Effect of different proportions of piper chinaroot and rhubarb on the dissolution rate of five effective components in rhubarb

Objective To study the effect of different proportions of piper chinaroot and rheum palmatum on the dissolution rate of five effective components (aloe emodin, emodin acid, emodin, emodin, emodin methyl ether). Methods The high performance liquid chromatography (HPLC) method was used to analyz the contents of five effective components of rheum palmatum in the extracts of different combination of piper chinaroot and rheum palmatum. The tests were carried out by Thermo C18 (250 mm×4.6 mm, 5 μm) by gradient elution with methanol and 0.1% phosphoric acid water solution as mobile phase at a flow rate of 1ml/min, the column temperature was 30 ℃ and the detection wavelength was 254 nm. Results The linear ranges of aloe emodin, emodin acid, emodin, emodin, emodin methyl ether were 0.018 5-0.741 8, 0.017 9-0.717 8, 0.015 9-0.635 5, 0.054 2-2.167 2, 0.016 2-0.646 4 μg, respectively. The average recoveries of aloe emodin, emodin acid, emodin, emodin, emodin methyl ether were 94.35%, 95.50%, 100.61%, 96.27%, 97.39%, and the RSDs were 1.81%, 1.99%, 2.84%, 2.71%, and 1.86%, respectively. Compared with rheum palmatumby single extract, the content of aloe emodin and emodin were increased by 5 proportions (3:1, 2:1, 1:1, 1:2, 1:3), while the content of emodin and emodin methyl ether were decreased. Conclusions The optimal compatibility proportion of piper chinaroot and rheum palmatum is 1:1. Key words: Piperis longi fructus; Rhei radix et rhizoma; Compatibility (TCD); Aloeemodin; Emodin; Chrysophanol; Rhein; Physcion; Assay (TCD)