Xây dựng và thẩm định phương pháp định lượng Polyphenol toàn phần trong hạt vải bằng quang phổ UV-VIS

Abstract

Objective: To develop and validate a UV-Vis spectrophotometric method for the determination of total polyphenol content in litchi seeds (Litchi chinensis Sonn.) according to AOAC & ICH guidelines, and to evaluate the actual total polyphenol content in Vietnamese litchi seeds in order to valorize this abundant agricultural byproduct rich in bioactive compounds.

Materials and Methods: The study was conducted on Vietnamese litchi seeds. The method was based on the formation of a colored complex with Folin-Ciocalteu reagent using gallic acid as the standard, with absorbance measured at 760 nm using a UV-Vis spectrophotometer. The optimal extraction procedure was established by univariate optimization. Method validation followed AOAC & ICH criteria, including specificity, linearity, precision (repeatability), and accuracy (recovery).

Results: The method showed a maximum absorption at 760 nm. The calibration curve was linear over the range of 20-70 µg/mL gallic acid (equation: y = 0,012x - 0,0421, R² = 0,9994). The UV-Vis absorption spectra of the sample solution and the standard solution in the wavelength range of 600-800 nm showed a single peak, with maximum absorption at 732,4 nm and 760 nm, respectively. Both repeatability and inter-day precision were acceptable, with relative standard deviation (RSD) values of ≤ 2,0%. Accuracy was satisfactory with recovery rates ranging from 98.12 to 101.76% (within the AOAC acceptable range of 98–102%). The total polyphenol content in litchi seed extract was 148.56 ± 1.61 mg GAE/g dry extract, equivalent to 9.58 ± 0.10 mg GAE/g raw material (extraction yield 5.7–6.3%).

Conclusion: A UV-Vis spectrophotometric method employing the Folin-Ciocalteu reagent for the determination of total polyphenol content was successfully developed and validated, meeting all validation criteria recommended by AOAC and ICH guidelines. The results demonstrated that Vietnamese lychee seeds are a rich source of polyphenols, exhibiting higher polyphenol content than that reported in several international studies. These findings highlight the potential of lychee seeds as a valuable raw material for the development of functional foods and pharmaceutical products from agricultural by-products.