Tikrit Journal of Pure Science Vol. 27 (2) 2022 16 Tikrit Journal of Pure Science ISSN: 1813 – 1662 (Print) --- E-ISSN: 2415 – 1726 (Online) Journal Homepage: http://tjps.tu.edu.iq/index.php/j Synthesis of new thioester derivative of aspirin and study its effect on some biochemical parameters in blood serum of rabbits Zaid Abdalkader Dawood 1 , Firas Shawqi Algburi 2 , Nazar Ahmad Naji 1 Department of chemistry. College of science. Tikrit University, Tikrit . Iraq Department of biology. College of science. Tikrit University, Tikrit . Iraq https://doi.org/10.25130/tjps.v27i2.62 A r t i c l e i n f o. Article history: -Received: 23 / 10 / 2021 -Accepted: 28 / 12 / 2021 -Available online: / / 2022 Keywords: thioester, Aspirin, biochemical parameters Corresponding Author: Name: Zaid Abdalkader E-mail: zaid.abdulqader.dawood.chem@st.tu.edu.iq dr.firas.shawki@tu.edu.iq Tel: ABSTRACT This presented work was included synthesis of new thioester derivatives by reaction of Aspirin (a non-steroidal anti- inflammatory drugs) (NSAIDs) and Captopril as a carrier which is used as an antihypertensive drug and an inhibitor for angiotensin- converting enzyme (ACE). Aspirin was converted into acid chloride of aspirin then reacted with SH group of captopril to afforded of 1- (3-((2-acetoxybenzoyl)thio)-2-methylpropanoyl)pyrrolidine-2- carboxylic acid and characterized by FT-IR and 1 HNMR spectroscopy. The effect of synthesized compound was studied on some biochemical parameters in the blood serum of rabbits. Results of this study indicated: significant increase in the level of total fucose, total protein and globulin. Non- significant increase in the level of albumin, creatinine, glutathione and uric acid, significant decrease in level of Triglycerides and non-significant decrease in the level of Cholesterol, and malondialdehyde. Introduction Most of the drugs have undesired properties, therefore many scientists and researchers are trying to enhancing and increasing of drug efficiency through performing some of the modifications[1]. The prodrug is a chemical modification that include adding some of the group which usually calling promoiety with the parent drug to improve its properties. The additive group must be possessing specific advantages such as no toxic, no side effects and deleting easily out the body. The design of prodrug solving of several problems of an original drug such as stability, target specificity and bioavailability[2]. Captopril is one of the drugs that inhibit of ACE enzyme, which is responsible for increasing blood pressure[3]. Thus preventing heart failure and myocardial infarction[4]. also captopril catalyzing to accumulation of bradykinin through inhibition of bradykininase enzyme[5]. Recently, many studies were revealed captopril reduce and slow developing of some cancer types such as prostate cancer, lung tumor[6],[7]. Aspirin or acetyl-salicylic acid is a nonsteroidal anti- inflammatory drug (NSAID), widely used as an antipyretic, analgesic, and anti-inflammatory. The effect of aspirin is summarized by blocking of prostaglandins pathway which are participating in the formation of inflammation and prevents the formation of thromboxane, which prevents the aggregation of blood platelets and thus contributes to the prevention of thrombus formation and increases blood flow in clotting cases[8]. This occurs due to the inhibition of COX enzymes, which are responsible for the conversion of arachidonic acid into prostanoids and thromboxane[9]. However, the majority of today's some NSAIDs are associated with side-effects such as gastrointestinal (GI) ulceration because of the acidity of the carboxyl group [10]. Protein in the plasma is made up of albumin and globulin, the globulin in turn is made up of α1, α2, β1, β2 and γ globulins. Many serum protein are synthesized in the liver , but the blood cells and lymphocyte of the immune system synthesized immunoglobulins and proteins of complement system are synthesized by macrophage as well as hepatic cells[11]. Carbohydrates form one of the major groups of biological macromolecules in living organisms. Many