LU502460B1 - Preparation of porphyra haitanensis polysaccharide with low molecular weight - Google Patents

Abstract

A preparation method of Porphyra haitanensis polysaccharide with low molecular weight comprises: using self-made P. haitanensis polysaccharide as raw material, under the condition of ultrasonic wave, adding 30 percent of 6 percent -10 percent hydrogen peroxide to the polysaccharide solution, controlling the reaction temperature at 55 degrees Celsius-75 degrees Celsius, and degrading for 1-3 h; then, dialyzing the degraded polysaccharide product with a 3 kDa dialysis bag, concentrating it under reduced pressure, precipitating it with 5 times of 95 percent ethanol, and freeze-drying it to obtain a low molecular weight P. haitanensis polysaccharide product with a molecular weight of about 200 kDa. The method is simple, convenient and rapid, can obtain P. haitanensis polysaccharide degradation products with concentrated molecular weight distribution and good uniformity. On the basis of retaining the structure of raw polysaccharide, the product also increased the content of total sugar and sulfate groups, and was further purified.

Description

DESCRIPTION LU502460

PREPARATION OF PORPHYRA HAITANENSIS POLYSACCHARIDE WITH LOW MOLECULAR WEIGHT

TECHNICAL FIELD The invention relates to a preparation method of Porphyra haitanensis polysaccharide with low molecular weight, belonging to the technical field of research and development of marine bioactive substances.

BACKGROUND Porphyra haitanensis is an important economic red alga in China, mainly distributed in Zhejiang, Fujian, and Guangdong provinces. Porphyra haitanensis has rich nutritional value, and its polysaccharide accounts for about 20-40%, which is mainly composed of agarobiose repeating units connected with B-(1—3)-D-galactose and a-(1—4)-3,6-endo-ether-L-galactose. It has many physiological functions such as oxidation resistance, blood glucose reduction, anti-tumor, anti-bacteria and anti-virus, and great application prospect in the fields of health-care food, marine medicine, cosmetic, etc.

However, the biological properties of many polysaccharides were limited owing to their large molecular weight, complex structure, poor solubility and high viscosity. It was reported that the polysaccharides with high molecular weight cannot easily span cell membrane barriers, thus, restricting the absorption of polysaccharides in body and their applications. Studies have shown that the degradation of polysaccharides by appropriate methods to obtain low molecular weight fragments is beneficial for biological digestion, absorption and utilization, and can effectively reduce the antigenicity and toxic side effects. For example, low molecular weight heparin has better biological activity. It was reported that polysaccharides derived from P. haitanensis with relative molecular weight of 100-200 kDa had the strongest antioxidant activities. Notably, polysaccharides with molecular weight of 5-10 kDa have no activities. Therefore, degradation of P. haitanensis polysaccharide by appropriate methods is the key point to give full play to its activity.

Nowadays, the preparation methods of low molecular weight P. haitanensis polysaccharide mainly include chemical, physical and enzymatic methods. Each degradation methods have the following disadvantages:

1. Chemical degradation method LU502460 The efficiency of chemical degradation is high, but it is easy to destroy the structure and composition, and the homogeneity of the product is poor. Moreover the by-products pollutes the environment greatly and is not easy to remove. Chemical degradation methods mainly include acid degradation and alkali degradation, among which: under acidic conditions, the molecular weight distribution of P. haitanensis polysaccharide degradation products is difficult to control, the dispersion coefficient of the products is large, and the content of sulfate groups changes greatly. Under alkaline conditions, a large number of sulfate groups of P haitanensis polysaccharide often fall off, which affects the activity of polysaccharide products.

2. Physical degradation method Physical degradation is simple and less polluting, mainly including ultrasonic and microwave degradation methods. However, this method has high energy consumption, high requirements for instruments and equipment, and small sample processing capacity. Therefore, it is not conducive to industrial production.

3. Enzymatic hydrolysis The advantages of biodegradation method is not only mild in conditions and easy to control in molecular weight, however, the enzyme preparation is expensive, easy to inactivate and the specific enzyme is difficult to obtain, which makes this method unable to be popularized and applied.

The ultrasonic-assisted hydrogen peroxide degradation method used in this experiment belongs to free radical degradation, it has not been reported in the application of degradation of P haitanensis polysaccharide.

SUMMARY Aiming at the shortcomings of the present degradation methods of P haitanensis polysaccharide, the present invention provides a preparation method of P haitanensis polysaccharide with low molecular weight. The preparation method is a free radical degradation method, which has the advantages of high degradation efficiency, simple process and low cost. The obtained product has the same characteristic structure as the raw polysaccharide, and is not accompanied by other by-products. In addition, this method can further purify polysaccharide in the degradation process, and its sulfate group content and polysaccharide content are increased.

In addition, the molecular weight of degradation products is concentrated, the dispersiddJ502460 coefficient is small, and the molecular weight range can be controlled. More importantly, this degradation method can retain the activity well, and the antioxidant activity of P. haitanensis polysaccharide degradation products has been effectively improved compared with the raw polysaccharide.

The task of the invention is realized by the following technical scheme: a preparation method of P. haitanensis polysaccharide with low molecular weight is developed. The method takes self-made P. haitanensis polysaccharide as raw material, and the specific method includes the following steps: (1) Accurately weighing P. haitanensis polysaccharide powder, heating and dissolving in distilled water, and uniformly stirring to prepare P. haitanensis polysaccharide solution; (2) Adding 6%-10% of 30% hydrogen peroxide into the polysaccharide solution under the condition of ultrasonic assistance; (3) Controlling the temperature of the reaction system at 55°C-75°C and the degradation time at 1-3 h; (4) After the reaction, adjusting the pH value of the solution to neutral with 0.01 mol/L NaOH, and dialyzing the reaction solution to remove the residual hydrogen peroxide and small molecular impurities.

(5) Concentrating the dialysate in step (4) under reduced pressure, then precipitate the concentrated solution with 5 times volume of alcohol, placing it in a refrigerator for 12 h, centrifuging at 14000 r/min, and freeze-drying the precipitate to obtain the low molecular weight P. haitanensis polysaccharide product.

The raw material of polysaccharide with a molecular weight of larger than 670 kDa is extracted from P. haitanensis by using hot water bath.

In step (1), the concentration of polysaccharide solution is 5 mg/mL.

In step (2), the ultrasonic-assisted condition is 40 kHz, the addition amount of 30% hydrogen peroxide is 6%-10%, and the volume fraction of hydrogen peroxide is controlled in the degradation reaction liquid system, so that the molecular weights of P haitanensis polysaccharide products are different.

In step (3), the temperature of the degradation reaction system is controlled at 55-75°C.

In step (3), the controlled degradation reaction system time is 1-3 h, and the reaction time k$/502460 about 1.5 h, so that the molecular weight of polysaccharide degradation product is about 400 kDa.

In step (3), the controlled degradation reaction system time 1s 1-3 h, and the reaction time 1s about 2.5 h, so that the molecular weight of polysaccharide degradation product is about 200 kDa.

In step (3), the dialysis conditions are: 3 kDa dialysis bag, tap water dialysis for 2 days, distilled water dialysis for 1 day.

In step (5), the concentration condition is 55°C rotary evaporation concentration to 1/4 volume, the alcohol precipitation condition 1s 5 times the volume of 95% ethanol precipitation, and it is placed in the refrigerator for 12 h and centrifuged at 14000 r/min; the freeze-drying conditions are that the precipitate is pre-frozen at -80°C for 1 day and freeze-dried at -50°C for 1 day.

Compared with that prior art, the invention has the advantages that: As the preparation method of the low-molecular-weight P. haitanensis polysaccharide of the invention utilizes the combined degradation of ultrasonic waves and hydrogen peroxide, among them, ultrasonic degradation mainly causes the glycosidic bond to break randomly through the mechanical effect and thermal effect generated by ultrasonic waves, but the degradation degree is low; the degradation of hydrogen peroxide mainly captures the H atom on the glycosidic bond of polysaccharide through the formed active free radicals, which makes it break, and the degradation degree is high; when ultrasonic is used to degrade hydrogen peroxide, there is a synergistic effect between them. On the one hand, the "cavitation" of ultrasonic makes the solution highly homogeneous, and the polysaccharide molecules are fully stretched, which increases the contact opportunity between glycosidic bond and oxidant. On the other hand, ultrasonic wave can increase the energy of P. haitanensis polysaccharide and hydrogen peroxide, promote the ionization of hydrogen peroxide to produce a large number of highly oxidizing -OH, -O2H and -H, accelerate the oxidative rupture of polysaccharide molecular chains, and make the degradation of polysaccharide higher and faster. Therefore, the preparation method has the advantages of high degradation efficiency, simple process, low cost, and easy separation and removal of excess hydrogen peroxide. In addition, the invention can effectively control the molecular weight of degradation products by controlling the concentration and time of hydrogédJ502460 peroxide in the degradation reaction system. The degradation product obtained by the method of the invention has the same characteristic structure as the raw polysaccharide, and is not accompanied by the generation of other by-products. In addition, this method can further purify polysaccharide in the degradation process, and its sulfate group content and polysaccharide content are increased, and its water solubility is improved. Due to the bleaching effect of hydrogen peroxide, the polysaccharide sample became pure white powder. In addition, the molecular weight of degradation products is concentrated and the dispersion coefficient is small. More importantly, this degradation method can retain the activity well, and the antioxidant activity of P. haitanensis polysaccharide degradation products has been effectively improved compared with the raw polysaccharide. The method of the invention has large treatment capacity, and is beneficial to industrial production and large-scale popularization.

BRIEF DESCRIPTION OF THE FIGURES The figures of the invention are further explained as follows: Fig. 1 shows the ultraviolet full-wavelength scanning spectrum of Porphyra haitanensis polysaccharide.

Fig. 2 shows the GPC chart of Porphyra haitanensis polysaccharide under different degradation conditions.

Fig. 3 shows the GPC chart of PP and LPP before and after degradation of Porphyra haitanensis polysaccharide.

Fig. 4 shows the infrared spectra of PP and LPP before and after degradation of Porphyra haitanensis polysaccharide.

DESCRIPTION OF THE INVENTION The invention is further illustrated by the following examples, but the scope of protection of the invention is not limited to the following examples.

The extraction examples of Porphyra haitanensis polysaccharide of the invention are as follows: Take 100 g P. haitanensis, crush it, sieve it with 40 mesh sieve, add 1000 ml of 95% ethanol, put it in an ultrasonic cleaner to help degrease and remove small molecular pigments for 1 h, filter it, and take the filter residue, dry it in an oven to get light gray P. haitanensis dry powder,

take the dry powder, and put it in a water bath for 3 h with the ratio of material to liquid of 1: 400502460 add 0.05% papain to hydrolyze protein in crude polysaccharide solution at 55°C for 3 h, centrifuge, put the polysaccharide solution into a 7 kDa dialysis bag for dialysis with running water for 2 days and distilled water for 1 day, after the polysaccharide solution is properly concentrated, add 4 times the volume of absolute ethanol, and stir while adding; standing overnight, centrifuging to obtain precipitate, vacuum drying for 24 h, ultrafine grinding the extract to obtain P. haitanensis polysaccharide (PP), drying and preserving. The purity of the product is verified by ultraviolet full-band scanning as shown in Figure 1.

The low molecular weight PR haitanensis polysaccharide of the invention is prepared by taking the P. haitanensis polysaccharide as raw materials, and the specific examples are as follows: Embodiment 1 Accurately weigh P. haitanensis polysaccharide, prepare 5 mg/mL sugar solution, add 10% hydrogen peroxide by volume, mix well, react at 65°C, control different degradation time, cool the reaction solution to room temperature, adjust the pH value of the solution to neutral with 0.01 mol/L NaOH, dialyze with 3 kDa dialysis bag for 2 days and distilled water for 1 day; rotate and evaporate the dialysate to 1/4 of its original volume, then precipitate it with 5 times of 95% ethanol, place it in a refrigerator for 12 h, centrifuge at 14000 r/min, pre-freeze the precipitate at -80°C for 1 d, and then dry it in a vacuum freeze dryer for 1 d to obtain samples PP-1, PP-2 and PP-3. (Note: The salicylic acid method is used to test whether the hydrogen peroxide is removed).

The determination method of molecular weight is: HPGPC method; differential refractive light detector; 0.2 mol/L sodium sulfate; flow rate: 0.7 mL/min; column temperature: 40°C; sample volume: 10 pL; the molecular weight change of each sample is shown in Fig. 2, and the physical and chemical properties are shown in Table 1.

Table 1 Physical and chemical parameters of Porphyra haitanensis polysaccharide raw LU502460 material PP and the products PP-1-3 Polysac Total Protein ~~ Sulfuric 3,6-Endoet Relative Reten Molecu charide sugar (%) acid her viscosity tion lar samples (%) group Galactose time weight (%) (%) /kDa PP 90.80+0. 7.13+0. 11.310. 12.63+0.45 5.8603 14.74 >67000 77 21 88 1 0 0 PP-1 90.99+0. 5.9240. 12.780. 9.794066 4.74+0.0 15.19 399894 18 06 61 6 8 PP-2 9512+0. 4.0740. 14870. 8.62+0.52 3.6700 15.51 237113 31 23 16 9 8 PP-3 9629+0. 3.2240. 17.480. 6.780.07 3.50+00 15.52 235835 76 89 28 7 4 PP: PR haitanensis polysaccharide raw material; PP-1: degraded for 1.5 h; under the set conditions; PP-2: degraded for 2 h under the set conditions, PP-3: degraded for 2.5 h under the set conditions.

Embodiment 2 Taking the scavenging ability of P. haitanensis polysaccharide to DPPH free radical as an index, P haitanensis polysaccharide with higher activity was prepared by degradation under the conditions of different polysaccharide solution concentration, hydrogen peroxide addition, temperature and reaction time.

After cooling the reaction solution to room temperature, adjust the pH value of the solution to neutral with 0.01 mol/L NaOH, dialyze with 3 kDa dialysis bag running water for 2 days and distilled water for 1 day; concentrate the dialysate to 1/4 of the original volume, then precipitate with 5 times of 95% ethanol, centrifuge in refrigerator for 12 h at 14 000 r/min, pre-freeze the precipitate at -80°C for 1 d, and then dry it in vacuum freeze dryer for 1 d to obtain polysaccharide sample LPP with strong antioxidant activity. Compared with PP, LPP has better DPPH scavenging effect. Through logarithmic fitting, the ICso value of PP was 5.81+0.24 mg/mL, and after degradation, the ICso value of LPP decreased to 1.71+0.36 mg/mL, which obviously reflected that the scavenging effect of LPP on DPPH was higher than that of PP. The molecular weight change is shown in Fig. 3, and the infrared spectrum is shown in Fig. 4.

Referring to the physical and chemical parameters of P. haitanensis polysaccharide rakd502460 material PP and products PP-1-3 in Table 1, it shows that with the degradation, the total sugar content of P. haitanensis polysaccharide increases and it is further purified. The content of sulfuric acid groups increased obviously, and the degradation exposed the active groups. The smaller the molecular weight, the more serious the exposure was. The degradation of 3,6-endo-galactose has a significant effect, indicating that the sugar ring on the sugar chain may be attacked during degradation.

See the ultraviolet full-wavelength scanning spectrum of P. haitanensis polysaccharide in Figure 1. There are no characteristic absorption peaks at 260 nm and 280 nm, indicating that the polysaccharide has no nucleic acid and protein impurities, and its purity is high.

See Fig. 2 GPC chart of P. haitanensis polysaccharide under different degradation conditions. In the initial stage of degradation (within 2 hours), the free radicals generated by the system make the degradation reaction proceed rapidly, which is mainly related to the relatively large molecular weight of the polysaccharide and the exposure of more degradation sites at the beginning.

Referring to the GPC chart of PP and LPP before and after degradation of P. haitanensis polysaccharide in Fig. 3, the molecular weight of P haitanensis polysaccharide PP is greater than 670 kDa, the weight average molecular weight Mw of degradation product polysaccharide LPP is 205198 Da, the number average molecular weight Mn is 117088 Da, the peak molecular weight Mp is 235835 Da, the viscosity average molecular weight Mz is 306754 Da, and the dispersion coefficient is 1.752512, which indicates that the degraded polysaccharide LPP is uniform, the long and short chains are evenly distributed, and the purity is high.

See Fig. 4 for infrared spectra of PP and LPP before and after degradation of P. haitanensis polysaccharide. The characteristic absorption peak of PP still exists after degradation, the basic types of functional groups have not changed, and the basic structure and active groups of polysaccharides have not been destroyed. The strong absorption peak at about 3420 cm 7! is the telescopic vibration of “OH. C-H strong absorption peak was around 2933 cm“. C=0 elastic vibration absorption peak is around 1630 cm”!. The C-O absorption peak was at 1074 cm-1, and the weak absorption peak at about 933 cm”! was the characteristic absorption peak of 3,6- internal ether galactose. About 128 cm”! and 810 em”! are characteristic absorption of sulfate groups: about 1228 cm”! is O=S=0 asymmetric stretching vibration, about 810 cm“! is C-018J502460 stretching vibration connected to primary hydroxyl groups, and the connection position of sulfate groups is C-6. About 91 cm”! is B-D-galactose, and 775 cm! may be symmetric stretching vibration of a-pyran ring.

The above examples are only partial examples of the present invention, but they are not taken as limitations on the scope of protection of the present invention. Any improvements and variations based on the concept of the present invention fall within the scope of protection of the present invention, and the specific scope of protection is subject to the claims.

Claims (10)

CLAIMS LU502460

1. À preparation method of Porphyra haitanensis polysaccharide with low molecular weight, characterized in that P haitanensis in Raoping, Guangdong Province is used as raw material, and P. haitanensis polysaccharide powder is prepared by ultrasonic-assisted 80% ethanol removal, boiling water extraction for 3 h—, enzymolysis protein by papain, —7 kDa dialysis for impurity removal, alcohol precipitation and freeze-drying.

2. The preparation method of low molecular weight P. haitanensis polysaccharide according to claim 1, characterized in that the method takes self-made P. haitanensis polysaccharide as the raw material and comprises the following steps: (1) accurately weighing P haitanensis polysaccharide powder, heating and dissolving in distilled water, and uniformly stirring to prepare P. haitanensis polysaccharide solution; (2) adding 6%-10% of 30% hydrogen peroxide into the polysaccharide solution under ultrasonic assistance; (3) controlling the temperature of the reaction system at 50°C-70°C and the degradation time at 1-3 h; (4) after the reaction, adjusting the pH value of the solution to neutral with 0.01 mol/L NaOH, and dialyzing the reaction solution to remove the residual hydrogen peroxide and small molecular impurities; (5) concentrating the dialysate in step (4) under reduced pressure, then precipitating the concentrated solution with 5 times volume of alcohol, placing in a refrigerator for 12 h, centrifuging at 14000 r/min, and freeze-drying the precipitate to obtain the low molecular weight P. haitanensis polysaccharide product.

3. The preparation method of low molecular weight P. haitanensis polysaccharide according to claim 2, characterized in that the raw material of P. haitanensis polysaccharide is a hot water-extracted P. haitanensis polysaccharide with a molecular weight of not less than 670 kDa.

4. The preparation method of low molecular weight P. haitanensis polysaccharide according to claim 2, characterized in that in step (1), the concentration of P. haitanensis polysaccharide solution is 5 mg/mL.

5. The preparation method of low molecular weight P. haitanensis polysaccharide according to claim 2, characterized in that in step (2), the ultrasonic-assisted condition is 40 kHz, the addition amount of 30% hydrogen peroxide is 6%-10%, and the volume fraction of hydrogé#/502460 peroxide is controlled in the degradation reaction liquid system, so that the molecular weights of P. haitanensis polysaccharide products are different.

6. The preparation method of low molecular weight P. haitanensis polysaccharide according to claim 2, characterized in that in step (3), the temperature of the degradation reaction system is controlled at 55-75C.

7. The preparation method of low molecular weight P. haitanensis polysaccharide according to claim 2, characterized in that in step (3), the controlled degradation reaction system time is 1-3 h; when the reaction time is about 1.5 h, the molecular weight of P. haitanensis polysaccharide degradation product is about 400 kDa.

8. The preparation method of low molecular weight P. haitanensis polysaccharide according to claim 2, characterized in that in step (3), the controlled degradation reaction system time is 1-3 h, and the reaction time is about 2.5 h, so that the molecular weight of P haitanensis polysaccharide degradation product is about 200 kDa.

9. The preparation method of low molecular weight P. haitanensis polysaccharide according to claim 2, characterized in that in step (4), the dialysis conditions are: 3 kDa dialysis bag, tap water dialysis for 2 days, distilled water dialysis for 1 day.

10. The preparation method of low molecular weight P haitanensis polysaccharide according to claim 2, characterized in that in step (5), the concentration condition is at 55°C rotary evaporation concentration to 1/4 volume, the alcohol precipitation condition is 5 times the volume of 95% ethanol precipitation, and it is placed in the refrigerator for 12 h and centrifuged at 14000 r/min; the freeze-drying conditions are as follows: the precipitate is pre-frozen at -80°C for 1 day and freeze-dried at -50°C for 1 day.