Optimization of reactions between reducing sugars and 1-phenyl-3-methyl-5-pyrazolone (PMP) by response surface methodology.

Reducing sugars have strong reactivity with 1-phenyl-3-methyl-5-pyrazolone (PMP) to form the sugar-PMP derivatives, which can be more accurately analyzed by HPLC-UV at 248 nm. Glucose and glucosamine reacted with the PMP based on the response surface methodology within a range of temperature between 60 °C and 80 °C, and time between 60 and 180 min. The optimal conditions for the glucose-PMP and glucosamine-PMP reactions were obtained at 71 °C for 129 min, and 73 °C for 96 min, respectively. Subsequently, other sugars and their derivatives, including xylose, ribose, fructose, galactose, mannose, lactose, maltose, sucrose, glucuronic acid, sorbitol, mannitol, xylitol, and cyclodextrins were investigated and compared under the optimized condition for glucose. All of the above compounds, except the fructose, sugar alcohols and non-reducing sugars, could form the sugar-PMP derivatives. This study demonstrated that different chemical structures of sugars and their derivatives could significantly influence the rate and yield of the PMP derivatization.