Abstract
A series of novel l-lactic acid-based deep eutectic solvents (DES) were tested for polyphenol extraction performance, using organically grown, native Greek medicinal plants. The extractions were ultrasonically-assisted and the effect of the addition of β-cyclodextrin (β-CD) as extraction booster was also tested, at a concentration of 1.5% (w/v). The estimation of total polyphenol yield (YTP) suggested that DES composed of l-lactic acid and nicotinamide and l-lactic acid and l-alanine, both at a molar ratio of 7:1, are promising solvents giving significantly higher yields compared with 60% (v/v) aqueous ethanol and water. However, when β-CD was combined with DES comprised of l-lactic acid and ammonium acetate (molar ratio 7:1), the extraction yields obtained in some instances were equal of even higher. The pattern was not consistent when the yield in total flavonoids (YTFn) was considered, indicating water, 60% (v/v) aqueous ethanol and l-lactic acid:sodium acetate (molar ratio 7:1) to be the most efficient solvents. In this case, the effect of β-CD was of rather lower magnitude. The examination of the antioxidant activity of the extracts generated showed that there is a close correlation mainly with their concentration in total polyphenols.
Highlights
The use of medicinal plants to sustain a good health status and to reduce disorders and degenerative diseases has been recognised since antiquity and to date they offer a potential advantage because they comprise of an array of components with multiple beneficial effects
An extensive screening of L-lactic acid-based deep eutectic solvents (DES) with different amino-bearing hydrogen bond acceptor (HBA) indicated that the nature of HBA plays a prominent role in the polyphenol extraction efficiency [18]
It was shown for the first time that a novel bio-based DES, composed of L-lactic acid and nicotinamide, in combination with ultrasonication, can be a highly performing solvent for the extraction of antioxidant polyphenols from various medicinal plants
Summary
The use of medicinal plants to sustain a good health status and to reduce disorders and degenerative diseases has been recognised since antiquity and to date they offer a potential advantage because they comprise of an array of components with multiple beneficial effects. DES display attractive attributes, including negligible vapour pressure, tunability, lack of toxicity, low cost, etc These features make DES ideal extraction solvents, possessing unique characteristics, whereas limitations associated with similar materials, such as conventional organic solvents and ionic liquids, may be overcome [7]. DES are usually less expensive, easy to produce (use of bulk commodity chemicals) and biodegradable and, depending on the composition, they may be compatible with foods, pharmaceuticals and cosmetics Tailoring their physicochemical properties could be crucial to manipulating their extraction potency, because several parameters (polarity, viscosity, hydrogen bonding) central to mass transport phenomena may be effectively regulated [8]. This investigation was undertaken with the aim to screening the performance of polyphenol extraction from various organically grown native Greek medicinal plants, using a combination of β-CD with a series of L-lactic acid-based DES
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