Methods for stabilizing 5-azacytidine in plasma
The invention provides methods for stabilizing 5-azacytidine against hydrolysis in plasma. By extracting the 5-azacytidine into acetonitrile and zinc sulfate, the 5-azacytidine can be stored for at least about 3 hours at about room temperature, and for at least about 4 days at about −70° C. If the acetonitrile is removed and evaporated to dryness, the 5-azacytidine in the resulting residue is stable for at least about 14 months at about −70° C. The invention also provides methods for determining the 5-azacytidine in acetonitrile, or in the acetonitrile residue, using, for example, high-performance liquid chromatography. The methods of the invention permit a significant time interval between the initial processing of the whole blood sample and the time of 5-azacytidine determination.
1. A method for preparing a sample of plasma containing 5-azacytidine for quantitative analysis of said 5-azacytidine, the method comprising:
a) mixing said plasma with acetonitrile and zinc sulfate;
b) separating the mixture from step a) by centrifugation; and
c) storing the centrifuged mixture from step b) at a temperature less than or equal to about room temperature for at least about 3 hours.
2. The method of claim 1 , wherein the ratio of plasma to acetonitrile/zinc sulfate solution in step (a) is less than or about equal to 1:20 (v/v).
3. A method for quantitating 5-azacytidine in plasma comprising:
a) mixing said plasma with acetonitrile and zinc sulfate;
b) separating the mixture from step a) into an acetonitrile layer and a plasma layer by centrifugation;
c) storing the centrifuged mixture from step b) at a temperature less than or equal to about room temperature for at least about 3 hours; and
d) measuring the amount of 5-azacytidine in said acetonitrile layer using high-performance liquid chromatography.
4. The method of claim 3 , wherein the ratio of plasma to acetonitrile/zinc sulfate solution in step (a) is less than or about equal to 1:20 (v/v).
5. A method for preparing a sample of plasma containing 5-azacytidine for quantitative analysis of said 5-azacytidine, the method comprising:
a) mixing said plasma with acetonitrile and zinc sulfate;
b) separating the mixture from step a) into an acetonitrile layer and a plasma layer by centrifugation;
c) removing at least a portion of said acetonitrile layer; and
d) evaporating said removed acetonitrile layer to yield a residue comprising 5-azacytidine.
6. A method for quantitating 5-azacytidine in plasma comprising:
a) mixing said plasma with acetonitrile and zinc sulfate;
b) separating the mixture from step a) into an acetonitrile layer and a plasma layer by centrifugation;
c) removing at least a portion of said acetonitrile layer;
d) evaporating said removed acetonitrile layer to yield a residue comprising 5-azacytidine; and
e) measuring the amount of 5-azacytidine in said residue.
7. The method of claim 6 wherein the residue of step d) is stored at about minus 70° C. for between about 3 hours and about 14 months prior to step e).
8. The method of claim 6 wherein 5-azacytidine is measured in step e) using high-performance liquid chromatography with mass spectrometric detection.