Synephrine and phenylephrine act as α-amylase, α-glycosidase, acetylcholinesterase, butyrylcholinesterase, and carbonic anhydrase enzymes inhibitors.

In this paper, synephrine and phenylephrine compounds showed excellent inhibitory effects against human carbonic anhydrase (hCA) isoforms I and II, α-amylase, α-glycosidase, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE). Synephrine and phenylephrine had Ki values of 199.02 ± 16.01 and 65.01 ± 5.00 μM against hCA I and 336.02 ± 74.01 and 92.04  ±  18.03 μM against hCA II, respectively. On the other hand, their Ki values were found to be 169.10  ±  80.03 and 88.03  ±  5.01 nM against AChE and 177.06  ±  6.01 and 78.03  ±  3.05 nM against BChE, respectively. α-Amylase and α-glycosidase enzymes were easily inhibited by these compounds. α-Glycosidase inhibitors, generally defined to as starch blockers, are anti-diabetic drugs that help to decrease post comestible blood glucose levels.