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Isolation and Structure Elucidation of New Secondary Metabolites from New Zealand Marine Red Algae

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posted on 2021-11-04, 22:05 authored by Popplewell, Wendy Lynne

The natural product analysis of New Zealand red algae has been neglected in recent years, and there is obvious scope for the chemical re-evaluation of New Zealand marine red algae. This study describes the isolation and structure elucidation of 12 new and eight known compounds from four different genera of red algae. To aid in this process, 34 red algae were screened in order to generate a digital HSQC spectra mask, a screening tool developed by the VUW Marine Natural Products group to identify extracts of interest for further analysis. All 34 algal extracts were screened using the HSQC mask and four extracts were identified as interesting and analysed in detail. Examination of extracts of the red algae Plocamium costatum and Ballia callitricha lead to the isolation of three known metabolites. Eleven new oxylipins, labillarides A to K, are reported from the alga Phacelocarpus labillardieri. Labillarides A to H are polyunsaturated alpha-pyrone macrocycles, all of which show similarities to the previously reported compounds isolated from southern Australian collections of the algae. Labillarides E to H are of particular interest as they represent the two diastereomeric pairs associated with variation at the C-3 and C-8 chiral centres. Labillarides I and J are related enol macrocycles while labillaride K is a furan-3-one oxylipin, all of which have biogenic significance to the macrocyclic alpha-pyrones. Labillarides A, B and I exhibit moderate cytotoxicity while labillaride C shows moderate antibacterial activity. A new nitrogenous bromophenol, colensolide A, was isolated from the alga Osmundaria colensoi along with five known bromophenols. The presence of nitrogen-containing sidechains in bromophenols is unusual but not unprecedented. The bicyclic nitrogenous moiety observed in colensolide A is proposed to be of histidine origin. Several of the known bromophenols exhibit antibacterial activity and one shows moderate cytotoxicity.

History

Copyright Date

2008-01-01

Date of Award

2008-01-01

Publisher

Te Herenga Waka—Victoria University of Wellington

Rights License

Author Retains Copyright

Degree Discipline

Chemistry

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level

Doctoral

Degree Name

Doctor of Philosophy

Victoria University of Wellington Item Type

Awarded Doctoral Thesis

Language

en_NZ

Victoria University of Wellington School

School of Chemical and Physical Sciences

Advisors

Northcote, Peter