The work embodied in this dissertation covers the isolation and characterization of chemical constituents obtained from two medicinal plants of Pakistan. The isolated constituents were either new or previously reported in the literature from other sources. They were characterized via various sophisticated spectroscopic techniques available at International Center for Chemical and Biological Sciences (ICCBS), University of Karachi (Pakistan). The dissertation is divided into three chapters:
The first chapter is a general article entitled, ‚€œSuccessive Development in Natural Product Chemistry‚€Ě , describing the importance of natural products in last two decades, choice of plants for bioactive natural products, sources of natural products, systems of traditional medicines, role of National Cancer Institute (NCI) in the development of phytomedicines, Intellectual Property Rights (IPR), various chromatographic techniques, structure elucidation of phytochemicals, their bio-testing, synthesis and many many more issues related to the bioactive natural products.
The following two plants were investigated for the search of new chemical constituents: Euphorbia wallichii Hook F. (Euphorbiaceae) Salvia nubicola Wall. ex Sweet. (Lamiaceae) The second chapter entitled, "Euphorbia wallichii Hook F." deals with the chemical analysis of titled plant. E. wallichii was collected from Malumjabbah (a northern hilly region of Pakistan).
As a result of this study, two new and seven reported constituents have been obtained. Among the new constituents: a rearranged pentacyclie triterpene of multiflorane class (wallichiione) and a cerebroside (wallichiioside) could be obtained. The known constituents include: a tetracyclic triterpenoid (24-methylenecycloartan-3B-01), two pentacyclic triterpenoids of glutinane class (3a-acetoxy-D: B-friedoolean-5-ene & alnusenol), a fatty acid ester of steroid (B-sitosterol palmitate), a flavone (kaemferol), an ester (ethylgallate), and a glycoside (ellagic acid 4-a-L-arabinopyranosyl) of gallic and ellagic acids, respectively.
Structures of all the purified constituents were elucidated with the aid of modern spectroscopic techniques including 2D-NMR. Medicinal features of the genus Euphorbia together with botanical descriptions of titled source and highlights of the family Euphorbiaceae are also included in this chapter.
The third and last chapter of dissertation entitled, ‚€œSalvia nubicola Wall‚€Ě deals with the isolation and characterization of five new and four reported constituents from S. nubicola which was collected from Quetta (Pakistan).
Among the new constituents: three sesquiterpene-Iactones [a germacranolide (nubtrienolide) and two guaianolides (nubenolide and nubdienolide)], an epimeric-lupane (3-a-hydroxy-20-oxo-30-norlupane), and a ceramide (nubenamide) were obtained. The known constituents include: a flavone (crismaritin), a steroid (B-sitosterol), a steroidal glycoside (B-sitosterol-glucoside) and a pentacyclic triterpene (oleanolic acid).
Structures of all the purified constituents were elucidated with the aid of modern spectroscopic techniques including 2D-NMR. However, structures of nubtrienolide, nubenolide and crismaritin were further confirmed via single crystal x-ray crystallography while the stereochemistry of 3-a-hydroxy-20-oxo-30-norlupane was determined by means of n.O.e experiment. Crismaritin is a known constituent but its x ray data were not reported.
Pharmacology (phytotoxicity, antibacterial and antifungal activities) of nubtrienolide, 3a-hydroxy-20-oxo-30-norlupane and nubenamide could also be studied and it was concluded that among the three tested metabolites, 3a-hydroxy-20-oxo-30 norlupane was found the most active constituents among the three tested metabolites.
Botanical descriptions of S.nubicola, biological and medicinal features of the genus Salvia with the basic features of the family Lamiaceae are also included in the same chapter.
During the phytochemical investigations, altogether seven new and eleven known constituents were obtained from the two investigated plants. As a result, five papers have been published and one is in process of publication. In the end of the dissertation, a list of publications by author and relevant published papers (to-date) are included.
It is to clarify here that each chapter has separate scheme, table, figure and compound numbers. Highlights of biosyntheses related to the obtained constituents, chemical literature survey of corresponding source and references are also included in each chapter independently.