OBJECTIVETo probe into the influences of different granule sizes and to prepare procedures on rational clinical usage of rhubarb based on chemical equivalence.

METHODThe effects of particle size, extract solvent, extract time and repeat times, and pre-extract or pro-extract of rhubarb on the extract amounts of the anthraquinones (AQs) were compared.

RESULTThe different prepare procedures investigated in the paper revealed significant influence on the extract amounts of the AQs and those extracts were not chemical equivalent. Ethanol extracted more AQs than water did, when other conditions were same. When extracted with water, the rhubarb of piece size 0.8-1.2 cm could extract relatively high amount of AQs nearly equal to superfine grinded powders, and the former was cheap. The water extraction of AQs showed an increasing trend with the extraction time extended. And pro-extract manner with water could extract more AQs than pre-extract manner with a extraction time of 30, 60 min. The water extraction of AQs repeated two times exceeded half of the amount of totally six times. When extracted with ethanol, the rhubarb of fine powders could extract relatively high amount of AQs nearly equal to superfine grinded powders. And pre-extract manner with ethanol could extract more AQs than pro-extract manner. The ethanol extraction of AQs increased in 30 min and then increased slower. The ethanol extraction of AQs repeated two times exceeded 70% of the amount of totally six times. So, the optimal conditions for water extraction rhubarb were pro-extract, two times repeated and 30 min per time; and the optimal conditions for ethanol extract were pre-extract, two times repeated and 30 min per time.

CONCLUSIONThe different prepare procedures showed significant influence on the extraction of rhubarb AQs. There is great need to establish a good usage practice (GUP) for Chinese Materia Medica to maintain rational clinical usage.