Metabolite marine brown algae

FIGURE 6.3 Examples of secondary metabolites from marine brown algae. 

Fungus Epicoccum sp. was isolated from the marine brown alga Fucus vesiculosus. From the cultivated fungus, a new secondary metabolite 4,5,6-trihydroxy-7-methylphthalide 336 (epicoccone) was found. 336 was found to be potently active, showing 95% DPPH radical scavenging effects at 25 pg mL. It also inhibited the peroxidation of linolenic acid in the TEARS assay (62 % inhibition at 37 pg mL ). 

An unusual steroid derivative, ergosterimide (195), was characterized from the culture extract of A. niger EN-13, an endophytic fungus isolated from the Chinese marine brown alga C. sinuosa Chemically, 195 is a Diels-Alder adduct of a suitably substituted ergosteroid and maleimide. The latter has a widespread use in technical applications, and is commonly used as an adduct for Diels-Alder reactions due to its high reactivity. If maleimide indeed was a metabolite of the fungus under study, 195 would represent the first natural Diels-Alder adduct of this type. 

In a more recent application of this type of reaction, Capon et al. (14) converted 1,10,13 -nonadecatriene to a mixture of stereoisomerie bisepoxides that formed ace-toxyhydroxytetrahydrofiuans when treated with acetic acid at 100°C. These were hydrolyzed to dihydroxrytetrahydrofiirans, some stereoisomers of which had previously been recognized as metabolites of the marine brown alga Notheia anomala. In essence, this series of reactions converts a 1,4-diene to a dihydroxytetrahydrofuran via the bisepoxides in a high-yield process see Scheme 10. 

Venkateswarlu S, Panchagnula GK, Gottumukkala AL, Subbaraju GV (2007) Synthesis, structural revision, and biological activities of 4 -chloroaurone, a metabolite of marine brown alga Spatoglossum variabile. Tetrahedron 63 6909... 

Stockeyia indica is a brown marine benthic alga, occurring in mid to lower littoral pools, novel linear metabolite (18) has been isolated and its structure has been established w the help of modern spectroscopic techniques. 

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