Discovery and semisynthesis of coniochaetones N-P: antimicrobial and antioxidant heterocyclics from an Antarctic-derived fungus Penicillium sp. S2014503.

Penicillium sp. S2014503 is a fungus found in the Antarctic. Herein, we report a new heterocyclic (1) and two semi-synthesized ones (2-3) derived from citrinin (4), the main product of S2014503. Absolute configurations of 1 and 4 were deduced by single crystal X-ray diffraction analyses. Compound 2 was analyzed to be a diastereomeric mixture. The structure of compound 3 was determined by NMR and X-ray diffraction analyses. Compounds 2 and 3 showed strong antibacterial activity. Furthermore, compounds 1-4 exhibited excellent synergistic effects against Candida albicans SC5314 by inhibiting its mycelia formation. Compound 3 also displayed significant antioxidant activities.