Da Qing Ye

ISATIDIS FOLIUM (大青叶, Daqingye) Dyers Woad Leaf The dried leaf of Isatis indigotica Fort. (Fam. Cruciferae). The drug is collected 2–3 times in summer and autumn, freed from foreign matter, and dried in the sun. Description Mostly crumpled and rolled, sometimes broken. When intact, long-elliptical to oblong-oblanceolate, 5–20 cm long and 2–6 cm wide. Upper surface dark greyish-green, sometimes bearing small, darker-coloured prominences. Apex obtuse; margin entire or slightly undulate; base attenuate and decurrent into the petiole, appearing wing-shaped. Petiole 4–10 cm long, pale brownish-yellow. Texture fragile. Odour slight; taste slightly sour, bitter, and astringent. Identification (1) Powder Greenish-brown. Anticlinal walls of the lower epidermal cells slightly sinuous and somewhat beaded. Stomata anomocytic, surrounded by 3–4 subsidiary cells. Mesophyll tissue indistinctly differentiated. Mesophyll cells containing blue fine granules and hesperidin-like crystals. (2) To 0.5 g of the powder add 20 ml of chloroform, heat under reflux for 1 hour, filter, and evaporate the filtrate to 1 ml as the test solution. Dissolve indigotin CRS and indirubin CRS in chloroform to produce a mixed reference solution containing 1 mg of each per ml. Carry out the method for thin-layer chromatography (0502), using silica gel G as the coating substance and a mixture of cyclohexane, chloroform, and acetone (5 : 4 : 2) as the mobile phase. Apply separately 5 μl of each solution to the plate. After developing, remove the plate and dry in air. The blue spot and the pale purplish-red spot in the chromatogram obtained with the test solution correspond in position and colour to those in the chromatogram obtained with the reference solution. Water Not more than 13.0% (0832, Method 2). Extractives Carry out the method for determination of ethanol-soluble extractives (2201, hot extraction method), using ethanol as the solvent; not less than 16.0%. Assay Carry out the method for high-performance liquid chromatography (0512). Chromatographic System and System Suitability Use octadecylsilane-bonded silica gel as the stationary phase and a mixture of methanol and water (75 : 25) as the mobile phase. The detection wavelength is 289 nm. The number of theoretical plates is not less than 4000, calculated with reference to the peak of indirubin. Reference Solution Dissolve indirubin CRS, accurately weighed, in methanol to produce a solution containing 2 μg/ml. Test Solution Accurately weigh 0.25 g of the fine powder into a Soxhlet extractor. Add an appropriate quantity of chloroform and macerate for 15 hours. Heat under reflux until the extract becomes colourless. Recover the solvent to dryness. Dissolve the residue in methanol and transfer to a 100 ml volumetric flask. Dilute to volume with methanol and mix well. Procedure Inject accurately 20 μl each of the reference solution and the test solution into the chromatograph. Calculate the content. It contains not less than 0.020% of indirubin (C₁₆H₁₀N₂O₂), calculated with reference to the dried drug. Prepared Slices Processing Eliminate foreign matter, wash rapidly, cut into pieces, and dry. Description In irregular sections. Leaves dark greyish-green, sometimes with small darker-coloured prominences on the upper surface. Petiole pieces pale brownish-yellow. Texture fragile. Odour slight; taste slightly sour, bitter, and astringent. Identification As required for the crude drug. Water Not more than 10.0%, following the method for the crude drug. Assay As required for the crude drug. Property and Flavor Cold; bitter. Meridian Tropism Heart and Stomach meridians. Actions To clear heat, remove toxin, cool the blood, and resolve maculae. Indications Warm diseases with fever, coma, maculae, eruptions, parotitis, throat bi disorder, erysipelas, and swelling abscesses. Administration and Dosage 9–15 g. Storage Preserve in a ventilated and dry place, and protect from mould.