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Polyphenolic compounds derived from medicinal plants have attracted considerable attention due to their antioxidant, antimicrobial, and pharmacological properties. In recent years, deep eutectic solvents (DESs) have emerged as environmentally friendly alternatives to conventional organic solvents for the extraction of bioactive compounds, supporting the principles of green chemistry.
The extraction of polyphenolic compounds from Salvia officinalis L. (sage) was investigated using a series of deep eutectic solvents (DESs) as sustainable alternatives to conventional organic solvents. Nineteen choline chloride-based DES systems were prepared and evaluated, while 70% methanol was used as a reference solvent. Plant samples were subjected to ultrasound-assisted extraction, and the resulting extracts were analyzed by high-performance liquid chromatography coupled with diode-array detection and mass spectrometry (HPLC-DAD-MS).
Quantitative analysis focused on the major classes of bioactive compounds present in sage extracts, including phenolic acids, flavonoids, procyanidins, and terpenoids. The results demonstrated that 70% methanol provided the highest extraction yield of phenolic acids (26.55 mg/g) and terpenoids (1.64 mg/g). However, several DES systems exhibited superior selectivity toward specific classes of compounds. In particular, choline chloride–tartaric acid [ChT(1:2)] achieved the highest flavonoid content (81.31 mg/g), substantially exceeding that obtained with methanol (16.49 mg/g). Choline chloride–urea [ChU(1:2)] and choline chloride–acetic acid [ChA(1:2)] also showed enhanced flavonoid extraction efficiency. The extraction of procyanidins remained relatively low in all investigated systems, although ChA(1:2) and ChU(1:2) provided slightly higher yields than methanol.
The findings indicate that the composition and physicochemical properties of DESs strongly influence their extraction performance and selectivity. While methanol remains highly effective for the extraction of phenolic acids and terpenoids, DES systems based on tartaric acid and urea represent promising green alternatives for the selective extraction of flavonoids. Their low toxicity, biodegradability, and tunable properties support their potential application in sustainable extraction processes for natural bioactive compounds.
Keywords: Salvia officinalis L.; deep eutectic solvents (DESs); green extraction; polyphenolic compounds; flavonoids; HPLC-DAD-MS; sustainable solvents