Adsorption characteristics and separation of taxol from yew tree by NP-HPLC

Abstract

Abstract Taxol (Paclitaxel) is a powerful anticancer produced by the pacific yew. Taxol shows promise for the treatment of a variety of human cancers, including leukemia and certain ovarian, breast and lung tumors. Industries and governmental research institutes have actively studied to produce highly pure taxol on a commercial scale. In this work, the separation of taxol from yew tree was studied with solvent extraction and normal phase liquid chromatography (NP-HPLC). The content of taxol in the tree was found to be 0.064 mg/g of dry powder. The solvent used in extraction was methanol and the extract was concentrated by the partition of water and methylene chloride. Impurities were removed in the pretreatment step with open column, where silica packings (10–40 μm, YMC) were packed. In this step, the first mobile phase was methylene chloride/acetone, 97/3 vol.% and the second mobile phase methylene chloride/acetone, 75/25 vol.%. The sample was further separated by varying the composition of solvent, flow rate, and injection amount in analytical chromatography. Also experiments were performed to obtain the correlation equation between the optimum resolution and the mobile phase composition. The experimental resolution of cephalomannine/taxol was 1.81 and that of taxol/10-deaccetyltaxol was 5.43. The values calculated from the correlation equation were 2.32 and 6.32, respectively, and in good agreement with the experimental values. In the column (3.9×300 mm) with larger particle sizes (Lichrospher Si 60, 15 μm), the mobile phase composition was hexane/2-propanol/MeOH, 90/4/6 vol.% in isocratic mode. At 1.5 ml/min of mobile phase flow rate, 2.58 μg of taxol was collected in the experimental conditions. The purified taxol was used to determine the adsorption isotherm of taxol. From the experimental results, the adsorption isotherm was obtained as the following Langmuir type. C S = 59.5C M 1+2.0C M To obtain the adsorption isotherm, only two injections of small and large amount of taxol were required and the Langmuir adsorption parameters were calculated from the assumption of the monolayer coverage on the solid surface. Analytical experimental conditions were extended to preparative liquid chromatography. In preparative column (22×250 mm) packed by the same packing with the same mobile phase composition, at 16 ml/min 2.41 mg of taxol was purified in the single run.