| Pterocarpus macrocarpus is a kind of semi-evergreen arbor belonging to the family Papilionaceae.The national standard GB/T18107-2017 stipulates that it is one of the rosewood,commonly known as Burmese rosewood,distributed in Myanmar,Thailand,Laos,Cambodia,Vietnam and other regions.In this study,the pigment extraction rate was used as a measurement index to explore the best extraction process for the heartwood pigment of Pterocarpus macrocarpus.Compare the adsorption and desorption rate of 10 kinds of macroporous resins to the heartwood pigment,and select the best adsorption resin and process parameters.The pigment composition in the heartwood of Pterocarpus macrocarpus was determined by liquid-phase mass spectrometry.and its anti-oxidation ability and stability were studied.The main research conclusions are as follows:This study found that the heartwood pigment of Pterocarpus macrocarpus was easily solved in alcohol solvents,and its maximum color difference in ethanol solution was 55.15.The heartwood pigment was scanned with a wavelength of 190-1 100 nm,and 486 nm was selected as the measuring wavelength.A standard curve based on the concentration of the heartwood pigment was established,and the pigment concentration was in the range of0.1-3.0 g/L.The pigment components in the heartwood were extracted by ultrasound,and the effects of the ethanol concentration,the ratio of material to liquid and the extraction time on the extraction rate of the heartwood pigment were investigated.The single factor experiment determined the level of each factor for the orthogonal experiment.The influence of ultrasonic assisted extraction on the extraction rate of heartwood pigment was investigated through orthogonal experiment,range analysis and variance analysis,and the optimal process conditions were finally determined: the ethanol concentration was 70%,and the material-to-liquid ratio was 1:30(g/m L),the extraction time is 120 min,and the extraction rate is 23.17%.In the static adsorption process,the best adsorption value of 10 kinds of macroreticular resins for pigments was DA-201.The adsorption capacity and adsorption rate of DA-201 are respectively 10.07 g/L and 80.19%,and the desorption capacity and desorption rate are respectively 7.06 g/L and 70.07%.The analytical conditions are best when the static adsorption p H is 4 and the eluent ethanol volume concentration is 100%.In the dynamic adsorption process,the pigment mass concentration was used as an indicator to explore the influence of different factors on resin purification.The optimal dynamic adsorption conditions were determined as follows: the adsorption flow rate 2.0 m L/min,the mass concentration of the sample solution 2 g/L;The optimum conditions of desorption effect were at the flow rate 1 m L/min and the eluent volume 100 m L.The color value of the purified heartwood pigment increased from 4.76 to 6.45.The chromogenic reaction and infrared spectrometry were used to investigate the pigments.The results showed that the pigments Pterocarpus macrocarpus were flavonoids and its content increased after purification.The purified heartwood pigment was analyzed by ultra-high performance liquid chromatography tandem quadrupole-electrostatic field orbitrap high-resolution mass spectrometer technology,and 10 flavonoids,ketone and alcohol compounds were separated and identified.They are orientin,vitexin,genistein,resveratrol,chrysin,glycitein,isoliquiritin,nocaketone,formononetin,and ketoprofen.The content of glycitein in the heartwood pigment is0.2788mg/g,the content of isoliquiritin is 2.289mg/g,the content of nocaketone is 0.521mg/g,the content of formononetin is 2.140mg/g,and the content of ketoprofen is 0.095mg/g.The ABTS and DPPH method were used to investigate the inoxidizability of the purified heartwood pigment of Pterocarpus macrocarpa.The results showed that the pigment of the heartwood had better antioxidant activity in vitro.Its ability to scavenge ABTS free radicals is higher than Vc.In the range of0.1-0.6g/L,the scavenging ability of heartwood pigments on ABTS free radicals gradually increases,and the scavenging rate is higher than Vc,and the scavenging rate reaches 99.38% at 0.6g/L.But its ability to scavenge DPPH free radicals is lower than Vc;at 0-0.45g/L,the heartwood pigment’s effect on DPPH free radicals gradually increases.At 0.45g/L,the clearance rate was 97.62%,which was equivalent to the effect of Vc.At the same time,the stability of the heartwood pigment was explored.The results showed that low temperature conditions are beneficial to the preservation of heartwood pigments,and the pigments are unstable when the temperature is higher than 60℃ for a long time.When the heartwood pigment is exposed to ultraviolet light,the chromophore group of the flavonoids is unstable,which causes the absorbance value of the pigment to decrease and the color changes from red to lighter.Therefore,ultraviolet light has a certain damage effect on the pigment.The stability of heartwood pigment in acidic environment is better than alkaline environment.The weakly oxidizing metal ions have a certain color enhancement effect,and the highly oxidizing metal ions affect the color rendering effect of the pigment.After research,the optimal extraction process and macroreticular resins purification process for the heartwood pigment of Pterocarpus macrocarpus were determined;The chemical composition of the heartwood pigment was identified,and its antioxidant and stability were explored.The results show that the pigment from the heartwood of Pterocarpus macrocarpus had a higher extraction rate under ultrasonic-assisted extraction,and its main components were flavonoids,ketones,alcohols,etc.,which had good antioxidant activity and stability.This research provides a preliminary exploration for the utilization of Pterocarpus macrocarpus resources,and also established the foundation for the formation mechanism of heartwood and sapwood. |
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