The western area of Senegal was the site of a basic volcanism in the Tertiary and Quaternary. That volcanism had caused the formation of alkaline olivine basalts, basanites and nephelinites from microlitic and porphyr...The western area of Senegal was the site of a basic volcanism in the Tertiary and Quaternary. That volcanism had caused the formation of alkaline olivine basalts, basanites and nephelinites from microlitic and porphyritic texture to dolerite texture. The geochemistry of major elements shows that the Quaternary basalts are more aluminous and more siliceous, but they contain less magnesium, less iron and less calcium than the Tertiary basalts. Two types of basalt occur here, based on the characteristics of the major elements in the Tertiary lavas: the highly undersaturated basalts of the Cape Verde Peninsula and the slightly undersaturated basalts of the Thiès Plateau. The characteristics of the trace elements reveal shallow interactions due to the contamination and/or assimilation, and to the fractional crystallization, but not due to the heterogeneity of the source. The strong enrichment in light rare earth elements (LREE) and the slight enrichment in heavy rare earth elements (HREE), the anomalies which are negative in K and Pb and positive in Nb, Ta and Eu of the Tertiary and Quaternary basalts of Western Senegal and similar anomalies of the same elements (Pb not analyzed) described in the Cape Verde islands, allow us to establish links between the petrogenetic mechanisms that had caused the formation of the basalts of this Islands and Western Senegal. Moreover, the volcanic activity in Western Senegal (of continental lntraplate type) and that of the Cape Verde Islands (oceanic intraplate type) are probably related to the hot spot located on the vertical of the Cape Verde.展开更多
Phytochemical investigation of Sanrafaelia ruffonammari Verd and Ophrypetalum odoratum Diels that belongs to the rare genera confined to East African coastal forests led to the isolation of enantiomeric styrylpyrone d...Phytochemical investigation of Sanrafaelia ruffonammari Verd and Ophrypetalum odoratum Diels that belongs to the rare genera confined to East African coastal forests led to the isolation of enantiomeric styrylpyrone dimer,(±)-5-methoxy-7-phenyl-[4-methoxy-2-pyronyl]-1-(E)-styryl-2-oxabicyclo-[4.2.0]-octa-4-en-3-one(1)alongside(?)-6-styryl-7,8-epoxy-4-methoxypyran-2-one(2)and the enantiomeric(?)-(3)and(-)-6-styryl-7,8-dihydroxy-4-methoxypyran-2-ones(4).Their structures were established by means of spectroscopic methods.In this paper we reveal for the first time the occurrence of styrylpyrones in East African biodiversity.(?)-6-Styryl-7,8-epoxy-4-methoxypyran-2-one(2)and the dihydroxystyrylpyrone enantiomer(3)showed in vitro antifungal activity against Candida albicans at a concentration of 24.4 and 26.2 lM with zones of inhibition of 17 and 9 mm,respectively.Compound 2 exhibited strong activity in the brine shrimp test with LC50=1.7 lg/mL.Their high cytotoxic and antifungal activities render them candidates for further scientific attention for drug development programs against cancer and microbial infections.展开更多
文摘The western area of Senegal was the site of a basic volcanism in the Tertiary and Quaternary. That volcanism had caused the formation of alkaline olivine basalts, basanites and nephelinites from microlitic and porphyritic texture to dolerite texture. The geochemistry of major elements shows that the Quaternary basalts are more aluminous and more siliceous, but they contain less magnesium, less iron and less calcium than the Tertiary basalts. Two types of basalt occur here, based on the characteristics of the major elements in the Tertiary lavas: the highly undersaturated basalts of the Cape Verde Peninsula and the slightly undersaturated basalts of the Thiès Plateau. The characteristics of the trace elements reveal shallow interactions due to the contamination and/or assimilation, and to the fractional crystallization, but not due to the heterogeneity of the source. The strong enrichment in light rare earth elements (LREE) and the slight enrichment in heavy rare earth elements (HREE), the anomalies which are negative in K and Pb and positive in Nb, Ta and Eu of the Tertiary and Quaternary basalts of Western Senegal and similar anomalies of the same elements (Pb not analyzed) described in the Cape Verde islands, allow us to establish links between the petrogenetic mechanisms that had caused the formation of the basalts of this Islands and Western Senegal. Moreover, the volcanic activity in Western Senegal (of continental lntraplate type) and that of the Cape Verde Islands (oceanic intraplate type) are probably related to the hot spot located on the vertical of the Cape Verde.
基金This work was financially supported by the Norwegian Agency for International Development(NORAD)through the NORAD Chemistry Project.
文摘Phytochemical investigation of Sanrafaelia ruffonammari Verd and Ophrypetalum odoratum Diels that belongs to the rare genera confined to East African coastal forests led to the isolation of enantiomeric styrylpyrone dimer,(±)-5-methoxy-7-phenyl-[4-methoxy-2-pyronyl]-1-(E)-styryl-2-oxabicyclo-[4.2.0]-octa-4-en-3-one(1)alongside(?)-6-styryl-7,8-epoxy-4-methoxypyran-2-one(2)and the enantiomeric(?)-(3)and(-)-6-styryl-7,8-dihydroxy-4-methoxypyran-2-ones(4).Their structures were established by means of spectroscopic methods.In this paper we reveal for the first time the occurrence of styrylpyrones in East African biodiversity.(?)-6-Styryl-7,8-epoxy-4-methoxypyran-2-one(2)and the dihydroxystyrylpyrone enantiomer(3)showed in vitro antifungal activity against Candida albicans at a concentration of 24.4 and 26.2 lM with zones of inhibition of 17 and 9 mm,respectively.Compound 2 exhibited strong activity in the brine shrimp test with LC50=1.7 lg/mL.Their high cytotoxic and antifungal activities render them candidates for further scientific attention for drug development programs against cancer and microbial infections.
