| Lepidium meyenii,known as maca,belongs to the Brassicaceae family.It is a native plant in Peru,South Africa and grows in Andes.As an important class of substances,polysaccharides have sufficient nutrition value to ensure normal body functioning.Due to their advantages of non-cytotoxic properties,low cost,availability and renewability,polysaccharides have become increasingly important in healthcare products.Up to now,the biological activities of effective compounds from maca in Peru are mainly focused on the roots.Little is known on the characterization and biological effects of polysaccharides isolated from its leaves.The polysaccharides from Yunnan maca leaves were extracted and purified.Then,the structural characterization and functional activities of the purified polysaccharide were elaborated.The main results are as follows.1.All dried maca leaves were pulverized to obtain a fine powder in a grinder.The dried powder was mixed with petroleum ether for 4h in a Soxhlet apparatus and then dissolved in 95%ethanol at 4?C for 12h.The polysaccharide was extracted by hot water extraction.The crude Lepidium meyenii leaves polysaccharide?CLMLP?was obtained after deproteinized process.Then the CLMLP was fractionated on a DEAE-52 cellulose column.There were three independent peaks named DLMLP-1,DLMLP-2 and DLMLP-3 eluted by distilled water,0.1M and 0.3M NaCl solution,respectively.The main peak fraction DLMLP-3 was collected,dialyzed against distilled water and lyophilized.Then DLMLP-3 was further purified using a SephadexG-100 column.The relevant fractions were collected,concentrated and finally lyophilized to obtain the purified Lepidium meyenii leaves polysaccharide?LMLP?.2.The molecular weight of LMLP was analyzed by gel filtration chromatography with a SephadexG-100 column.The average molecular weight of LMLP was calculated to be 58.43 KDa.The monosaccharide composition of LMLP was analyzed using GC chromatography.LMLP was composed of galactose,arabinose,rhamnose,glucose and mannose with a relative molar ratio of5.51:4.05:1.15:0.77:0.01.The weight percentage of uronic acids in LMLP was calculated to be 27.34%by the method of colorimetric.Combined with the monosaccharide composition of LMLP,galactose was found to be in higher amount?47.95%?,followed by arabinose?35.25%?and D-glucuronic acid?27.34%?and the remaining mono sugars were recorded as rhamnose,glucose and mannose.LMLP had no absorption at 280 nm and 260 nm in UV analysis,indicating that the LMLP was absence of protein and nucleic acid.The infrared spectrum revealed the major functional groups and the chemical bounds of the compound investigated.There were absorptions in 3286.62cm-1,2933cm-1,1734.99cm-1,1605.69cm-1,1239.86cm-1,1020.29cm-1,535.71cm-1.It indicated that LMLP contain stretching vibration of hydroxyl groups,stretching vibration of the O-H bond,C-H bond,C=O stretching,pyranose ring and?-configurations.The results of periodate oxidation of LMLP indicated that 1-linked,1,6-lingked and non-reducing ends and one or more of1–2,1–4,1–2,6 or 1–4,6 linkages might exist.The results of Smith degradation of periodate-oxidized LMLP indicated that 1–2 or 1–6 linked,1–3 linked and 1–4linkages glycosidic bonds might exist in the main chain or branch.3.The antioxidant activity of LMLP was tested by DPPH free radical scavenging activity and reducing power.Antioxidant activity results showed that LMLP presented an EC50 of 3.72 mg/mL in scavenging DPPH radical,and it also had reducing power?OD700 nm being 0.079 at 1 mg/mL?.LMLP possessed the potential on stimulating immune response of RAW264.7 cells.It could promote proliferation,strengthen phagocytosis function,enhance the expression of CD80,and increase the secretion of?NO?and IL-10 in a dose-dependent manner.All of these results suggested that LMLP could be used as a natural ingredient for functional food.It also provides theoretical basis for the development and utilization of maca. |
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