Browsing by Author "Rwekika, Emil"

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    Phytochemical studies on some species of family ebeneceae.
    (University of Dar es Salaam, 1990) Rwekika, Emil
    The isolation and subsequent identification of naphthoquinones and triterpenoids from five Diospyros and one Euclea species is discussed. In the present investigation, diosindigo A has been either isolated or detected in the root and stem barks of all Diospyros species studied. The potential of diosindigo A as a biological marker for the family Ebeneceae is also discussed. a-Amyrin, betulinic acid and lupeol were isolated from the leaves of E. natalensis, D. natalensis and D. mafiensis. Betulinic acid and lupeol were also found in the leaves of D. greeniwayi. Lupeol and 7-methyljuglone were found in the root barks of D. greeniwayi and D. mafiensis while 7-methyljuglone was also found in the stem barks of the two species . Diosquinone and a new tetramer of 7-methyljuglone (5,5',5",5"'-Tetrahydroxy-7,7',7",7"'-tetramethyl 8, 8' ; 6' , 8 " ; 6 " , 8"' -tetranaphthalene-1 ,.1' ,1";l''1, 4 , 4', 4",4-tetron ), were isolated from the root barks of D. ma fiensis. A new dimer of plumbagin (5,5'-Dihydroxy-2,2'-dimethyl3',8-binaphthalene-1,1',4,4'-tetrone) (3',8-Biplumbagin) was isolated from the root bark of D. greeniraayi. The seasonal dependance of lupeol and 7-methyljuglone in the root bark of E. natalensis was investigated. 7-methyljuglone is more abundant in the dry weather, while lupeol is more abundant in the wet season. A common new biogenetic pathway utilizing mevalonic acid as common precursor is proposed.