Distribution and Amounts of Taxol in Different Shoot Parts of Taxus cuspidata

Abstract

Different fresh shoot parts of male and female plants of Taxus cuspidata were extracted and analysed for taxol concentration by high performance liquid chromatography (HPLC). Extracted parts included: young needles (first 10 top needle pairs of 30cm long branches), old needles (last 10 needle pairs of 30cm long branches), green bark, dark bark (with intense secondary growth), young wood (originally surrounded by green bark), wood (originally surrounded by dark bark), young stems (surrounded by green bark and devoid of needles), and mature male cones. Dichloromethane extracts were analysed by HPLC and diode array spectroscopy. Taxol identification was done by retention time, U.V. spectra, and spiking with an authentic taxol standard; ¹H-NMR analysis was done for needle extracts. All parts except male cones had measurable amounts of taxol; no effect of plant sex on taxol levels of the plant parts analysed was observed. Results indicated that the bark accounted for almost all the taxol present in stems devoid of needles. Needles showed the highest levels of taxol (overall average of 0.035 ± 0.006% of the extracted dry weight), significantly higher than those displayed by dark bark samples (0.012 ± 0.001% of the extracted dry weight). Different needle post-harvesting procedures were evaluated in relation to taxol yields, 96 h dark incubation at -12°C and 96 h dark incubation at 25°C under vacuum gave taxol yields equivalent to those of freshly extracted samples. However, results obtained for 96 h dark incubation at 60°C indicated some extent of taxol degradation.

Key words

Taxol - Taxus cuspidata - shoot distribution - needle extraction - HPLC