Tailor-made natural deep eutectic solvents for green extraction of isoflavones from chickpea (Cicer arietinum L.) sprouts

Natural deep eutectic solvents (DESs) have received increasing attention in recent years as emerging green solvents for efficient extraction of bioactive compounds from natural resources. In this study, we aimed to evaluate the potential and effectiveness of DESs with different polarities for extraction of isoflavones from chickpea sprouts. To this end, we examined 20 different DESs based on choline chloride, betaine, and l-proline as hydrogen bond acceptors in combination with different hydrogen bond donors (carboxylic acids, alcohols, sugars, and amine). Extraction efficiency was evaluated based on the extraction yields of four isoflavones (ononin, sissotrin, formononetin, and biochanin A), total flavonoid content, and anti-oxidant activity. On the basis of the results obtained, choline chloride-based DESs containing propylene glycol as a hydrogen bond donor (molar ratio of 1:1) with 30% (v/v) of water was the most effective at extracting isoflavone compounds from chickpea sprouts, compared to conventional solvents. Subsequently, in order to examine the factors contributing to optimal ultrasound-assisted extraction conditions, a Box-Behnken design paired with response surface methodology was implemented. DES water content and extraction temperature were accordingly found to have prominent effects on the extraction yields of isoflavones. Our results indicate that DESs can be used as suitable green solvents for extracting bioactive compounds from various biomaterials.