Pro- and antioxidant activity of curcuminoids with lecithin in sunflower oil

Abstract

Introduction. Curcumin present as a major constituent amongst curcuminoids in turmeric has attracted significant attention due to wide range of biological and pharmaceutical activities. It reveals various therapeutic activities such as anti-inflammatory, nematocidal, anti -parasitic, antispasmodic and anticarcinogenic. Additionally, it is a powerful scavenger of reactive oxygen species. On the other hand, the pro -oxidant effect of curcumin has also been observed.Materials and methods. The study has been carried out to evaluate the activity of curcuminoids in crude and refined sunflower oil containing synthetic antioxidant. The various blends of oil were prepared. The oxidative stability of oil blends was checked at 60 degrees C for 30 days at regular interval of 5 days according to the AOCS Official Methods by peroxide value (in meq/kg), p-anisidine value and total oxidation (Totox) value (in meq/kg).Results and discussion. The tendency of curcumin to exhibit keto-enol tautomerism determines its physicochemical and antioxidant properties. It has been observed that curcuminoids showed noticeable dissimilar behavior in both oils. The hydrogen atom donation in case of curcumin is from the active methylene group, which exists only in keto form. The keto form predominates in neutral and acidic solutions whereas the enol form predominates in alkaline solution. In alkaline medium, curcumin undergoes degradation. The same theory is also applicable to other two curcuminoids, i.e., demethoxycurcumin and bisdemethoxycurcumin. Hence, it becomes crucial to maintain the curcuminoids in keto form to be used as antioxidant.In crude sunflower oil, because of the presence of free fatty acids, curcuminoids did not undergo degradation imparting marginal antioxidant activity. Lecithin chelated metal ions present in oil, which promote oxidation of oil thereby inhibiting the autoxidation of oil. However, the synergistic activity of curcuminoids and lecithin revealed remarkable antioxidant activity.In refined sunflower oil containing tertiary butylhydroquinone (TBHQ), curcuminoids showed pro-oxidant activity due to lack of acidic medium. Lecithin exhibited synergistic activity with TBHQ in refined sunflower oil. Nevertheless, the pro-oxidant effect of curcuminoids is not observed in presence of lecithin and TBHQ. Thus, the lecithin and TBHQ stabilized refined sunflower oil in presence of curcuminoids.Conclusion. The structure-activity relationship plays an important role in determining the activity (antioxidant or pro oxidant) of a particular compound. Thus, a constituent should exist in a proper structural form to be used as an antioxidant. PU - NATL UNIV FOOD TECHNOLOGIES PI - KYIV PA - VUL VOLODYMYRSKA 68, KYIV, 01601, UKRAINE