Synthesis, computational studies and enzyme inhibitory kinetics of benzothiazole-linked thioureas as mushroom tyrosinase inhibitors.

Herein, we report synthesis of a set of benzothiazole-thiourea hybrids with aromatic and aliphatic side chains (BT1 to BT9) using an elegant synthetic strategy. The newly synthesized benzothiazole-thiourea conjugates were subjected to In-vitro tyrosinase inhibition and free radical scavenging activity. Majority of the compounds indicated inhibition considerably improved than the standard; compound (Kojic acid with IC50 = 16.8320 ± 1.1600 µM) BT2 with IC50 = 1.3431 ± 0.0254 µM was found to be the best inhibitor. A non-competitive mode of inhibition of BT2 was disclosed with Ki value of 2.8 µM. In order to study enzyme-inhibitor interactions SAR analysis molecular docking was carried out. The amino groups of thiourea were involved in hydrogen bonding with Glu322 showing the bond length of 1.74 and 2.70 Å, respectively. Moreover, the coupling of π-π was displayed between benzothiazole and benzene rings of His244 and His263, respectively. The outcome of this study might help to develop new inhibitors of melanogenesis, important for cosmetic and food products. Communicated by Ramaswamy H. Sarma.

Drug-1,3,4-Thiadiazole Conjugates as Novel Mixed-Type Inhibitors of Acetylcholinesterase: Synthesis, Molecular Docking, Pharmacokinetics, and ADMET Evaluation.

A small library of new drug-1,3,4-thiazidazole hybrid compounds (3a⁻3i) was synthesized, characterized, and assessed for their acetyl cholinesterase enzyme (AChE) inhibitory and free radical scavenging activities. The newly synthesized derivatives showed promising activities against AChE, especially compound 3b (IC50 18.1 ± 0.9 nM), which was the most promising molecule in the series, and was substantially more active than the reference drug (neostigmine methyl sulfate; IC50 2186.5 ± 98.0 nM). Kinetic studies were performed to elucidate the mode of inhibition of the enzyme, and the compounds showed mixed-type mechanisms for inhibiting AChE. The Ki of 3b (0.0031 µM) indicates that it can be very effective, even at low concentrations. Compounds 3a⁻3i all complied with Lipinski's Rule of Five, and showed high drug-likeness scores. The pharmacokinetic parameters revealed notable lead-like properties with insignificant liver and skin-penetrating effects. The structure⁻activity relationship (SAR) analysis indicated π⁻π interactions with key amino acid residues related to Tyr124, Trp286, and Tyr341.