Denigrins A–C: new antitubercular 3,4-diarylpyrrole alkaloids from Dendrilla nigra
Chemical diversity is vital to antitubercular drug discovery as it ensures a novel bioactivity profile. Marine sponges have so far provided more than 1000 new bioactive molecules. Ethyl acetate extract of the marine sponge Dendrilla nigra on bioactivity-guided screening yielded three new compounds denigrins A–C, with potent antitubercular activity. Spectral and chemical analyses confirmed that these three compounds belong to the 3,4-diaryl pyrrole alkaloid category. The presence of monohydroxy substitution on benzene rings is not very common in lamellarin and related 3,4-diaryl pyrrole alkaloids isolated from marine invertebrates. Among these, denigrin C showed highest potency (minimum inhibitory concentration 4 μg/mL) against Mycobacterium tuberculosis H37Rv.