Robert C. Hansen,
Department of Food, Agricultural, and Biological Engineering,
Ohio Agricultural Research and Development Center,
The Ohio State University,
Wooster, Ohio.
Robert G. Holmes,
Department of Food, Agricultural, and Biological Engineering,
The Ohio State University,
Columbus, Ohio.
Ralph B. Shugert Jr.,
Zelenka Nursery, Inc.,
Grand Haven, Mich.
Edward M. Croom Jr.,
Research Institute of Pharmaceutical Sciences,
School of Pharmacy,
The University of Mississippi,
University, Miss.
Hala N. ElSohly,
Research Institute of Pharmaceutical Sciences,
School of Pharmacy,
The University of Mississippi,
University, Miss.
Harold M. Keener,
Department of Food, Agricultural, and Biological Engineering,
Ohio Agricultural Research and Development Center,
The Ohio State University,
Wooster, Ohio.
Kenneth D. Cochran,
Secrest Arboretum,
Ohio Agricultural Research and Development Center,
The Ohio State University Agricultural Technical Institute,
Wooster, Ohio.
Presented at the National Cancer Institute Workshop on Taxus, Taxol, and Taxotere. Alexandria, Va. September 23-24, 1992.
Taxus x media 'Hicksii' has been identified as a potential renewable source of Taxol (Witherup et al., 1990; Croom, 1991). 'Hicksii' is somewhat unique because new shoots generally grow vertically, thus facilitating mechanization of clipping and capture. Ornamental yews are pruned on an annual basis as a part of standard cultural practices in nurseries. Other than for purposes of propagation, Taxus clippings have not been routinely harvested, dried, or stored. Taxus x media 'Hicksii' clippings have been found to have concentrations of Taxol equal to or greater than 0.02 percent (Croom, 1991).
A mechanical harvester for clipping and collecting 'Hicksii' clippings was designed and developed. The height of the machine can be adjusted as plant height varies. A reel and canvas conveyor transports clippings to a 5 ft. x 2-1/2 ft. x 1-1/2 ft. pallet after cutting. When full, the pallets can be conveniently transferred to four-wheel trailers and towed from the field to any specified storage building. The harvester was successfully field tested during the spring 1992 pruning season.
A commercial 27-ft.-diameter bin dryer was used to dry Taxus x media 'Hicksii' clippings and whole plants in a shallow bed in preparation for storage (Hansen et al., 1992). Variations in drying temperatures were recorded throughout the three- to five-day period during which drying occurred for 10 lots of biomass. Data were analyzed using statistical process control charts. Results suggested that commercial grain bin drying systems are not effective in meeting currently accepted tolerances for drying Taxus biomass and may require extensive modification.
To facilitate design of a more effective drying system, thin-layer drying studies of Taxus x media 'Hicksii' clippings, needles, and stems were conducted in a laboratory dryer (Hansen et al., 1993). The thin-layer drying equation (Keener, 1991) was found to be applicable to drying rates for the Taxus materials tested at 30°, 40°, 50°, and 60°C drying temperatures. Parameters for the drying equations were successfully determined. The results showed that drying rates increased dramatically as drying temperatures increased. Also, stems were found to dry at a faster rate than needles, and needles dried at a faster rate than whole clippings.
More than 100,000 lbs. (wb) of Taxus clippings and/or needles were harvested, dried, and stored in preparation for Taxol extraction and purification. Each 200-lb. lot of the clippings and/or needles was randomly sampled and analyzed for Taxol content at each stage of the process preparatory to extraction, i.e., before drying, after drying, and after storage (two to four months), and after transporting to the extractors (Grand Haven, Michigan, to South Hackensack, New Jersey; Grand Haven, Michigan, to Long Mount, Colorado). Percent Taxol yield was maintained at an acceptable level throughout all stages of processing. However, Taxol yield was found to be most sensitive to drying protocol.
Croom, E. M. Jr. 1991. Private communication.
Hansen, R. C., R. B. Shugert Jr., E. M. Croom Jr., H. N. ElSohly, and H. M. Keener. 1992. Evaluation of bin drying of Taxus biomass. Paper No. 926534. American Society of Agricultural Engineers. St. Joseph, Mich.
Hansen, R. C., H. M. Keener, and H. N. ElSohly. 1993. Thin-layer drying of cultivated Taxus clippings. Transactions of the ASAE. 36(6):1873-1877.
Keener, H. M. 1991. Solar grain drying. In: Solar Energy in Agriculture. B. F. Parker, Ed. Energy in World Agriculture. Vol. 4. B. A. Stout, Ed. pp. 295-314. Amsterdam: Elsevier Science Publishers B. V.
Witherup, K. M., S. A. Look, M. W. Stasko, T. J. Ghiorzi, and G. M. Muschik. 1990. Taxus spp. needles contain amounts of Taxol comparable to the bark of Taxus brevifolia: analysis and isolation. Journal of Natural Products. 53(5): 1249-1255.