2, used as acid-base indicator, pH 7.8 (yellow) -9.2 (reddish brown).
3. Curcumin, mono-demethoxycurcumin and di-demethoxycurcumin were isolated from the turmeric extract. Four curcumin derivatives were synthesized by introducing carboxylic acid groups, acetylation and hydrogenation, and their tyrosinase inhibitory activities were tested. The results showed that the activity of demethoxycurcumin in natural curcumin compounds was the strongest, and the IC5 1 was 0.076 mmol/L. Among the structural modification compounds of curcumin, curcumin derivatives containing carboxyl groups showed strong inhibitory activity, with IC50 of 0.056 mmol/L. The study of inhibition kinetics showed that the inhibition of tyrosinase by mono-demethoxycurcumin and curcumin derivatives containing carboxyl groups belonged to non-competitive inhibition type. Curcumin is a pigment extracted from turmeric, a ginger plant, and also exists in other ginger plants. Modern research has found that curcumin has the effects of inhibiting inflammatory reaction, antioxidation and anti-rheumatoid. The American magazine VITY Vitamins reported: "The main pharmacological effects of curcumin include anti-oxidation, anti-inflammation, anticoagulation, lipid-lowering, anti-atherosclerosis, anti-aging, scavenging free radicals and inhibiting tumor growth. From June 5438 to October 2006 10, an article in the American journal Arthritis and Rheumatism pointed out that curcumin can prevent joint swelling and arthritis, and it is also effective for cardiovascular diseases and cancer.