TLC-MS-Bioautographic identification of antityrosinase compounds and preparation of a topical gel formulation from bioactive fraction of RSM optimized alcoholic extract of Rubia cordifolia L. stem.

Abstract

Rubia cordifolia L., Rubiaceae, is globally reported to treat skin-related problems. The study aimed to assess the antityrosinase potential of RC and the development of gel formulation. 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 ICH guidelines, also the bioautographic study for evaluation of antityrosinase effects was performed, anthraquinone enriched fraction (AEF)-loaded gel formulation was developed and so evaluated which could be used to reduce skin pigmentation. 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 AEF, along with TLC-MS-bioautographic identification for antityrosinase compounds: purpurin (m/z 256.21) and ellagic acid (m/z 302.19). Evaluation of AEF-loaded gel formulation by in vitro and ex vivo permeation studies was performed. ARC extraction parameters optimized by RSM, and bioautographic study helped identify antityrosinase compounds. The development of gel formulation could be a cost-effective option for the treatment of depigmentation in the future.