The Study Of AuNPs Biosynthesized By Flavoniods And The Correlation Of Antioxidation

Gold nanoparticles(AuNPs) have emerged as attractive nanomaterials for biological and biomedical applications because of their chemical stability and unique optical properties. To apply in medicine, the way to synthesize non-toxic AuNPs with cleaning surface is critical. An ecofriendly reducing agent, a benign particle-stabilizing and capping agent and an environmentally acceptable solvent system are three selection criteria for this goal. The biosynthesis method conforms to it. Biological reduction is developed as a promising method because of its special advantages such as sufficient material sources, mild reaction conditions, and good dispersion of obtained nanoparticles.This study exploited six kinds of flavonoids (Myrcetin, Quercetin, Kaempferor, Galanginl, Dihydromyricetin, Taxifolin) with similar molecular structure as reductant and stabilizer to quickly synthesize AuNPs. The propensity of flavonoid to inhibit free-radical assay and computational approach are used to figure out the relationship between AuNPs biosynthesis with the antioxidant activity of flavonoids. The plausible explanations for mechanisms of AuNPs synthesized by flavonoids can be elaborated by studying the antioxidant-structure-activity relationships. Mainly contents of this paper1)Six flavonoids acting as reductant and stabilizer can quickly synthesize AuNPs in aqueous solutions for one-pot, without any toxic additives protecting nanoparticles from agglomerating. The obtained AuNPs can keep stable for a long time. The UV-Vis absorption spectra for the formation of AuNPs at different reaction conditions were observed by a model UV-2450 spectroscopy. Size and shape of the nanoparticles were obtained by TECNAI G2 FEI F12 instrument. The formation of AuNPs is mainly relative to the concentration of flavonoids. Flavonoids with two or more phenolic hydroxyl group on the B ring are more favorable to reduce AuNPs than those only have one or none phenolic hydroxyl group on the B ring. Four flavonoids(Myr\Quc\Dmy\Tax) can synthesize AuNPs arranged as the dendritic structure with a layer of transparent membranes on the surface of the particles. The well-defined AuNPs reduced by flavonoids occurred under a pH value range from 4 to 8. The number of AuNPs decreased as the pH value increased.2)The antioxidant capacity of flavonoids was to compared by different methods(DPPH. ABTS, ORAC). The relationship of antioxidant activity to the molecular structure of flavoniods were also study. The sequence of obtained antioxidant ability is: Myr>Quc>Dmy>Tax>Kae>Gal.3)Based on Computational approach of quantum chemistry, Some quantum parameters like the Mulliken Charges of Hydroxy atom in the hydroxyls MC are gotted. From geometry, hydroxyl activity, frontier molecular or bital and orbital energy analysis, the most probably reaction sites are decided. The results indicated the sequence of antioxidant activity is:Myr>Quc>Dmy>Tax>Kae>Gal.4)The possible mechanism by flavonoids have contributed to the synthetic process is yet to be the bioreduction of Au(III) to Au(0). The presence of phenolic hydroxyl groups liberate reactive hydrogen that responsible for the conversion of Au3+ to Au0. The flavonoid abosorbed on the surface of AuNPs through covalent bond. Flavonoids can also form hydrogen bond to stabilize the formed AuNPs. The elemental analysis of AuNPs was observed by energy dispersive X-ray spectroscopy (EDX). The reducing capacity of the flavoniods are Myr>Quc>Dmy>Tax>Kae>Gal. To recognize the bio-groups that bound distinctively on gold surface and involved in the synthesis of AuNPs, the flavonoids solution and bio-reduced solution were analyzed by FTIR Nicolet Avatar. From all the assay, we can infer that the interaction of flavonoids with AuCl4- can take place through several points:3’OH/4’OH/5’OH,3OH/4C=O,5OH/4C=O. Phenolic hydroxyls on the B ring is the reaction site. Multiple hydroxyl groups on the B ring confer upon the molecule substantial antioxidant activity, and can also contribute to the formed AuNPs arranged regularly with a layer of transparent membranes on the surface of the particles. A double bond and carbonyl function in the heterocycle of the nuclear structure increases activity by affording a more stable flavonoid radical through conjugation and electron delocalization. Further investigation of the relationship between structure-activity relationships of these flavonoids is extended to build index to choose flavoniods to the formation of AuNPs.