NADES-Assisted Extraction of Polyphenols from Coriander Seeds: A Systematic Optimization Study

Coriandrum sativum L. seeds are widely recognized for their traditional use in medicine. Among the most investigated components, the terpenoid linalool and monounsaturated petroselinic acid have attracted interest for their nutritional value. Instead, minor attention was paid to the polyphenolic fraction, resulting still being incomplete today. This study aimed to develop a systematic approach in which green natural deep eutectic solvents (NADES) were combined with conventional (maceration, MAC) or non-conventional (ultrasound-assisted extraction, UAE) techniques in a one-step methodology to recover polyphenols from coriander seeds. The NADES system choline chloride-citric acid (ChCl:CA, 1:1) was firstly evaluated, coupled with MAC or UAE, and then compared with ChCl-Urea (ChCl:Ur, 1:1) and ChCl-Glucose (ChCl:Glu, 1:1) under optimal conditions (20 min extraction time). The system ChCl:Ur UAE significantly improved the extraction of chlorogenic acid and its isomer (453.90 ± 4.77 and 537.42 ± 1.27 µg/g, respectively), while the system ChCl:Glu UAE improved the extraction of protocatechuic, caffeic and p-coumaric acids (131.13 ± 6.16, 269.03 ± 4.15 and 57.36 ± 0.06 µg/g, respectively). The highest levels of rutin were obtained with ChCl:CA-based NADES when the MAC technique was applied (820.31 ± 28.59 µg/g). These findings indicate that the NADES composition could be appropriately modulated to tailor extraction towards higher levels of a desirable bioactive for further applications.