C19H28O8
Relative molecular mass. 384.4
Chemical name. (3R,5aS,6R,8aS,9R,10S,12R,12aR)-Decahydro-3,6,9-trimethyl-3,12-epoxy-12H-pyrano[4,3-j]-1,2-benzodioxepin-10-ol, hydrogen succinate; CAS Reg. No. 182824-33-5.
Description. A fine, white crystalline powder.
Solubility. Very slightly soluble in water; very soluble in dichloromethane R; freely soluble in ethanol (~750 g/l) TS and acetone R.
Category. Antimalarial drug.
Storage. Artesunate should be kept in a well-closed container and protected from light.
Requirements
Artesunate contains not less than 96.0% and not more than the equivalent of 102.0% of C19H28O8 using Assay method A, and not less than 99.0% and not more than the equivalent of 101.0% of C19H28O8 using Assay method B, both calculated with reference to the anhydrous substance.
Identity tests
• Either test A alone or tests B, C, and D may be applied.
A. Carry out the examination as described under 1.7 Spectrophotometry in the infrared region. The infrared absorption spectrum is concordant with the spectrum obtained from artesunate RS or with the reference spectrum of artesunate.
B. Carry out the test as described under 1.14.1 Thin-layer chromatography, using silica gel R6 as the coating substance and a mixture of 5 volumes of ethyl acetate R and 95 volumes of toluene R as the mobile phase. Apply separately to the plate 2μl of the following 2 solutions in toluene R containing (A) 0.10 mg of Artesunate per ml, and (B) 0.10 mg of artesunate RS per ml. After removing the plate from the chromatographic chamber, allow it to dry in air, spray with anisaldehyde/methanol TS, and heat the plate to 120 °C for 5 minutes. Examine the chromatogram in ultraviolet light (254 nm).
The principal spot obtained with solution A corresponds in position, appearance, and intensity with that obtained with solution B.
C. Dissolve 0.1 g of Artesunate in 40 ml of dehydrated ethanol R, shake, and filter. To half of the filtrate (keep the remaining filtrate for test D) add about 0.5 ml of hydroxylamine hydrochloride TS2 and 0.25 ml of sodium hydroxide (~80 g/l) TS. Heat the mixture in a water-bath to boiling, cool, add 2 drops of hydrochloric acid (~70 g/l) TS and 2 drops of ferric chloride (50 g/l) TS; a light red-violet colour is produced.
D. Evaporate the remaining filtrate from test C on a water-bath to a volume of about 5 ml. Place a few drops of the mixture on a white porcelain dish, add 1 drop of vanillin/sulfuric acid TS1; a reddish-brown colour is produced.
Melting range. 132 - 135°C.
Specific optical rotation. Use a 10mg/ml solution in dichloromethane R;
Heavy metals. Use 1.0 g for the preparation of the test solution as described under 2.2.3 Limit test for heavy metals, Procedure 3; determine the heavy metals content according to Method A; not more than 20μg/g.
Sulfated ash. Not more than 1.0 mg/g.
Water. Determine as described under 2.8 Determination of water by the Karl Fischer method, Method A, using 2 g of Artesunate; the water content is not more than 5 mg/g.
pH value. pH of an aqueous suspension containing 10 mg/g, 3.5 - 4.5.
Related substances
• Either test A or test B may be applied.
A. Carry out the test as described under 1.14.4 High-performance liquid chromatography, using the conditions given below under Assay method A.
Inject alternately 20μl each of solutions A and C.
Measure the areas of the peak responses obtained in the chromatograms from solutions A and C, and calculate the content of the related substances as a percentage. In the chromatogram obtained with solution A, the area of any peak, other than the principal peak, is not greater than that obtained with solution C (1.0%). Not more than one peak is greater than half the area of the principal peak obtained with solution C (0.5%). The sum of the areas of all peaks, other than the principal peak, is not greater than twice the area of the principal peak obtained with solution C (2.0%). Disregard any peak with an area less than 0.1 times the area of the principal peak in the chromatogram obtained with solution C.
B. Carry out the test as described under 1.14.1 Thin-layer chromatography, using silica gel R1 as the coating substance and a mixture of 48 volumes of light petroleum R1, 36 volumes of ethyl acetate R and 1 volume of glacial acetic acid R as the mobile phase. Apply separately to the plate 10μl of each of the following 3 solutions in dichloromethane R containing (A) 5.0 mg of Artesunate per ml, (B) 0.05 mg of Artesunate per ml, and (C) 0.025 mg of Artesunate per ml. After removing the plate from the chromatographic chamber, allow it to dry in air, and spray with vanillin/ sulfuric acid TS1. Examine the chromatogram in daylight.
Any spot obtained with solution A, other than the principal spot, is not more intense than that obtained with solution B (1.0%). Furthermore, not more than one such spot is more intense than that obtained with solution C (0.5%).
Assay
• Either method A or method B may be applied.
A. Determine by 1.14.4 High-performance liquid chromatography, using a stainless steel column (12.5cm × 3.5mm) packed with particles of silica gel, the surface of which has been modified with chemically bonded octadecylsilyl groups (5μm). As the mobile phase, use a mixture of equal volumes of acetonitrile R and buffer pH 3.0 (dissolve 1.36g of potassium dihydrogen phosphate R in 1000 ml of water and adjust the pH to 3.0 with phosphoric acid (~1440 g/l) TS).
Prepare the following solutions in acetonitrile R: solution (A) 4.0 mg of Artesunate per ml; solution (B) 4.0 mg of artesunate RS per ml; and for solution (C) dilute solution A to obtain a concentration equivalent to 0.04 mg of Artesunate per ml.
Operate with a flow rate of 0.6 ml per minute. Maintain the column temperature at 30 °C and use an ultraviolet spectrophotometer set at a wavelength of about 216nm.
Inject alternately 20μl each of solutions A and B.
Measure the areas of the peak responses obtained in the chromatograms from solutions A and B, and calculate the percentage content of C19H28O8 with reference to the anhydrous substance.
B. Dissolve about 0.25 g of Artesunate, accurately weighed, in 25 ml of neutralized ethanol TS and titrate with sodium hydroxide (0.05 mol/l) VS, using 2 drops of phenolphthalein/ethanol TS as indicator.
Each ml of sodium hydroxide (0.05 mol/l) VS is equivalent to 19.22mg of C19H28O8.
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