Preparation of curcumin microemulsions with food-grade soybean oil/lecithin and their cytotoxicity on the HepG2 cell line

The choice of surfactants and cosurfactants for preparation of oral formulation in microemulsions is limited. In this report, a curcumin-encapsulated phospholipids-based microemulsion (ME) using food-grade ingredients soybean oil and soybean lecithin to replace ethyl oleate and purified lecithin from our previous study was established and compared. The results indicated soybean oil is superior to ethyl oleate as the oil phase in curcumin microemulsion, as proven by the broadened microemulsion region with increasing range of surfactant/soybean oil ratio (approx. 1:1–12:1). Further preparation of two formula with different particle sizes of formula A (30 nm) and B (80 nm) exhibited differential effects on the cytotoxicity of hepatocellular HepG2 cell lines. At 15 μM of concentration, curcumin-ME in formula A with smaller particle size resulted in the lowest viability (approx. 5%), which might be explained by increasing intake of curcumin, as observed by fluorescence microscopy. In addition, the cytotoxic effect of curcumin-ME is exclusively prominent on HepG2, not on HEK293, which showed over 80% of viability at 15 μM. The results from this study might provide an innovative applied technique in the area of nutraceuticals and functional foods.