FUNCTIONAL GROUP IDENTIFICATION USING FTIR AND ANTHOCYANIN PROFILING BY HPLC IN PURPLE SWEET POTATO (IPOMOEA BATATAS L.)

Background. Purple sweet potato (PSP) has attracted increasing scientific and industrial interest due to its distinctive purple flesh, which is primarily attributed to anthocyanins. Although PSP is produced in large quantities in Vietnam, comprehensive information on its functional groups and anthocyanin pigment composition remains limited. Therefore, characterization of functional groups and identification of anthocyanin pigments are essential to support both scientific research and industrial applications of this raw material. Materials and methods. PSP tubers were collected from farms in Vinh Long Province, Vietnam. The tubers were washed, peeled, sliced, and steam-blanched at 100°C for 3 min, dried at 50°C for 8 h, and milled into powder. Functional groups were characterized using Fourier transform infrared (FTIR) spectroscopy. Anthocyanins were extracted with acidified methanol and analyzed using high-performance liquid chromatography (HPLC) with external standards for pigment identification and quantification. Results. FTIR analysis revealed 14 characteristic absorption bands in PSP grown in Vietnam within the wavenumber range of 3288.63–418.55 cm⁻¹. These bands corresponded to hydroxyl, C–H/O–H/N–H, aromatic (C=O and C=C), ester C–O–C, glycosidic, and pyran ring functional groups, consistent with structural features typical of anthocyanin compounds. HPLC analysis detected three main anthocyanin pigments with retention times of 7.85, 8.77, and 9.93 min, identified as delphinidin, cyanidin, and peonidin, respectively. Their concentrations were 4.034 µg/g (2.2%), 28.490 µg/g (15.5%), and 151.206 µg/g (82.3%). Conclusion. These results indicate that PSP is a promising source of anthocyanins and has strong potential for use as a functional food with health-promoting properties.