STUDIES ON SYNTHESIS AND STRUCTURE-ACTIVITY-RELATIONSHIPS AGAINST CYTOPROTECTIVE ACTIVITY OF TRITERPENOIDAL DIGLYCOSIDES WITH AN ACID SACCHARIDE, D-GLUCOPYRANOSURONIC ACID

Several triterpenoid alpha- and beta-diglycosides of oleanoic acid (1) , 11-deoxoglycyrrhetic acid (4) and 11-deoxoglycyrrhetol (5) were synt hesized. The synthetic diglycosides induced one or both D-glucopymanos uronic acids as sugar components. Cytoprotective activities of the dig lycosides against carbon tetrachloride-induced hepatotoxicity were inv estigated using mice. The activities of the synthetic diglycosides wer e estimated by assay of aspartate transaminase and alanine transaminas e, which were released from the injured hepatocytes and compared with that of glycyrrhizin (9). The beta-diglycosides of 1 and 4 showed pote nt activities in contrast to those of 5; none of the alpha-glycosides showed remarkable activity. Reduction of the carbonyl group (C=O) at C -11 on the C-ring of the aglycons slightly enhanced the activity over that of 9, and replacement of the carboxyl group (COOH) on the aglycon s by a hydroxylmethyl group (CH2OH) drastically decreased the activity .