This thesis presents the work on three medicinal plants of Pakistani origin. Part A describes the studies on the leaves of Buxus papilosa. Investigation on the alkaloidal contents of the leaves of B.papilosa have led to the isolation and characterization of twenty two new steroidal bases. In addition, three more alkaloids have also been reported for the first time from this plant. A separate chapter in the introduction section of Part A describes some spectral generalizations made for Buxus alkaloids based on a thorough literature search and personal observations. These generalizations provide valuable information for checking the proposed structures. Biosynthetic routes to various types of Buxus alkaloids are also proposed in the introduction section of Part A.
New Steridal Alkaloids from Buxus Papilosa i(+)-Buxaquamarine (53) ii(-)-Cyclobuxoviricine (54) iii(-)-Cycloxobuxoviricine (55) iv(-)-31-Acetoxy-Na-Benzoylbuxidienine (56) v(+)-N-Benzoyl-16α-acetoxycloxobuxidine-F (57) vi(+)-Buxabenzamidienine (58) vii(+)-16-α-Acetoxybuxabenzamidienine (59) viii(+)-Buxotrienine (60) ix(-)-Buxanoldine (61) x(+)-Buxanaldinine (62) xi(+)-Buxabenzamidine (63) xii(+)-Homobuxaquamarine (64) xiii(+)-Norcyclomicrobuxeine (65) xiv(+)-Buupapine (66) xv(+)-Nb-Norbuxupapine (67) xvi(+)-Buxaprogestine (68) xvii(-)-Buxapapinolamine (69) xviii(-)-E-Cyclobuxaphylamine (70) xix(-)-Z-Cyclobuxaphylamine (71) xx(+)-N-Formylharappamine (72) xxi(+)-N-Formylpapilicine (73) xxii(+)-N-Formylcyclomicrobuxeine (74)
Known Alkaloids Isolated for the First Time from Buxus Papilosa i(+)-Buxaminol-B (75) iiCyclobuxoviridine (76) iii(+)-N-Benzoylcycloxobuxidine-F (77) and iv(+)-Sinapic acid methyl ester (78)
Part B of the thesis describes studies on the alkaloidal constituents of Catharanthus roses which have resulted in the isolation of the two new indole alkaloids. One of them, namely (-)-bannucine, is the first Aspidosperma alkaloid bearing a five-membered lactam ring. A known dimeric alkaloid, Catharine, which was not reported from C. roseus was also islated and detailed temperature-dependent NMR experiments confirmed its existence in two non-separable conformers. Detailed mass and 13C-NMR studies on (-)-cathovaline, another unreported alkaloid from C.roseus, have been carried out. The following alkaloids were thus isolated from C.roses
New Indole Alkaloids from Catharanthus Roseus i(+)-Rosamine (4) ii(-)-Bannucine (5)
Known Alkaloids Isolated for the first time from Catharanthus Roseus iCatharine (6) iiCathovaline (7)
Part C of the thesis presents work done on the aerial parts of Cissampelos pareira, which resulted in the isolation of a new bisbenzylisoquinoline alkaloid norcurine (8).
Modern spectroscopic methods were employed to determine their structures including two-dimesional NMR experiment (2D J resolved, COSY 45°, NOESY). DEPT and GASPE experiments were carried out to determine the multiplicities of various carbon atoms. The stereochemistry of various asymmetric centers was established by extensive NOE difference studies.