Figure 11.

(A) Proposed mechanism for the formation of the carbohydrate-derived βCs 1a/b in foods following reaction of tryptophan with the 3-deoxyglucosone intermediate formed from sugars. (B) Proposed mechanism for the formation of the βCs 2 and 3 following dehydration of 3-deoxyglucosone and reduction (βC 2), or further dehydration (βC 3) before cyclization to give the βCs. The βC 5 might come similarly from dehydration of 3-deoxyglucosone. The reaction of cyclization with tryptophan to give the βCs occurs as for 1a/b.