Isosorbide-based aspirin prodrugs: II. Hydrolysis kinetics of isosorbide diaspirinate

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Abstract

Aspirin prodrugs have been intensively investigated in an effort to produce compounds with lower gastric toxicity, greater stability or enhanced percutaneous absorption, relative to aspirin. This report describes the hydrolysis kinetics and aspirin release characteristics of isosorbide diaspirinate (ISDA), the aspirin diester of isosorbide. ISDA underwent rapid hydrolysis when incubated in phosphate buffered human plasma solutions (pH 7.4) at 37 °C, producing appreciable quantities of aspirin. In 30% human plasma solution the half-life was 1.1 min and 61% aspirin was liberated relative to the initial ester concentration. The hydrolysis kinetics of ISDA were monitored in aqueous solution at 37 °C over the pH range 1.03–9.4. The aqueous hydrolysis followed pseudo-first-order kinetics over several half-lives at all pH values, resulting in a U-shaped pH rate profile. Salicylate esters and salicylic acid were formed during these processes. The hydrolysis characteristics of ISDA were also investigated in pH 7.4 phosphate buffered solutions containing α-chymotrypsin [EC 3.1.1.1] (t1/2=200.9 min), carboxyl esterase [EC 3.1.1.1] (t1/2=31.5 min), human serum albumin (t1/2=603 min), purified human serum butyrylcholinesterase [EC 3.1.1.8] (80 μg/ml; t1/2=9.4 min; 55% aspirin), purified horse serum butyrylcholinesterase (100 μg/ml; t1/2=1.85 min;11% aspirin) and in 10% human plasma solution in the presence of physostigmine (3 μM). The results indicate that a specific enzyme present in human plasma, probably human butyrylcholinesterase, catalyses aspirin release from isosorbide diaspirinate.

Introduction

Aspirin prodrugs have been extensively investigated for many years as a means of depressing gastric toxicity (Jones, 1985) or increasing percutaneous absorption (e.g. Lofttson et al., 1981). The major reason for the lack of progress in this area is that the aspirin O-acetyl ester, so essential to its unique pharmacological profile, is rendered highly susceptible to plasma-mediated hydrolysis relative to aspirin itself by esterification of the aspirin carboxylic acid group (Nielsen and Bungaard, 1989). A successful aspirin prodrug must undergo hydrolysis at the carrier ester at a greater rate than at the O-acetyl group, whose hydrolysis the carrier group greatly accelerates.

Strategies to overcome this problem may be grouped into those that exploit ester types that are intrinsically chemically unstable, or those that use carrier groups capable of acting as enzyme substrates, thus competing with the rapid O-acetyl hydrolysis. Examples of the former approach include aspirin anhydrides (Levy and Gagliardi, 1963), benzodioxinone derivatives (Ankersen et al., 1989, Nielsen and Senning, 1990), acylal derivatives (Hussain et al., 1974, Hussain et al., 1979, Truelove et al., 1980), N-(hydroxyalkyl) amides (Bundgaard et al., 1988), and 2-formylphenyl derivatives (Abordo et al., 1998). One limitation of this approach is that increasing ester lability diminishes drug stability. The enzyme targeting approach has been more intensively pursued, as successful candidates, although highly susceptible to enzyme-mediated decomposition, might also be chemically stable. Examples in this group include alkyl and aryl esters (Rainsford and Whitehouse, 1976, Rainsford and Whitehouse, 1980), triglycerides (Kumar and Billimoria, 1978, Paris et al., 1979, Paris et al., 1980), acyloxyalkyl esters (Los et al., 1982), sulfinyl or sulfonyl esters (Lofttson and Bodor, 1981a, Lofttson and Bodor, 1981b, Lofttson et al., 1981), phenylalanine derivatives (Banerjee and Amidon, 1981a, Banerjee and Amidon, 1981b, Banerjee and Amidon, 1981c, Muhi-Eldeen et al., 1985), amino acid derivatives (Tsunematsu et al., 1991), glycolamide esters (Nielsen and Bungaard, 1989), and indolediones as hypotoxic tissue targeting agents (Jaffar et al., 1999). Of these attempts, only some of the glycolamides reported by Nielsen and Bungaard (1989) can be considered successful, as these compounds combine good aqueous stability with the ability to liberate significant amounts of aspirin (50–55%) in human plasma. Interest in the aspirin prodrug area has been renewed with the advent of the so-called NO–aspirins (Del Soldato et al., 1999). These are mutual prodrugs in which aspirin is connected via an ester group to a nitric oxide releasing moiety such as a nitrate ester. The prototype drug in this class, NCX-4016, exhibits greater gastric tolerability than aspirin in several animal models (Takeuchi et al., 1998, Tashima et al., 2000) and appears to depress platelet aggregation, partially through COX-1 inhibition, but also through nitric oxide-dependent mechanisms (Wallace et al., 1999).

We have recently reported on the hydrolysis and antiplatelet effects of ISMNA, the isosorbide mononitrate ester of aspirin (Gilmer et al., 2001). ISMNA undergoes hydrolysis almost exclusively to aspirin in rabbit plasma and is a more potent inhibitor of arachidonic acid-induced platelet aggregation in rabbit platelet-rich plasma than aspirin. The unusually favourable hydrolysis properties of ISMNA in plasma appear to be due to a structural feature of the isosorbide carrier group that promotes hydrolysis through the productive pathway (liberating aspirin), while simultaneously inhibiting hydrolysis at the critical O-acetyl group (leading to the salicylate ester). In the light of this discovery it seemed reasonable to speculate that isosorbide might be useful as a building block in the construction of other aspirin prodrug types for potential use in thrombotic or inflammatory disorders. We report here on the synthesis of the isosorbide aspirin diester (ISDA), its ability to liberate aspirin in human plasma and its hydrolysis by other enzyme types. The stability of the prodrug towards aqueous hydrolysis, a critical feature influencing its potential utility, was also investigated. Two previously reported aspirin esters, Benorylate (4-acetamidophenyl acetylsalicylate or paracetamol aspirinate; Williams et al., 1989) and guaiacol aspirinate (Qu et al., 1990) were also prepared and their hydrolysis characteristics in human plasma compared with ISDA.

Section snippets

Materials

Acetylsalicyloyl chloride (95%) was purchased from Fluka. Aspirin, paracetamol, guaiacol, salicylic acid, rabbit liver carboxyl esterase [EC 3.1.1.1], α-chymotrypsin [EC 3.4.21.1], human serum albumin, human and horse serum butyrylcholinesterase [EC 3.1.1.8], and eserine (physostigmine), were purchased from Sigma. HPLC grade acetonitrile was purchased from Rathburn. All other reagents and chemicals were of analytical grade.

Human blood collection

Healthy male and female volunteers were consented as blood donors for

Chemistry

ISDA (2, Fig. 1) was prepared in good yield by treating a suspension of isosorbide in toluene with two equivalents of acetylsalicoyl chloride in the presence of triethylamine. The product following crystallisation was >99% pure by HPLC and was characterised by NMR, MS and elemental analysis. Two other aspirin esters, 4-acetamidophenyl acetylsalicylate (benorylate) and guaiacol aspirinate (2-methoxyphenyl acetylsalicylate), were prepared by treating paracetamol or guaiacol, respectively, with

Conclusions

Isosorbide diaspirinate, the aspirin diester of isosorbide, is stable towards aqueous hydrolysis and in the presence of α-chymotrypsin. However, it undergoes rapid hydrolysis in the presence of human plasma solution, liberating significant amounts of aspirin. Besides the isosorbide mononitrate ester of aspirin which we recently reported (Gilmer et al., 2001) and the diaspirinate ester ISDA (2) reported herein, only the glycolamide esters of Nielsen and Bungaard (1989) may be regarded as true

References (40)

  • P Masson et al.

    Butyrylcholinesterase-catalysed hydrolysis of aspirin, a negatively charged ester, and aspirin-related neutral esters

    Biochim. Biophys. Acta

    (1998)
  • Z Muhi-Eldeen et al.

    Kinetics and mechanism of hydrolysis of aspirin phenylalanine ethyl ester

    Int. J. Pharm.

    (1985)
  • K Tashima et al.

    Lack of gastric toxicity of nitric oxide releasing aspirin, NCX-4016, in the stomach of diabetic rats

    Life Sci.

    (2000)
  • J.L Wallace et al.

    In vivo antithrombotic effects of a nitric oxide-releasing aspirin derivative, NCX-4016

    Thromb. Res.

    (1999)
  • M Ankersen et al.

    Synthesis, properties and prodrug potential of 2-methyl-2-oxy- and 2-methyl-2-thio-4H-1,3-benzodioxinones

    Acta Chem. Scand.

    (1989)
  • H Bundgaard et al.

    Aspirin prodrugs: synthesis and hydrolysis of 2-acetoxybenzoate esters of various N-(hydroxyalkyl) amides

    Int. J. Pharm.

    (1988)
  • B.E Cham et al.

    Simultaneous liquid-chromatographic quantitation of salicylic acid, salcyluric acid, and gentisic acid in plasma

    Clin. Chem.

    (1979)
  • N Chapuis et al.

    The esterase-like activity of serum albumin may be due to cholinesterase contamination

    Pharm. Res.

    (2001)
  • A Chatonnet et al.

    Comparison of butyrylcholinesterase and acetylcholinesterase

    Biochem. J.

    (1989)
  • H.S Harned et al.

    The ionisation constant of water in potassium chloride solution from electromotive forces of cells without liquid junctions

    J. Am. Chem. Soc.

    (1933)
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