A CHEMICAL STUDY ON THE CONSTITUENTS OF STEPHANIA ROTUNDA AND TRISTELLATEIA AUSTRALASIAE

Abstract

Part I provides a study on the isolation of some chemical constituents from a Stephania species, Stephania rotunda Lour, which belongs to the Menispermaceae family and was obtained from a hilly region of lower Burma (Myanmar). Chapter 1 is concerned with a brief introduction of natural products, mainly alkaloids and sterols. A survey on isoquinoline type alkaloids and a list of the isoquinoline alkaloids isolated from various Stephania species is presented. Methods of identification of sterols arc also provided. Chapter 2 and Chapter 3 deal with the isolation and characterization of four tertiary basic tetracyclic tetrahydroprotoberberine type alkaloids, namely-(-)-tetrahydropalmatine, (-)-xylopinine(syn.norcoralydine), (-)-capaurine, (-)-tetrahydrostephabine and a hasubanan type alkaloid, (-)-delavaine as major alkaloids and a quaternary basic protoberberine alkaloid, pseudopalmatine and a new alkaloid related to delavaine as minor alkaloids from the hexane extract of the air dried root-tubers. In addition to these alkaloids, two new sterols, stigmasta-5,8,22-trien-3?-ol and stigmasla-5,8-dien-3?-ol were also isolated as minor constituents. Structure elucidation of the isolated compounds was achieved mainly by a combination of chemical, NMR ( COSY, HMQC, HMBC , 1H and 13C ) and mass spectrometric studies. Part II provides an investigation of the chemical constituents of Tristellateia australasiae A. Rich. (Thours), which belongs to the Malpighiaceae family and was collected in the campus of the National University of Singapore. Chapter 1 is concerned with a brief introduction of terpenoids and a triterpenoid, friedelin, together with dulcitol, an acyclic hexitol commonly found in plants. Chapter 2 describes the isolation and characterisation of the acyclic hexitol , dulcitol, (syn. galactitol) and a flavonol, isorhamnetin, from the leaves and four triterpenes namely friedelin, epifriedelinol, ?-amyrin, lupeol and ?-sitosterol as well as dulcitol from the stems of this plant.