Antibacterial, antioxidant, and cytotoxic potential of an endophytic Fusarium verticillioides from yacon (Smallanthus sonchifolius) leaves

Abstract

Endophytic fungi, residing within plant tissues without causing disease, serve as an important reservoir of bioactive compounds with pharmaceutical potential. This research focuses on isolating and identifying endophytic fungi from the leaves of Smallanthus sonchifolius and evaluating their antioxidant, antibacterial, and cytotoxic activities. A total of five fungal isolates (DY1–DY5) were obtained and subjected to in vitro bioassays and molecular identification. Internal transcribed spacer (ITS) sequencing revealed that isolate DY5 corresponded to Fusarium verticillioides, which consistently demonstrated notable bioactivities. Antioxidant activity was confirmed through the DPPH radical scavenging assay, where DY5 exhibited an IC₅₀ value of 241.23 μg/mL. Antibacterial evaluation against Escherichia coli ATCC 25922 revealed an inhibition zone of 12.22 ± 0.98 mm and a minimum inhibitory concentration (MIC) of 500 μg/mL. Cytotoxic screening using the Artemia salina lethality assay indicated moderate toxicity, with LC₅₀ values of 197.54 μg/mL for DY1 and 386.32 μg/mL for DY5, thereby meeting the threshold of bioactive extracts. This study provides evidence that endophytic fungi from S. sonchifolius, notably F. verticillioides (DY5), can serve as potential sources of bioactive compounds with pharmaceutical relevance. Further research focusing on metabolite profiling, compound isolation, and mechanistic evaluation is warranted to elucidate their chemical diversity and therapeutic significance in drug discovery efforts