Phloroglucinol Derivatives From The Twigs And Leaves Of Rhodomyrtus Tomentosa

The plant Rhodomyrtus tomentosa(Ait.)Hassk.is an evergreen shrub of family Myrtaceae and widely distributed in south China,including Guangdong,Guangxi,Yunnan and Fujian provinces.The whole plant of R.tomentosa was used as folk medicine for the treatment of colic diarrhea,dysentery,hemorrhage,abscesses,rheumatic arthritis and hepatitis.A series of triterpenes,phloroglucinols,flavonoids,tannins and essential oil have been isolated from this plant.Phloroglucinols are one of the characteristic components of R.tomentosa,some of which showed potent antibacterial,antimalarial and anticancer activities.To date,however,only 10 phloroglucinols have been isolated from R.tomentosa.As a part of our onging program to search for structurally unique and biologically interesting phloroglucinol derivatives,we carried out systematically phytochemical investigation on the twigs and leaves of R.tomentosa,which led to the isolation of 20 phloroglucinol derivatives.Their structures were established based on extensive spectral methods.They are tomentone A(RT-1),tomentone B(RT-2),tomentone C(RT-3),tomentone D(RT-4),rhodomyrtosone R(RT-5),rhodomyrtosone U(RT-6),rhodomyrtosone V(RT-7),rhodomyrtosone C(RT-8),tomentosone A(RT-9),rhodomyrtone(RT-10),rhodomyrtosone B(RT-11),rhodomyrtosone J(RT-12),rhodomyrtosone M(RT-13),rhodomyrtosone O(RT-14),rhodomyrtosone S(RT-15),rhodomyrtosone I(RT-16),rhodomyrtosone K(RT-17),rhodomyrtosone N(RT-18),rhodomyrtosone P(RT-19)and endoperoxide G3(RT-20).Among them,RT-1?RT-7,RT-12?RT-15 and RT-17?RT-19 are 14 new phloroglucinol derivatives.Especially,RT-1?RT-4 are four new phloroglucinol-terpene adducts possessing a novel skeletal type.