| || || Mani, Luke.|
| || || The isolation and characterization of antibacterial compounds from the marine sponge, Suberea clavata.|
Institution: University of the South Pacific.
Subject: Marine sponge
Call No.: Pac QL 372 .8 .F5 M36 2005
Copyright:60-80% of this thesis may be copied without the authors written permission
Abstract: A crude organic extract of the Fijian marine sponge, Suberea clavata, was found to inhibit the bacterial pathogens, methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococcus faecium (VREF). MRSA and VREF pose serious challenges to antibiotic therapy because the antibiotics, methicillin and vancomycin, to which they are respectively resistant, are considered "last line of defense" drugs. Sponges of the genus Suberea have recently furnished compounds of diverse chemistry that are biologically active. The S. clavata species meanwhile has not been chemically studied. S. clavata was therefore investigated in the hope of isolating and characterising novel antibacterial compound(s) with therapeutical potential against MRSA and VREF. To obtain the pure, active compounds, a crude organic extract of S. clavata was subjected to various steps of purification guided by MRSA and VREF bioassays which furnished the main principle and biologically active 039-lk-A and a minor, non-active constituent, 039-lk-B. Mass spectral and two-dimensional NMR data suggested the structure of 039-lk-A to be the known compound, aeroplysinin-1 30 isolated previously as the (1R,6S)-configured (+) isomer from the New Caledonian sponge S. creba165 and the (1S,6R)-configured (-) isomer from the related Ianthela ardis. Optical rotation suggest 039-lk-A is the (+)isomer. The determination of the structure of compound 039-lk-B was on the basis of mass spectral and two-dimensional NMR data which suggested it to be the known bicyclic lactone, aeroplysinin-2 M previously isolated from Aplysina aerophoba. This is the first report of aeroplysinin-2 from the genus Suberea.