Evaluation of Biological Activities and Cytotoxicity of Peristrophe bivalvis (L.) Merr Extracts and Investigation of Its Novel Natural Active Ingredient-Loaded Nanoemulsion and Stability Assessment

Peristrophe bivalvis (L.) Merr. (Acanthaceae family) has traditionally been used as a natural food colorant and in the treatment of various diseases. However, its biological activities—particularly its anti-glycation and anti-lipid peroxidation properties—as well as the development of novel nanoemulsions incorporating crude P. bivalvis leaf extracts for cosmetic applications, have not yet been reported. The aim of this study was to explore the potential of P. bivalvis leaf crude extracts as an active ingredient in nanocosmetics. Various solvents, including deionized water, 95% ethanol, and 1% HCl in 50% ethanol were used to macerate the plant material. These crude extracts were subsequently screened for their phytochemical constituents, total phenolic and flavonoid contents, as well as antioxidant, anti-glycation, anti-lipid peroxidative activities, and fibroblasts cytotoxicity. In addition, a nanoemulsion containing P. bivalvis crude extracts was formulated using high-speed homogenization. The formulation was characterized in terms of pH, viscosity, particle size, polydispersity index, and entrapment efficiency. Furthermore, its stability was evaluated under accelerated conditions and at different storage temperatures (room temperature, 4 °C, and 45 °C). The results indicated that P. bivalvis extracts obtained using deionized water and 95% ethanol contained various phytochemical constituents, along with higher contents of total phenolic and flavonoid contents, antioxidant, anti-glycation, and anti-lipid peroxidative activities, as well as the lowest fibroblast cytotoxicity, compared to extracts obtained with 1% HCl in 50% ethanol. The nanoemulsions loaded with P. bivalvis ethanolic extracts exhibited a reddish-orange color, whereas those containing P. bivalvis water extracts exhibited a reddish-purple coloration, depending on its pH value. These nanoemulsions demonstrated greater stability at low temperatures, with particle sizes within the nanoscale range and a narrow polydispersity index. These findings suggest that P. bivalvis extracts obtained from deionized water and 95% ethanol are potential active ingredients that were successfully incorporated into nanoemulsion-based cosmetics formulation.