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New Halogenated Secondary Metabolites from Red Algae of the South Pacific

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posted on 2021-11-22, 21:46 authored by Victoria WoolnerVictoria Woolner

An NMR- and MS-directed study led to the isolation and structure elucidation of several halogenated secondary metabolites from a New Zealand and a Tongan red alga. An extensive investigation was carried out on the New Zealand red alga Rhodophyllis membranacea following mass spectrometric evidence for an unusual tetrahalogenated indole with the exceptionally rare inclusion of bromine, chlorine and iodine within a fraction of a semi-purified extract. Due to the difficulty associated with the structure elucidation of proton deficient molecules, a strategic isolation and structure elucidation of several polyhalogenated indoles was employed in order to unequivocally assign the halogen positions on the indolic core. This resulted in the isolation and characterisation of 11 new tetrahalogenated indoles (123–133), four of which contain bromine, chlorine and iodine (124 and 129–131) and represent the first isolation of such compounds. Additionally, four new pentahalogenated indoles (134–137) and an uncharacterised tribromotrichloroindole were isolated. The synthetically known compound 4-chloroisatin (138) was isolated as a new marine natural product, while 4-chloro-3-hydroxyl-3-(2-oxopropyl)-2-oxindole (139) was established to be an artefact of isolation. Several compounds were found to exhibit antifungal properties against Saccharomyces cerevisiae.  A detailed examination of the Tongan alga Callophycus serratus led to the isolation of six new meroditerpenoids: callophycol C (227), iodocallophycols E (228) and F (229), iodocallophycoic acid B (230), deiodocallophycoic B (231) and callophycoic acid I (232). The relative configurations in compounds 228–231 are proposed to differ from closely related compounds in the literature. Iodocallophycol E (228) exhibited moderate cytotoxicity against the HL-60 cell line with an IC50 value of 6.0 μM.


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Te Herenga Waka—Victoria University of Wellington

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Te Herenga Waka—Victoria University of Wellington

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Doctor of Philosophy

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Victoria University of Wellington Item Type

Awarded Doctoral Thesis



Victoria University of Wellington School

School of Chemical and Physical Sciences


Northcote, Peter; Keyzers, Rob