Study On Allelochemicals In Secondary Metabolites In The Mountains

Chemical herbicides have defects of high toxicity,high residue and plant resistance.Natural botanical herbicides were derived from allelochemicals in plants,which is the trend of the development of green and efficient herbicides.In this research,the secondary metabolites in Michelia maudiae Dunn were studied under the bioassay-guidance of inhibition of seed germination experiment.Forthemore,some secondary metabolites isolated by us were tested the inhibition activity of seed germination.Michelia maudiae Dunn belonging to Michelia L.,Magnoliaceae,was an endemic and evergreen tree in the south region of China.In this research,the eluates of the bark with inhibition activity of seed germination were purified by silica gel column chromatography,Sephadex LH-20 column chromatography,and preparative thin layer chromatography.The structures of 19 secondary metabolites isolated from the bark of Michelia maudiae Dunn were identified by spectroscopic techniques including nuclear magnetic resonance,UV-visible spectroscopy,Fourier transform infrared spectrometer,High resolution electrospray ionization mass spectroscopy,and comparison their physical constants and spectroscopic data with those reported in the references.The compounds include three germacrane sesquiterpenes:dihydroparthenolide-2,8-diol(1),parthenolide(2),dihydroparthenolide(3);three aromodendrane sesquiterpenes:aromadendrane-4?,10?,15-triol(4),alloaromadendrane-4?,lOa-diol(5),spathulenol(6);one carryophyllane sesquiterpene:caryophyllene oxide(7);one farmesane sesquiterpene:nerolidol(8);one cumulated diolefins norsesquiterpenoid:Lyratol F(9);five camphane monoterpenes:biondinin C(10),bornyl caffeate(11),bornyl acetate(12),2-exo-3-exo-camphane-2,3-diol(13),and bomeol(14);one menthane monoterpane:a-terpineol(15);two phenolic acids:vanillic acid(16),and p-hydroxybenzaldehyde(17);two sterols:?-sitosterol(18),and 7?-hydroxysitosterol(19).Compound 1 is a new compound,and compound 9 is isolated from Michelia L.for the first time.Moreover,coumpounds 3,5,10,11,16,19 were test seed germination activity on the seeds of Lolium perenne.L.,Sorghum sudanense(Piper)Stapf,Lactuca sotiva L.var.angustana Irish ex Bremer,respectively.As a result,compounds 3 inhibited the germination of Sorghum sudanense(Piper)Stapf(EC50 = 4.05×104 M);compounds 10 inhibited the germination of Lolium perenne L.(EC50 = 4.51×10-5 M);compounds 16 inhibited the germination of Sorghum sudanense(Piper)Stapf(EC50 = 1.49×10-5 M);compounds 19 inhibited the germination of Lolium perenne L.(EC50 = 2.18×10-4 M).The results support the conclusion on terpenoids,phenolic acids,sterols are important sources of natural plant hormones.And it gives precursor compounds,which can be used to develop the new plant source herbicides of the allelochemicals from Michelia maudiae Dunn.