Phloroglucinol Derivatives From The Leaves Of Cleistocalyx Operculatus

The plant Cleistocalyx operculatus(Roxb.)Merr.& Perry is an evergreen arbor of family Myrtaceae,which is widely distributed in southern China,India,Indonesia,Malaysia,etc.The buds,leaves,roots and barks of C.operculatus could be used as folk medicine for the treatment of dispelling the wind,relieving exterior syndrome,helping digestion,dewetting and relieving itching.Previously phytochemical investigations on this plant resulted in the isolation of a series of terpenes,phenols,sterols,etc.As a part of our ongoing program to search for structurally unique and biologically interesting phloroglucinol derivatives from plants of family Myrtaceae,a series of novel phloroglucinols with new carbon skeletons had been isolated.However,there is no report about phloroglucinols of C.operculatus.Our preliminary experiment suggested the existence of phloroglucinol derivatives in the petroleum ether soluble fraction of the 95% Et OH extract of the leaves of C.operculatus.The following phytochemical investigation led to the isolation of 18 phloroglucinol derivatives.Their structures were elucidated by extensive spectral methods,X-ray diffraction analysis and computational analysis.These compounds were identified as cleistoperlone A((±)-SW-1),cleistoperlone B((±)-SW-2),operal A(SW-3),crinatusin A1((±)-SW-4),cleistoperal A((±)-SW-5),cleistoperal B((±)-SW-6),cleistoperal C((±)-SW-7),cleistoperal D((±)-SW-8),cleistoperal E((±)-SW-9),operlone A(SW-10),operlone B((±)-SW-11),operlone C(SW-12),operlone D(SW-13),operal B(SW-14),operal C(SW-15),operal D(SW-16),operal E(SW-17)and 3'-formyl-4',6'-dihydroxy-2'-methoxy-5'-methyl-chalcone(SW-18).Among them,there were 16 new phloroglucinol derivatives including ten phloroglucinols possessing six novel skeletal types.In addition,the separation of eight racemic mixtures by chiral HPLC led to the isolation of eight pairs of enantiomers,the absolute configurations of which were also elucidated by experimental and calculated electronic circular dichroism methods.