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Acetylsalicylic acid


Aspirin, 2-Acetoxybenzoic acid, ASA, O-Acetylsalicylic acid
Linear Formula:
CAS Number:
Molecular Weight:
EC Number:
MDL number:
PubChem Substance ID:

Quality Level

biological source








pKa (25 °C)



134-136 °C (lit.)


H2O: 10 mg/mL at 37 °C(lit.)
H2O: 3 mg/mL at 25 °C(lit.)
ethanol: 50 mg/mL
aqueous base: decomposes

ε (extinction coefficient)

190 at 298 nm in aqueous base at 1 mM
409 at 231 nm in aqueous base at 1 mM
466 at 230 nm in aqueous acid at 1 mM
68 at 278 nm in aqueous acid at 1 mM

SMILES string




InChI key


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100, 250, 500 g in poly bottle
1 kg in poly bottle

Biochem/physiol Actions

Blocks the production of prostaglandins by inhibiting cyclooxygenase (prostaglandin H synthase), with greater selectivity toward the COX-1 isoform. The antithrombotic effect is due to the inhibition of COX-1 in platelets that blocks thromboxane production and platelet aggregation. Chemopreventive against colorectal and other solid tumors.


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Signal Word


Hazard Statements

Precautionary Statements

Hazard Classifications

Acute Tox. 4 Oral

Storage Class Code

11 - Combustible Solids



Flash Point(F)

482.0 °F

Flash Point(C)

250 °C

Personal Protective Equipment

dust mask type N95 (US), Eyeshields, Gloves

Certificate of Analysis

Enter Lot Number to search for Certificate of Analysis (COA).

Certificate of Origin

Enter Lot Number to search for Certificate of Origin (COO).

  1. Which document(s) contains shelf-life or expiration date information for a given product?

    If available for a given product, the recommended re-test date or the expiration date can be found on the Certificate of Analysis.

  2. How do I get lot-specific information or a Certificate of Analysis?

    The lot specific COA document can be found by entering the lot number above under the "Documents" section.

  3. How do I find price and availability?

    There are several ways to find pricing and availability for our products. Once you log onto our website, you will find the price and availability displayed on the product detail page. You can contact any of our Customer Sales and Service offices to receive a quote.  USA customers:  1-800-325-3010 or view local office numbers.

  4. What is the Department of Transportation shipping information for this product?

    Transportation information can be found in Section 14 of the product's (M)SDS.To access the shipping information for this material, use the link on the product detail page for the product. 

  5. How does aspirin act as an anticlotting agent?

    There may be multiple modes of action which result in the anticlotting properties of aspirin. Some studies have indicated a decrease in thrombin levels and others reduced clotting properties of fibrinogen.

  6. Is Product A5376, Acetylsalicylic acid, offered by Sigma-Aldrich different from that found in aspirin tablets from the drug store?

    The active ingredient acetylsalicylic acid offered by Sigma-Aldrich is the same chemical as found in aspirin tablets. However, chemicals for pharmaceutical use are manufactured, tested, and packaged under the regulation of the FDA, but chemicals sold for research use do not have the same regulatory oversight.

  7. How should solutions of Product A5376, Acetylsalicylic acid, be prepared and stored?

    Acetylsalicylic acid is slightly soluble in water, with a limit of solubility reported as approximately 3 mg/ml at 25 Deg C.  It is also soluble in ethanol at 50 mg/ml and will dissolve in solutions of alkali hydroxides and carbonates with decomposition.  Aqueous solutions of acetylsalicylic acid are most stable at pH 2 - 3, but to assure full activity, fresh solutions are recommended.

  8. My question is not addressed here, how can I contact Technical Service for assistance?

    Ask a Scientist here.

Niels Hulsman et al.
Journal of medicinal chemistry, 50(10), 2424-2431 (2007-04-20)
Hybrid drug 1 (NO-ASA) continues to attract intense research from chemists and biologists alike. It consists of ASA and a -ONO2 group connected through a spacer and is in preclinical development as an antitumor drug. We report that, contrary to
Connie N Hess et al.
Journal of the American College of Cardiology, 66(7), 777-787 (2015-08-14)
Bleeding limits anticoagulant treatment in patients with acute coronary syndromes (ACS). We investigated whether background concomitant antiplatelet therapy influences the effects of apixaban after ACS. This study examined high-risk ACS patients who were treated with aspirin or aspirin plus clopidogrel
Andrew O Maree et al.
Journal of the American College of Cardiology, 46(7), 1258-1263 (2005-10-04)
We investigated whether use of low-dose enteric-coated (EC) aspirin for secondary prevention of cardiovascular events has sufficient bioavailability to achieve complete platelet cyclooxygenase (COX) inhibition in all individuals. Aspirin reduces cardiovascular morbidity and mortality in patients with pre-existing vascular disease;
Katarzyna Palus et al.
PloS one, 10(11), e0143661-e0143661 (2015-11-26)
This experiment was designed to establish the localization and neurochemical phenotyping of sympathetic neurons supplying prepyloric area of the porcine stomach in a physiological state and during acetylsalicylic acid (ASA) induced gastritis. In order to localize the sympathetic perikarya the
Laurent Arnaud et al.
Autoimmunity reviews, 13(3), 281-291 (2013-11-06)
We performed a meta-analysis to determine whether aspirin has a significant protective effect on risk of first thrombosis among patients with antiphospholipid antibodies (aPL+). Observational and interventional studies identified from the Medline, Embase and Cochrane databases were selected if they

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