This dissertation presents phytochemical investigations on two medicinal plants, Buxs sempervirens and B. papillosa. Chapter 4 describes the chemical studies on the roots of B. sempervirens of Trkish origin. Investigations on the chemical constituents of B. sempervirens have led to the isolation and characterization of seven new steroidal alkaloids along with three known steroidal bases isolated for the first time from this plant. Chapter 5 describes phytochemical studies on the leaves of B. papillosa of Pakistani origin which have resulted in the isolation and identification of four new steroidal alkaloids along with six known steroidal bases reported for the first time from the leaves of B. papillosa. Based on structural variation of steroidal alkaloids isolated from different species of genus Buxus, some chemotaxonomic generalizations have been deduced and are included in a separate section of Chapter-2. Pharmacological activities of steroidal alkaloids are discussed in Chapter 2, as a separate section. Biosynthetic routes to various types of Buxus alkaloids are also proposed in chapter 3.
New Steroidal Alkaloids Isolated From the Roots of Buxus Sempervirens:
Phytochemical investigations on the roots of B. sepervirens have resulted in the isolation of seven new steroidal alkaloids, (+)-16a-hydroxy-Na-benzoylbuxadine (90), (+)-30-hydroxycyclomicrobuxene (91), (-)-semperviroxazolidine (92), (-)-16a-hydroxybuxaminone (93), (-)-Nb-demethylcyclo-mikuranine (94) (+)-semperviraminone (95), (+)-Na-demethylsemperviraminone (96), along with the known steroidal alkaloids, (-)-E-cyclo-bxaphylamine (97), (-)-Z-cyclobuxaphylamine (98) and (+)-cyclomicrobuxeine (99 isolated for the first time from the roots of Buxus sempervirens.
New Steroidal Alkaloids Isolated From the Leaves of B. papillosa:
Our recent phytochemical studies on the leaves of B. papillosa of Paksitani origin have yielded four new steroidal bases, (+)-papillozine-C (100), (-)-2a, 16a-diacetyl-9β,11β-epoxybuxamidine (101), (+)-Na,Nb-dimethyl-buxupapine (102) and (+)-16a-hydroxypapillamidine (103) along with the known steroidal alkaloids, (+)-cyclomicrobuxinine (104), (-)-cyclosuffro-buxinine-M (105), (-)-E-buxenone (106), (-)-Z-bxenone (107), (+)-irehine (108) and (-)-sempervirone (109) isolated for the first time from the leaves of B. papillosa. (-)-Sempervirone has exhibited CNS depressant activity in mice.
The structures of all these known and new steroidal alkaloids were established on the basis of extensive spectroscopic studies including two-dimensional and inverse two-dimensional NMR experiments.