108 Acta Chim. Slov. 2018, 65, 108–118 Pervez et al.: Synthesis and in vitro Bio-activity Evaluation ... DOI: 10.17344/acsi.2017.3649 Scientifc paper Synthesis and in vitro Bio-activity Evaluation of N 4 -benzyl Substituted 5-Chloroisatin- 3-thiosemicarbazones as Urease and Glycation Inhibitors Humayun Pervez, 1, * Nazia Khan, 1 Jamshed Iqbal, 2 Sumera Zaib, 2,3 Muhammad Yaqub 1 and Muhammad Moazzam Naseer 4 , * 1 Institute of Chemical Sciences, Organic Chemistry Division, Bahauddin Zakariya University, Multan 60800, Pakistan 2 Centre for Advanced Drug Research, COMSATS Institute of Information Technology, Abbottabad 22060, Pakistan 3 Department of Bioinformatics & Biotechnology, International Islamic University, Islamabad 44000, Islamabad, Pakistan 4 Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan * Corresponding author: E-mail: pdhpervez@hotmail.com; moazzam@qau.edu.pk Received: 19-06-2017 Abstract A series of ffeen N 4 -benzyl substituted 5-chloroisatin-3-thiosemicarbazones 5a–o were synthesized and screened main- ly for their antiurease and antiglycation efects. Lemna aequinocitalis growth and Artemia salina assays were carried out to determine their phytotoxicity and cytotoxicity potential. All the compounds proved to be extremely efective urease inhibitors, demonstrating enzyme inhibition much better than the reference inhibitor, thiourea (IC 50 values 1.31 ± 0.06 to 3.24 ± 0.15 vs. 22.3 ± 1.12 μM). On the other hand, eight out of ffeen compounds tested, i.e. 5b, 5c, 5h–k, 5m and 5n were found to be potent glycation inhibitors. Of these, fve viz. 5c, 5h–j and 5n proved to be exceedingly efcient, displaying glycation inhibition greater than the reference inhibitor, rutin (IC 50 values 114.51 ± 1.08 to 229.94 ± 3.40 vs. 294.5 ± 1.5 μM). Keywords: 5-Chloroisatin, Glycation inhibition, Heterocyclics, Schif bases, Tiosemicarbazones, Urease inhibition 1. Introduction Isatin and its derivatives are known to have a diversi- ty of chemotherapeutic activities. 1–35 Of the isatin deriva- tives, isatin-thiosemicarbazones have been found to ex- hibit a range of biological properties, including antiulcer, 1 anticancer, 1,4,7,12,21–23 antimicrobial, 1–3,5,7,22,24,25 antitubercu- losis, 26–28 antiviral 1,2,5,7,12,28 and enzyme inhibitory activi- ties. 1,4,11,17 Incited by these fndings and as a part of our synthetic work on bioactive isatin derivatives, we have re- cently reported the synthesis of numerous N 4 -aryl substi- tuted isatin-3-thiosemicarbazones (thiourea derivatives) as antimicrobial, 36–39 cytotoxic, 38–42 phytotoxic, 38–41,43 antile- ishmanial 44 and more importantly antiurease 36–40,43,45 com- pounds. SAR studies in the synthesized thiosemicarba- zones disclosed that in some cases the nature and location of the substituent on the phenyl ring attached to thiosemi- carbazone N 4 and/or the existence of lipophilic/inductively electron-withdrawing functions (Cl, F, F 3 CO, NO 2 ) at po- sition 5 of the isatin moiety played a signifcant role in in- ducing and/or increasing certain activities, including ure- ase inhibition. In view of this and as an extension of our earlier studies 36–47 aiming to the synthesis of novel isatin derivatives with enhanced or diverse biological activities, we very recently reported the synthesis of a series of N 4 -benzyl substituted 5-nitroisatin-3-thiosemicarbazones (derivatives of thiourea, a substrate-like urease inhibitor) as highly efective urease inhibitors. 48 Interestingly, all these compounds demonstrated either induced or in- creased urease inhibitory activity in comparison to the re- spective N 4 -phenyl substituted derivatives tested in our earlier assays. 38,45 Furthermore, a number of other deriva- tives of thiourea are reported to show promising glycation inhibitory activity. 49–53 Also, some isatin-derived imines (Schif bases) have been recognized as potent inhibitors of glycation. 54,55 Prompted by these observations and as a continuation of our previous studies on bioactive isatin