Advances in Biology & Earth Sciences

Cell membranes undergo structural changes under the influence of adverse environmental factors. Secondary metabolites protect the membrane from damage. Saponins, widely used in industry, are such a metabolite. By creating a native model of damaged thylakoid membrane in wheat seedlings (Triticum aestivum L.) grown at low temperatures (4 ⁰C), the antioxidant properties of steroidal saponins isolated from the roots of Yucca aloifolia L. were studied. Antioxidant activity was determined using the stable DPPH radical model. Analysis of the characteristics of chlorophyll a recombination fluorescence (ms DF Chl a) revealed that by 24 hours of low-temperature stress, the electron transfer reaction (e^-) to the quinone acceptors Q_A-Q_B in the PS II electron transport chain is blocked and the absorption capacity of Chl a 680 and Chl b 645 decreases in untreated seedlings. In the presence of saponins, a corrective effect on the fluidity of the thylakoid membrane lipid layer damaged by cold was observed, resulting in the restoration of the function of protein transporters of e^- and consequently, the rate of e^- transfer at the P680⁺-Q_A-Q_B site. The absorption spectrum demonstrated the restoration of the accumulation and absorption capacity of light-harvesting pigments. The use of saponins resulted in a reduction in the PNRSV viral load in the Gizella 6 cherry rootstock and the emergence of healthy foliage. Saponins, with their antiradical and antioxidant properties, are capable of quenching oxygen radicals (O₂^- and OH•) formed during stress, maintaining redox equilibrium in the photochemical reactions of the thylakoid membrane.