Research On The Material Basis Of Antibacterial Function Of Apocynum Fiber And The Binding Mechanism Of Natural Polyphenolic Compounds And Fibers

Apocynum venetum L.(A.venetum)fiber has been proven to possess significant antibacterial activity,but as of now,no conclusive interpretations regarding antibacterial compounds that are responsible for this effect has been reported.In this article,we propose an “insoluble antibacterial substances deposition” mechanism from the perspective of the transformation behavior of antibacterial bioactive ingredients in bast during degumming process and performed a preliminary verification.The mechanism of polymerization of polyphenols in A.venetum under degumming conditions was suggested.A novel fabric finishing strategy was developed based on polymerization of natural compound.(1)Changes in molecular structure and antibacterial properties of polyphenols in the bast of A.venetum during the two processes of chemical degumming and bio-chemical degumming were investigated by developing phloem cell in vitro simulation systems of degumming.The origin of antibacterial functionality of A.venetum fiber was revealed.The study showed that water-soluble flavonoids and their mixtures with tannins can react to form red-brown precipitates with more complex chemical structures under the high temperature and strongly alkaline chemical degumming conditions.These substances were the reaction products of polyphenols polymerization and exhibited greatly amplified antibacterial activity in comparison to parent polyphenols.The second derivative infrared and Raman spectroscopy showed the presence of these insoluble polyphenols derivatives in A.venetum fiber after degumming.This may be the reason why A.venetum fiber possesses antibacterial property.(2)Quercetin was selected as a model compound of flavonoids in A.venetum bast to explore the chemical reaction pathway undergoing chemical degumming process.Mechanism of evolution of flavonoids in A.venetum under this condition was elucidated.Results showed that quercetin undergone significant structural changes after strongly alkaline treatment at high temperature.Six new compounds were identified from quercetin derivatives by MALDI-TOF spectrometry analysis,two of which were polymers.It is speculated that quercetin undergoes both cleavage and polymerization reactions during the chemical degumming process.(3)A clean and efficient one-bath dyeing and finishing method of protein fiber with natural flavonoids based on in-situ polymerization and covalent fixation of A.venetum flavonoids on fiber was designed.Results showed that the wool fabric dyed and treated with A.venetum flavonoids had deep color strength and good color fastness to rubbing and soaping.The finishing process did not cause obvious damage to the fabric.The treated wool fabric showed inhibition up to 82.8% in S.aureus and55.4% in E.coli.