[1] Natl Res Ctr, Pharmaceut Ind Res Div, Chem Nat & Microbial Prod Dept, Cairo, Egypt
[2] Univ Hohenheim, Inst Chem, Bioorgan Chem, Garbenstr 30, D-70599 Stuttgart, Germany
[3] Univ Marburg, Fachbereich Chem, Hans Meerwein Str 4, D-35032 Marburg, Germany
[4] Univ Hohenheim, Inst Biol Chem & Ernahrungswissensch, Garbenstr 30, D-70599 Stuttgart, Germany