Electronic Supplementary Information Organocatalyzed and Mechanochemical Solvent-free Synthesis of Novel and Functionalized bis-Biphenyl Substituted Thiazolidinones as Potent Tyrosinase Inhibitors: SAR and Molecular Modeling Studies Sadaf Mutahir,a Muhammad Asim Khan,b Islam Ullah Khan, a* Muhammad Yar,c Muhammad Ashraf,d Sidra Tariq,a Ren-long Ye b and Bao-jing Zhou b* a
Department of Chemistry, Government College University, Lahore, 54000, Pakistan. E-Mail:
[email protected] (I. U. Khan) b
School of Chemical Engineering, Nanjing University of Science and Technology, Xiaolingwei 200,
Nanjing 210094, China. E-Mail:
[email protected] (B. Zhou) c
Interdisciplinary Research Center in Biomedical Materials, COMSATS Institute of Information
Technology, Lahore, 54000, Pakistan. d
Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur-63100, Pakistan.
Table of Contents 1. Scanned spectra 2. Molecular docking 3. Effect of incubation time on the tyrosinase enzyme activity
1. 1HNMR and 13CNMR spectra of all Compounds:
1H-NMR
of 3a
13C-NMR
of 3a
1H-NMR
of 3b
13C-NMR
of 3b
DEPT 90 13C-NMR of 3b
1H-NMR
of 3c
13C-NMR
of 3c
1H-NMR
of 3d
13C-NMR
of 3d
1H-NMR
of 3e
13C-NMR
of 3e
1H-NMR
of 3f
13C-NMR
of 3f
1H-NMR
of 4a
13C-NMR
of 4a
1H-NMR
of 4b
13C-NMR
of 4b
1H-NMR
of 4c
13C-NMR
of 4c
1H-NMR
of 4d
13C-NMR
of 4d
1H-NMR
of 4e
13C-NMR
of 4e
1H-NMR
of 4f
13C-NMR
of 4f
2. Molecular docking The binding pocket of the tyrosinase is very special, which contains both spacious and narrow regions for binding large as well as small molecules. The two copper ions located at the bottom of binding pocket are coordinated to the six histidine residues from the enzyme. The inhibitor tropolone present in the protein structure (PDB code: 2Y9X) is small enough to be bound deeply in the binuclear copper-binding site (Fig. S1) and its oxygen atom can have a short distance of ~ 3.5 Å to either copper ion. In contrast, the large inhibitors synthesized in this work (the inhibitor 3c in Fig. S1) adopt much shallower binding modes. In general, the four large inhibitors are positioned at the enzyme surface, occupying and blocking the pocket so that small ligands such as tropolone cannot enter.
Fig. S1: The comparison of the binding modes of tropolone (smaller molecule bound inside the pocket) and the inhibitor 3c (larger molecule bound at the surface) inside the binding pocket.
Absorbance 490 nm
Time (mins)
Fig. S2: A representative graph of the effect of incubation time on the tyrosinase enzyme activity. Activity was measured in terms of the absorbance units employing the standard assay conditions as given in the text. The enzyme units used, the concentration of substrate and the incubation temperature were optimized in such a way that the assay could be run for 30 minutes as shown here. Data is mean of three independent experiments.