In vitro activity: Dihydromyricetin shows antioxidant activity as an effective scavenger of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH). It also inhibits the increase of lipid peroxidation (LPO) values in linolei acid system catalyzed by FeSO4-edetic acid. DHM (1 μM) as a novel anti-alcohol intoxication medication antagonizes both acute EtOH-induced potentiation of GABA(A)Rs and EtOH exposure/withdrawal-induced GABA(A)R plasticity and increases in GABA(A)R alpha4 subunit expression in hippocampus and cultured neurons.

Kinase Assay: A rapid spectrophotometric assay is used to determine the enzymatic activity for hydantoinase, allantoinase, dihydroorotase, and imidase. Dihydrouracil, 5-propyl-hydantoin, and phthalimide are used as substrates. Unless explicitly stated otherwise, Dihydrouracil (2 mM) is used as the substrate in the standard assay of dihydropyrimidinase. Briefly, the decrease in absorbancy at 230, 248, and 298 nm is measured upon hydrolysis of Dihydrouracil, 5-propyl-hydantoin, and Phthalimide as the substrate at 25°C, respectively. To start the reaction, the purified dihydropyrimidinase (10-70 μg) is added to a 2 mL solution containing the substrate and 100 mM Tris-HCl (pH 8.0). Substrate hydrolysis is monitored with a UV/vis spectrophotometer. The extinction coefficient of each substrate is determined experimentally by direct measurement with a spectrophotometer. The extinction coefficients of Dihydrouracil, 5-propyl-hydantoin, and Phthalimide are 0.683 mM-1cm-1 at 230 nm, 0.0538 mM-1cm-1 at 248 nm, and 3.12 mM-1cm-1 at 298 nm, respectively. The initial rates of change are a function of enzyme concentration within the absorbance range of 0.01-0.18 min-1. A unit of activity is defined as the amount of enzyme catalyzing the hydrolysis of 1 μmol substrate/min, and the specific activity is expressed in terms of units of activity per milligram of enzyme. The kinetic parameters Km and Vmax are determined from a non-linear plot by fitting the hydrolyzing rate from individual experiments to the Michaelis-Menten equation.

Cell Assay: Hippocampus and cortex tissue samples are homogenized in lysis buffer containing 20 mM Tris (pH 7.5), 135 mM NaCl, 2 mM EDTA, 2 mM DTT, 25 mM β-glycerophosphate, 2 mM sodium pyrophosphate, 10% glycerol, 1% Triton X-100, 1 mM sodium orthovanadate, 10 mM NaF, 10 μg/mL aprotinin, 10 μg/mL leupeptin, and 1 mM PMSF for 30 min on ice and centrifuged at 12000×g at 4°C for 30 min. The supernatant is collected and protein quantification is carried out using a BCA kit. The protein samples are boiled in the presence of sample buffer at 95°C for 5 min. The target protein is separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), transferred to nitrocellulose membrane, and then probed by corresponding primary and secondary antibodies. Finally, the target protein is visualized by enhanced chemiluminescence (ECL) reagent exposure to X-ray film.

Yao Xue Xue Bao. 2003 Apr;38(4):241-4; J Neurosci. 2012 Jan 4;32(1):390-401.