Modern Techniques for Flavonoid Extraction—To Optimize or Not to Optimize?

Abstract

Flavonoids, specialized metabolites found in plants, have a number of beneficial properties and are important for maintaining good health. Efficient extraction methods are required to extract the most bioactive compounds from plant material. Modern techniques are replacing conventional methods of flavonoids extraction in order to reduce energy and solvent consumption, increase extraction efficiency, and satisfy growing market demand as well as environmental legislation. The extraction of bioactive molecules compounds is affected by a number of variables. To determine the conditions that ensure the highest extraction yield, it is advisable to analyze the interactions between the above in parallel. In this work, an overview of the advantages and performance of modern methods (microwave-assisted extraction, ultrasound-assisted extraction, pressurized liquids-assisted extraction, and supercritical fluids extraction) for the extraction of flavonoids is presented. This work also presents the application of extraction process optimization and extraction kinetics for flavonoid extraction, using different types of experimental designs for different flavonoid sources and different extraction methods. The general conclusion of all the studies listed is that an experimental design combined with RSM modeling reduces the number of experiments that should be performed to achieve maximum extraction yield.

Tissue-Specific Profiling of Biflavonoids in Ginkgo (Ginkgo biloba L.)

“…Flavonoids have a 15 carbon- atom flavone skeleton, C6-C3-C6, with two benzene rings (A and B) joined by a trinuclear pyran ring (C). The position of the B catechol ring on the C pyran ring, as well as the number and position of hydroxyl groups on the catechol group of the B ring, have a major influence on the chemical properties and biological activity of flavonoids [ 1 , 2 , 3 ]. In addition, flavonoids can be conjugated, glycosylated, or methylated, which also affects their biological properties and function in plants [ 1 ].…”

Nontargeted Screening for Flavonoids in Salicornia Plant by Reversed-Phase Liquid Chromatography–Electrospray Orbitrap Data-Dependent MS2/MS3

“…Indeed, the use of ultrasounds may help disrupt cell walls, favoring the release of flavonoids interacting with cellular matrix [ 22 , 32 ]. Moreover, the application of a lower pH in NH 4 Ac medium may increase the extraction efficiency, as it was reported in the literature [ 48 , 49 ]. In both extraction conditions, high amounts of quercetin-3-β- d -glucoside and luteolin were achieved in Salicornia europaea and may confer valuable antioxidant properties [ 20 , 45 , 50 ].…”

“…To compare the global distribution of flavonoids and the individual proportion of each candidate compound in the total fraction, the developed nontargeted method was applied to the Salicornia e europaea extracts prepared in triplicate using either 30 mM Tris-HCl pH 7 or 10 mM NH 4 Ac pH 5.4 under sonication. Extractions were performed in acidic media to improve the release of flavonoids present in forms of esters, glycosides or polymers in plant matrices and to prevent their oxidative degradation over their extraction assisted with ultrasounds or their further long-term storage [ 46 , 48 , 49 ].…”

Flavonoids and other constituents of plants from the genus Knema (Myristicaceae) and their pharmacological studies: An updated review

“…The position and number of these hydroxyl groups determine the specific type of flavonoids, and more than 6,000 flavonoids have been identified to date. [ 3 ]…”

“…The position and number of these hydroxyl groups determine the specific type of flavonoids, and more than 6,000 flavonoids have been identified to date. [3] One of the essential properties of flavonoids is their antioxidant activity. Flavonoids can scavenge free radicals and prevent oxidative damage to cells and tissues.…”