Inhibitory effect of encapsulated curcumin on ultraviolet-induced photoaging in mice

Photoaging is the superposition of photodamage (ultraviolet [UV] radiation-induced) on the aging process. It is a major damaging consequence of free radical action. Curcumin (diferuloylmethane) is a phytochemical with diverse antioxidant and antiinflammatory properties. However, it shows a poor topical bioavailability. Therefore, we encapsulated curcumin in elastic vesicles (EVs) and investigated different doses (1, 3, 5 and 10 micromol) for its in vivo antiaging activity in mice. VICCO turmeric served as the marketed control, and free curcumin dispersed in an ointment base was another control. The dorsal depilated skin surface was exposed to the whole UV range for 5 sec, five times a week for 6 weeks. Each exposure was followed by treatment with encapsulated curcumin (at different doses), free curcumin ointment, and VICCO turmeric. The effectiveness was established in terms of macroscopic and histopathological evaluation of skin, pinch test, and redox homeostasis of skin homogenates. Skin evaluation demonstrated that 5- and 10-micromol doses of curcumin EVs and the marketed formulation were effective in preventing the formation of lesions and other changes. The pinch test showed that the reduction in recovery time with the 10-micromol dose of curcumin EVs was highly significant (p < 0.05). Histopathological studies further confirmed the protective role of curcumin EVs. The normal redox balance was restored with a 10-micromol dose, whereas a 5-micromol dose and the marketed formulation showed significant and equivalent activity. The free curcumin ointment group showed no improvement in redox levels. This study provides the first preclinical evidence for the use of topically delivered curcumin to attenuate photoaging.