Preparation and evaluation of Dendrobium formosum extract-loaded microemulsions for anti-aging purpose

Skin aging is a complex process caused by oxidative stress, leading to a growing need for cosmeceuticals with effective antioxidant and matrix metalloproteinase-1 (MMP-1) inhibitory activities. D. formosum has shown various biological activities; however, an appropriate delivery system is required to enhance its efficacy. Our study firstly explored the protective effects of D. formosum extract on UVB-irradiated human keratinocytes (HaCaT) and human fibroblasts (BJ), and then developed topical microemulsion (ME) containing D. formosum extract. Our results show that D. formosum extract demonstrates anti-aging properties by reducing intracellular reactive oxygen species (ROS) in UVB-irradiated HaCaT and BJ, and inhibiting MMP-1 expression. Pseudo-ternary phase diagrams were constructed using the water titration method. The optimized microemulsion base (MEB) contained trilaureth-4 phosphate: propylene glycol (surfactant: cosurfactant; 2:1, 57.50%), isononyl isononanoate (oil, 17.50%), and deionized water (25.00%). The 0.40% w/w D. formosum extract, called DME1, was loaded into the MEB. This formulation exhibited desirable characteristics, including size, polydisperse index (PDI), zeta potential, and viscosity. DME1 was physicochemically and chemically stable. The DME1 also significantly increase skin retention and was safe to human skin cells. Our findings highlight D. formosum extract as a novel active ingredient and its potentially topical delivery for anti-aging purpose.