Chemical Constituents Of Three Liverworts And Their Biological Activities

Bryophytes are considered to be the first plant type to successfully make the transition from water to land,which are divided into three classes,liverworts(Hepaticae),mosses(Musci)and hornworts(Anthocerotae)and taxonomically placed between the algae and the pteridophytes.There are more than 6000 liverworts worldwide,about 800 species of which have been found in china.Among the bryophytes,liverworts are the rich source of terpenoids and aromatic compounds with intriguing biological activities such as cytotoxic,antifungal,allelopathic,insect antifeedant,andantioxidant properties,which might due to the appealing,characteristic cell organelles they possessed:cellular oil bodies,morphologically.In this research,three Chinese liverworts,Jamesoniella autumnalis(DC.)Stephani collected from Jilin Provence,Pellia epiphylla(L.)Corda collected from Yunnan Province,and Pallavicinia ambigua(Mitt.)Stephani collected from Zhejiang Province,were phytochemically investigated.A total of 66 compounds,including 47 diterpenoids and 3 oxidation derivatives,3 diterpene dimmers,10 sesquiterpenoids and 3 bibenzyls,were isolated and identified on the basis of NMR,MS,single crystal X-ray diffraction analysis,and time-dependent density functional theory(TDDFT)ECD calculations.54 of them were new compounds,including new skeleton labdane diterpenoids and diterpene dimmers.Tautomeric equilibrium of two pairs of novel skeleton labdanes was investigated,which was validated to be intramolecular transesterification between ?-lactone and ?-lactone ring.Clerodane diterpenoids exhibited moderate anti-inflammatory activity.Sacculatane diterpenoids displayed moderate antioxidant effect.Further investigation of pellianolactone B revealed its neuroprotective effect.Nine previously undescribed clerodane-type diterpenoids,jamesoniellides M-T(1-9)and one ent-labdane-type diterpenoid(10),five new phytane-type diterpenoidsj amesautumins A-E(12-16),seven new eudesmane-type sesquiterpenoids jamesonins A-G(18-24),as well as five known analogues,were isolated from the Chinese liverwort Jamesoniella autumnalis.Inhibition on LPS-induced NO production in RAW 264.7 murine macrophages was investigated,and the results showed that jamesoniellides Q-S exhibited moderate anti-inflammatory activity,with 50-80%maximum inhibition rate of NO production under the nontoxic tested concentration.Eight previously undescribed sacculatane diterpenoids,epiphyllins A-H(28-35),and one unknown bibenzyl-basedisopentene(36)along with seven known compounds were isolated from the Chinese liverwort Pellia epiphylla.The quinine reductase-inducing activity evaluation demonstrated that epiphyllins A-D,1?-hydroxysacculatanolideand pellianolactone B displayed moderate antioxidant effect.Further investigation of pellianolactone B revealed its protective effects on H2O2-induced oxidative insults and apoptosis in PC12cells.Twenty three compounds,including fiveunprecedented labdane-type diterpenoids bearing bicyclo[2.2.2]octane pallamolide A-E(44-48)and three oxidized derivatives pallamolide F-H(49-51),three labdane dimmers pallamins A-C(52-54),eleven new labdanes and seco-labdanes(55-65),and one known compound ent-pallavicinin(66)were isolated from Chinese liverwort Pallavicinia ambigua.Among them,tautomeric equilibrium of two pairs of novel skeleton labdanes pallamolides B-E(45-48)was investigated,which was validated to be intramolecular transesterification between ?-lactone and ?-lactone ring by extensive NMR-spectroscopic studies and kinetic calculations.As an ongoing research of our groups' and many other predecessors'phytochemical investigation of liverworts,this study further indicated the abundantly rich and novel secondary metabolites of liverworts,which greatly enriched the database of natural products.Some of these compounds also show satisfactory biological activity.Some genera also showed unique components,which will also be valuable for chemical classification.