IntroductionAlthough drugs are often used in the treatment of metabolic diseases, their bioavailability as well as resistance to diseases and decrease in effects pose serious challenges. For these reasons, the importance of plants in the treatment and prevention of diseases is increasing day by day, and herbal sources have been in use since ancient times. Parsley is an easy-to-produce herb that is used as food around the world. It continues to be used in scientific studies due to its high phenolic and nutritional content. Due to its antihyperglycemic, antihyperlipidemic, anticoagulant, antioxidant, antimicrobial, and laxative activities, it still remains popular among scientific researchers. Adenosine deaminase, xanthine oxidase, neuraminidase, and acetylcholinesterase are biomarkers of many metabolic diseases such as cancer, diabetes, Alzheimer's disease, and influenza. The aim of this study is to investigate the inhibitory activities of aqueous parsley extract on adenosine deaminase, xanthine oxidase, neuraminidase, acetylcholinesterase, as well as its antioxidant activities. MethodsStandard methods were used to determine the inhibitory effect of aqueous parsley extract on adenosine deaminase, xanthine oxidase, neuraminidase, and acetylcholinesterase. Also, total phenolic content, DPPH (1,1′-diphenyl-2-picrylhydrazyl) radical scavenging activity and reducing power of the extract were evaluated. ResultsAqueous parsley extract inhibited adenosine deaminase, xanthine oxidase, neuraminidase and acetylcholinesterase. The phenolic compounds of parsley are potentially responsible for both antioxidant activities and enzyme inhibition activities of the plant. ConclusionThe results showed that parsley extract has inhibitory effects on the enzymes studied and has a very good antioxidant activity.