EFFECT OF WHITE-LIGHT ON TAXOL AND BACCATIN-III ACCUMULATION IN CELL-CULTURES OF TAXUS-CUSPIDATA SIEB AND ZUCC

Taxol is a diterpene amide derived from Taxus spp. and approved for the treatment of ovarian and breast cancer in the USA. Taxus cuspidata cell cultures represent an alternate source of taxol and related taxoids. We have previously described the development, growth, and taxoid accumulation of cell cultures of T. cuspidata. The present study examined the influence of white light on the accumulation of taxol and baccatin III callus and cell suspension cultures of T. cuspidata. Results showed that taxol and baccatin III accumulations were approximately three times higher in dark-grown calli. Dark-grown suspensions also displayed three times more total volumetric taxol relative to light-grown suspensions; baccatin III amounts were similar in dark and light grown suspensions. Growth of suspensions was two to three-fold higher in darkness. Taxol accumulation peaked at stationary phase (d27 to d45) in dark-grown cells (14mg . kg(-1)edw). The peak of baccatin III accumulation (180 mg . kg(-1)edw) preceded the taxol peak (d18 to d27) and the content of this taxoid decreased as taxol increased. Baccatin III accumulation in the culture medium was similar in dark and light-grown suspensions (peaked at 6.2 mg . L(-1) on d9). Taxol accumulation in the medium was higher in darkness (0.3 mg . L(-1) on d9 and d27 to d36) than in light (0.08 mg . L(-1) on d9). Down-regulation of taxol steady-state amounts may be related to the effect of light on microsomal 3-hydroxy-3-methylglutaryl-coenzyme A reductase and mevalonate supply; the enzyme had significantly lower activity in light-grown cells.