The high molecular weight polyphloroglucinols of the marine brown alga Fucusvesiculosus L.: degradative analysis

The high-molecular-weight polyphloroglucinol tannin of Fucusvesiculosus has been islated in pure form as judged by 1H and 13C nmr. Acetate and methyl derivatives were prepared and examined by uv and ir spectroscopy. Calcium – liquid ammonia degradation of the methyl ether derivative liberated numerous aryl compounds including fragments arising from ether-linked phloroglucinol end groups, internal ortho-, meta-, and para-oriented diethers, vic- and (tentatively identified) sym-triethers, internal phloroglucinol-derived biphenyls (three isomers), probable terminal biphenyls, terphenyl(s), and from qua-terphenyl(s). No evidence was found for vic-trihydroxylated end groups. In all, 63 fragments were identified by gc–ms, and abundances of the major fragments were estimated by quantitative gc. The data indicate that the F. vesiculosus tannins – or at least the portion represented by these fragments – are highly branched structures consisting entirely of phloroglucinol units.