Myrothenones A and B, cyclopentenone derivatives with tyrosinase inhibitory activity from the marine-derived fungus Myrothecium sp.

New 3-amino-5-ethenylcyclopentenones, myrothenones A (4) and B (5), were isolated together with known 6-n-pentyl-alpha-pyrone (1), trichodenone A (2), and cyclonerodiol (3) from the marine algicolous fungus of genus of Myrothecium. The structure and absolute stereochemistry of the new compounds were established by spectral interpretation and X-ray analysis. Compounds I and 4 exhibited a tyrosinase inhibitory activity with IC50 value of 0.8 and 6.6 mu m, respectively, which are more active than kojic acid (IC50, 7.7 mu m) currently being used as a functional personal-care compound.