The polyphenolic compoundsextract rich in gallo-catechol tannins submitted to complementary analytical techniqueswas evaluated. The whole plantspecies screened were of the condensed type except Acacia seyal var. fistuala, Acaciaseyal var. seyal, Casuarina equistifolia, and Pithecellobium dulcewere of mixedhydrolysable-condensed(gallo-catechol) type. The quantitative data indicated that 5 parts (bark) out of 12 species, when extracted, contained more than 10% tannins (oven-dry basis), the level of commercial interest. The catechin numbers indicated that all the studied species contained condensed tannin in varying amounts (0.6-45.7), while the presence of both gallic acid and catechin means that the tannin is of mixed type. Thin-layer and paper chromatography with different solvent systems confirmed the presence of catechin and gallic acid, and showed that tannic acid, fisetin, epicatechin and some unidentified phenolics were present. However, dihydrofisetin and robinetin, which were used as standards, were not detected. Astringency values shows that the Acacia mellifera(0.18), Acacia seyalvar.fistuala(0.18), Pithecellobium dulce (0.15), Acacia senegal (0.14), Acacia farnesiana (0.13), Calotropis procera (0.13)barks could be used in place of A. mearnsii(international commercial tannin materials) (0.16) because the degree of relative astringency or the ability of their tannin to combine with protein is close to that of A. mearnsii in other words these six species can give leather with characteristics comparable with that of A. mearnsii.
COMPLEMENTARY ANALYTICAL TECHNIQUES PAPER, THIN-LAYER, HIDE-POWER, AND COMBINED METHODS FOR CHARACTERIZATIONOF TANNIN IN PLANTS
