THIN-LAYER DRYING OF CULTIVATED TAXUS CLIPPINGS

A promising cancer chemotherapeutic agent, taxol, is currently schedul ed for full clinical development by the National Cancer Institute. The ornamental yew, Taxus x media 'Hicksii', has been identified as a ren ewable source of taxol. However, clippings from the plant must be prop erly and efficiently harvested dried, and stored. Thin-layer drying st udies of Taxus clippings, needles, and stems were conducted. Parameter s for the thin-layer drying equation were successfully determined for drying temperatures of 30, 40, 50, and 60 degrees C. The results showe d that drying rates increased 28-, 15-, and 3-fold as drying temperatu res increased from 30 degrees, 40 degrees, and 50 degrees C to 60 degr ees C, respectively. Also, stems dried at a faster rate than needles a nd needles dried at a faster rate than whole clippings. Taxol yields ( g/100 g, d.b.)from stems were nearly constant for the four temperature s tested. However, yields from needles increased linearly as drying te mperatures increased from 30 to 60 degrees C. The highest taxol yields were obtained from clippings. Nearly constant yields were obtained (s imilar to 0.014 g/100 g, db.) for drying temperatures of 40, 50, and 6 0 degrees C. The lowest yields for all three plant components occurred when the drying temperature was set at 30 degrees C. The results sugg est 60 degrees C is the best temperature setpoint for drying Taxus x m edia 'Hicksii' but temperatures higher than 60 degrees C should be eva luated.