Endophytic fungus Fusarium sp. MCXR isolated from the fruit pulp of Annona muricata L. and its cytotoxic effect on MCF-7 breast cancer cells

Abstract

Annona muricata (A. muricata, Annonaceae) is a medicinal plant containing diverse bioactive compounds, including acetogenins, which have been widely investigated for their cytotoxic and anticancer potential. Endophytic fungi associated with A. muricata may represent an additional source of bioactive metabolites; however, information on endophytic fungi residing in soursop fruit remains limited. This study aimed to isolate and identify endophytic fungi from the fruit pulp of A. muricata grown in Vietnam, and preliminarily evaluate the cytotoxic activity of the fungal crude extract. A fungal isolate, designated MCXR, was obtained and identified as Fusarium sp. based on macroscopic and microscopic morphological characteristics together with internal transcribed spacer (ITS) DNA sequence analysis. The fungal ethanolic crude extract showed a positive qualitative reaction with Kedde’s reagent, suggesting the possible presence of acetogenin-related compounds. Its cytotoxic activity was evaluated in vitro against the human breast cancer cell line MCF-7. The extract inhibited MCF-7 cell proliferation in a concentrationdependent manner, with an IC₅₀ value of 134 μg/ml. These findings suggest that A. muricata-associated endophytic fungi may represent a potential source of bioactive metabolites. Further studies are required to chemically identify the active compounds, assess their selectivity, and elucidate their mechanisms of action.