We have already reported (El S i s s i et al., 1965, 1966 a) that the tannins of the leaves of Rhus coriaria and Mangifera indica (both belonging to Anacardiaceae) amount to 23.35% and 9.27% respectively.After acid hydrolysis of the methanol extract of R. coriaria leaves, the flavonols myricetin, quercetin and kaempferol, together with gallic acid, m-digallic acid, methyl gallate and ellagic acid were clearly identified (El S i s s i et al., 1966 a). In addition, glucose and rhamnose were also released as proved by reference paper chromatography. It should be pointed out, however, that the hydrolysed ethyl acetate extract gave similar chromatographic patterns.As the flavonols myricetin, quercetin and kaempferol could not be identified in the ethyl acetate or in the methanol extracts prior to acid hydrolysis, trials were then made to isolate and identify the present glycosidic flavonoids and polyphenolics including the gallotannin which is known to be the main polyphenolic component of R. coriaria (sumach) leaves.Among the polyphenolic components of M. indica leaves, the presence of gallic acid, protocatechuic acid and ellagic acid was demonstrated, beside d-catechin, quercetin and kaempferol which could be regarded as prototypes of condensed tannin (El S i s s i and E l A n s a r i , 1966b).Also the yellow pigment mangiferin, whose structure has been recently fully established as 1,3,6,7-tetrahydroxyxanthone-2-glucopyranoside, especially after its synthesis by B h a t i a and S e s h a d r i (1968) proved to be present in M. indica leaves up to .7.1%. This polyphenolic pigment which is slightly soluble in water does not precipitate gelatin from solution. Attention was then paid to extend the studies concerning the polyphenolic constituents of mango leaves to search for those constituents adsorbed by hide powder and hence responsible for tanning action. E 1 A n s a r i (1968) has recently indicated that mango panicles contain a polyphenolic component of the gallotannin type.Gallotannins, belonging together with ellagitannins to the hydrolysable tannins are of great importance in view of the extent of their use in tannage. Sumach (R. coriaria), Chinese (R. semialata) and Turkish (Quercus infectoria) tannins are considered as typical representatives of the subgroup gallotannins, beside tara tannin, hamameli tannin etc.
