RELATIONSHIP BETWEEN HYDROPHOBICITY AND STRUCTURE OF HYDROLYZABLE TANNINS, AND ASSOCIATION OF TANNINS WITH CRUDE DRUG CONSTITUENTS IN AQUEOUS-SOLUTION

The hydrophobicity values of hydrolyzable tannins were evaluated by me asuring the distribution of the compounds between n-octanol and water, Of 8 gallotannins and 13 ellagitannins examined, pentagalloylglucose (7), the major polyphenol of Paeoniae Radix, showed the largest partit ion coefficient value, In aqueous solution, pentagalloylglucose associ ated with various crude drug constituents, such as paeoniflorin, glycy rrhizin potassium salt, aconitine trifluoroacetate, liquiritin apiosid e and amygdalin. The H-1-NMR spectroscopic examination suggested that the association occurred preferentially at the most hydrophobic sites of the molecules. The association with these compounds inhibited the d istribution of pentagalloylglucose into the n-octanol phase and adsorp tion on hide powder. In addition, the water solubility of the biologic ally active polymeric proanthocyanidins of rhubarb was increased by as sociation with rhein 8-O-glucoside potassium salt, the major anthraqui none glycoside of rhubarb.