Objective: To compare the content of catechin in radix and rhizoma of Rheum tanguticum at different growing stages and harvesting stages and with different fertilizer doses in Donggou Village

Huzu County

Qinghai province

in order to determine the best harvesting stage and fertilizer dose. Method: Three harvesting stages were designed in May

July and October every year

and two-year-old

three-year-old and four-year-old R. tanguticum radix and rhizoma were fertilized with phosphorus (superphosphate) and potassium (potassium sulfate) fertilizers. The methanol extracts were analyzed through HPLC. Platisil SB-C18 (4.6 mm×250 mm

5 μm) was adopted and eluted with acetonitrile-0.1% formic acid as mobile phase in a gradient mode. The column temperature was 25℃

the injection volume was 15 μL

the flow rate was 0.8 mL·min-1; the wavelength was 224 nm. Result: The linear ranges of catechin was 0.424-10.60 μg (r=0.999 9)

the content of catechin gradually increased with the rise of growing years; the average content of catechin came to the maximum in May

which was followed by July

and the least content was observed in October; the content of catechin in fertilizer group was higher than that of the control group. Conclusion: With the catechin content as the harvesting indicator

three or four-year-old R. tanguticum radix and rhizoma is suitable for harvesting

the optimal harvesting stages are May

and P2O5 45 kg·ha-1 was the most appropriate. Catechin content of three or four-year-old R. tanguticum radix and rhizoma exceeded 20 mg·g-1. Therefore

catechin content is suggested to be no less than 20%

which provides a basis for the quality control of R. tanguticum radix and rhizoma.