Sugar-based natural deep eutectic solvent (NADES): Physicochemical properties, antimicrobial activity, toxicity, biodegradability and potential use as green extraction media for phytonutrients

In the pursuit of sustainability, green technology frequently seeks out novel and environmentally friendly solvents to replace petrochemical solvents that are commonly utilized in the industries. These traditional solvents have been known to pose threats to both the ecosystem and living beings. Alternative green solvents such as ionic liquid (IL), supercritical fluid, and agrochemical fluid have gained much attention over the past two decades. However, their efficiency, cost, biodegradability, and environmental friendliness are frequently questionable. Thus, there is a need of green, sustainable, efficient, and low-cost solvents that are safe for human consumption to recover valuable bioactive compounds such as rutin, flavonoids and phenolic compounds from various materials and media. Deep eutectic solvent (DES) is an alternative green solvent to replace IL and it is formed by the complexation of Lewis or Brønsted acid with Lewis base which is normally a halide anion. Later, natural deep eutectic solvent (NADES), was discovered by using plant metabolites such as sugar, amino acid, and organic acid as the starting materials. The use of NADES as extraction solvents is a potential strategy in several industries including nutraceuticals, pharmaceuticals, foods and cosmetics. It happens due to the unique physicochemical properties, being inexpensive, low toxicity, biodegradability, and biological activity of NADES. Studies had reported that sugar-based NADES exhibited high extraction efficiency on different biomasses at low toxicity. Glucose (Glu), sucrose (Suc) and fructose (Fru) are commonly used as the sugar molecules in the formation of sugar-based NADES. This represents an area of interest that has sparked interest in the scientific communities especially when safety is of upmost importance during solvent selection. To date, review on sugar-based NADES is absent and hence this work serves as an addition on the introduction of sugar-based NADES, the formation, physicochemical properties, toxicity and biodegradability, and the applications in extraction technology. Additionally, the effectiveness of sugar-based NADES in extracting different bioactive compounds is evaluated and the performance of sugar-based NADES in comparison to other NADES varieties, including acid-based, polyol-based, DES, and conventional organic solvents are critically assessed in this review.