Environmentally Friendly Methods for Flavonoid Extraction from Plant Material: Impact of Their Operating Conditions on Yield and Antioxidant Properties

Abstract

The flavonoids are compounds synthesized by plants, and they have properties such as antioxidant, anticancer, anti-inflammatory, and antibacterial, among others. One of the most important bioactive properties of flavonoids is their antioxidant effect. Synthetic antioxidants have side toxic effects whilst natural antioxidants, such as flavonoids from natural sources, have relatively low toxicity. Therefore, it is important to incorporate flavonoids derived from natural sources in several products such as foods, cosmetics, and drugs. For this reason, there is currently a need to extract flavonoids from plant resources. In this review are described the most important parameters involved in the extraction of flavonoids by unconventional methods such as ultrasound, pressurized liquid extraction, mechanochemical, high hydrostatic pressure, supercritical fluid, negative pressure cavitation, intensification of vaporization by decompression to the vacuum, microwave, infrared, pulsed electric field, high-voltage electrical discharges, and enzyme-assisted extraction. There are no unified operation conditions to achieve high yields and purity. Notwithstanding, progress has been achieved in the development of more advanced and environmentally friendly methods of extraction. Although in literature are found important advances, a complete understanding of the extraction process in each of the unconventional techniques is needed to determine the thermodynamic and kinetic mechanisms that govern each of the techniques.

Antioxidant Capacity and Total Phenolic and Flavonoid Contents of Methanolic Extracts of Urtica dioica L. by Different Extraction Techniques

“…In addition, the large difference between the concentrations of analyte in the cell solution and in the solvent is maintained throughout, due to multiple digestion of a plant material and continuous extraction while a fresh portion of a solvent is delivered [46]. Despite the drawbacks of conventional methods, Soxhlet is considered as a reference method and generally is used for comparison with the more sophisticated methodologies recently developed [47]. Table 2 shows the results of antioxidant capacity of nettle methanolic extracts, measured by FRAP and DPPH assays.…”

The Hallmarks of Flavonoids in Cancer

“…Flavonoids′ concentration and composition also vary depending on the different parts of the plant. Leaves and the peels of fruits are commonly rich sources of flavonoids due to increased susceptibility to stress [ 4 , 5 , 6 ].…”

Extracting flavonoid from Ginkgo biloba using lignocellulolytic bacteria Paenarthrobacter sp. and optimized via response surface methodology

“…Even though the use of the microbe requires more time in extracting the flavonoids, it can extract more flavonoids and does not require the use of organic solvent. Furthermore, our study suggested that the extraction can be conducted under mild conditions (low pressure and low temperature), which can avoid damaging the flavonoids and other value‐added by‐products 81 …”