Thielavins: tuned biosynthesis and LR-HSQMBC for structure elucidation

A series of thielavins I, V, and Q (1-3) and the previously undescribed thielavin Z(8) (4) were isolated from cultures of a fungal Shiraia-like sp. (strain MSX60519) that were grown under a suite of media and light conditions, with enhanced biosynthesis noted using rice as a substrate with 12:12 h light:dark cycles. Conversely, oatmeal medium and continuous white light-emitting diode light exposure negatively affected the production of these compounds, at least by strain MSX60519. The structure of 4 was determined using NMR spectroscopic data and mass fragmentation patterns. Of note, the utility of LR-HSQMBC and NOESY NMR experiments in the structural elucidation of these hydrogen-deficient natural products was demonstrated. Compounds 1-4 exhibited cytotoxic activity at the micromolar level against human breast, ovarian, and melanoma cancer cell lines.

Automated summary

The study revealed that fungal Shiraia-like sp. showed enhanced biosynthesis of thielavins when using rice as a substrate and with a 12:12 hour light:dark cycle. The structure of the previously undescribed thielavin Z was determined using NMR experiments, demonstrating the utility of LR-HSQMBC and NOESY NMR experiments in structural elucidation of these hydrogen-deficient natural products. Compounds 1-4 exhibited cytotoxic activity against human breast, ovarian, and melanoma cancer cell lines at the micromolar level.