Cary 60 ultraviolet visible uv vis spectrophotometer

The TPC was estimated by the Folin-Ciocalteu colorimetric method [27 ]. The freeze-dried skin or seed samples were solubilized in methanol (1/200: w/v). 20 μL of the diluted extract, 1.58 mL of water, and 100 μL of Folin-Ciocalteu reagent were mixed. After 30 s, 300 μL of 20% sodium carbonate solution (w/v) was added. The reaction mixture was thoroughly shaken and left for 2 h in the dark at room temperature (20 °C). Then, the specific absorbance was measured at 700 nm against the blank prepared for each series of determination in such a way that the sample was replaced by the methanol, using an Agilent Cary 60 Ultraviolet-Visible (UV-Vis) spectrophotometer (Santa Clara, CA, United States). The calibration curve of gallic acid was used to determine the concentration of polyphenol in samples. All tests were carried out in triplicate and the results were expressed as gram of Gallic Acid Equivalent (GAE) per kilogram of FW.