Bioactivities of natural product geodin congeners and their preliminary structure activity relationship

A series of 6 novel ester derivatives 2-7 of natural product geodin 1 were designed and semi-synthesized through one mild step reaction with high yield. Compounds 2-7 showed strong inhibitory activities against Staphylococcus aureus in the range of 2.35-9.41 μM. Compounds 4 and 7 showed very strong inhibitory activities against antifouling bacteria Aeromonas salmonicida with MICs of 2.42 μM and 4.56 μM respectively. Most notably compounds 3-7 showed potent antifungal activities against Candida albicans in the range of 0.59-2.44 μM. Particularly, compound 3 showed the highest antifungal activity against C. albicans with a MIC value of 0.59 μM. The preliminary structure activity relationship of these derivatives showed that replacement of 4-OH group with benzoyl substituents could enhance the antibacterial and antifungal activities of geodin 1.