Fagopyrum cymosum complex is a traditional Chinese medicinal herb, which is rich in flavonoids and has great medicinal value. In this work, the optimum extraction conditions of flavonoids from F. cymosum complex leaves were investigated by orthogonal design. Six methodological factors (including alcohol concentration, material-liquid ratio, reaction temperature, distilled time, extraction times and ultrasonic power) were studied using an L18 (3⁷) orthogonal test table. The results showed that the effects of each factor on the extraction of flavonoids in order were as follows: alcohol concentration > materials-liquid ratio > ultrasonic power > extraction times > distilled time > reaction temperature, the effect of alcohol concentration on extraction was extremely significant, while the effect of other factors was not. The highest yield was obtained when alcohol concentration, liquid material ratio, ultrasonic power, extraction times, distillation time, reaction temperature were 60 %, 1:20 (w/v), 70 % (175 w), three times, 20 min and 40 ºC, respectively. And the crude extract of flavonoids was determined using four kinds of spectrophotometric methods, The results show that the method D (HAC-AlCl₃ spectrophotometric method) was the best. It's a simple, accurate and precise method for the determination of flavonoids content in leaves of F. cymosum complex.

Spectrophotometric method, Flavonoids, Fagopyrum cymosum complex, Orthogonal design, Polyphenol.

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