A small molecule antioxidant from biomass, its preparation method and applications

Abstract

The present invention belongs to the technical field of antioxidants, and particularly relates to a biomass small molecule antioxidant, a preparation method thereof and an application. Weigh ethyl cyanoacetate and biomass aldehyde, dissolve them in an organic solvent, then add 1 - 2 drops of base, and stir and react at 25 - 60 °C for 6 - 24 h to obtain a light yellow liquid; add the obtained liquid to dichloromethane for dissolution, wash with saturated sodium bisulfite solution and dry with anhydrous magnesium sulfate, and then filter; concentrate and dry the obtained filtrate to obtain the antioxidant. The biomass small molecule antioxidant synthesized by the present invention has a strong ability to scavenge DPPH free radicals and extremely strong antioxidant activity. At the same time, the antioxidant activity of this antioxidant is little affected by temperature and shows good stability at high temperatures. The antioxidant activity of this antioxidant is little affected by pH value and is effective within a relatively wide pH range.

Description

Technical Field

[0001] The present invention belongs to the technical field of antioxidants, and particularly relates to a biomass small molecule antioxidant, a preparation method thereof, and an application thereof. Background Art

[0002] In the food field, antioxidants refer to food additives that can prevent or delay food oxidation, improve food stability, and extend the storage period. In the pharmaceutical field, antioxidants refer to substances that can help capture and neutralize free radicals, thereby removing the damage of free radicals to the human body. The redox reactions that occur naturally and continuously in the human body play a crucial role in the control of the human metabolic system. A large amount of relevant data shows that molecules can gain or lose electrons and be converted into free radicals. Free radicals are very reactive because they contain unpaired electrons. Free radicals are harmful compounds produced in the oxidation reaction of the human body. They have strong oxidizing properties and can damage the tissues and cells of the body, thereby causing chronic diseases and aging effects. The harms of free radicals to the human body include aging, atherosclerosis, cerebral thrombosis, reperfusion injury of the brain, Parkinson's disease, cataract, skin cancer, inflammatory diseases such as rheumatoid arthritis, diabetes, etc. Research has found that antioxidants can terminate or prevent the formation of free radicals and protect cells from oxidative stress by supplying hydrogen or electrons to free radicals. Humans have a long history of using antioxidants. As early as in ancient China before Christ, there were records of drinking green tea (containing natural antioxidant tea polyphenols). Antioxidants have been widely used in many fields such as atherosclerosis, diabetes, and kidney diseases. Currently, antioxidants are mainly used in industrial production, food processing and storage, production and storage of cosmetic daily necessities, etc. They are almost everywhere, widely used, and have a large usage amount.

[0003] Therefore, there is an urgent need for a preparation method and application of a biomass small molecule antioxidant that is less affected by external conditions and has strong antioxidant activity. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a biomass small molecule antioxidant, a preparation method thereof, and an application thereof, so as to solve the problems of high antioxidant dosage, great influence by external conditions, and low antioxidant activity in the existing technology.

[0005] To achieve the above purpose, the present invention adopts the following technical scheme: A biomass small molecule antioxidant has the structure shown in formula Ⅰ below.

[0006]

[0007] A preparation method of a biomass small molecule antioxidant.

[0008] Using ethyl cyanoacetate and biomass aldehyde as raw materials, under the action of an alkali catalyst, a small molecule antioxidant is obtained through a reaction. The reaction formula is as follows.

[0009]

[0010] Further, the specific preparation steps include:

[0011] Weigh ethyl cyanoacetate and biomass aldehyde, dissolve them in an organic solvent, then add 1 - 2 drops of base, and stir and react at 25 - 60 °C for 6 - 24 h to obtain a light yellow liquid;

[0012] Add the obtained liquid to dichloromethane for dissolution, wash it with saturated sodium bisulfite solution and dry it with anhydrous magnesium sulfate, then filter; concentrate and dry the obtained filtrate to obtain the antioxidant.

[0013] Further, the biomass aldehyde is one of carvone, citronellal, hydroxycitronellal, citral, furfural, benzaldehyde, vanillin, cinnamaldehyde.

[0014] Further, the base catalyst is 0.5% - 1% of the molar amount of ethyl cyanoacetate, and the base catalyst is one of 1,8 - diazabicycloundec - 7 - ene, pyridine, dimethylaminopyridine, imidazole, 2 - methylimidazole.

[0015] Further, the organic solvent is one of absolute ethanol, dichloromethane, chloroform, dimethylformamide, tetrahydrofuran.

[0016] Further, the molar ratio of ethyl cyanoacetate to biomass aldehyde is 1:1.05 - 1.2.

[0017] An application of a biomass small - molecule antioxidant, and the antioxidant is used for antioxidation.

[0018] Further, the antioxidation step is as follows:

[0019] Dissolve the antioxidant in methanol, then mix the antioxidant methanol solution and the DPPH methanol solution evenly, place it in the dark at room temperature for 30 minutes, measure the absorbance (Abs) at 517 nm using a spectrophotometer, and calculate the DPPH free - radical scavenging activity as the inhibition percentage according to the following formula:

[0020] DPPH scavenging rate (%) = ((Abscontrol - Abssample) / Abscontrol)·100

[0021] Where Abscontrol is the initial absorbance of the DPPH solution, and Abssample is the absorbance of the antioxidant exposed to the DPPH solution.

[0022] Further, the volume ratio of the antioxidant methanol solution to the DPPH methanol solution is 1:1, and the molar ratio is 8:1.

[0023] Advantages of a biomass small molecule antioxidant, its preparation method and application of the present invention:

[0024] The biomass small molecule antioxidant synthesized by the present invention has a strong ability to scavenge DPPH free radicals, is little affected by temperature and pH value, and has extremely strong antioxidant activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a diagram of the antioxidant synthesized by the present invention;

[0026] Figure 2 It is an antioxidant effect diagram of the antioxidant of the present invention;

[0027] Figure 3 It is an NMR diagram of the antioxidant synthesized in Example 7 of the present invention;

[0028] Figure 4 It is an NMR diagram of the antioxidant synthesized in Example 9 of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0029] The following further elaborates on its specific implementation manners in conjunction with the drawings.

[0030] The reagents and instruments in the following examples are all conventional experimental reagents and instruments.

[0031] Example 1:

[0032] A biomass small molecule antioxidant has the following structure shown in Formula I,

[0033]

[0034] A preparation method of a biomass small molecule antioxidant,

[0035] Using ethyl cyanoacetate and biomass aldehyde as raw materials, under the action of an alkali catalyst, a small molecule antioxidant is obtained, and the reaction formula is,

[0036]

[0037] Example 2:

[0038] A preparation method of a biomass small molecule antioxidant includes the following steps:

[0039] Weigh 1.10 g of ethyl cyanoacetate and 1.24 g of carvone, dissolve them in 6 mL of absolute ethanol, then add 1 - 2 drops of 1,8 - diazabicyclo[5.4.0]undec - 7 - ene (DBU), stir and react at 25 °C for 24 h to obtain a pale yellow liquid; add the obtained liquid to dichloromethane for dissolution, wash with saturated sodium bisulfite solution and dry with anhydrous magnesium sulfate, then filter; concentrate and dry the obtained filtrate to obtain ethyl carvone - substituted cyanoacrylate, with a yield of 80%. In this example, the saturated sodium bisulfite solution was specifically used for washing 3 times to remove the reaction residues in the sample. Figure 1 The obtained product is shown in a of.

[0040] Example 3:

[0041] A preparation method of a biomass small - molecule antioxidant, comprising the following steps:

[0042] Weigh 1.42 g of ethyl cyanoacetate and 2.32 g of citronellal, dissolve them in 6 mL of absolute ethanol, then add 1 - 2 drops of DBU, stir and react at 25 °C for 24 h to obtain a pale yellow liquid; add the obtained liquid to dichloromethane for dissolution, wash with saturated sodium bisulfite solution and dry with anhydrous magnesium sulfate, then filter; concentrate and dry the obtained filtrate to obtain ethyl citronellal - substituted cyanoacrylate, with a yield of 80%. In this example, the saturated sodium bisulfite solution was specifically used for washing 3 times to remove the reaction residues in the sample. Figure 1 The obtained product is shown in b of.

[0043] Example 4:

[0044] A preparation method of a biomass small - molecule antioxidant, comprising the following steps:

[0045] Weigh 1.21 g of ethyl cyanoacetate and 2.21 g of hydroxycitronellal, dissolve them in 6 mL of absolute ethanol, then add 1 - 2 drops of DBU, stir and react at 25 °C for 24 h to obtain a pale yellow liquid; add the obtained liquid to dichloromethane for dissolution, wash with saturated sodium bisulfite solution and dry with anhydrous magnesium sulfate, then filter; concentrate and dry the obtained filtrate to obtain ethyl hydroxycitronellal - substituted cyanoacrylate, with a yield of 80%. In this example, the saturated sodium bisulfite solution was specifically used for washing 3 times to remove the reaction residues in the sample. Figure 1 The obtained product is shown in c of.

[0046] Example 5:

[0047] A preparation method of a biomass small - molecule antioxidant, comprising the following steps:

[0048] Weigh 1.33 g of ethyl cyanoacetate and 2.15 g of citral, dissolve them in 6 mL of absolute ethanol, then add 1 - 2 drops of DBU, and stir and react at 25 °C for 24 h to obtain a pale yellow liquid; add the obtained liquid to dichloromethane for dissolution, wash it with saturated sodium bisulfite solution and dry it with anhydrous magnesium sulfate, then filter; concentrate and dry the obtained filtrate to obtain ethyl citral - substituted cyanoacrylate, with a yield of 80%. In this example, the washing with saturated sodium bisulfite solution was specifically carried out 3 times to remove the reaction residues in the sample. Figure 1 The obtained product is shown in d.

[0049] Example 6:

[0050] A preparation method of a small - molecule antioxidant from biomass includes the following steps:

[0051] Weigh 1.25 g of ethyl cyanoacetate and 1.27 g of furfural, dissolve them in 6 mL of absolute ethanol, then add 1 - 2 drops of DBU, and stir and react at 25 °C for 24 h to obtain a pale yellow liquid; add the obtained liquid to dichloromethane for dissolution, wash it with saturated sodium bisulfite solution and dry it with anhydrous magnesium sulfate, then filter; concentrate and dry the obtained filtrate to obtain ethyl furfural - substituted cyanoacrylate, with a yield of 80%. In this example, the washing with saturated sodium bisulfite solution was specifically carried out 3 times to remove the reaction residues in the sample. Figure 1 The obtained product is shown in e.

[0052] Example 7:

[0053] A preparation method of a small - molecule antioxidant from biomass includes the following steps:

[0054] Weigh 1.41 g of ethyl cyanoacetate and 1.59 g of benzaldehyde, dissolve them in 6 mL of absolute ethanol, then add 1 - 2 drops of DBU, and stir and react at 25 °C for 24 h to obtain a pale yellow liquid; add the obtained liquid to dichloromethane for dissolution, wash it with saturated sodium bisulfite solution and dry it with anhydrous magnesium sulfate, then filter; concentrate and dry the obtained filtrate to obtain ethyl benzaldehyde - substituted cyanoacrylate, with a yield of 80%. In this example, the washing with saturated sodium bisulfite solution was specifically carried out 3 times to remove the reaction residues in the sample. The formation of ethyl benzaldehyde - substituted cyanoacrylate was confirmed by nuclear magnetic resonance hydrogen spectrum (1H - NMR). Figure 1 The obtained product is shown in f. Figure 3 The nuclear magnetic resonance hydrogen spectrum of the product is shown in.

[0055] Example 8:

[0056] A preparation method of a small - molecule antioxidant from biomass includes the following steps:

[0057] Weigh 1.12 g of ethyl cyanoacetate and 1.81 g of vanillin, dissolve them in 6 mL of absolute ethanol, then add 1 - 2 drops of DBU, stir and react at 25 °C for 24 h to obtain a pale yellow liquid; add the obtained liquid to dichloromethane for dissolution, wash it with saturated sodium bisulfite solution and dry it with anhydrous magnesium sulfate, then filter; concentrate and dry the obtained filtrate to obtain ethyl vanillin - substituted cyanoacrylate, with a yield of 80%. In this example, the washing with saturated sodium bisulfite solution was specifically carried out 3 times to remove the reaction residues in the sample. Figure 1 The obtained product is shown in g.

[0058] Example 9:

[0059] A preparation method of a small - molecule antioxidant from biomass, comprising the following steps:

[0060] Weigh 1.15 g of ethyl cyanoacetate and 1.61 g of cinnamaldehyde, dissolve them in 6 mL of absolute ethanol, then add 1 - 2 drops of DBU, stir and react at 25 °C for 24 h to obtain a pale yellow liquid; add the obtained liquid to dichloromethane for dissolution, wash it with saturated sodium bisulfite solution and dry it with anhydrous magnesium sulfate, then filter; concentrate and dry the obtained filtrate to obtain ethyl cinnamaldehyde - substituted cyanoacrylate, with a yield of 80%. In this example, the washing with saturated sodium bisulfite solution was specifically carried out 3 times to remove the reaction residues in the sample. The formation of ethyl cinnamaldehyde - substituted cyanoacrylate was confirmed by 1H - NMR (nuclear magnetic resonance hydrogen spectrum). Figure 1 The obtained product is shown in h. Figure 4 The 1H - NMR spectrum of the product is shown in.

[0061] Example 10:

[0062] An application of a small - molecule antioxidant from biomass, wherein the antioxidant is used for antioxidation

[0063] Carry out antioxidant tests on the small - molecule antioxidants from biomass obtained in Examples 2 - 9. The specific test method is as follows:

[0064] Antioxidant activity determination method: Prepare the small - molecule antioxidant from biomass dissolved in methanol. Then mix 1.5 ml of the antioxidant methanol solution (6.67 mM) with 1.5 ml of DPPH solution (methanol solution of 0.83 mM DPPH) evenly. Place the solution in the dark at room temperature for 30 minutes. Then measure the absorbance (Abs) at 517 nm using a spectrophotometer. Calculate the DPPH radical scavenging activity as the inhibition percentage according to the following formula:

[0065] DPPH scavenging rate (%) = ((Abscontrol - Abssample) / Abscontrol)·100

[0066] Where Abscontrol is the initial absorbance of the DPPH solution (without sample), and Abssample is the absorbance of the small molecule antioxidant of biomass when exposed to the DPPH solution.

[0067] The results are as Figure 2 shown. It can be clearly seen from the figure that the color of the solution becomes lighter, indicating that the DPPH free radicals are captured, proving that the sample has excellent antioxidant properties. Among them, A1 corresponds to Example 2, A2 corresponds to Example 3, A3 corresponds to Example 4, B1 corresponds to Example 5, B2 corresponds to Example 6, B3 corresponds to Example 7, C1 corresponds to Example 8, C2 corresponds to Example 9, and C3 is the control group.

[0068] Its antioxidant effect is as follows:

[0069] Table 1 Antioxidant effects of Examples 2-9

[0070]

[0071] This application is a small molecule antioxidant formed based on biomass olefins and a small molecule antioxidant formed by the Knoevenagel reaction of ethyl cyanoacetate and biomass aldehyde under the catalysis of DBU. It is also the first study to extend the Knoevenagel reaction to the preparation of small molecule antioxidants from biomass.

[0072] The above examples are only used to illustrate the technical concept and characteristics of the present invention. The purpose is to enable those of ordinary skill in the art to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method of a biomass small molecule antioxidant, characterized in that: The structure of the antioxidant is shown in the following formula Ⅰ, Using ethyl cyanoacetate and biomass aldehyde as raw materials, under the action of an alkali catalyst, a small molecule antioxidant is obtained through a reaction. The reaction formula is, Specific preparation steps include: Weigh ethyl cyanoacetate and biomass aldehyde, dissolve them in an organic solvent, then add 1 - 2 drops of alkali, and stir and react at 25 - 60 °C for 6 - 24 h to obtain a light yellow liquid; Dissolve the obtained liquid in dichloromethane, wash it with saturated sodium bisulfite solution and dry it with anhydrous magnesium sulfate, then filter; Concentrate and dry the obtained filtrate to obtain the antioxidant; The biomass aldehyde is carvone; The alkali catalyst is 0.5% - 1% of the molar amount of ethyl cyanoacetate; The alkali catalyst is one of 1,8 - diazabicycloundec - 7 - ene, pyridine, dimethylaminopyridine, imidazole, 2 - methylimidazole; The organic solvent is one of anhydrous ethanol, dichloromethane, chloroform, dimethylformamide, tetrahydrofuran; The molar ratio of ethyl cyanoacetate to biomass aldehyde is 1:1.05 - 1.

2.

2. An application of a biomass small molecule antioxidant, and the antioxidant is prepared according to the method described in claim 1, characterized in that: The antioxidant is used for antioxidation; The antioxidation step is: Dissolve the antioxidant in methanol, then mix the antioxidant methanol solution and the methanol solution of DPPH evenly, place it in the dark at room temperature for 30 minutes, measure the absorbance (Abs) at 517 nm using a spectrophotometer, and calculate the DPPH free radical scavenging activity as the inhibition percentage according to the following formula: DPPH scavenging rate (%) = ((Abscontrol - Abssample) / Abscontrol)·100 where Abscontrol is the initial absorbance of the DPPH solution, and Abssample is the absorbance of the antioxidant exposed to the DPPH solution; The volume ratio of the antioxidant methanol solution to the methanol solution of DPPH is 1:1, and the molar ratio is 8:1.

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