Studies On Phloroglucinol Derivatives From Two Myrtaceae Species And Their Bioactivities

Phloroglucinol derivatives are widely presented in the plants of Clusiaceae,Myrtaceae,Euphorbiaceae,Asteraceae,and so on.These compounds not only possess various skeletons with highly complex multi-ring systems and polychiral centers,but display a wide spectrum of bioactivities,such as antimicrobial,anti-inflammatory,anticancer,antiviral,antioxidative,and enzyme inhibitory activity.Previously,a number of phloroglucinol derivatives responsilble for antibacterial and anticancer properties have been reported from Psidium guajava,Eucalyptus tereticornis,and Callistemon salignus by our research group.In order to search for more active phloroglucinol derivatives from Myrtaceae family,the investigations on chemical consitituents and their bioactivities of the fruits of Eucalyptus robusta and Rhodomyrtus tomentosa were carried out.The first chapter reviewed the phloroglucinol derivatives and their bioactivities isolated from the species of Eucalyptus,Eugenia,Myrtus,Decaspermum,and Cleistocalyx genera.A total of 108 molecules with antimicrobial,anti-inflammatory,anticancer,antiviral,antioxidative,and enzyme inhibitory effects were summarized.The second chapter,a total of 25 compounds including 13 new ones were obtained and established by a combination of normal and reverse phase silica gel,Sephadex LH-20,and semi-preparative high performance liquid chromatography(HPLC),combined with nuclear magnetic resonance(NMR),mass spectrum(MS),electronic circular dichroism(ECD)calculations,and X-ray single crystal diffraction methods.Among them,1-3 were dimeric phellandrene-derived meroterpenoids featuring an unprecedentedly fused skeletons between two phellandrene and two acylphloroglucinol subunits,and their structures and absolute configurations were further confirmed by X-ray single crystal diffraction and ECD calculations.The bioactivity studies showed that compounds 1-3 had a certain inhibitory activity of acetylcholinesterase(AChE),and compounds 4 and 19 displayed significant antimicrobial activity againstEscherichia coli,while compounds l4-16 displayed significant antimicrobial activityagainst Monilia albican.The last chapter,the details of the isolation and structural elucidation of one new compounds and four known analogues form Rhodomyrtus tomentosa fruits were described.Compound 31 is a reported phloroglucinol derivative and its stereochemistry has not been determined in the literature.This study found it to be a racemate by X-ray single crystal diffraction.We conducted a chiral separation on it first time,and confirmed its absolute configuration by ECD calculation.