Study on interaction of bile salts with curcumin and curcumin embedded in dipalmitoyl-sn-glycero-3-phosphocholine liposome

Curcumin, often used as a food spice, is a natural polyphenol that has various medicinal benefits such as anti-cancer, anti-amyloid, anti-oxidant, and anti-inflammatory properties, among others. The interaction between bile salts having physiological significance and curcumin suggests the aggregation of bile salts dramatically alters the absorption and fluorescence parameters of curcumin. The fluorescence emission maximum as well as the intensity can easily detect critical micellar concentration of sodium cholate and sodium deoxycholate respectively to be 16 and 6 mM at room temperature. The mechanism of interaction of curcumin with bile salts has been presented at low, intermediate and high bile salt concentrations and depends on temperature. In the presence of bile salts the DPPH scavenging activity was preserved, though less than in the presence of curcumin alone. The effect of submicellar concentration, 5–50 μM, of bile salt with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes in solid gel and liquid crystalline phases has been investigated using curcumin as an embedded probe in the membrane. The curcumin based fluorescence probing method indicates even at very low concentration, ∼5 μM, incorporation of monomeric bile salt molecules disorders the membrane properties. Expulsion of curcumin from the membrane in the presence of bile salt is ruled out, suggesting wetting of membrane. Alteration of membrane fluidity by bile salts is found to have an opposing effect in the liquid crystalline phase compared to in the solid gel phase, and is sensitive to the nature of bile salt. The permeability in the liquid crystalline phase decreases in the presence of bile salt. The phase transition temperature of the membrane is influenced by bile salt.