Isolation, Structure, Synthesis, and Antimitotic Properties of Combretastatins B-3 and B-4 from Combretum caffrum

Abstract

Further investigation of a CH2Cl2 fraction prepared from the South African tree Combretum caffrum for substances inhibitory to the murine P-388 lymphocytic leukemia (PS system) cell line has led to the isolation of two new bibenzyls, designated combretastatins B-3 and B-4, accompanied by the previously known bibenzyls 7, 8, and 9. The structure of each substance was ascertained by results of mass and nmr spectral analyses and confirmed by crystal structure determination (for 7) or synthesis. Combretastatins B-3 and B-4 gave PS ED50 values of 0.4 and 1.7 micrograms/ml, respectively, and bibenzyls 7, 8, and 9 were comparably cell growth inhibitory against the PS cell line with ED50 results of 1.7, 2.5, and 0.25 ug/ml, respectively. All the bibenzyls caused leukemia cells to accumulate in mitosis at cytotoxic drug concentrations; however, a wide range of in vitro activity against the protein tubulin (the major component of the mitotic spindle) was observed.

Pterostilbene, an Active Constituent of Blueberries, Suppresses Aberrant Crypt Foci Formation in the Azoxymethane-Induced Colon Carcinogenesis Model in Rats

“…Pterostilbene was synthesized following a published procedure with minor modifications, and its structure confirmed by UV, mass spectrometry, and nuclear magnetic resonance spectra (ref. 27; Fig. 1).…”

Phytochemical Constituents of Combretum Loefl. (Combretaceae)

“…Coumarin 261 scopoletin C. yannanense [54] 6,7-dihydroxy-2,3,4-trimethoxy-9,10-dihydrophenanthrene (217) and 4,6,7-trihydroxy-2,3-dimethoxy-9,10-dihydrophenanthrene (218) from C. apiculatum; 7-hydroxy-2,4,6-trimethoxy-9,10-dihydrophenanthrene (219), 7-hydroxy-2,3,4,6-tetramethoxy-9,10-dihydrophenanthrene (220), 2,7-dihydroxy-3,4,6-trimethoxy-9,10-dihydrophenanthrene (221), 2,6,7-trihydroxy-3,4-dimethoxy-9,10-dihydrophenanthrene (222) C. Psidioides, 3,6-dihydroxy-2,4,7- trimetho-xy-9,10-dihydrophenanthrene (223) from C. Hereroense for 9, 10-dihydrophenanthrebnes [56][57][58][59][60].…”

Structural properties of methoxy derivatives of benzyl bromide, determined from powder X-ray diffraction data

“…The bromine atom of the CH 2 Br group lies out of the plane of the phenyl ring, and the two O -CH 3 bonds lie close to the plane of the phenyl ring and are oriented parallel to each other in a syn,syn conformation ͓the designations syn and anti refer to the orientations of the C͑3͒O-CH 3 and C͑5͒O-CH 3 bonds relative to the orientation of the C͑4͒-H bond͔. With regard to this feature, other molecules containing 3,5-dimethoxyphenyl rings ͑with hydrogen atoms in the 2-, 4-, and 6-positions͒ display a range of different conformations, including other examples with syn,syn conformations ͑Lin et al ., 1979;Bartholomew et al, 2000͒, examples of syn,anti conformations ͑Lynch et al, 1994Peters et al, 1993;Pettit et al, 1988͒, an example with two independent molecules in the asymmetric unit with anti,anti and syn,anti conformations ͑Yin et al, 2002͒, and an example with two independent 3,5-dimethoxyphenyl moieties in a given molecule that adopt syn,syn and syn,anti conformations ͑Yin and Zhang, 2002͒.…”