Type-I Hemins and Free Porphyrins from a Western Australian Sponge Isabela sp.

Abstract

Two novel free porphyrins, isabellins A and B, as well as the known compounds corallistin D and deuteroporphyrin IX were isolated from a marine sponge Isabela sp. LC-MS analysis of the crude extract revealed that the natural products were present both as free porphyrins and iron(III) coordinated hemins, designated isabellihemin A, isabellihemin B, corallistihemin D and deuterohemin IX, respectively. Structures were determined via high-resolution mass spectrometry, UV-Vis spectroscopy and extensive NOESY NMR spectroscopic experiments. The type-I alkyl substitution pattern of isabellin A and isabellihemin A was assigned unambiguously by single crystal X-ray diffraction. Biological evaluation of the metabolites revealed potent cytotoxicity for isabellin A against the NS-1 murine myeloma cell line.

Diverse enzymatic chemistry for propionate side chain cleavages in tetrapyrrole biosynthesis

“…Recently, isabelline A ( 55 ) with a type-I methyl substitution pattern (D 4h symmetry) and derivatives thereof were isolated from the Western Australian sponge Isabela sp. (Sala et al, 2023 ). Considering the structural similarity between these compounds and tolyporphins, one might speculate that the biosynthesis of bonellin ( 5 ), corallistins (such as 6 ), and isabellins (such as 55 ) involves the decarboxylation of the propionate side chains (catalyzed by a HemF-like enzyme) of 9 or 54 , followed by vinyl group removal (catalyzed by a TolI-like enzyme) to generate the unsubstituted pyrrole carbons, in a mechanism similar to that in tolyporphin biosynthesis.…”

Marine Natural Products as Anticancer Agents 2.0

“…Sala and collaborators [6] isolated two novel free porphyrins, isabellin A and B, and the known compounds corallistin D and deuteroporphyrin IX from the marine sponge Isabella sp., previously collected in the hard substrate off Zuytdorp, Western Australia. The new free porphyrin, isabellin A, exhibited a marked cytotoxic effect on the NS-1 malignant myeloma cell line, similar to the positive control sparsomycin.…”