*4.6. Determination of NO Production*

Nitrite (NO2 −) was measured as an indicator of NO synthesis and was estimated using the Griess reagent [62]. A NO detection kit (Beyotime, Shanghai, China) was used according to the manufacturer's instructions. In brief, 50 μL samples were mixed with an equal volume of Griess reagents I and II at room temperature. The absorbance was determined at 540 nm and calibrated with a nitrite standard curve to determine the nitrate concentration in samples.
