| Dendrobium Sw.,the second largest genus of Orchidaceae.Dendrobium is one of the most important ornamental plants in the international flower market because of its beautiful and colorful flowers.In addition to certain ornamental value,Dendrobium has some medicinal value.Modern pharmacological studies have proved that Dendrobium has the pharmacological effects of enhancing immunity,anti-tumor and anti-oxidation.Alkaloids and polysaccharides are two important bioactive components of Dendrobium,and their contents and types directly affect the quality of medicinal materials.In this study,the growth and development characteristics of Dendrobium nobile and Dendrobium capillipes were observed and recorded,and the accumulation rule of alkaloids and polysaccharides was understood by studying the dynamic changes of total alkaloids and polysaccharides in different organs of two Dendrobium species with seasons.At the same time,the alkaloids and polysaccharides in Dendrobium nobile and Dendrobium capillipes were analyzed qualitatively and quantitatively by UPLC-Q-Exactive Plus Qrbitrap MS and GC-MS.The main findings are as follows:(1)Through the observation of the growth of two kinds of Dendrobium,it is found that the growth period of Dendrobium nobile stem is about 180 days,and that of Dendrobium capillipes stem is about 120 days.They have similar growth rhythm:the peak of stem growth is mainly in July and August,and then it enters the slow growth stage,the growth basically stops in December.At this time,the stem height of Dendrobium nobile is 36.1±0.9 cm,the stem diameter is 1.26±0.12 cm,the stem height of Dendrobium capillipes is 15.1±2.4 cm,and the stem diameter is 1.18±0.15 cm.Dendrobium nobile sprouts early and grows for a long time,so its biomass is always larger than that of Dendrobium capillipes.(2)The accumulation rule of total alkaloids is as follows: the total alkaloids in leaves of Dendrobium nobile are higher than those in stems,the total alkaloids in stems decrease with the increase of growth years,and the total alkaloids in one-year stems are the most;the total alkaloids in one-year stems,two-year stems and three-year stems are all accumulated from June to November,and the maximum value in November is 0.503±0.013%,0.494±0.024% and0.458±0.015%,respectively.The total alkaloids in leaves increased twice in August and November,respectively,reaching 0.543±0.019% and 0.528±0.009%.The content of total alkaloids in leaves of Dendrobium capillipes was higher than that in stems,with a maximum value of 0.374±0.017% in September,the content of total alkaloids in the stem increased with the increase of growth years,and the accumulation of total alkaloids in the three-year stem was up to 0.238±0.026%,which remained relatively stable during the harvest period.Therefore,the one-year stem and leaves of Dendrobium nobile,leaves and three-year stems of Dendrobium capillipes were collected before defoliation.In this way,the alkaloids can be retained to the greatest extent.(3)The accumulation rule of total polysaccharide is as follows: The content of total polysaccharide in the stem of Dendrobium nobile decreased with the increase of growth years.The total polysaccharidecontent in the one-year stem was higher than that in other parts,reaching the maximum value of 11.70±0.71% in October;the accumulation of total polysaccharide in the two-year and three-year stems reached the maximum value of6.49±1.14% and 5.25±0.40% in November.The total polysaccharide content of the two-year stem of Dendrobium capillipes was higher than that of other parts,reaching the maximum value of 16.40±1.44% in July.Therefore,the one-year stem of Dendrobium nobile was harvested before defoliation,and the two-year stem of Dendrobium capillipes was harvested in summer to retain its polysaccharide to the greatest extent.(4)17 alkaloid compounds were identified from Dendrobium nobile and Dendrobium capillipes by UPLC-Q-Exactive Plus Qrbitrap MS,including ten sesquiterpenoid alkaloids,such as findlayine D(2),dendrine(3),dendrobine(4),and mubirone B(5),dendramine(6),dendronobiline A(7),nobiline(8),dendrobine(11),6-hydroxydendroxine(13)and6-hydroxynobiline(14);four amide alkaloids are N-p-coumaroyl-tyramine(10),N-p-feruloyl-tyramine(12),N-p-cinnamoyl-tyramine(15)and N-p-caffeoyl-tyramine(16),two octahydroindolizine alkaloids are dendrocrepine(9),crepidine(17),a pyrrolidine alkaloids are shihunidine(1).17 kinds of compounds can be extracted by chloroform and methanol.The content of the alkaloids extracted by chloroform method is higher than that by methanol method in 9 kinds of alkaloids in Dendrobium nobile and 10 kinds of alkaloids in Dendrobium capillipes.Therefore,It is suggested that chloroform is the main method and methanol is the auxiliary method,and Dendrobium nobile and Dendrobium capillipes were identified as dendrobine,dendroxine and 6-hydroxynobiline by relative quantitative analysis.(5)13 kinds of sugar components were identified and analyzed in Dendrobium nobile and Dendrobium capillipes by GC-MS.11 kinds of monosaccharides were glucose(1),D-fructose(2),D-arabinose(3),D-galactose(4)Inositol(5),Xylitol(6),L-rhamnose(7),L-fucose(8),D-sorbitol(9),four disaccharides: trehalose(10),maltose(11),sucrose(12)and lactose(13),12 of which are distributed in the stems and leaves of Dendrobium nobile and Dendrobium capillipes,while lactose only exists in the leaves of Dendrobium nobile.(6)Through the absolute quantitative analysis of 13 kinds of sugar components,it can be seen that the content of polysaccharide of Dendrobium nobile and Dendrobium capillipes is as follows: the content of sucrose,glucose,D-fructose is higher than 1mg/g,the content of D-arabinose,D-galactose and Inositol is higher than 0.1mg/g,the content of xylitol,L-rhamnose,L-fucose,D-sorbitol,trehalose and maltose are present in the stems and leaves,but the content is lower than 0.1mg/g.The sugar content of Dendrobium nobile and Dendrobium capillipes increased first and then decreased with the increase of growth years.The glucose,D-galactose and D-arabinose content in plants decreased with the increase of growth years.The inositol,D-galactose and glucose content of Dendrobium capillipes were the highest in the one-year stems,and decreased with the increase of growth years There was no significant change in other sugar components.Therefore,the main sugar components of Dendrobium nobile and Dendrobium capillipes are sucrose,glucose and D-fructose.Among them,sucrose accumulates the most in the two-year stem and glucose and fructose accumulates the most in the one-year stem,indicating that the sugar content is related to the different growth stages of Dendrobium.In conclusion,from July to August,the growth peak of Dendrobium nobile and Dendrobium capillipes was observed.The content of total alkaloids of the one-year stems with leaves in Dendrobium nobile and the three-year stems with leaves of Dendrobium capillipes was the highest in November.The main alkaloids of the two kinds of Dendrobium were dendrobine,dendrobine and 6-hydroxydendrobinone.The total polysaccharide content of one-year stem of Dendrobium nobile in October and two-year stem in of Dendrobium capillipes in July was the highest,and the main sugar components of the two kinds of Dendrobium were sucrose,glucose and D-fructose.The alkaloid is the dominant component of Dendrobium nobile,and the polysaccharide is the dominant component of Dendrobium capillipes.Therefore,the one-year stem of Dendrobium nobile in November and the two-year stem of Dendrobium capillipes in July can be used as the best harvesting time and location.The growth of Dendrobium nobile is large and its medicinal value is high.It can be given priority in planting.The above results and analysis enrich the research on alkaloids and polysaccharides of Dendrobium nobile and Dendrobium capilipes,and provide reference for the development of medicinal resources and the utilization of effective substances of Dendrobium. |
PDF Full Text Request