Preparation, Analysis Of Anthocyanin Dyes Extracted From Morus Rubra Fruits And Its Dyeing Investigation On Cotton Fabrics

Anthocyanins are flavonoids commonly found in cell sap of flower petals, stems, fruits and leaves, which could be used to produce orange, red, violet and blue colors. Anthocyanins are considered secondary plant metabolites in nature. Researches show that anthocyanins contain strong oxidation resistance, antibacterial property, and can inhibit the growth of inflammation and cancerous cells. However, the application and development of natural anthocyanin dyes in cellulosic fiber dyeing are insufficient due to low substantivity of dyes towards the substrates. In order to solve this problem, graft modificaitons of cotton cellulose were studied and applied in dyeing with natural anthocyanin dyes extracted from mulberry(Morus rubra) fruits with high yields. The dyeing performance of natural anthocyanin dyes on cotton fabrics after chemical modification were significantly improved. Furthermore, antibacterial and oxidation resistance functionality of cotton fabrics were developed besides coloration of the fabrics. The exploitation of functional cotton fabrics dyed with anthocyanin dyes has important application values.Ten anthocyanins and five flavonols in mulberry(Morus rubra) fruits were identified by high performance liquid chromatography with diode array detection coupled to electrospray ionization tandem mass spectrometry(HPLC-DAD-ESI-MS). Among anthocyanins, cyanidin-3-glucoside and cyanidin-3-rutinoside took up more than 90% of the total anthocyanin content in chromatogram. A new quantitative technique for the simultaneous quantification of the individual anthocyanins from the mulberry(Morus rubra) fruit extracts based on the pH differential method and high-performance liquid chromatography with diode array detection is proposed in this paper, which provide a quantitative evaluation for practical production and application.By the graft modification of succinic acid on cotton fabrics, the natural anthocyanin dyes extracted from mulberry(Morus rubra) fruits has been sucessfully used to dye cotton fabrics for the first time, with a dyeing property performance good enough for potential commercial applications. Brilliant red and deep purple are two main shades of cotton fabrics dyed with anthocyanin dyes. Within them, deep purple shade(h* = 313.58°) produced by tin mordanting dyeing is rare in dyed cotton fabrics with natural dyes. The colour fastness to perspiration, crocking, light, and washing of fabric dyed with tin mordanting was found to be acceptable, with a grey scale grade of at least 3. Furthermore, the suitable dyeing parameters for applying anthocyanin pigments on the cotton fabric modified by succinic acid are discovered as: pH value of dyeing bath below 4.0, the dyeing time 40-60 min and the dyeing temperature controlled at 60 ℃ and below. As for home laundering, the shade of dyed cotton fabrics is more stable in neutral soapy solution(pH 7.0-8.0) than in alkaline soapy solution(pH 11.0-12.0), especially modified cotton fabrics with metal mordants.To further improve the substantivity of anthocyanin pigments from mulberry(Morus rubra) fruits onto cotton fabrics, a reactive anionic agent 4-(4,6-dichloro-1,3,5- triazinylamino)-benzenesulfonate was successfully prepared and firstly applied to fabrics, which provide another novel method for natural dyeing of cotton fabrics with anthocyanin dyes from mulberry(Morus rubra) fruits. The dye uptakes of anthocyanin dyes onto cotton fabrics modified with anionic agent were greatly improved. Dyed cotton fabrics had a shade of brilliance and saturation red. The brilliance and saturation red shade of cotton fabrics provided is an important supplement to the red line of natural dyes in the dyeing of cotton fabrics.Pseudo first order and pseudo second order kinetics models were used to study the adsorption kinetics of anthocyanin pigments on cotton fibers. Nernst, Freundlich and Langmuir isotherms were used to simulate the thermodynamic performances of anthocyanin pigments on cotton fibers. The adsorption kinetics results indicated that the adsorption kinetics of anthocyanin pigments onto cotton fibers followed the pseudo second order kinetics model with higher regression coefficient(R2 > 0.98). The isotherm studies indicated that the adsorption of anthocyanin pigments onto anionic cotton followed the combination of Langmuir and Freundlich isotherms. Meanwhile, the adsorption of anthocyanin pigments onto control cotton followed the Nernst isotherm. The Arrhenius activation energies(Ea) of 120.73 or 78.26 kJ/mol indicated that the adsorption of anthocyanin dyes onto cotton fabric may be a chemisorption process.Antibacterial activity and DPPH scavenging activity of mulberry(Morus rubra) fruit extract were also studied. The results indicated that the mulberry(Morus rubra) fruit extracts exhibited high antibacterial and antioxidant activities, which were retained when applied on cotton fabrics. Although the antibacterial and antioxidant activities of the dyed fabrics deceased after repeated washings, the fabrics retained mostly properties after 5 cycles of washing. Mordanting with metal salts had a positive effect on the antibacterial and antioxidant activities of dyed fabrics evaluated after repeated washings.In addition, the ultrasound extraction process of mulberry anthocyanins and its efficiency are analyzed and optimized. A method base on color index is established to describe the stabilities of anthocyanin pigments from mulberry(Morus rubra) fruit and its chelation with metal ions. Thus, a solid foundation is established for quantitative evaluation for the natural anthocyanins pigment in textile application.