Five 4-hydroxyphenylethyl substituted pyridine enhanced, precatalyst, preparation, stabilization, and initiation-Pd-N-heterocyclic carbene (PEPPSI-Pd-NHC) complexes are synthesized in a straightforward way. All PEPPSI-Pd-NHC complexes were prepared by mixing 4-hydroxyphenylethyl substituted NHC precursors, palladium chloride, potassium carbonate, and potassium bromide in pyridine. All complexes were screened for human carbonic anhydrase I (hCA I) and hCA II, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and α-glucosidase (α-Glu) inhibitory activities. The ChE inhibitory activities of the new PEPPSI-Pd-NHC complexes bearing the 4-hydroxyphenylethyl group (1a-e) against α-Glu, AChE, and BChE were determined by the Tao and Ellman methods. The results indicated that all the synthetic complexes exhibited potent inhibitory activities against all targets as compared to the standard inhibitors, revealed by IC50 values. The Ki values of the new PEPPSI-Pd-NHC complexes 1a-e for hCA I, hCA II, AChE, BChE, and α-Glu were obtained in the ranges of 18.98-32.65, 22.95-38.13, 3.67-11.65, 4.09-9.36, 186.92-287.45 µM, respectively. Among the synthesized complexes, the most potent complexes were 1c toward hCA I and II with Ki values 18.98 and 22.95 µM, and 1d toward AChE and BChE with Ki = 3.67 and 4.09 µM, respectively.
Keywords: NHC complexes; PEPPSI; enzyme inhibition; molecular docking; α-glucosidase.
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