Asian Research Thesis Index

Abstract

The work embodied in this dissertation is mainly concerned with the  isolation and characterization of natural chemical constituents having some  biological importance. The isolated compounds were either new or  previously been reported in the literature and they were characterized by  various sophisticated spectroscopic techniques. The dissertation deals with purification and biological screening of  secondary metabolites isolated from three indigenous medicinal plants of  Pakistan namely Launaea nudicaulis, Launaea intybacea and Carissa  opaca. The whole dissertation is divided into six chapters. The chapter 1  entitled as “Human Health and Role of Natural products” describes  significance of terrestrial plants in Human life for the cure of various  diseases, some FDA approved natural product drugs, natural products  under clinical trials for FDA approval and new challenges in the field of  natural products research.  The second chapter entitled as “The Genus Launaea and its  Importance” describes the genus Launaea, its economical, pharmacological  and phytochemical properties. In this chapter the pharmacology of various  isolates from the genus Launaea and biological activities of various species  v   or their extract has been discussed. Almost all secondary metabolites  isolated up to date from the different species of Launaea have been  described year wise.  The third chapter entitled as “Phytochemical Investigations on  Launaea nudicaulis” deals with the phytochemical studies on Launaea  nudicaulis collected from Cholistan desert covers the isolation, structure  elucidation and experimental detail of eight new and same number of  known secondary metabolites. The methanolic extract of this plant was  divided into n-hexane and ethyl acetate fractions. The n-hexane soluble  part yielded four new sphingolipids: nudicualin A (112), nudicualin B  (113), nudicualin D (114), nudicualin C (115) together with known  compounds, 1-hexatriacontanol (109), elaidic acid (110), oleanolic acid  (111) and β-sitosterol glucoside (67). The column chromatography of ethyl  acetate part yielded four new compounds: a sesquiterpene lactone,  nudicholoid (116), a diacetylene derivative, trideca-12-ene-4,6-diyne 2,8,9,10,11-pentaol (119), quinic acid derivative,cholistaquinate (121) and  a flavonoid di-C-glycoside, cholistaflaside (123) along with four known  compounds, ergosta-7,22-diene-3,5,6-triol (117), benzyl glucopyranoside  (118), 3,7,12-trihydroxycholan-24-oic acid (120) and 20-hydroxyecdysone  (122). Their structures were assigned by ID and 2D-NMR in combination  with EIMS, HR-MS and FAB-MS techniques. Structures of the known  compounds were determined by spectroscopic analyses and in comparison  with the literature.

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