New methods of analyzing tannins¹

Recently found antitumor, antiperoxidation, antivirus, and other activities of tannins, which are largely dependent on the structure of each tannin, enhanced the need for precise analyses of tannins. Centrifugal partition chromatography, combined with gel-column chromatography, facilitated preparative separation of tannins. In addition to fabms and highperformance gel permeation chromatography (hp-gpc), normal-phase hplc promptly indicated the extent of condensation of both hydrolyzable and condensed tannins and is particularly usable for the analysis of oligomeric hydrolyzable tannins. Components of the isomer mixture formed by a tannin due to the presence of a free anomeric hydroxyl group or of a hemiacetal group were separated by reversed-phase hplc. Fabms is applicable, without derivatization of each tannin, to the mol wt determinations of tannins that are highly polar, thermolabile, and involatile. In the^lH- and¹³C-nmr spectra of various types of hydrolyzable tannins, the signals of glucose moieties were fully assigned based on¹H-¹H and^lH-¹³C selective decoupling and 2D-nmr techniques. These data established a widely applicable way of determining the location and type of sub-stituents on the sugar moiety in each molecule of hydrolyzable tannin. The absolute configurations of the chiroptical aromatic substituents were directly determined by the cd spectra. The esr measurements proved the radical scavenging effect in the inhibition of lipid peroxidation by tannins.