Eco-physiological Function Of Riccardin D On A Liverwort And Chemical Constituents Of A Special Liverwort

Plants cannot avoid hazards from its surroundings by moving,although they are sensitive.Fortunately,plants have evolved a variety of effective resistance mechanisms on morphology and physiology,such as the secondary metabolites on which their capabilities to adapt to the environment,reduce diseases and avoid pests biting are based.Different secondary metabolites in a plant are independent of each other in synthesis,transport and accumulation.Production and storage of the secondary metabolites are strictly limited by many factors such as developmental phase,special organs,specialized cells.Moreover,even in the same kind of plants,different secondary metabolites are produced in different environment.In addition,in different parts of the same plant,secondary metabolites are also produced differently The research on the relationship between secondary substances and plant resistance has become an attractive field in many subjects.With the in-depth research,it has been found that Bryophytes can produce kinds of active secondary metabolites,among which Bisbibenzyls are special ones.These chemicals belonging to phenols family may be considered as molecular markers of liverworts,for they exist in many kinds of Bryophytes.Until recently,reports on the ecological function of this kind of compounds on liverworts themselves are seldom found.In this study,liverwort P.appendiculatum was selected as study object,since this species has been successfully introduced into the greenhouse in our group.Compared with other liverworts,this species is water-deficit tolerant and easy to increase the biomass by spores.It is worth noting that the secondary metabolites of P.appendiculatum are mainly Bisbibenzyl compounds(Riccardin D,Marchantin B,Riccardin C and Perrottetin E).In addition,the content of Riccardin D is over 1.0‰(w/w)in dry weight,Moreover,Riccardin D has been successfully total synthesized in our group and provided sufficient standard for the research.Therefore determination the trend of Riccardin D in P.appendiculatum,can reveal biological functions of Bisbibenzyls on liverworts and provide clues for further investigation.The results of water stress demonstrated that with enhanced water-deficit,relative pathway genes of Riccardin D expression level increase,and production of Riccardin D is improved.Reports on ecology function of Phenolic compounds suggested that the main secondary metabolite-Riccardin D with polyhydroxyl groups in the plant may take part in protecting the plants against water-deficit stress as antioxidants.The data suggested that the plant is suitable for slightly dry environment,the optimal relative humidity of substrate surface is 30±5%RH.Activities of SOD,POD,CAT,soluble protein,and MDA content could be used as stress tolerance index to measure the damage of the liverwort under others stress treatments.The experiments also selected the UV-B radiation,NaCl stress,MeJa stimulation,chitosan simulation,and showed that under these forms of stress,the RD content in P.appendiculatum increased,but after longtime of high levels of stress,RD synthesis would be restrained.Interestingly,RD content is found to be higher in the female gametophyte than male gametophyte and different in different parts of this plant.The causes of this phenomenon are discussed in this paper.The existence of the symbolic skeleton compounds may prove the relationship between two species,and have an important value in establishing the system status of the species,which is the principle and meaning of Chemotaxonomy.It is agreed that secondary metabolites of plants are determined by genetic factors.Therefore,according to the traditional classical taxonomy in certain place on the Phylogenetic Tree,the type of secondary metabolites or the probability of novel skeleton compound may be able to predicted.As a result,we chose a primitive species Haplomitrium mnioides as study object.17 compounds have been isolated and identified,including 14 labdane-type diterpenoids:Haplomitrenonolides A-H,Haplomintrins A-F,a novel norditerpenoid(18),and 1 Hailimane-type diterpenoid(16),1 Hailimane-type liked novel diterpenoid(17).All of them are new compounds,except compounds 6-8.Haplomintrins A-F are novel labdane-type diterpenoids:Haplomintrins A-B with six-ring systems formed by intramolecular cyclization,Haplomintrins C-F have highly modified A/B labdane rings.Haplomintrins G(18)is a novel norditerpenoid.NMR spectroscopy,HRESIMS and X-ray diffraction analysis were employed to determine their planar structure and absolute configuration.The results of light-driven reactions of Haplomitrenonolide A(6)and Haplomitrenonolide D(8),demonstrated that the formation of 1 and 2 from 8 and 6 have experienced a light-driven[2+2]cycloadditon procedure.Elongation of reaction time leads to the formation and identification of haplomintrins E-I(10-14)with more appealing labdane skeletons,which provide a intriguing way to diversify natural products.Taken together,our work illustrated the natural labdane diterpenoids can be diversified through enzyme catalyzed biosynthesis pathway while the UV/Vis light either participating in the biosynthesis step in vivo or photo-driven transformation in vitro will be access to more complex structures.In this paper,the results showed that on the basis of the special position on the phylogenetic to find specific secondary metabolites has certain feasibility.Isolated compounds allelopathic activity and anti-inflammatory activity on Arabidopsis thaliana and IL-6 respectively have been evalued and their potential bioactivities have been found.