Abstract:

As typical degradation products of carbohydrates, alpha-dicarbonyls including glyoxal, pyrualdehyde and butandione were individually used for comprising model systems with L-leucine to investigate their roles in the formation of isovaleraldehyde in the Strecker degradation of L-leucine. A high pressure vessel was used for the reaction between alphadicarbonyls and L-leucine in phosphate buffer solution and the effects of molar ratio of reactants, temperature and pH value on isovaleraldehyde yield were examined using orthogonal array design. Results showed that among three alpha-dicarbonyls, the system containing glyoxal gave the highest isovaleraldehyde yield of around 24% under the reaction conditions of 140 ℃, pH 5 and 6:1 molar ratio of glyoxal to L-leucine, while isovaleraldehyde yield was only around 14% when pyrualdehyde or butandione was used instead of glyoxal. This demonstrates the highest reactivity of glyoxal for the formation of isovaleraldehyde. Among three reaction conditions tested, pH had the most obvious effect, and an acidic condition favored the formation of isovaleraldehyde.

Key words: L-leucine, &alpha, -dicarbonyls, Strecker degradation, isovaleraldehyde