U 2800 double beam uv vis spectrophotometer

Determination of total phenol was according to Stoilova et al. [50] (link) using a modified Folin-Ciocalteau method. Determination of the total phenol content of Java tea leaf extract was carried out spectrophotometrically using the Folin-Ciocalteu reagent and gallic acid as a comparison. A total of 1 mL of sample was taken in a test tube, then added 5 mL of 7.5% Folin-Ciocalteu reagent, vortexed
until homogeneous and allowed to stand for 8 min in a dark room. The mixture was then added with 4 mL of 1% NaOH and then vortexed until homogeneous and placed in a dark room for 1 h. The absorbance of the solution was measured using the Hitachi U-2800 Double Beam UV/VIS Spectrophotometer at a wavelength of 730 nm. Quantitative analysis of total phenol was carried out by making standard curves of 0, 10, 30, 50, 70, and 100 ppm concentrations of gallic acid. Total phenol is reported as gram of gallic acid equivalent (GAE)/g of extract.

The determination of antioxidant content of the leaf extract refers to the method of Re et al. [40] . ABTS radical solution was prepared by mixing 10 mL of 7 mM ABTS with 5 mL of 2.45 mM K2S2O8 for 12-16 h in a dark place. A total of 180 µL of ABTS radicals were reacted with 20 µL of extract and incubated at room temperature for 15 min. The absorbance of the mixture was then measured at a wavelength of 734 nm using the Hitachi U-2800 Double Beam UV/VIS Spectrophotometer. Trolox was used as standard and its antioxidant activity was reported in mg of Trolox equivalent (TE)/g of extract.