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Urupocidins A and B (1 and 2), bisguanidine alkaloids with an unprecedented skeleton system, derived from polyketide precursors and containing an unusual N-alkyl-N-hydroxyguanidine moiety, have been isolated from the sponge Monanhora pulchra. The structures of 1 and 2, including absolute configuration, were established using the detailed analysis of 1D and 2D NMR, CD, and mass spectra as well as chemical transformations. Compound 1 increases nitric oxide production in murine macrophages via inducing iNOS expression.

New marine natural products, pulchranins B and C (2 and 3), were isolated from the marine sponge Monanchora pulchra and their structures were established using NMR and MS analysis. Compounds 2 and 3 were moderately active as inhibitors of TRPV1 (EC50 value of 95 and 183 μM, respectively) and less potent against TRPV3 and TRPA1 receptors.

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The guanidine alkaloids, dihydropulchranin A (2), prepared from pulchranin A from the sponge Monanchora pulchra, and hexadecylguanidine (3), a synthetic analog of pulchranins, were studied for their TRPV channel-regulating activities. Compound 2 was active as an inhibitor of rTRPV1 and hTRPV3 receptors with EC 50 values of 24.3 and 59.1 M, respectively. Hexadecylguanidine (3) was not active against these receptors.