DEODORIZING ACTIVITY OF DITERPENES FROM THE LEAVES OF RABDOSIA-TRICHOCARPA AND OF SEVERAL ALPHA,BETA-UNSATURATED CARBONYL-COMPOUNDS AGAINSTMETHANETHIOL

Fourteen diterpenes containing one novel compound from the leaves of R abdosia trichocarpa had significant deodorizing activity against metha nethiol (CH3SH), the main source of halitosis. The compounds generated from the reaction between oridonin, the main compound of the 14 diter penes and CH3SH were isolated and determined to be two adducts, 17 alp ha-CH3S-oridonin and 17 beta-CH3S-oridonin. This implies that CH3SH re acted with oridonin, which had an exocyclic methylene group conjugated with a ketone, by 1,4-addition. Oridonin reduced the bad odor by conv erting CH3SH to these non-volatile compounds. Oridonin showed signific ant deodorizing effect in the basic pH range, and had almost no effect in the acidic pH range. The rate of the deodorizing action of oridoni n was relatively faster than that of tea catechins, which are widely u sed as oral deodorizers. The deodorizing effect of several alpha,beta- unsaturated carbonyl compounds against CH3SH was also determined.