In vitro synergistic evaluation of tyrosinase inhibition and antioxidant activities of Mimosa pudica and Glycyrrhiza glabra plant extracts for the treatment of hyperpigmentation

Purpose: This study aimed to evaluate the tyrosinase inhibitory activity of a combination of Mimosa pudica and Glycyrrhiza glabra extracts to explore potential synergistic effects and to assess the antioxidant activity of the individual extracts. The findings support the development of a polyherbal topical formulation for hyperpigmentation treatment.
Methods: The ethanolic extract of G. glabra roots was obtained via reflux condensation at 60°C, while the methanolic extracts of M. pudica leaves and seeds were prepared at 50°C. The mushroom tyrosinase inhibition assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay were conducted in triplicate to evaluate the extracts' enzyme inhibitory and antioxidant activities, respectively. M. pudica leaves extract, M. pudica pods extract, and G. glabra roots extract were tested as a formulated mixture (1:1:2 ratio) for tyrosinase inhibition. A brine shrimp lethality assay was conducted to assess toxicity.
Results: The extract mixture exhibited potent tyrosinase inhibition, with a 50% inhibitory concentration (IC₅₀) of 47.47 ± 0.42 μg/mL, surpassing the standard inhibitor, kojic acid (IC₅₀ = 76.61 ± 0.80 μg/mL). The M. pudica leaves extract exhibited antioxidant activity with an IC₅₀ of 34.26 μg/mL, followed by M. pudica pods extract at 75.09 μg/mL, and G. glabra roots extract at 95.82 μg/mL, compared to the standard inhibitor ascorbic acid at 11.56 μg/mL. All three plant extracts were non-toxic to brine shrimp at concentrations that exhibited tyrosinase inhibition and antioxidant activity.
Conclusion: The combination of M. pudica leaves and seed extracts with G. glabra root extract exhibited notable tyrosinase inhibition and antioxidant activities at concentrations below 100 μg/mL, supporting its potential as a polyherbal topical formulation for hyperpigmentation management. Notably, M. pudica leaf extract demonstrated prominent antioxidant activity.