| Dendrobium officinale Kimura et Migo is a kind of orchid plant,and it is mainly distributed in the southern and southwestern China,such as Guangdong,Guangxi,Yunnan,Guizhou and other places.Dendrobium candidum is not only one of the most precious Dendrobium species,but also is a valuable Chinese herb which has lots of pharmacology effect,such as nourish Yin,clear heat,benefit stomach and fluid.It also can be used in the clinical treatment of hypertension,diabetes,anti-tumor and anti-aging,etc.In this research,the separation,purification and identification of the chemical constituents from Dendrobium candidum were studied,while the antioxidant and antihypertensive activities of each extract were learned.The results may provide a scientific basis for the quality evaluation,comprehensive development and utilization of Dendrobium candidum.By using various chromatographic techniques,such as silica and ODS gel column chromatography and HPLC,22 compounds were obtained from the ethyl-acetate and n-butanol extraction of the stems of Dendrobium candidum.The structures of 17 compounds of them were elucidated on the basis of physic-chemical property and spectroscopic analysis.They are Dendrocandin Z(1),(+)-syringaresinol(2),syringaresinol-4’-O-β-D-monoglucoside(3),conicaoside(4),syringin(5),4-allyl-2,6-dimethoxyphenyl glucoside(6),4-(3’-hydroxypropyl)-2,6-dimethoxy-phenol-3’-O-β-D-glucoside(7),3,4,5-trimethoxy-phenyl-1-β-D-glucopyranoside(8),2,6-dimethoxy-4-hydroxyphenol-1-O-β-D-glucoside(9),2-methoxyphenyl-β-D-glucopyranoside(10),benzyl-O-β-D-glucopyranoside(11),naringenin(12),4,4’-dihydroxy-3,5-dimethoxybibenzyl(13),3,4’-dihydroxy-5-methoxybibenzyl(14),thymidine(15),methyl pyroglutamate(16),p-hydroxybenzoic acid(17).Among them,compound 1 was a new compound,compouds 4,7-9,11 and 16 were isolated from the Dendrobium species for the first time,and 5,15 were isolated from Dendrobium candidum for the first time.In addition,besides these compounds,there are still five other compounds that needs further physicochemical properties and spectral data to determine their structures.To determine the contents of polysaccharides,mannose and glucose in Dendrobium candidum of Guilin,Rongxian,Baishilin and Yunnan,spectrophotometer and HPLC were used.And the esults showed that every contents of polysaccharides from different areas is about 30%,and the most is Yunnan’s,which can reache 35%.The contents of mannose and glucose of Dendrobium candidum were different of them,and the ratio were between 1:1 to 4:1.Scavenging effects and reducibility of petroleum ether,ethyl-acetate,n-butyl alcohol and water solvent extracted materials were tested on DPPH and hydroxyl free radicals by anti-oxidation experiments in vitro.The investigation showed that every extractive matter has antioxidant capacities,especially ethyl-acetate dissolving part worked better than BHT.So the ethyl-acetate part is a good natural antioxidant,and has great value in research.By HPLC method and in an in vitro model,the angiotensin-converting enzyme inhibition activity of ethyl-acetate,n-butyl alcohol extract and water-soluble part were rapidly detected.The HPLC method was simple,rapid,short analysis time,and better separation.The experimental results show that the relative inhibitory activity on the ACE of ethyl-acetate extract reached more than half of that of the synthetic drugs Captopril,and this prove that ethyl-acetate part may have good antihypertensive effect. |
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