The Investigation On The Extraction And Purification Of The Active Components In Corn Silk And Its Biological Activities

Corn silk,also named as Maydis Stigma,is frequently used in traditional Chinese herbal medicines.It is made from stigma,the yellowish thread like strands from the female flower of corn?Zea mays L.?Poaceae??with various therapeutic values with no documented toxicity.As a traditional Chinese herbal medicine,it is commonly used in the treatment of difficult urination,hypertension and diabetes.Modern pharmacology also confirms that corn silk has a variety of pharmacological activities,such as antioxidant,hypoglycemic,anti-obesity,anticancer activities.In order to clarify the chemical components of corn silk and promote the development and utilization of corn silk,the chemical constituents,bioactivities and related application have been investigated in this study.First,the physicochemical properties and antidiabetic activities of the polysaccharides from corn silk were studied.A polysaccharide obtained from corn silk?PCS2?was isolated and the physicochemical properties were characterized by gel permeation chromatography?GPC?,FT-IR,SEM and GC methods.The hypoglycemic effects were determined using the high-fat diet and streptozocin induced type 2 diabetic mellitus?T2DM?insulin resistance mice.The results showed that PCS2 was a novel polysaccharide with the average molecular weight of 45.5 kDa.Treatment of PCS2 could reduce the body weight loss,decrease the blood glucose and serum insulin levels,and improve the glucose intolerance.The levels of serum lipid profile were regulated and the levels of glycated serum protein,non-esterified fatty acid were decreased significantly?P<0.01?.The activities of superoxide dismutase,glutathione peroxidase and catalase were notably improved?P<0.05?.PCS2 also exerted cytoprotective action from the histopathological observation.Second,the extraction,separation and bioactivities of small molecules in corn silk were studied.In order to clarify the active parts of corn silk,the chemical composition,antioxidant activity and digestive enzyme inhibitory activity of different polar parts of corn silk ethanol extract?petroleum ether fraction,ethyl acetate fraction and n-butanol fraction?NBF??were compared and studied.It was found that NBF showed the highest antioxidant activity in DPPH radical scavenging activity and ferric reductive activity assays.For the digestive enzyme inhibition test,NBF showed higher inhibitory activity than positive drug acarbose.NBF was speculated to mainly contain polyphenols like flavonoid glycosides,alkaloids and polyalcohol compounds according to the LC-MS.The treatment of NBF significantly reduced the body weight loss and decreased the blood glucose and serum insulin levels?P<0.05?of T2DM mice.The glucose intolerance was improved,the levels of lipid profile were regulated and the activities of antioxidant enzymes were notably improved?P<0.05?after the treatment of NBF in T2DM mice.These results suggested that NBF of corn silk ethanol extract could be a good candidate of functional food or medicine for T2DM treatment.Guided by bioactivity,the NBF were then separated.Five flavonoid glycosides were isolated by PHPLC and three of them were identified as apigenin-6-C-glucopyranosyl-8-C-arabinopyranoside,apigenin-6-C-glucopyranosyl-8-C-rhamnopyranoside,chrysoeriol-6-C-boivinopyranosyl-7-O-glucopyranoside by¹HNMR,¹³CNMR and previous studies.Third,silver nanoparticles?AgNPs?was prepared and characterized.The reducing property of corn silk aqueous extract was successfully used for the biosynthesis of stable AgNPs.These nanoparticles were characterized combining UV-vis,FT-IR,DLS,SEM and EDX methods.The synthesized AgNPs showed effective antibacterial and anticancer activities.In conclusion,this green,simple and rapid procedure for preparing nanoparticles could be adopted for large-scale production and accepted as a cost effective alternative for antimicrobial,biomedical,and nanotechnological applications.In conclusion,the active components of the corn silk were isolated and purified,and the bioactivities in vivo and in vitro were carried out.It may have a good prospect in the application of health food and antidiabetic adjuvant.However,the specific mechanism of the antioxidant and hypoglycemic activities of corn silk polysaccharides and liposoluble constituents are unclear.The activity of single small molecular and its synergistic effect with other substances need further study.All of these will become an important research direction of this project.