TLC-MS-Bioautographic Identification of Antityrosinase Compounds and Preparation of a Topical Gel Formulation from a Bioactive Fraction of an RSM-Optimized Alcoholic Extract of Rubia Cordifolia L. stem.

Background: Rubia cordifolia L., Rubiaceae, is globally reported to treat skin-related problems. The study aimed to assess the antityrosinase potential of Rubia cordifolia (ARC) and the development of gel formulation.

Methods: The AutoDock Vina (version V.1.2.0) program package was used for molecular docking to check for the binding affinity of ligands with protein. Response surface methodology (RSM) software was used to optimize extraction parameters for an alcoholic extract of Rubia cordifolia (ARC). The developed HPTLC method for the quantification of purpurin in ARC was validated as per the International Conference on Harmonization (ICH) guidelines. A bioautographic study for the evaluation of antityrosinase effects was performed; an anthraquinone-enriched fraction (AEF)-loaded gel formulation developed and evaluated physicochemically which could be used to reduce skin pigmentation.

Results: Purpurin showed optimum binding affinity (-7.4 kcal/mol) with the molecular target (tyrosinase) when compared to that of standard kojic acid (-5.3 kcal/mol). Quantification of purpurin in ARC, optimized by RSM software, was validated and physiologically significant results were observed for the antityrosinase potential of an AEF, along with TLC-MS-bioautographic identification for antityrosinase compounds: purpurin (m/z 256.21) and ellagic acid (m/z 302.19). Evaluation of an AEF-loaded gel formulation by in vitro and ex vivo permeation studies was performed.

Conclusion: ARC extraction parameters optimized by RSM, and a bioautographic study helped identify antityrosinase compounds. The development of a gel formulation could be a cost-effective option for the treatment of depigmentation in the future.

Highlights: A TLC-MS-Bioautography-based Identification of Antityrosinase Compounds and development of AEF-loaded Topical Gel formulation from a Bioactive Fraction of an RSM-Optimized Alcoholic Extract of Rubia Cordifolia L. stem, which could help with promising results in reducing skin pigmentation and maintaining even tone.