Antimalarial dihydrochalcones and other constituents of Uvaria Species (Pande)

This dissertation reports on the phytochemical investigation of the antimalarial plant Uvaria sp. (Pande). It has been observed in this study that C-benzylated dihydrochalcones are the major constituents of the plant. One of these compounds,viz. uvaretin, has been shown to be one of the antimalarial principles of the plant, having an IC50 value of 3.4 mg/ml. In chapter two of the dissertation a new ortho- hydroxybenzyl dihydrochalcone, isochamuvaritin, is reported to have been isolated, together with the known dihydrochalcones uvaretin, diuvaretin, and a mixture of uvaretin, isouvaretin and diuvaretin as well as a mixture of triuvaretin and isotriuvaretin. The known sesquiterpene guaiol, was also isolated from the root bark. The structures of the known compounds were established by comparing their spectral and other physical properties with those of authentic samples. The structure of isochamuvaritin was established spectroscopically and by comparison of its melting point (m.p.) with that of chamuvaritin. The occurrence of isochamuvaritin in Uvaria sp. (Pande) further demonstrates the uniqueness of Uvaria species in accumulating ortho-hydroxybenzylated compounds. This dissertation also describes the isolation of the pentacyclic triterpenoid aglutin-5-en-3-ol and the partial identification of an aromatic compound USPS 5.6. The structure of a-glutinol was established spectroscopically and by comparison with the spectra of an authentic compound. Compound USPS 5.6 could not be fully identified due to the inconsistency of its spectral properties (1H-NMR, 13C-NMR and MS) with each other. Indeed this compound as well as the complex mixtures of dihydrochalcones and other compounds need further investigations. The taxonomical description of Uvaria sp. (Pande) is in progress at the Royal Botanical Gardens, Kew (UK).