Inhibition of lipoxygenase 1 by phosphatidylcholine micelles-bound curcumin

Curcumin (diferuloyl methane) from rhizomes of Curcuma longa L. binds to ph osphatidylcholine (PC) micelles. The binding of curcumin with PC micelles w as followed by fluorescence measurements. Curcumin emits at 490 nm with an excitation wavelength of 451 nm after binding to PC-mixed micelles stabiliz ed with deoxycholate. Curcumin in aqueous solution does not inhibit dioxyge nation of fatty acids by Lipoxygenase 1 (LOX1). But, when bound to PC micel les, it inhibits the oxidation of fatty acids. The present study has shown that 8.6 mu M of curcumin bound to the PC micelles is required for 50% inhi bition of linoleic acid peroxidation. Lineweaver-Burk plot analysis has ind icated that curcumin is a competitive inhibitor of LOX1 with K-i of 1.7 mu M for linoleic and 4.3 mu M for arachidonic acids, respectively. Based on s pectroscopic measurements, we conclude that the inhibition of LOX1 activity by curcumin can be due to binding to active center iron and curcumin after binding to the PC micelles acts as an inhibitor of LOX1.