Weigh and mix the contents of not less than 20 Khamin Chan Capsules. Transfer an accurately weighed portion of capsule contents, containing about 300 mg of turmeric, to a 10-ml volumetric flask. Add tetrahydrofuran to volume and mix. Set aside at room temperature for 24 hours with frequent shaking. Dilute 1.0 ml of the clear supernatant liquid with methanol to produce 25.0 ml. Transfer 1.0 ml of this solution into a 50-ml volumetric flask, dilute to volume with methanol and mix well.