INTERACTION OF METHYLFURALDEHYDE AND FUCOSE WITH CYSTEINE AND O-CRESOL IN SULFURIC-ACID MEDIUM

Fucose, rhamnose and methylfuraldehyde in 75% sulfuric acid in presenc e of heat, condensed with cysteine to form chromogens (thiazolidones) with lambda max of 400 nm and the epsilon values of the products were respectively, 7380, 8720 and 13500. While fucose and rhamnose reacted fairly efficiently with o-cresol to form semiquinonoids, with lambda m ax of 490 nm (epsilon:6330 and 13400, respectively), methylfuraldehyde reacted poorly (epsilon:1100). While cysteine had no effect on intera ction of methylpentoses with o-cresol, it enhanced condensation of met hylfuraldehyde 14.3 fold even at a low concentration of one mg. In 60% acid, cysteine (5 mg) increased chromogen formation for methylfuralde hyde, fucose and rhamnose with o-cresol, 6.7 fold, 2.3 fold and 2.2 fo ld, respectively. Ih the two stage assay, in which dehydration with 60 % acid was effected at elevated temperature and condensation with o-cr esol was performed at room temperature, cysteine (5 mg) significantly enhanced chromogen formation for fucose (6.3 fold, epsilon at 490 nm, 25700), rhamnose (5.6 fold, epsilon at 490 nm, 28700) and methylfurald ehyde (6.3 fold, epsilon at 490 nm, 44900).