Estimation of the Antioxidative Properties of the Natural Polyphenols in the Oxidation Process of Model Liposome Membranes

The experiment was conducted to proof the new natural plant extracts (Fagopyrum Mill. (buckwheat), Crataegus ex L., (hawthorn), Hypericum L. (St -John's -wort's) and Helichrysum arenarium) and selected flavonoids as reference substances for the in vitro. The probing was performed as considering four different parameters: the antioxidant activity, the antiradical activity – DPPH test, the DPH test and the CF test. The results of antioxidative test of studied extracts show high antioxidant activity against UVC induced peroxidation of phosphatidylcholine (PC) liposomes membranes (except Helichrysum). The main consident parameter for antioxidant activity was IC50 (Inhibition Concentration 50 PC – the concentration of antioxidant which reduces peroxidation intensity of phosphatidylcholine liposomes about 50%). Values of IC50 were following: buckwheat – hulls (20,8 mg/L) ≥ hawthorn – cortex (21,6 mg/L) > Hypericum L. (25,4 mg/L) > hawthorn – leaves (26,8 mg/L) > buckwheat – stems (29,1 mg/L) >> Helichrysum (121,6 mg/L). The DPPH free radical test results (IC50 – the concentration of antioxidant which reduces the free radical DPPH about 50%) show the high antiradical activity of majority extracts (IC50 = 2,7 – 7,4 mg/L), except Helichrysum (IC50 = 34,0 mg/L). The similar relationship between antiradical activity (IC50) and antioxidant activity (IC50) for the Hypericum L., buckwheat – stems and hawthorn – leaves, suggest possible mechanisms of the extracts activity, as the free radical scavengers (scavenger = substance that can deactivates Reactive Oxygen Species or Reactive Nitrous Species). The examination the possibility association of studied extracts to liposomes membrane was one of other aims. His realization was used with the DPH method to assignment the coefficient of constant association (1/KD). The values of 1/KD of the test extracts (ranged 709 – 999 L/mg) with PC liposomes membrane, may suggest their role as substances to protect the membrane from reactive oxygen species. The influence of studied extracts on structure of PC liposome membranes was also verified using CF test. The intensity of leakage from liposomes under presence of investigated flavonoids was examined using the carboxyfluorescein (CF) marker. It shown that compounds in general (except buckwheat stems) do not trigger malicious actions on the PC membrane liposomes. Percentage of carboxifluorescein leakage at various concentration of extract for witch got the IC50, didn’t cross the 2 % (except buckwheat stems = 10,90 %). The obtained results demonstrate possibility of using them (except Helichrysum) as antioxidants in food and pharmaceutical or cosmetics industry.