Sesquiterpenoid isolated from <i>Colletotrichum truncatum</i> derived from <i>Gynura japonica</i>: isolation, structure elucidation, and biological activity

The aim of this research was isolation, structure elucidation, and biological activities of terpenoids from endophytic fungus obtained from <i>G. japonica</i>. An endophytic fungus, <i>Colletotrichum truncatum</i>, was isolated from the roots of <i>G. japonica. C. truncatum</i> was cultivated and extracted to give the crude extract. The crude extract was fractionated using vacuum liquid chromatography followed by separation and purification with column chromatography to obtain a terpenoid derivative (12.8 mg). The compound was characterised for its structure using FT-IR and NMR spectra. Based on spectral analysis, the isolated compound was identified as sydonic acid. The isolated sydonic acid was active against three tested bacterial strains and also demonstrated antioxidant activity with an IC₅₀ value of 76.5 ± 0.93 μg/mL. Interestingly, chemical research on the terpenoid derivative from the fungus <i>C. truncatum</i> associated with <i>G. japonica</i> is first reported herein.