OPTIMIZATION OF EXTRACTING SOLUTION OF TOTAL SOLUBLE PHENOLIC COMPOUNDS FROM RYEGRASS USING WHITE TECHNOLOGY ASSISTED BY LOW-FREQUENCY ULTRASOUND

Exploring new food sources was innovative for the food industry, highlighting ryegrass, a cereal little explored in human food, rich in phytochemicals that have good prospects to assist in combating non-degenerative chronic diseases. Regarding to the phytochemicals, the phenolic compounds stand out, a large group that differs by chemical structure, presenting different solubilities. This work optimized the extractor solution of total soluble phenolic compounds (TSPC) from ryegrass using the Response Surface Methodology (RSM). The performance of water, methanol, acetone and acetic acid was evaluated through a Simplex-Centroid Mixture Design (P<0.05; R2>0.95), followed by exhaustive extraction in cycles to maximize TSPC extraction. Extraction (200mg of sample and 1500µL) was assisted on low-frequency ultrasound (40Hz/100W, 5min/20°C), followed by centrifugation (5000g/10min at 20°C) and the final volume was measured at 2000µL. The Folin-Ciocalteu method was used to determine the aliquots’ absorbance (750 nm) in a microreader. The extraction was favored by the binary components between water and acetic acid (β14 = 0.842; P<0.001), water and acetone (β13 = 0.633; P<0.001) and methanol and acetic acid (β24 = 0.568, P<0.001). The optimal point was obtained with 41% water, 3% methanol, 12% acetone and 43% acetic acid, with a desirability of 1.0. The mathematical model was validated in triplicate, with a relative deviation of 3.48 %. For maximum TSPC extraction, seven cycles were performed, with absorbances ranging from 0.512 in the first cycle and 0.019 in the last cycle, and 98.34% of these phytochemicals were solubilized in the sixth cycle. Synergism between solvents allows us to infer that ryegrass TSPC has a wide range of chemical structures (aromatic rings and organic carboxylic acid), many functional groups (hydroxyls, carbonyls, carboxylic acids, methyl groups) and distinct polarities, encompassing phenolic acids (hydroxybenzoic and hydroxycinnamic acids), flavonoids and nonflavonoids.