Microwave-ultrasound hybrid technology assisted extraction of pigments with antioxidant potential from red corn

Abstract

Current trends in the use of new pigments of natural origin have led to the investigation of novel technologies for obtaining them. The objectives of this study were to evaluate the extraction process by microwave (MAE) and ultrasound (UAE) assisted techniques and a treatment using simultaneously both techniques (hybrid way) (HM-UE) of pigments from corn with different shades of red (highly pigmented corn = RA, moderately pigmented corn = RM and poorly pigmented corn = RB), and to determine the color, content of hydrolyzable polyphenols, condensed tannins, and antioxidant potential by DPPH, ABTS and FRAP tests. Finally, the pigments obtained by HM-UE underwent thermogravimetric analysis (TGA) and were characterized by Fourier transform infrared spectrometry (FTIR) and HPLC-MS. Results indicated that hybrid-assisted extraction (HM-UE) yields higher extraction yields (p < 0.05) compared to the individual techniques, and the hydrolyzable polyphenol content in HM-UE was 15.5 % higher than that of MAE and 77.3 % higher than that of UAE. In addition, the condensed tannin content was 43.6 % and 62.8 % higher than that of UAE and MAE, respectively. On the other hand, the concentration of condensed tannins and hydrolyzable polyphenols of the pigments obtained from RA with HM-UE showed concentrations of 1.49 and 0.33 mg/g of sample. The compounds identified in these pigments were derivatives belonging to the flavonoid family, such as Apigenin arabinoside-glucoside, 7,4′-Dihydroxyflavone, and Apigenin 6,8-di-C-glucoside, to which their high antioxidant potential is attributed. These results allowed to visualize that the hybrid microwave-ultrasound technique is a viable option for obtaining pigments with antioxidant potential from red corn.