Studies On Composition, Property And Applications Of The Pigments From Loropetalum Chinense Var. Rubrum Flower

Although great economic benefits may exist by applying of Loropetalum chinense var.rubrum,however a large amount of the flowers and leaves in annual seedlings have been throwing away.The best microwave extraction conditions of the flower pigment from Loropetalum chinense var.rubrum was using 20%ethanol for 4 min.Seven water-soluble pigment components from the flower were separated by the microwave extraction,followed by organic solvent refining and TLC purification. Among the pigment components,four of them were found red or purple in color, and the other three were basically colorless.According to ultraviolet(UV)-visible light spectral characterization,the red-related colors were mainly characteristics of flavonoids,and identified as two water-soluble pigment monomers:while No.â‘ may be isoflavone,and the No.â‘¡may either be isoflavones or anthocyanidin.The red pigments from the flower were found similar to the pigments of the red leaves of the plant(Nenyehong).Among the eight macro-porous resins,the X-5 macro-porous resin was found more appropriate for the refining and purification of the flower pigments.The largest pigment absorption capacity of the X-5 macro-porous resin(moisture content 70.8%),was 123mg pigments/g-wet-resin. After refining and purification with X-5 macro-porous resin,the color index of the red pigment from Loropetalum chinense var.rubrum flower was found increased from 70.5 to 198.Through the stability study,the results showed that the flower pigments were intolerant to alkaline conditions,and the color change of the pigment solution was typically as anthocyanin's change under different pH conditions.Cu²⁺,Pb²⁺,Fe²⁺, Fe³⁺ ions were the main damage salt ions on the flower's pigments,but the color change in Pb²⁺,Fe²⁺ ions was similar to the color changes of the anthocyanin under the same conditions.The flower pigments were quite stable under heating and UV radiation for a long time.Although the flower pigments were sensitive to reductants, they have a high stability to H₂O₂,citric acid,sodium benzoate and sucrose.The antibacterial property of the flower pigments on Staphylococcus aureus,E. coli and Shigella were also investigated.The results showed that the pigment extracts and their purification products,namely extractsâ… ,extractâ…¡and extractâ…¢all could strongly inhibit the growth and reproduction of the above mentioned bacteria.The maximum antibacterial activity of the pigment extracts on the three tested bacteria was equivalent to inhibitory effect of 0.1 mg/ml Norfloxacin of 0.646, 0.629 and 0.655,respectively.Their MICs of the pigment extracts to the tested bacteria were 0.1g/ml,0.5g/ml and 0.5g/ml of pharmacognosy concentration, respectively.The antibacterial activity of the pigment extracts on the three bacteria was stable in neutral and acidic environment,but decreased when pH >8.In the high-temperature processing and UV radiation treatment,the antibacterial activities of the pigment extracts on the three bacteria were also seen stable.Our data also demonstrated that before the ethyl acetate extraction and equivalent to 6.7mg/L pharmacognosy concentration,the pigment extracts and their refined fluids were able to remove the lipid radical DPPH·to 75%.But after being extracted by the ethyl acetate,the radical elimination efficiency of the pigment was reduced greatly.In summary,biochemical and potential medical functions of the flower pigment of Loropetalum chinense var.rubrum were studied using techniques of extraction,separation,purification and spectral characterization.Remarkable anti-bacterial and anti-oxidative properties of extracted pigments were identified and characterized.