Effect of light exposure on secondary metabolite production and bioactivities of syncephalastrum racemosum endophyte

Endophytes have drawn the attention of researchers regarding their abilities to produce novel and bioactive compounds having medicinal values. Some studies reported that light could affect fungal secondary metabolite production. This study examined the effect of light exposure to metabolite profiles of an endophytic fungus isolated from the stem of Coleus amboinicus and its consequences on bioactivity. The endophytic fungi identified as Syncephalastrum racemosum was isolated from the stem of C. amboinicus and was cultured in Potato Dextrose Broth for two weeks under dark and light conditions. The metabolite profiles were examined using TLC analysis and gas chromatography. The conducted bioactivity testing included antibacterial, cytotoxic and DPPH antioxidant assays. In this study, two compounds namely methyl hexadecanoate and methyl (Z)-octadec-9-enoate were present in both C. amboinicus stem and S. racemosum extracts under dark condition. These substituents were diminished when the fungus was cultured and subjected to the light. Additional compounds were observed upon light exposure and this affected bioactivity. Antioxidant activity of extract exposed to light was better than that of in the dark condition (41.84 ± 0.38 vs 57.19 ± 0.88 µg/mL). A similar trend was seen in antibacterial activity, although the differences were insignificant. On the contrary, the extract from dark condition was found to be more cytotoxic against T47D cells compared to that of the one exposed to light, with IC50 value of 420.06 ± 12.98 and >500 µg/mL, respectively. © 2021 the authors.