| Popis: |
The polyphenolic compoundsextract rich in gallo-catechol tannins submitted to complementary analytical techniqueswas evaluated. The whole plantspecies screened were of the condensed typeexcept Acacia seyal var. fistuala, Acaciaseyal var. seyal,Casuarina equistifolia, andPithecellobium 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 theAcacia 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 ofA. 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 ofA. mearnsiiin other words these six species can give leather with characteristics comparable with that ofA. mearnsii. |
