Analysis of the total phenolic content from different species of grapes by using pulp and skin in two different solvents; water and methanol / Muhd Farizul Md Ismail

Nowadays, study in total phenolic content from natural products has been actively carried out. As a raw material, different species of grapes was chosen. This study was designed to analysis of the total phenolic content from different species of grapes by using pulp and skin in two different solvents; water and methanol. The total phenolic content was determined by using the Folin Ciocalteu assay. Gallic acid was selected as the standard in order to determine the calibration curve of TPC. The grapes were extracted with methanol according to ratio 4:6 while the others grapes were extracted with distilled water and both flasks were incubated in 30 minutes for further analysis. The experiment was conducted in UiTM Negeri Sembilan laboratory by using UV-visible spectrophotometer. From this study, it indicated that black grapes species contain the highest value of TPC which is 8.963 mg GAE/L than red and green grape varieties in all parts of grapes studied. Methods validation is also evaluated under the factor of linearity and calibration, limit of detection, limit of quantification, laboratory fortified blank, laboratory reagent blank and precision. For the gallic acid calibration curve, the linear coefficient obtained is 0.9999 which is absorbance is directly proportional to the concentration. The value of LOD, LOQ, LRB and LFB is 0.069 ppm, 0.076 ppm, 3.1123 mg GAE/L ± 0.6655 and 19.9790 mg GAE/L ± 0.7185. Besides that, the percentage of precision achieved was 119.1% which indicated that the results was in the favorable range.