Small molecule antioxidants in marine organisms from the Great Barrier Reef, Japan and USA

Full description

Specimens of the zoanthid, Palythoa tuberculosa and the ascidian, Lissoclinum patella were collected using SCUBA from 2-4 m depth at Davies Reef in June 1990. Specimens were stored at -20°C until extracted. Coral trout (Plectropomus leopardus) were caught by handline at the same reef and the ocular lenses excised and frozen. Freeze dried red alga samples were sourced from 2 locations: Porphyra tenera was a gift from the Yamamoto Nori Research Institute, Ota-ku, Tokyo, and Mastocarpus stellatus, collected from Schoodic Point, Maine, USA, was provided by Professor JM Shick.Methanolic aqueous extracts containing mycosporine-like amino acids (MAAs) were prepared from tissue samples from each species and the MAAs were separated and quantified by reverse-phase, isocratic high-performance liquid chromotography (HPLC).Phosphatidylcholine peroxidation inhibition assay (PC-assays) were conducted using 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) and soybean phosphatidylcholine (PC) as radical inititor and lipid substrate, respectively.AAPH-initiated oxidation reactions of MAAs in sample tissue extracts were conducted without phosphatidylcholine as a competing substrate.Mycosporine-Gly was fractionated from the Palythoa extract and after processing was quantified by photometric analysis using published molar absorptivity data. The antioxidant activity of mycosporine-Gly was determined with the addition of appropriate quantities of sample to give 15 and 30 µM concentrations of mycosporine-Gly in the PC-assay. Ascorbic and uric acids were used for comparison of PC peroxidation inhibition rates.In these sample extracts, mycosporine-glycine was reactive to peroxyl radicals whereas iminomycosporine-like amino acids (shinorine, porphyra-334, palythine, asterina-330 and palythinol) were oxidatively robust. Purified mycosporine-glycine inhibited peroxyl radical-initiated autoxidation of phosphaditylcholine in a concentration-dependent manner. These results suggest that mycosporine-glycine may function as a biological antioxidant in marine organisms.
This research was undertaken to examine the antioxidant activities of extracts from tissues of different marine species by their peroxyl radical-trapping ability using the phosphatidylcholine peroxidation inhibition assay (PC-Assay).

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Statement: Statement: The procedures for separation and quantification of MAAs are described in:Dunlap WC, Chalker BE (1986) Identification and quantitation of near-UV absorbing compounds (S-320) in a hermatypic scleractinian. Coral Reefs 5, 155-159.Dunlap WC, Williams DMcB, Chalker BE, Banaszak AT (1989) Biochemical photoadaptations in vision: UV-absorbing pigments in fish eye tissues. Comp. Biochem. Physiol. 93B, 601-607.Shick JM, Dunlap WC, Chalker BE, Banaszak AT, Rosenzweig TK (1992) Survey of ultraviolet radiation absorbing mycosporine-like amino acids in organs of coral reef holothuroids. Mar. Ecol. Prog. Ser. 90, 139-148.The method used for Phosphatidylcholine peroxidation inhibition assays (PC-assays) is described in:Kohen R, Yamamoto Y, Cundy KC and Ames BN (1988) Antioxidant activity of carnosine, homocarnosine and anserine present in muscle and brain. Proc. natn. Acad. Sci. U.S.A. 85: 3175-3179.The molar absorptivity data used in the photometric analysis of micosporine-Gly were published in:Ito S and Hirata Y (1977) Isolation and structure of a mycosporine from the zoanthid Palytoa tuberculosa. Tetrahedron Lett. 28, 2429-2430.

Notes

Credit
Dunlap, Walter C, Dr (Principal Investigator)