MULTIVARIATE ANALYSIS AND WHITE CHEMISTRY AS STRATEGIES FOR OPTIMIZING THE EXTRACTION OF ANTHOCYANINS FROM SUDAN GRASS (Sorghum sudanense (Piper) Stapf.) ASSISTED BY LOW-FREQUENCY ULTRASOUND

Sudan grass (SG) is a cereal with a purple to reddish pericarp, high resistance to water stress, and is mainly used for animal feed. It has a potential for application in the food industry due to its physicochemical composition, rich in phytochemicals. Optimizing a chemical solution for extracting total monomeric anthocyanins from SG seeds is essential to understanding the best conditions for obtaining extracts with minimal chemical waste. This study aimed to optimize (P<0.05; R2>0.95) the anthocyanin extraction solution in SG seeds using a Simplex-Lattice Mixture Design with seven solvents (water, ethanol, methanol, 2-propanol, acetone, acetonitrile, and formic acid), totaling 39 trials. SG flour was obtained using a ball mill, and a 200 mg aliquot was weighed into Eppendorf tubes (2000μL), and 1500μL of the extraction solution was added. The tubes were vortexed to ensure homogeneous sample suspension, and extraction was performed using low-frequency ultrasound (40Hz/100W) for 30min, followed by a 20-min rest and another 30-min extraction at room temperature (20°C). The tubes were centrifuged (5000xg/10min/20°C), and the final volume was adjusted to 2000 μL. The absorbance of anthocyanins at pH 1.0 was measured at 520 nm. The absorbance values ranged from 0.013 to 1.850 and were primarily favored by formic acid (β7=1.859; P<0.001), ethanol (β3=0.686; P<0.001), acetone (β6=0.655; P<0.001), and 2-propanol (β7=0.508; P<0.001). Absorbance was also influenced by binary components such as methanol-formic acid (β27=1.176; P<0.016), 2-propanol-acetonitrile (β45=1.134; P<0.020), and ethanol-acetonitrile (β35=1.086; P<0.026). The results were explained by an R2=0.938 (P<0.001; F=23.18) for the mathematical model. The optimized point was identified using 100% formic acid (desirability of 1.0), possibly because it was used in its pure form (analytical grade). However, other solvents, including ethanol, methanol, acetone, and 2-propanol, exhibited significant extraction capabilities, while water did not have a significant effect on anthocyanin extraction, inferring that more studies are needed.