Effect of pH on fractional precipitation for pre-purification of paclitaxel from plant cell cultures

Fractional precipitation is a simple, efficient method for pre-purifying paclitaxel from plant cell cultures of Taxus chinensis. The pH, a key process variable in fractional precipitation, was optimized in terms of the yield and purity of paclitaxel with a fixed methanol concentration in water (61.5%, v/v), paclitaxel content in the crude extract (0.5%, w/v), and storage time (14 hr). The maximum yield (similar to 99%) and purity (similar to 84.4%) of paclitaxel were obtained at pH 8.0 with potassium phosphate buffer. The precipitate from fractional precipitation was an amorphous state paclitaxel by analysis of XRD and SEM. Also, the particle size distribution of dried precipitate was a range of approximately 119-411 mu m. The use of fractional precipitation in the pre-purification process allowed for rapid and efficient separation of paclitaxel from interfering compounds, and dramatically increased the yield and purity of the crude paclitaxel for subsequent purification steps.