The present investigations embodied in this thesis comprises of two parts. The first part designated as Part-A deals with the isolation, structure elucidation and characterization of various secondary metabolites from the plant Asparagus dumosus Baker. In addition, bioactivity studies have also been carried out. This work was done under the supervision of Prof Dr. Viqar Uddin Ahmad at H.E.J. Research Institute of Chemistry, University of Karachi.
The second part entitled as Part-B is related to the synthesis of some biotin analogues, azidosphingosine and tetrahydrothiophene type compounds. These studies were completed under the guidance of Prof. Dr. Richard R.Schmidt at the Faculty of Chemistry, University of Konstanz, Germany.
PART – A: Isolation and Structure Elucidation of Compounds From Asparagus Dumosus
The Part-A is composed of five chapter (I-V). The first chapter describes a general introduction in which saponins have been discussed in detail, while most of the compounds which were isolated are saponins. Then a biosynthetic route has been given. In the second chapter a brief description of the plant Asparagus dumosus was given along with a detailed literature survey on the genus Asparagus.
The third chapter deals with the present work which describes the structure elucidatin of five sterioidal saponins, six sterols, two triterpenes and a flavoring compound. Phytochemical investigations were carried out for the first time on this plant, therefore, all of the secondary metabolities isolated were considered new from this source. Dumoside (48) is a new saponin which is being reported for the first time. The four other saponins named as methylprotoneodioscin (49), trigonelloside (50), pregnadienolone 3-O-β-chacotrioside (51) and blechnoside (54) are being reported for the fist time from A. dumosus. All these compounds were characterized with the help of (1D) and (2D) MR e.g. 2D, J-resolved, COSY 450, NOESY, Hetero COSY, HOHAHA, HMBC, HMQC, as well as DEPT experiments.
Beside the phytochemical investigations, bioactivity studies have also been done including antibacterial and antifungal activities, brine shrimp lethality test and Lemna minor bioassay. These tests were carried on the crude extracts of the plant including methanolic and ethylacetate fractions with a pure steroid ecdysterone (53). The results were given in the tabulated form of this chapter
The fourth chapter comprises of the experimental part in which at first general instrumentation has been specified. Then the materials and methods of the plant are given which follows on with detailed physico-chemical data of all the isolated compounds. The fifth and last chapter of this part depicts all of the references present in Part-A of this thesis.
PART – B: Syntheses of Biotin Analogues and Related Compounds