| As a flower with both ornamental and medicinal values,rose contains bioactive substances such as polyphenols,flavonoids,and cellulose.Among them,rose anthocyanin is a natural pigment with brilliant color and p H sensitivity,which can be adjusted to different colors according to demand and has a wide application prospect and market.However,the traditional solvent extraction method for rose anthocyanin has low efficiency and serious pollution.Furthermore,the stability of anthocyanin in light,high temperature and alkaline environment is poor.Therefore,in this study,a green and efficient ultrasound-assisted acidic low eutectic solvent(DES)method was developed for extracting rose hopsin.Moreover,the extracted rose hopsin was modified by lipase to improve stability of rose hopsin.The main contents are as follows.Rose anthocyanin from Hengshui Feng Hua No.1 was extracted by ultrasonic-assisted DES method and traditional extraction solvent ethanol,respectively.The effects of water content,solid-liquid ratio,ultrasonic temperature,time,power,and extraction times on the extraction amount of rose anthocyanin were investigated,and the best process conditions for the extraction of rose anthocyanin were obtained through single-factor experiment: DES(choline chloride-lactic acid)was selected as the best extractant,water content was 30%,material-to-liquid ratio was 1/30 g/m L,ultrasonic temperature was 50 ℃,ultrasonic power was 400 W,and ultrasonic time was 10 min.Under optimal conditions,the accumulation of rose anthocyanin was 8.265 mg/g when DES was used twice repeatedly The extraction amount of anthocyanin by choline chloride-lactic acid DES was 1.73 times higher than that of the traditional solvent ethanol,and the acidic solution played a good color fixation effect on rose anthocyanin and reduced the loss of anthocyanin during the extraction process.In addition,DES can be recycled and reused,which is more efficient and environmentally friendly compared with the traditional extraction method.The NKA-9 macroporous adsorption resin was selected for the purification of rose anthocyanin by comparing the static adsorption and resolution amounts of different resins.The optimum process conditions for dynamic adsorption of NKA-9 resin were determined by single-factor test using the water content of the sample,the concentration of the resolving solution and the p H of the resolving solution as indicators: i.e.,the rose anthocyanin solution with 40% water content was used for the adsorption of the sample,and the 90% ethanol aqueous solution with p H 1.0 was used for the elution of the resolution.Under these conditions,the adsorption rate of rose anthocyanins was 79.98%,desorption rate was 87.15% and the final recovery was 70.55%.The purified rose anthocyanin was analyzed by high pressure liquid-liquid-mass spectrometry with comparing primary and secondary fragment ion analysis.The results showed that the extracted rose anthocyanin mainly contained the following species:centaureidin-3,5-O-biglucoside,paeoniflorin-3,5-O-biglucoside,paeoniflorin-3-O-glucoside,centaureidin-3-O-glucoside,paeoniflorin-3-(5’-rutinoside)-O-glucoside,and felisin.Unlike previous studies,this study detected a significant amount of paeoniflorin fragments in rose at 84.21%.Paeoniflorin-3,5-O-bis-glucoside monomer was present at 65.93%.The stability of rose anthocyanin was improved by acylation modification using lipase.The effects of donor type,reaction temperature,time,amount of enzyme and donor addition on the acylation rate were investigated on the acylation rate.The acylation process was determined by single-factor optimization as follows: 0.25 g of anthocyanin was dissolved in 2.5 m L of pyridine,4 m L of methyl benzoate was added and 400 mg of Novozym 435 lipase was mixed,and the reaction was carried out in a water bath at 50 ℃under negative pressure of 0.09 Mpa for 9 h.The acylation rate was 95.13% under optimal conditions.The stability of rose anthocyanin before and after acylation was studied in terms of light,temperature and p H.The results showed that the acylated rose anthocyanin was stable at 20 ℃ and 40 ℃ after 12 h of incubation under light.Furthermore,the loss of natural anthocyanin was as high as 46.19% at 60 ℃,while the loss of acylated anthocyanin was 11.52%.The loss of acylated anthocyanins was significantly smaller than that of natural anthocyanins,and the acylated anthocyanins were more stable and less likely to be inactivated under high temperature.The results indicated that the loss rate of acylated rose anthocyanin was significantly lower than that of natural anthocyanin.Meanwhile,the loss rate of natural anthocyanin was 23.97%,26.06% and 50.00% under the conditions of light avoidance,natural light and daylight for 12 h.However,the loss rate of acylated anthocyanin was only 0.80%,9.26% and 21.97%.The results exhibited that the loss rate of natural anthocyanin increased with the strengthening of light conditions.It was indicated that natural anthocyanin was unstable under light conditions.Besides,the acylated anthocyanins still showed red shift to high p H solutions,indicating that the acylated anthocyanins have better p H stability.The above results indicated that the acylation of rose anthocyanin could effectively improve its temperature,light and p H stability.The scavenging ability of rose anthocyanin on DPPH and ABTS radicals before and after acylation was investigated.The results showed that as the concentration of natural anthocyanin and acylated anthocyanin increased,their scavenging effects on DPPH and ABTS radicals were enhanced.Moreover,the scavenging ability of acylated rose anthocyanins was significantly higher than that of natural anthocyanins,indicating that acylated anthocyanins have higher antioxidant properties. |
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