Isolation and Structure Identification of Cyclic Dipeptides from Cordyceps militaris

Background: Cordyceps militaris (Cordycipitaceae) is a parasitic fungus that infects insects or larvae hosts and has been widely used to boost energy and enhance the immune system. A well-known nucleoside from C. militaris, cordycepin (3′-deoxyadenosine), has been reported to exhibit anti-inflammatory, anti-microbial, and anti-oxidant activities. Methods: In this study, nine compounds were isolated from C. militaris using chromatographic purification techniques, and their structures were elucidated using spectroscopic analyses, including UV and NMR. Results: Four tryptophan-containing cyclic dipeptides (1–4) were isolated from this species for the first time along with five known compounds, and the separation techniques for diketopiperazines were explained. The skeleton of the compounds 1–4 is reported for the first time from this species. Conclusion: By expanding the chemical profile of C. militaris, our results may open new avenues for investigating its various biological potentials.