CYCLIC DIPEPTIDES FROM SCHIZANDRA CHINENSIS AND THEIR SYNTHESES

AIM: To investigate cyclopeptides from the fruits of S.chinensis. METHODS: Use thin layer chromatography, repeated silica geland RP-18 column chromatography together with spectra as well as synthetic methods. RESULTS: Three naturally occurring cyclic dipeptides and a mixture composed of three other new naturally occurring cyclic dipeptideswere obtained. Their structures were determined as cyclo-(leucyl-prolyl)(1), cyclo-(phenyl-alanyl-prolyl) (2), cyclo-(phenylalanyl-leucyl) (3), cyclo-(phenylalanyl-valyl) (4), cyclo-(phenylalanyl-isoleucyl) (5) and cyclo-(phenylalanyl-phenylalanyl) (6). In addition, fourteen analogous cyclic peptides (7～20) were synthesized. CONCLUSION: Cyclopeptides were isolated from S.chinensis (Schizandraceae) for the first time. The bioactivity of some cyclic dipeptides on the contraction of rabbit aortastrips with KCl (40 mmol.L^-1) depolarization was tested. Cyclic dipeptides 2, 6 and 18 showed slight calcium antagonism and 19, 20 can increase the contractile effect in high concentration of potassium. Studies on the bioactivities of other cyclic dipeptides are in progress.