Molecular Structure, Formula Molecular Weight Of The Angelica Sinensis Polysaccharide Iron Complex

Angelica sinensis polysaccharide iron complex(APIC), a macromolecular complex synthesized by neutralization of Angelica sinensis polysaccharide(ASP) and ferric chloride solution , is a new iron supplement with dual hematonic effects:(1) it can supply the body with iron and thus treat IDA; (2) it can exert the effects of ASP to enrich blood, regulate menstrual cycles, stop discomforts of menstruation, and so on. This paper summarizes the results of molecular structure, formula molecular weight studies on APIC, mainly including the partial physicochemical properties of APIC; the molecular structure of APIC; the formula and molecular weight of APIC.PART ONE THE PARTIAL PHYSIOCHEMICAL PROPERTIES OF APICThe partial physicochemical properties were studied, so as to make a further understanding of the relationship between its properties and functions. The viscosity properties of APIC were studied with capillary viscometric measurements. The electrical conductivity of APIC were tested with conductometric measurements. The particle size and distribution were analyzed with laser diffraction. The capillary viscometric measurements show APIC is a collosol in aqueous solutions. The results of electrical conductivity measurements show APIC consists of weak electrolytes, and the core of the collosol is neutral particles. The average particle size of APIC is 142 nm. PART TWO THE MOLECULAR STRUCTURE OF APICThe molecular structure of APIC were studied, so as to understand the relationship between its stucture and functions. Fourier transform infrared spectroscopy(FTIR), X-ray powder diffraction(XRD), differential scanning calorimetry(DSC), transmission electron microscopy(TEM), electron paramagnetic resonance(EPR), thermogravimetric analysis(TG), and atomic force microscopy(AFM) were used to characterize APIC, including the thermal property, microscopic structure, spectra characteristics. The DSC result shows that the melting point of the complex is about 455℃. The microscopy result shows that the complex has an iron core of 40~50 nm in diameter. The results of XRD, IR and EPR analysis establish that the iron-containing core in the complex is ferrihydrite core linked by hydroxy and oxy bridges, ( Fe2O3·2.2H2O) m.PART THREE THE FORMULA AND MOLECULAR WEIGHT OF APICThe chromatograms of APIC were examined by and Sephacryl gel chromatography. A series of standard dextrans of known molecular weight were determined by gel chromatography to obtain a linear standard curve, from which the approximate molecular weight of the iron core, ASP and APIC was calculated. Then based on our studies, the model structure and molecular formula of APIC were proposed. Our studies indicate that when APIC is eluted by gel chromatography, two fractions can be obtained, one containing iron and Angelica sinensis polysaccharide (ASP), which is the main component of the complex, and has a polynuclear ferrihydrite core linked by hydroxy and oxy bridges and chelated by ASP chains; and the approximate molecular weight of which is determined to be about 253,000 Da, and the other ASP the approximate molecular weight of which is determined to be about 1,400 Da.Based on the results of our studies, the conclusion is come to that APIC is a macromolecule complex composed of ASP and iron. The structure of APIC was proposed to be a polynuclear ferrihydrite core chelated firmLy by an encircling framework of ASP chains, forming a core molecule, which is surrounded by a removable outer protective sheath of colloidal ASP. And the molecular formula of APIC was proposed to be {[(Fe2O3·2.2H2O)1043 (ASP)32](ASP)12}, with MW =270 000 Da.