Abstract
BackgroundDendrobium officinale as a precious traditional Chinese herb is widely used in medicines and health supplements. Thus the extraction, purification and biological activities of polysaccharides from the stem of Dendrobium officinale have significant meaning on theory and application value.MethodsThe crude Dendrobium officinale polysaccharide (DOP) was obtained by hot water extraction- ethanol precipitation method, and four new polysaccharide fractions (DOP-40, DOP-50, DOP-60, and DOP-70) were further obtained from the crude DOP by fractional precipitation with ethanol method, then four fractions were further purified by Toyopearl-H65F gel resin. The molecular weight and monosaccharide composition of four purified fractions were determined by high performance anion exchange chromatography and high performance liquid chromatography. The antioxidant activities of them were evaluated by the reducing power assay, and the superoxide anion, 2,2-diphenyl-1-picrylhydrazyl (DPPH), and hydroxyl free radicals scavenging assays, respectively. Finally, the anticancer activities of them were investigated via the MTT assay and the western blot analysis using HepG2 cells.ResultsAmong these four purified fractions were mainly composed of d-mannose and d-glucose with different molar ratios, and their average molecular weights were 999, 657, 243 and 50.3 kDa, respectively. What’s more, DOP-70 always exhibited the strongest antioxidant and anticancer activities, while DOP-40 and DOP-60 showed very close antioxidant and anticancer activities which were better than that of DOP-50. The western blotting analysis also showed that DOP-40, DOP-60, and DOP-70 induced apoptosis in HepG2 human liver cancer cells through the Bcl-2 and Bax-dependent pathway.ConclusionsFractional precipitation with ethanol could successfully apply to extract four new polysaccharide fractions from Dendrobium officinale stems, and the polysaccharide fractions possessed efficient antioxidant and anticancer activities, especially DOP-70.
Highlights
Dendrobium officinale as a precious traditional Chinese herb is widely used in medicines and health supplements
Dendrobium officinale polysaccharide (DOP)-70 contained the lowest content of protein, and the highest content of neutral sugar
The results showed that DOP-40, DOP-60, and DOP-70 induced apoptosis in HepG2 cells through the Bax- and Bcl-2-dependent pathway
Summary
Dendrobium officinale as a precious traditional Chinese herb is widely used in medicines and health supplements. Its stem has been traditionally consumed as both food and medicine recorded in “Pharmacopoeia of the People’s Republic of China”, and it has been proved to possess enhancing immunity, anti-inflammatory, antioxidant and anticancer activities [3,4,5]. Extensive studies have been demonstrated that polysaccharides from Dendrobium officinale stems possessed could protect RAW 264.7 cells against oxidative injury [8], inhibit TNF-a-induced apoptosis in A-253 cell line [9], and enhance intestinal mucosal immune activity [10]. The physicochemical properties and functions of polysaccharide fractions from Dendrobium officinale stems extracted by ethanol fractional precipitation method still remained unknown. Four new polysaccharide fractions were obtained via fractional precipitation, and their bioactivities were further evaluated with the purpose of providing novel natural antioxidant and anticancer compounds from Dendrobium officinale stems
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