Chiang Mai Journal of Science

Endophytic fungi from medicinal plants have been recognized to be a valuable source of metabolites and novel bioactive compounds. The present work was carried out to examine the antioxidant capacity of thirty-nine endophytic fungi obtained from five Thai medicinal plants which are commonly used in Thai traditional medicines. Their total phenolic content showed a positive correlation with ABTS⁺ radical scavenging activity (R²=0.4009) and reducing power (R²=0.7247) but was not correlated with DPPH radical scavenging activity. Phenolic compounds are the main antioxidant components of reducing power and other secondary metabolites may play a role as the main free radical scavengers. Among thirty-nine endophytic strains, Eupenicillium shearii CMU 18 showed the highest number of phenolic compounds, ABTS⁺ radical scavenging effect, highest reduction potential, and highest lipid peroxidation inhibition activity (IC₅₀ value of 43.46 mg ml^-1) in the rat liver tissue. According to the cytotoxicity test, E. shearii CMU 18 was not cytotoxic. The findings from the present study provide evidence that endophytic fungi from Thai medicinal plants have a potential as a source of antioxidants.