cubensis G1 PP8 mycelium was fractionated by open column chromatography (CC), allowing for the isolation of cytochalasin D. The MeOH extract and its EtOAc phase did not show antibacterial activity, but were toxic in the assay against A. salina, with LC50 = 84.02 μg/mL (MeOH extract) and 144.3 μg/mL (EtOAc phase). The results obtained in this study contribute to the chemical knowledge of the endophytic fungi of P. prancei, as well as their biological applicability.