Chemical & Biological Investigation on the Secondary Metobolites of Pakistani Medicinal Plants; Ehretia Acuminata and Atriplex Lasiantha

Abstract

Pakistan is blessed with hundereds of species of medicinal plants, however a very small fraction of these plants has been evaluated so far for their curative potentials. In Pakistan, most of the people trust on herbal medicines due to common belief of safety and economical reasons. Therefore, there is a need of systematic and well organized study of these plants to explore their therapeutic potential. Research described in this thesis is an effort to find new plants that could provide new principle leads to solve health issues of people by local sources. The present Ph. D. thesis deals with the, “Chemical and Biological Investigation on the Secondary Metabolites of Pakistani Medicinal Plants; E h r e t i a A c u m in a t a and Atriplex Lasiantha”. The whole dissertation has been divided into five chapters. Chapter 1 offers a comprehensive overview of role of natural products in human health and also provides a mini review of important bioactive secondary metabolites and drugs derived from different natural sources. In Chapter 2 a brief phytochemical survey of various species of the genus Atriplex has been incorporated. Chapter 3 covers detailed structure elucidation of the isolated compounds isolated from Atriplex lasiantha, evaluation of their biological activity, experimental procedures and spectroscopic data. The methanolic extract of Atriplex lasianta showed Summary ii anti-bacterial, anti-oxidant and enzyme inhibitory properties, therefore, the extract was partitioned into n- hexane, ethylacetate and water fractions. The ethyle acetate fraction was subjected to chromatographic purification. This fraction afforded 15 compounds out of which atrioleanoside (152) has been isolated for the first time from any natural source, whereas, others were decalred as from new source. The compounds isolated in sufficient quantity were tested for Anti-bacterial, Anti-oxidant and anti-urease activity. Among the tested compound, 152- 155 and 161 showed good results.Chapter 4 includes the literature survey of phytochemicals isolated from different species of the genus Ehretia. Chapter 5 describes detailed structure elucidation of the compounds isolated from Ehretia acuminata, evaluation of their biological activity, experimental procedures and spectroscopic data. The methanolic extract of Ehretia acuminata showed anti-bacterial, anti-oxidant and enzyme inhibitory properties, therefore, the extract was partitioned between n-hexane, ethylacetate and water fractions. n-Hexane fraction was subjected to chromatography to get three compounds 174, 235 and 236. Similarly ethyl acetate fraction was treated in the same fashion and afforded 10 compounds 171, 194, 227- 234. Overall 13 compounds were isolated from Ehretia acuminate. All these compounds are already reported from different natural sources; however these are isolated for the first time from Ehretia acuminata. The compounds isolated in sufficient quantity were tested for antibacterial, anti-oxidant and anti-urease activity. Compound 171, 174, 192, 227, 232, 234 and 236 showed good results for anti-oxidant activity and anti-bacterial activity but were inactive in anti-urease assay.