Natural Product-Based Phenols as Novel Probes for Mycobacterial and Fungal Carbonic Anhydrases

In order to discover novel probes that may help in the investigation and control of infectious diseases through a new mechanism of action, we have evaluated a library of phenol-based natural products (NPs) for enzyme inhibition against four recently characterized pathogen beta-family carbonic anhydrases (CAs). These include CAs from Mycobacterium tuberculosis, Candida albicans, and Cryptococcus neoformans as well as alpha-family human CA I and CA II for comparison. Many of the NPs selectively inhibited the mycobacterial and fungal beta-CAs, with the two best performing compounds displaying submicromolar inhibition with a preference for fungal over human CA inhibition of more than 2 orders of magnitude. These compounds provide the first example of non-sulfonamide inhibitors that display beta over alpha CA enzyme selectivity. Structural characterization of the library compounds in complex with human CA II revealed a novel binding mode whereby a methyl ester interacts via a water molecule with the active site zinc.