Research Of Nutritional And Health Function Evaluation Of Two Microalgal Natural Products

Functional food research and development has become the most potential hotspot in the food and big health industry.The excavation and development of new food materials with nutrition and health functions can effectively promote the rising of the health industry.Microalgae are a class of single-cell microorganisms,they widely exist in various water bodies.Microalgal cells can synthesize various unique compounds,such as polysaccharides and pigments,thus,microalgae are a kind of huge treasure trove of plant natural products.Microalgae products,like polysaccharide from Spirulina platensis(PSP)and astaxanthin from Haematococcus pluvialis(AST),have a variety of biological activities and the potential for developing new natural medicines.However,most of the current researches of the bioactivity of PSP and AST have only focused on the basic research such as anti-oxidation and anti-tumor.The related research lacks more accurate nutrition,like health function identification and its molecular mechanism.In this study,PSP and AST were obtained after extraction and purification,and ICR mice were used as model animals.The bioactivity mechanisms of these natural products on chronic functional constipation and acute liver injury were explored.We discovered new nutrition and health functions of PSP and AST.The main research results and contents of this article are as follows:(1)PSP was extracted by ultrasonic extraction and purified via the column chromatography,the purity of PSP could reach to 89.72%.High performance gel permeation chromatography(HPGPC)and PMP precolumn derivatization HPLC method(PMP-HPLC)were used to determine the molecular weight and monosaccharide composition of PSP.We found that the molecular weight of PSP was 29600 Da,and the main monosaccharide composition were rhamnose(24.7%),glucose(16.15%),galactose(13.32%),Ribose(9.7%),fucose(6.742%),xylose(5.4%),glucuronic acid(5.3%),galacturonic acid(3.34),and arabinose(2.648%);the purity of AST after purification by using column chromatography could reach to 94.90%.AST contained 1.40% of cis-astaxanthin and 93.5% of trans-astaxanthin.(2)A model of chronic constipation in mice was established by gavage with diphenoxylate.After successful modeling,PSP were administered orally at a dose gradient of 50 mg / kg BW,100 mg / kg BW,and 200 mg / kg BW.50 mg / kg BW’s phenolphthalein was used as the positive control;the defecation rate was counted daily,and the time of the first black stool was also counted.After the whole experiment,kit methods were used to determine the level of acetylcholin esterase(Ach E)and nitric oxide(nitric oxide,NO).The intestinal water content was determined based on the gravimetric method,and intestinal tissues were collected to prepare for pathological sections.The experimental results show that different concentrations of PSP could reduce the concentration of NO,promote intestinal motility,and ameliorate the symptoms of constipation;low concentrations of polysaccharides can significantly increase the Ach E activity;all treatment can reduce the intestinal water content;different doses of PSP could significantly alleviate the damage of intestinal villi,reduce inflammatory infiltration and lamina propria,and increase villous goblet cells.The effect of PSP on constipation is dose dependent.(3)qPCR and 16 s rDNA microbial diversity sequencing were used to analyze the expression of mouse intestinal neurotransmitter-related genes and the changes of intestinal microbial community.Experiments show that compared with the model group,various dosage of PSP could significantly down-regulate the expression of inducible nitric oxide synthase(i NOS),transient receptor potential vanillic acid receptor 1(TRPV1),and colonic aquaporin 3(AQP3).The low dosage of PSP could significantly increase the expression of Ach E;microbial sequencing shows that compared with the constipation group,PSP had significant effects on the gut microbiota,increasing the abundance of Akkermansia,Lactobacillus,Butyricimonas,Candidatus Arthromitus and Prevotella but reducing the abundance of Clostridium and Dorea.(4)A mouse liver damage model was established by intraperitoneal injection of doxorubicin;50mg./kg BW and 100 mg / kg BW astaxanthin were administered.During the modeling process,the model mice showed symptoms of decreased appetite,weight loss,ascites increased alanine aminotransferase(ALT)level,all of these indicated the model was successfully built.At the end of the experiment,the dry chemistry method was used to determine the urine routine,the kit method was used to measure the liver function,liver samples were collected to prepare for pathological sections,and the TUNEL reaction was used to evaluate the hepatocyte apoptosis.Results showed that AST can significantly ameliorate the loss of appetite and body weight,which caused by doxorubicin.AST could also reduce the level of four liver function enzymes,alleviate hepatocyte balloon-like changes and chromatin concentration,and ameliorate the hepatocyte apoptosis.The hepatoprotective effect of AST is dose dependent.(5)Using kit method and fluorescence spectrophotometry to determine total antioxidant capacity(TAOC),catalase(CAT)activity,superoxide dismutase(SOD)activity,glutathione peroxidase(GPX)activity,malondialdehyde(MDA),and reactive oxygen species(ROS)in mouse liver;the expression of Kelch-like epichlorohydrin-related protein-1(Keap1),nuclear factor-related factor E2(Nrf2),heme oxygenation(HO1),SOD,CAT and GPX was determined by qPCR.AST could interfere the expression of some related genes on the Keap1/Nrf2 signaling pathway by downregulating the expression of Keap1 and activating the transcription factor Nrf2,which upregulates downstream peroxiredoxins.Taken together,PSP can ameliorate constipation symptoms and promote the growth of beneficial intestinal bacteria,which is based on the gut brain axis;AST could interfere the expression of some related genes on the Keap1/Nrf2 signaling pathway by downregulating the expression of Keap1 and activating the transcription factor Nrf2,which upregulates downstream peroxiredoxins.The present research found and illustrated some new food functions and related molecular mechanisms of PSP and AST,indicating that AST could be used in therapies of chemotherapy induced side effects,which provides the scientific basis for the development of microalgal natural products.