| Rhodomyrtus tomentosa(Myrtaceae),an evergreen shrub,was known as rose myrtle and widely distributed throughout Southeast Asia and Southeast China.Its fruits were edible and usually used as ingredients of pies and jams.In addition,its stems and leaves had been widely used to treat a variety of illnesses including chronic dysentery,rheumatism,hepatitis,and hyperlipemia.In recent years,the phloroglucinols isolated from R.tomentosa showed antibacterial,antimalarial,metastatic inhibitory,anticancer,anti–inflammatory effects with the structural diversity,which attracted the attention of scientists of natural products.It was an important task for the modernization of Traditional Chinese Medicine to study the chemical composition and biological activity of the herbal medicines,to seek new drug lead compounds,and to clarify their pharmacological effects and pharmacological effects.Based on the diverse structures and biological activities of the phloroglucinols,the chemical constituents of R.tomentosa were isolated and identified and their biological activities were studied.22 compounds were isolated from the petroleum ether extracts of the leaves of R.tomentosa by using normal phase silica gel,reversed-phase silica gel C18,Sephadex LH-20 and high performance liquid chromatography(HPLC).Their structures were identified by a combination of nuclear magnetic resonance spectroscopy(NMR),mass spectrometry(MS),circular dichroism(CD),ECD calculations and X-ray diffraction analysis.Compounds 1-11 were new compounds.Among them,compounds 1 and 2 were two heterofluorene derivatives with a rare bifuran ring and compounds 3-11 were five new pairs of new β–triketone–sesquiterpene meroterpenoids.In addition,another 10 known analogues(12-22)were isolated and their structures were identified as rhodomyrtosone A(12),rhodomyrtosone C-D(13 and 14),rhodomyrtials A and B(15 and 16),tomentodiones A(17),tomentodiones C(18),watsonianone A(19),rhodomentones A and B(20 and 21),and tomentodione I(22).The antibacterial activities of compounds 1-13 were evaluated against four strains of Staphylococcus aureus,Escherichia coli,Pseudomonas asaeruginosa and Candida albicans.The results showed that all compounds showed weak antibacterial activity.Moreover,the anti-inflammatory activity of compounds 2,4-7,9,11-12 were evaluated and the inhibition rates of NO formation(%)of compounds 2,5,11 were 32.91 ± 1.40,43.14 ± 3.43,20.41 ± 3.49 at the concentration of 50 μM.it was found compared with the literature reported significant antibacterial activity of the compounds,meroterpenoid structure unit is the necessary groups antibacterial activity.It was found that the anti-inflammatory activity of the compound was related to steric configuration of chiral C in terpenoids,and also to the position of methyl attachment. |
