Lignan derivatives from the stem bark of Syzygium cumini (L.) Skeels

Phytochemical investigation of the stem bark of Syzygium cumini (L.) Skeels (Myrtaceae) yielded four new lignan derivatives characterised as (7alpha,8alpha,2'alpha)-3,4,5-trimethoxy-7,3',1',9'-diepoxylignan (cuminiresinol), (7alpha,7'alpha,8alpha,8'alpha)-3,4-dioxymethylene-3',4'-dimethoxy-7,9',7',9-diepoxylignan-5'-ol (5'-hydroxy-methyl-piperitol), (7alpha,7'alpha,8alpha,8'alpha)-3'-methoxy-9-oxo-7,9',7',9-diepoxylignan-3,4,4'-triol or 3-demethyl-9-oxo-pinoresinol (syzygiresinol A), (7alpha,7'alpha,8alpha,8'alpha)-9-oxo-7,9',7',9-diepoxylignan-3,4,3',4',5'-pentaol or 3,3'-didemethyl-9-oxo-pinoresinol (syzygiresinol B) along with the known lignans di-demethyl-5-hydroxypinoresinol, dimethylpinoresinol, didemethoxypinoresinol, pinoresinol and 4'-methyl-5'-hydroxypinoresinol. The structures of these lignans were elucidated on the basis of structural data analysis and chemical reactions.