Valorization of polyphenols from Stryphnodendron adstringens bark for use as a sustainable inhibitor of nitrogen volatilization in soil

Abstract

Urease (EC 3.5.1.5) activity is one of the processes that most contributes to urea loss by ammonia volatilization in agriculture. The present study describes the capacity of polyphenols extracted from barbatimão tree bark (Stryphnodendron adstringens (Mart.) Coville) on inhibiting the urease enzyme extracted from Canavalia ensiformis (L.) DC. Fourier transform infrared spectroscopy (FTIR) coupled to an attenuated total reflection (ATR) accessory was chosen to determine the enzymatic kinetics. This spectroscopic technique is used to perform more sustainable enzyme kinetic studies due to the decreased use of chemicals, including highly toxic reagents. The inhibition capacity of the polyphenols was compared with N-(n-butyl)thiophosphoric triamide (NBPT). The reactions occurred in 20 mM potassium phosphate buffer, pH 7.2, and the crude urease extract was used. The maximum intensity of asymmetric stretching of the bicarbonate functional group at 1361 cm–1 was measured to study the kinetics of urease. The kinetic constants Vmax and Km were determined by nonlinear fitting with the Michaelis–Menten model. The data obtained showed the strong potential of polyphenols from bark to be used as urease inhibitors on fertilizers in soil, decreasing the use of chemical reagents exogenous to the environment, such as NBPT.