In the current research, the inland genus Cassipourea of Rhizophoraceae in Kenya was pinpointed as a target for developing new medicinal resources. The field work on four species of Cassipourea, i. e. Cassipourea malosana, C. gummiflua, C. euryoides, and C. celastroides was carried out during three months in 1987, which all are grown in different habitats each other. It was proved with detective indicator (PdCl2) at field work that the barks of these trees contain some sulfur compounds as we had expected. The plant materials transfered from field to laboratory provided some sulfur compounds as results of chemical studies such as isolation of compounds and determination of their structures. These compounds were such various alkaloids as pyrrolidine and pyrrolizidine possessing 1, 2-dithiolane ring and bisdisulphide bridge system respectively. Among these alkaloids two new pyrrolidine alkaloids named guinesine-D and euryoidine have been isolated from Cassipourea euryoides. Guinesine-D has also been found in C. celastroides. Another new pyrrolizidine alkaloid named isocassipourine have been isolated from C. malosana and C. gummiflua. For these three compounds, structures 7, 8 and 4 were proposed respectively on the basis of spectroscopic evidence (Fig. 3). In biological activity screening tests, guinesines and cassipourine exhibited insecticidal activities and inhibitory effects on c-AMP phosphodiesterase (PDE) (Table 2).
Late Precambrian granitic rocks occurring in the Mahé and Praslin island groups of the Seychelles Islands are divided petrographically and chemically into two assemblages. One is older (ca. 710Ma) I-type assemblage of granodiorite and tonalite, and the other is younger (ca. 680Ma) A-type assemblage of sub-alkaline granite and typical alkaline granite. Fe and Na contents of the ferromagnesian minerals increase systematically from I-type granodiorite through A-type sub-alkaline granite to A-type alkaline granite. These evolutionary trends of the ferromagnesian minerals suggest an intimate genetic relation between I-type magma and A-type magma in Seychelles. The same association of I-type and A-type granites as in Seychelles occurs in the Hijaz region of the Arabian Shield, where the activity of I-type granite took place between 820 to 715Ma and that of A-type granite did between 686 to 517Ma. Such an association of granites is considered to occur extensively in the Arabian-Nubian Shield. Undoubtedly, the Seychelles Islands are continental fragment left behind as a result of the disruption of Gondwanaland and, as stated above, petrological correlation suggests that the Seychelles Islands originally joined with the Arabian Shield.