| The barks of Magnolia officinalis Rehd.et Wils.(M.officinalis)or Magnolia officinalis Rehd.et Wils.var.biloba Rehd.et Wils.(M.officinalis var.biloba),titled as "Cortex Magnoliae Officinalis" in Latin and "Houpo" in Chinese,as an traditional Chinese medicine(TCM),had a medicinal history of over two thousand years in China.However,Houpo was a kind of woody plant and it has a long growth cycle.According to medicinal requirements it needs to grow 15-20 years or more,the main way of harvesting was cutting down trees and peeling off their barks.For a majority of plants,bark was a non-renewable organ.Because of the unbridled deforestation,China's wild resources of Houpo were exhausted in the 1980s.And the destructive utilization pattern had already caused serious damage on the forest ecosystem.Therefore,a sustainable utilization pattern must be established to change this situation.Which parts of Houpo could be replaced?Previous research work had proved that the function of flower was weak,and the quality of leaf was different,only fruit,with similar chemical composition base to bark,showing a bright use of the prospects.M.officinalis and M.officinalis var.biloba fruits,which are nutritious reproductive organs of these plants,could be harvested each year,rich in biological resources.But their research and utilization remain unknown.Phenylpropanoids compounds are the main chemical constituents of M.officinalis and M.officinalis var.biloba barks,including phenolic compounds and phenylethanoid glycosides.Based on the concept of sustainable use of TCM resources,we focused on phenylpropanoids compositions of M.officinalis var.biloba fruits and the antioxidant activities.Research on the M.officinalis var.biloba fruits may help to broaden its application in medicine,resulting in greater use of this abundant resource,providing scientific basis for clarifying the active compontents and exploring the feasibility of alternative.The main results were as following:(1)To systematically study the phenolic compounds in M.officinalis var.biloba fruits,thirteen compounds were isolated by solvent extraction,reversed-phase silica gel,and preparative high-performance liquid chromatography(HPLC).Their structures were identified by various chromatography methods including NMR and MS spectrum.Thirteen phenylpropanoids,namely,magnolol(1),honokiol(2),obovatol(3),trans-p-coumaryl aldehyde(4),magnaldehyde E(5),randaiol(6),magnaldehyde B(7),magnaldehyde D(8),randainal(9),magnatriol(10),magnolignan C(11),magnolignan A(12),magnolignan J(13),respectively.Compound 13 was a new compound,and all compounds were obtained from M.officinalis var.biloba fruits for the first time.The experimental results and literature research found that,in addition to the new compound 13,the other compounds were also distributed in M.officinalis and M.officinalis var.biloba barks,indicating that the barks and fruits of M.officinalis and M.officinalis var.biloba have the similar chemical composition base in phenolic cormpounds.In addition,thirteen phenolic compounds were studied for their antibacterial activities in vitro.The results showed that their antibacterial activities were related to their structures.(2)For further phenylethanoid glycosides study of M.officinalis var.biloba firuits,nine phenylethanoid glycosides and one phenylethyl alcohol derivative were isolated.Their structures were elucidated by modern spectrum knowedge,including NMR,MS and FR,and HPLC analysis of sugar residue.Their names were magnoloside ?a(14),magnoloside ?c(15),crassifolioside(16),magnoloside ?b(17),magnoloside ?a(18),magnoloside ?a(19),magnoloside ?a(20),magnoloside ?b(21)and magnoloside Va(22),syringin(23).Compound 15,18,19 and 21 was new compounds,and all compounds were obtained from M.officinalis var.biloba fruits for the first time.The presence of abundant phenylethanoid glycosides in M.officinalis var.biloba fruits will bring new prospects for its future development and utilization.(3)Next,our study continues to focus on total phenylethanoid glycosides(PG)from M.officinalis var.biloba fruits.The total phenylethanoid glycoside content in PG was carried out by UV spectrophotomatry method and magnoloside Ia as standard.The reliability of the method was proved by methodology examination.The results showed that PG was rich in phenylethanoid glycoside content,which could reach 54.90 ± 1.09%,and the main components were compounds 14,15,16 and 17.The results of antioxidant activity in vitro showed that PG had good scavenging effects on three common free radicals(DPPH·,ABTS·+ and O2·-),and DPPH radical scavenging activity of PG was similar to that of positive control BHT.(4)The antioxidant activity in vitro of nine phenylethanoid glycosides was investigated by free radical scavenging activity and the protective effect against free radical-induced oxidative damage on different models.Nine phenylethanoid glycosides showed strong free radical scavenging activity,and their unit titers were far superior to the positive control drugs Vc and BHT.The analysis of the structure-activity relationship of these phenylethanoid glycosides in the free radical scavenging activity assay suggested that the presence of two adjacent phenolic groups in the molecule resulted in strong free radical scavenging activity.The more two adjacent phenolic groups were,the stronger the free radical scavenging activity was.Besides,for the two kinds of mitochondrial damage models of UVB radiation and Fe2+/H2O2,nine phenylethanoid glycosides showed good protective effects against free radical-induced oxidative damage,and their protective effects could be attributed to their radical scavenging activity.Comparing the above experimental results,we found that antioxidant activity of magnoloside ?a was optimal,followed by magnoloside ?c and magnoloside ?b.(5)In this paper,the photoprotective properties of PG and its representative magnoloside ?a against VB-induced phototoxicity were also investigated in vitro and in vivo.The results of photoprotection against UVB-induced phototoxicity in vitro showed PG and magnoloside ?a significantly inhibited the increase of malondialdehyde(MDA)and lipid hydrogen peroxide(LOOH)caused by UVB.At the same time,the results of photoprotection in vivo showed PG and magnoloside Ia could relieve the oxidative damage induced by UVB and prevent the decrease of collagen content in the skin by directly scavenging free radicals or enhancing the activities of antioxidant enzymes catalase(CAT),superoxide dismutase(SOD)and glutathione peroxidase(GPx),inhibiting the increase of MDA content.In the molecular mechanism,PG and magnoloside Ia played anti-inflammatory and photoprotective effects by inhibiting activation of MAPK/NF-?B signaling pathway.In conclusion,the phenylpropanoids compositions of M.officinalis var.biloba fruits and the antioxidant activities were investigated systematically in present study.These results may provide the scientific foundation for developing M.officinalis var.biloba fruits into high valued products and make full use of this alternative resource,as well as accomplish to "sustainable development". |
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