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STUDIES ON THE CHEMICAL CONSTITUENTS OF DELPHINIUM DENUDATUM AND BIOSYNTHESIS OF COLCHICUM ALKALODIS

Nasreen, Amber (1998) STUDIES ON THE CHEMICAL CONSTITUENTS OF DELPHINIUM DENUDATUM AND BIOSYNTHESIS OF COLCHICUM ALKALODIS. PhD thesis, University of Karachi, Karachi.

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Abstract

The work embodied in this dissertation comprises two parts. Part-A deals with investigations on the biosynthesis of colchicines in Colchicum autumnale plants. The work involved employing radiolabelled precursors in order to optimize the physiological parameters for feeding experiments by using different parts of the plant, different species of Colchicum and different developing stages of the seeds of C. autumnale. The 13C-labelled precursors were synthesized and applied, and the isolated colchicines was subsequently subjected to 13C-NMR analysis in order to finally allocate the exact site of enrichment after biosynthesis. The incorporation results showed that the (S) autumnaline serves as specific precursor of colchicines in Colchicum autumnale seeds. Studies on colchicines (32) biosynthesis revealed an enzymic complex which was isolated and characterized. It specifically catalyses a particular intramolecular oxidative phenolic coupling reaction in the biosynthetic pathway. In this case autumnaline was directly coupled to furnish isoandrocymbine, a dienone type compound.This oxidative phenolic coupling reaction was found to be catalysed by a highly region-and stereospecific microsomal bound cytochrome P-450 enzyme.The reaction was, furthermore, strictly dependent on NADPH and molecular oxygen. The Km value for (R, S) autumnaline was determined as 37.0 µM. Part-B of the thesis is concerned with the phytochemical investigations on the roots of Delphinium denudatum which resulted in the isolation and characterization of new diterpenoid alkaloids. The structure of 8-acetl heterophyllisine (219), a new heteratisine-type diterpenoid base, was elucidated with the assistance of extensive spectroscopic studies and confirmed by an X-ray diffraction method. In addition, five known compounds were also isolated from D. denudatum for the first time whereas the X-ray structures of 3-hdroxy-2-methyl-4-H-pyran-4-one (220) and panicutine (221) are also reported for the first time. One known compound, denudatine (214) has also beenisolated from the same species.

Item Type:Thesis (PhD)
Uncontrolled Keywords:delphinium denudatum, colchicum alkalodis, colchicum autumnale plants, colchicine, panicutine , vilmorrianone, atisinium chloride, bicolorine, denudatine
Subjects:Physical Sciences (f) > Chemistry(f2)
ID Code:860
Deposited By:Mr. Muhammad Asif
Deposited On:01 Nov 2006
Last Modified:04 Oct 2007 21:03

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