Biologically active substances of plant origin: Methods of extraction and analysis

Biologically active substances (BAS) of plant origin play a key role in the development of functional foods, bio-additives and medicines. Their use, however, is restricted by difficulties in extraction and low stability. This paper is devoted to investigation of the structure, characteristics and biological impact of the main BAS classes — phenolic compounds, among which flavonoids, stilbenes and lignans stand out. Their role as potent antioxidants and anti-inflammatory agents, as well as their effect on the health of the cardiovascular system, is emphasized. The review covers both traditional and modern methods for extraction of biologically active components from plants, such as maceration, distillation, extraction by the Soxhlet method, ultrasound, microwave and supercritical technologies of extraction. The authors describe in detail spectrophotometric methods DPPH, ABTS, as well as fluorescent method ORAC and its improved version ORAC-SIA, intended for the assessment of the total antioxidant capacity of individual compounds and their combination upon the physiologically relevant values of the acidity of the environment. The results of the study demonstrate the dependency of the BAS yield on the solvent type, hydromodule and a degree of comminution of raw materials. Extraction parameters such as temperature, pressure and pH significantly affect the preservation of thermolabile compounds. It has been found that modification of the structure of cyclotides increases the bioavailability of peptide preparations by 1.5–2 times. Analytical methods like ORAC and its modification ORAC-SIA allows for assessing the antioxidant activity of BAS in complex mixtures including food products. Based on the performed analysis, the conclusions were made regarding the need for optimization of “green” extraction methods, development of the standardized protocols of analysis and in-depth study of the interrelation “structure–activity” for targeted design of BAS.