Geng-Xian Zhao
Purdue University
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Featured researches published by Geng-Xian Zhao.
Pesticide Science | 1997
Kan He; Lu Zeng; Qing Ye; Guoen Shi; Nicholas H. Oberlies; Geng-Xian Zhao; C. Jesse Njoku; Jerry L. McLaughlin
The activities of 44 Annonaceous acetogenins, which were originally isolated by monitoring plant fractionations with the brine shrimp lethality test (BST), were evaluated in the yellow fever mosquito larvae microtiter plate (YFM) assay. The results clearly demonstrate that most acetogenins have pesticidal properties. The structure–activity relationships indicate that the compounds bearing adjacent bis-THF (tetrahydrofuran) rings with three hydroxyl groups are the most potent. Bullatacin (1) and trilobin (7) gave the best activities against YFM with LC50 values of 0·10 and 0·67 mg litre-1, respectively. Compounds showing LC50 values below 1·0 mg litre-1 in this assay are usually considered significant as new lead candidates for pesticidal development. In the BST, the corresponding LC50 values were 1·6×10-3 (1) and 9·7×10-3 (7) mg litre-1. This is the first report of pesticidal structure–activity relationships for a series of Annonaceous acetogenins which are known to act, at least in part, as potent inhibitors of mitochondrial NADH: ubiquinone oxidoreductase.
Tetrahedron | 1995
Geng-Xian Zhao; Zhe-ming Gu; Lu Zeng; Jin-Feng Chao; John F. Kozlowski; Karl V. Wood; Jerry L. McLaughlin
Abstract Trilobacin ( 1 ) is the only previously reported Annonaceous acetogenin with the erythro relative configuration between the adjacent bis-tetrahydrofuran (THF) rings. The relative configuration in the adjacent bis-THF moiety of 1 was corrected to threo/trans/erythro/cis/threo from C-15 to C-24, and the absolute configuration was determined as 4 R , 15 R , 16 R , 19 R , 20 S , 23 R , 24 R and 36 S by advanced Mosher ester methodology and the COSY and NOESY spectral analyses of its 4,24-diacetate ( 1a ). Further investigation of the EtOH extract of the stem bark of the paw paw tree, Asimina triloba , monitoring for bioactivity by brine shrimp lethality, led to a novel acetogenin, trilobin ( 2 ). Spectral and chemical methods identified 2 as a 4-deoxy-10-hydroxy isomer of 1 . The absolute configuration of 2 was determined as 10 R , 15 R , 16 R , 19 R , 20 S , 23 R , 24 R , and 36 S by analyses of its Mosher ester derivatives. 2 was selectively cytotoxic among three human solid tumor cell lines with over a billion times the potency of adriamycin.
Tetrahedron | 1991
Johari M. Saad; Yu-Hua Hui; J. Kent Rupprecht; Jon E. Anderson; John F. Kozlowski; Geng-Xian Zhao; Karl V. Wood; Jeny L. McLaughlin
Abstract A new bioactive monotetrahydrofuran acetogenin, reticulatacin, containing 37 carbons, has been isolated from a 95% EtOH extract of the bark of A. reticulata by directing the fractionation with brine shrimp lethality. Another previously reported highly potent antitumor, adjacent ring bistetrahydrofuran acetogenin, bullatacin, has also been isolated in large quantity. Two known diterpenes, (−)-kau-16-en-19-oic acid and methyl 16β,17-dihydro-(−)-kauran-19-oate and a known alkaloid, liriodenine, have also been isolated. Some of these compounds showed selective cytotoxic activities for certain human tumor cell lines.
Phytochemistry | 1993
Geng-Xian Zhao; Matthew J. Rieser; Yu-Hua Hui; Laura R. Miesbauer; David L. Smith; Jerry L. McLaughlin
In continuing our research with cytotoxic and pesticidal components from the stem bark of the North American paw paw, Asimina triloba, the novel cytotoxic monotetrahydrofuran Annonaceous acetogenins, cis- and trans-annonacin-A-one, cis- and trans-gigantetrocinone and cis-isoannonacin, in addition to the known compounds, trans-isoannonacin and squamolone, have been identified. Brine shrimp lethality testing was used to direct the fractionation. The structures were elucidated by spectral analysis and/or chemical synthesis. These acetogenins have potent cytotoxicities against the human tumour cell lines of A-549 (lung carcinoma), MCF-7 (breast carcinoma) and HT-29 (colon adenocarcinoma).
Bioorganic & Medicinal Chemistry | 1996
Geng-Xian Zhao; Jin-Feng Chao; Lu Zeng; Matthew J. Rieser; Jerry L. McLaughlin
A novel acetogenin, asiminocin (1), was isolated by activity-directed fractionation from the stem bark of the paw paw tree, Asimina triloba. By spectral and chemical methods, 1 was identified as (30S)-hydroxy-4-deoxyasimicin. The absolute configuration of 1, along with those of previously reported acetogenins asimin, asiminacin, bullatin, (30S)-bullanin, and (30R) bullanin, was determined by Mosher ester methodology. Compound 1 was highly inhibitory to three human solid tumor cell lines with over a billion times the potency of adriamycin.
Tetrahedron | 1996
Dorothée Alfonso; Trina Colman-Saizarbitoria; Geng-Xian Zhao; Guoen Shi; Qing Ye; Jon T. Schwedler; Jerry L. McLaughlin
Abstract Our continuing activity-directed search for new bioactive compounds led to the isolation of two new, unusual, acetogenins, aromin (1) and aromicin (2), from the stem bark of Xylopia aromatica (Annonaceae). Both represent a new type of non-adjacent, bis-THF ring acetogenins (one THF ring being at C-4 to C-7 and the other at C-16 to C-19). Both show significant cytotoxicities among six human tumor cell lines; however, the activity is notably reduced compared to other non-adjacent bis-THF ring acetogenins. The structures of 1 and 2 were elucidated by spectroscopic methods and by derivatization.
Bioorganic & Medicinal Chemistry | 1997
Kan He; Geng-Xian Zhao; Guoen Shi; Lu Zeng; Jin-Feng Chao; Jerry L. McLaughlin
Trilobalicin (1), a new nonadjacent bis-THF ring annonaceous acetogenin, 2,4-cis- (2) and 2,4-trans-trilobacinone (3), the ketolactones of trilobacin, an adjacent bis-THF ring acetogenin, were isolated from the stem bark of Asimina triloba (L.) Dunal (Annonaceae). Their structures were established based on chemical and spectral evidence. The relative stereochemistry of 1 was determined as trans/threo/threo/trans/erythro from C-10 to C-22 by comparisons of NMR data with those of model compounds. Compound 1 is the first example of a nonadjacent bis-THF acetogenin being isolated from the title species and represents a new type of these compounds. Bioactivities of these new structures against brine shrimp larvae and six human solid tumor cell lines were determined, and cytotoxic selectivities were shown for the lung (A-549) and breast (MCF-7) cell lines with up to a million times the potency of adriamycin.
Natural Toxins | 1996
Geng-Xian Zhao; Jin-Feng Chao; Lu Zeng; Jerry L. McLaughlin
Two novel bioactive ketolactone Annonaceous acetogenins, (2,4-cis)-asimicinone (1) and (2,4-trans)-asimicinone (2), have been isolated from Asimina triloba (Annonaceae) by bioactivity directed fractionation. The separation of these two epimeric compounds was achieved by HPLC methods using a Si gel normal phase column eluted with acetone in hexane gradients. The assignments of cis or trans stereochemistry of the ketolactone moieties were made on the bases of 1H-1H COSY and NOESY experiments. 1 and 2 showed selective cytotoxicities against A-549 (human lung cancer) and MCF-7 (human breast cancer) cell lines with ED50 values as low as < 10(-7) micrograms/ml with 2 being the more active isomer.
Phytochemical Analysis | 1993
Xin-ping Fang; Matthew J. Rieser; Zhe-ming Gu; Geng-Xian Zhao; Jerry L. McLaughlin
Journal of Natural Products | 1992
Geng-Xian Zhao; Yu-Hua Hui; J. K. Rupprecht; Jerry L. McLaughlin; Karl V. Wood