Usefulness of Lipidic Nanoparticles of Curcumin and Tetrahydrocurcumin for Skin Inflammation: A Comparative Study

Background: Yellow curcumin, the “Indian Gold” has been known since ancient times to modulate the activities of a wide variety of targets. The voluminous literature and several patents are proof of the therapeutic value of curcumin. Tetrahydrocurcumin (THC), however, has remained an unexplored molecule, although its cosmeceutical properties have been documented. Their compromised bioavailability, poor aqueous solubility (curcumin 11 ng/mL, THC 56ng/mL), and high log P (Cur: 3.28; THC: 2.98) are hurdles to being developed as potential drugs. Objective: This article discusses the usefulness of lipidic nanoparticles of curcumin and THC for skin inflammation. Method: Nanocouturing to produce lipidic nanoparticles (LNs) of curcumin and THC was done via an optimized microemulsification technique. LNs were characterized by FTIR, TEM, pharmacokinetics, and pharmacodynamic study. Results: FTIR reflected the suitable incorporation of drugs into LNs. TEM examination revealed a spherical to ellipsoidal shape with a particle size of <200 nm. In vitro release study indicated that the release of both drugs was between 70-80% within 24 h. Ex vivo permeation studies confirmed the ability of LNs to cross the stratum corneum. Stability studies (Q1AR2) indicated that both were stable, safe, and non-irritating (OECD 404). Xylene-induced ear edema model of inflammation showed both molecules to possess equivalent abilities to treat inflammation. Conclusion: Curcumin, being yellow coloured, is unstable at physiological pH and plasma and possesses poor bioavailability, while THC is a colorless stable molecule, making it a molecule of choice to be developed as an effective topical product.