Biomedical subjects
Publications and source records attributed to G M Cragg.
The Chinese medicinal plant Zephyranthes candida was found to contain a cytostatic constituent. Separation of a n-BuOH extract directed by results of a bioassay employing the P-388 lymphocytic leukemia led to trans-dihydronarciclasine [2] as the principal cytostatic agent with ED50 3.2 X 10(-3) micrograms/ml.
Bioassay-guided (P388 lymphocytic leukemia cell line) separation of a CH2Cl2/MeOH extract of Lychnophora antillana led to the isolation of two cytostatic (P-388, ED50 2.0 and 0.19 micrograms/ml, respectively) germacranolides designated lychnostatins 1 [1] and 2 [2]. Structural elucidation was based initially upon high field (400 MHz) nmr and electron impact mass spectral interpretations and unequivocally completed by X-ray crystal structure determinations.
The southwestern Indian paintbrush, Castilleja linariaefolia, yielded extracts that displayed in vivo activity against murine P-388 (PS) lymphocytic leukemia. Separation guided by PS cell line inhibition led to isolation of cytotoxic compounds that were identified as the known glycosides acteoside [1] (ED50 2.6 micrograms/ml) and isoacteoside [2] (ED50 10 micrograms/ml). The identifications were established by spectral measurements and degradation studies. Mannitol was also found in this plant.
New sources for the antitumor natural product taxol [1] are needed as demands for this promising cancer chemotherapeutic agent increase. Presently, supplies of taxol for clinical studies are obtained from the bark of Taxus brevifolia, a potentially limited source. Using analytical methods, the needles and stems of six Taxus species have been examined for taxol [1] and 10-deacetylbaccatin III [5], a related compound that can be converted to taxol through a semi-synthetic route. Amounts of taxol comparable to quantities reported from the bark of T. brevifolia were found in the needles of four of the Taxus species investigated. In addition, taxol was isolated from the needles of one Taxus species. Thus, Taxus needles may provide a renewable source of this valuable compound.