A chrysophanic acid-based natural flavor reconstituted molecular tool and a preparation method and application thereof

Abstract

The present application belongs to the technical field of industrial analysis and detection, and provides a chrysophanol-based natural perfume reconstituted molecular tool, a preparation method and application thereof. The method comprises the following steps: mixing a natural perfume solution and a chrysophanol solution to perform a dehydration condensation reaction, and obtaining the chrysophanol-based natural perfume reconstituted molecular tool. The raw material is abundant and belongs to a natural plant extract, the cost is low, the reagent required in the whole process is single, is non-toxic and harmless, and the final yield is also high. The obtained molecular tool has a stable chemical structure, can exist in a complex wax emulsion for a long time, has stable light signal release performance, can effectively release a light signal in a wax emulsion with various pH values, can maintain good light signal output in a long-term irradiation process, has a high viscosity sensitivity coefficient, and has a detection lower limit of viscosity as low as 1.23 cP, is suitable for measuring wax emulsion micro-area viscosity changes, and is helpful to realize rapid, efficient and visual preparation of wax emulsion consistency.

Description

Technical Field

[0001] This invention relates to the field of industrial analysis and testing technology, and in particular to a molecular tool for reconstructing rhein-based natural fragrances, its preparation method, and its application. Background Technology

[0002] Wax additives are important chemical auxiliaries that play a crucial role in coatings, inks, and even surface treatments. These include improving the scratch resistance of wood coatings, enhancing the surface durability of cans, improving the slip properties and abrasion resistance of coiled steel, and improving the friction resistance of digital printing. Among the many types of wax additives, wax emulsions are a product that the industry has been actively promoting in recent years. They are frequently used to protect transparent coatings and improve the abrasion resistance of coating surfaces. Adding only 0.1% to 3.0% can significantly improve the adhesion, durability, appearance, and feel of coatings on tin cans, coiled steel, wood, and packaging, making them an essential component for enhancing the performance of traditional coatings and inks. As a liquid functional coating, wax emulsions mainly consist of wax powder, emulsifiers, and stabilizers. To improve the film-forming properties, covering power, and overall performance of wax emulsions, various thickeners are added to enhance their viscosity and brushing smoothness. When increased flowability is required, the amount of thickener added is significantly reduced, resulting in a substantial decrease in viscosity. Therefore, to effectively improve wax emulsion formulation design and achieve precise customization according to customer needs, viscosity—its key physical parameter—is an indicator that can be used to quickly assess the formulation's process status.

[0003] Emulsion viscosity is a property that reflects a fluid's resistance to deformation or its inability to prevent relative flow between adjacent fluid layers. Traditional methods for emulsion viscosity analysis mostly rely on various viscometers, requiring large sample volumes, lengthy measurement times, and high equipment dependence. Furthermore, the results are macroscopic, easily disrupted by agitation, and the sensitivity to viscosity changes within the micro-regions of the emulsion is not readily apparent, making molecular-level measurements difficult. In industrial analytical testing, photochemical techniques, utilizing molecular tools, can respond to the viscosity of emulsion micro-regions, even observing the release of light signals. This static sensing method can effectively improve the control of wax emulsion viscosity. However, current molecular tools mostly possess complex molecular structures and rely on complex structural designs; few utilize the reconstruction of natural products to prepare molecular tools for measuring the micro-viscosity of wax emulsions. Therefore, providing a molecular tool based on the reconstruction of natural products is of great significance for emulsion formulation design, process improvement, and performance enhancement. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems existing in the prior art and provide a molecular tool for reconstructing rhein-based natural fragrances, its preparation method, and its application.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a molecular tool for reconstructing rhein-based natural fragrances, the structural formula of which is:

[0007]

[0008] This invention also provides a method for preparing the molecular tool for reconstructing the rhein-based natural fragrance, comprising the following steps:

[0009] A natural fragrance solution and a rhein solution were mixed and subjected to a dehydration condensation reaction to obtain the molecular tool for reconstructing the rhein-based natural fragrance.

[0010] Preferably, the natural fragrance is veratral;

[0011] The solvent for the natural fragrance solution is an alcohol solvent, which includes one or more of methanol, ethanol, propanol, isopropanol, n-butanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol and 1,3-butanediol.

[0012] Preferably, the concentration of the natural fragrance solution is 1–50 mol / L.

[0013] Preferably, the solvent for the rhein solution is an alcohol solvent, which includes one or more of methanol, ethanol, propanol, isopropanol, n-butanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol and 1,3-butanediol.

[0014] Preferably, the concentration of the rhein solution is 1–300 mol / L.

[0015] Preferably, the molar ratio of veratral in the natural fragrance solution to chrysophanol in the rhein solution is 1:1 to 100.

[0016] Preferably, the temperature of the dehydration condensation reaction is 20–90°C, and the time of the dehydration condensation reaction is 1–80 h.

[0017] This invention also provides the application of the molecular tool reconstructed from the rhein-based natural fragrance in the micro-area viscosity detection of wax emulsions.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) This invention provides a molecular tool for the reconstruction of rhein-based natural fragrances, which is obtained by one-step conjugation coupling of natural fragrance veratral and natural drug rhein. The required raw materials are abundant and belong to natural plant extracts, which are green, environmentally friendly and inexpensive. The overall application and preparation cost is low, and the reagents required in the whole process are of a single type, non-toxic and harmless, and the final yield is also high. It is suitable for large-scale preparation and conforms to the concept of low-carbon and sustainable development.

[0020] (2) The molecular tool reconstructed from rhein-based natural fragrance provided by the present invention has a stable chemical structure and can exist for a long time in complex wax emulsions. It has stable light signal release performance and can effectively release light signals in wax emulsions of various pH values. It can also maintain good light signal output during long-term irradiation. It also has a high viscosity sensitivity coefficient (x = 0.55) and a detection limit for viscosity as low as 1.23 cP, making it suitable for measuring the viscosity changes in micro-regions of wax emulsions.

[0021] (3) The molecular tool for reconstructing rhein-based natural fragrance provided by the present invention can convert the change in viscosity of wax emulsion micro-regions into light signals, which helps to achieve rapid, efficient and visual formulation of wax emulsion viscosity. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the mechanism of the molecular tool reconstructed from rhein-based natural fragrance in this invention for detecting the viscosity of wax emulsion micro-regions (Turn-off, Turn-on).

[0023] Figure 2 The mass spectrum of DDAD1 in Example 1;

[0024] Figure 3 The NMR spectrum of DDAD1 in Example 1;

[0025] Figure 4 The spectrum of DDAD1 obtained in Example 1 in mixed solutions of different viscosities;

[0026] Figure 5 The spectra of DDAD1 obtained in Example 1 in glycerol solutions of different viscosities are shown.

[0027] Figure 6 This is a linear fitting graph showing the relationship between the optical signal intensity and viscosity of DDAD1 obtained in Example 1;

[0028] Figure 7 The spectrum of DDAD1 obtained in Example 1 in solutions at different pH values;

[0029] Figure 8 The graph shows the photostability test results of DDAD1 obtained in Example 1 in glycerol and purified water;

[0030] Figure 9 The image shows a linear fit plot of the detection lower limit of DDAD1 obtained in Example 1. Detailed Implementation

[0031] This invention provides a molecular tool for reconstructing rhein-based natural fragrances, the structural formula of which is:

[0032]

[0033] This invention also provides a method for preparing the molecular tool for reconstructing the rhein-based natural fragrance, comprising the following steps:

[0034] A natural fragrance solution and a rhein solution were mixed and subjected to a dehydration condensation reaction to obtain the molecular tool for reconstructing the rhein-based natural fragrance.

[0035] In this invention, the natural fragrance is preferably veratral, and the structural formula of veratral is as follows:

[0036]

[0037] In this invention, the solvent of the natural fragrance solution is preferably an alcohol solvent, which preferably includes one or more of methanol, ethanol, propanol, isopropanol, n-butanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol and 1,3-butanediol.

[0038] In this invention, if more than one alcohol solvent is included, the various solvents are preferably mixed in equal volumes.

[0039] In this invention, the concentration of the natural fragrance solution is preferably 1-50 mol / L, more preferably 5-40 mol / L, and even more preferably 10-30 mol / L.

[0040] In this invention, the structural formula of the rhein is as follows: The solvent for the rhein solution is preferably an alcohol solvent, which preferably includes one or more of methanol, ethanol, propanol, isopropanol, n-butanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol and 1,3-butanediol.

[0041] In this invention, if more than one alcohol solvent is included, the various solvents are preferably mixed in equal volumes.

[0042] In this invention, the concentration of the rhein solution is preferably 1-300 mol / L, more preferably 5-250 mol / L, and even more preferably 10-200 mol / L.

[0043] In this invention, the molar ratio of veratral in the natural fragrance solution to chrysophanol in the rhein solution is preferably 1:1 to 100, more preferably 1:2 to 90, and even more preferably 1:5 to 80.

[0044] In this invention, the mixing method is preferably to add the rhein solution dropwise to the natural fragrance solution under stirring conditions to complete the mixing; the stirring temperature is preferably 20-25°C, more preferably 21-24°C, and even more preferably 22-23°C; the stirring speed is preferably 100-1200 r / min, more preferably 500-800 r / min, and even more preferably 600-700 r / min; the dropping rate is preferably 0.5-60 mL / min, more preferably 1-50 mL / min, and even more preferably 3-40 mL / min.

[0045] In this invention, the chemical formula of the dehydration condensation reaction (Knoevenagel dehydration condensation reaction) is:

[0046]

[0047] In this invention, the temperature of the dehydration condensation reaction is preferably 20–90°C, more preferably 30–70°C, and even more preferably 50–60°C; the stirring speed of the dehydration condensation reaction is preferably 100–1600 r / min, more preferably 500–1000 r / min, and even more preferably 800–900 r / min; and the time of the dehydration condensation reaction is preferably 1–80 h, more preferably 20–60 h, and even more preferably 40–50 h.

[0048] In this invention, after the dehydration condensation reaction is completed, the obtained sample is subjected to a first vacuum distillation, extraction, a second vacuum distillation, precipitation, centrifugation and drying in sequence to obtain the molecular tool of the reconstructed rhein-based natural fragrance.

[0049] In this invention, the purpose of the first vacuum distillation is to remove the solvent remaining in the reaction. The pressure of the first vacuum distillation is preferably -0.070 to -0.090 MPa, more preferably -0.075 to -0.085 MPa, and even more preferably -0.080 to -0.082 MPa.

[0050] In this invention, the reagent used for extraction comprises ethyl acetate and water, wherein the volume ratio of ethyl acetate to water is preferably 1 to 10:1, more preferably 2 to 8:1, and even more preferably 3 to 5:1.

[0051] In this invention, after extraction, the collected organic phase is subjected to a second vacuum distillation. The pressure of the second vacuum distillation is preferably -0.070 to -0.090 MPa, more preferably -0.075 to -0.085 MPa, and even more preferably -0.080 to -0.082 MPa.

[0052] In this invention, the precipitation comprises the following steps: mixing the sample obtained from the second vacuum distillation with ethanol, allowing it to stand, and completing the precipitation; the solid content of the resulting solution is preferably 1-50 mg / mL, more preferably 5-36 mg / mL, and even more preferably 10-25 mg / mL; the standing temperature is preferably 5-20°C, more preferably 10-15°C, and even more preferably 12-13°C; the standing time is preferably 1-48 h, more preferably 10-35 h, and even more preferably 18-30 h.

[0053] In this invention, the centrifugation includes the following steps: performing a first centrifugation on the solution obtained from precipitation, taking the precipitate after the first centrifugation, mixing the precipitate with water, performing a second centrifugation, taking the precipitate after the second centrifugation, and repeating the steps of mixing with water and centrifuging; the rotation speed of the first centrifugation is preferably 1000-10000 r / min, more preferably 2000-8000 r / min, and more preferably 4000-6000 r / min; the first centrifugation time is preferably 0.5-8.0 h, more preferably 2.0-6.0 h, and more preferably 4.0-5.0 h; mixing the precipitate with water... The solid content of the mixed solution is preferably 1-30 mg / mL, more preferably 5-26 mg / mL, and even more preferably 10-20 mg / mL; the rotation speed of the second centrifugation is preferably 1000-10000 r / min, more preferably 2000-8000 r / min, and even more preferably 4000-6000 r / min; the second centrifugation time is preferably 0.5-8.0 h, more preferably 2.0-6.0 h, and even more preferably 4.0-5.0 h; the number of repetitions is preferably 0-4 times, more preferably 1-3 times, and even more preferably 2 times.

[0054] In this invention, the precipitate obtained by centrifugation is dried to obtain the molecular tool reconstructed from the rhein-based natural fragrance; the drying temperature is preferably -30 to 0°C, more preferably -25 to -5°C, and even more preferably -20 to -15°C; the drying time is preferably 1 to 60 hours, more preferably 20 to 40 hours, and even more preferably 25 to 30 hours.

[0055] This invention also provides the application of the molecular tool reconstructed from the rhein-based natural fragrance in the micro-area viscosity detection of wax emulsions.

[0056] This invention also provides a method for applying the molecular tool reconstructed from the rhein-based natural fragrance to the micro-area viscosity detection of wax emulsions, comprising the following steps:

[0057] Molecular tools reconstructed from rhein-based natural fragrances were mixed with wax emulsions and then tested.

[0058] In this invention, the concentration of molecular tools in the mixed solution is preferably 5 to 100 μmol / L, more preferably 10 to 80 μmol / L, and even more preferably 20 to 60 μmol / L.

[0059] In this invention, the molecular tool reconstructed from rhein-based natural fragrance is obtained by one-step conjugation coupling of the natural fragrance veratral and the natural drug rhein. It is a pale yellow powder, readily soluble in various common solvents such as paraffin wax, palm wax, beeswax, N,N-dimethylformamide, tetrahydrofuran, and dimethyl sulfoxide. This molecular tool possesses a good alternating conjugated structure, low hygroscopicity, and insensitivity to moisture, making it suitable for long-term storage. Its conjugated structure exhibits different rotational states in emulsion atmospheres of varying viscosities, releasing light signals of varying intensities, thus making the control of wax emulsion viscosity visible. This molecular tool is not easily affected by various components of the wax emulsion, such as Tween 80, stearic acid, Span 60, higher alcohols, and hexadecyltrimethylammonium chloride. It has a wide pH range and a low detection limit, making it particularly suitable for the precise determination of micro-region viscosity changes in wax emulsions.

[0060] In this invention, the molecular tool reconstructed from rhein-based natural fragrance ultimately exhibits a typical chemical structure of alternating single and double bonds. The resulting conjugated structure can rotate freely in a low-viscosity wax emulsion. When irradiated by an external excitation light source, the dissipation of excited-state energy is mainly through mechanical rotation, resulting in a weak or even nonexistent observable optical signal. As the viscosity of the wax emulsion gradually increases, the mechanical rotation of the resulting conjugated structure is suppressed. When irradiated by an external excitation light source, the dissipation of excited-state energy is mainly through radiative transitions, resulting in a stronger observable optical signal. Furthermore, the signal intensity exhibits a typical linear relationship with the logarithm of viscosity. The Hoffmann relation (logI = C + xlogη) holds true. Therefore, a higher observed light signal indicates a thicker wax emulsion with poorer fluidity, but stronger covering power, adhesion, film-forming properties, and coating properties. Conversely, a weaker observed light signal indicates a thinner wax emulsion with stronger fluidity, but stronger leveling, brushing, and spreading properties. Based on this, this molecular tool can act as a molecular switch to identify the physical parameter of micro-area viscosity, serving as an effective monitoring method for wax emulsion viscosity adjustment. The intensity of the released light signal allows for visual monitoring of viscosity adjustment, which is significant for meeting the specific and efficient mixing and brushing needs of different customers. The rhein-based natural fragrance reconstructed molecular tool prepared in this invention can release a strong light signal in the wavelength range of 490–700 nm under an external excitation light source of 440 nm, effectively measuring the micro-area viscosity of the wax emulsion and significantly promoting its viscosity adjustment.

[0061] A schematic diagram illustrating the mechanism of the molecular tool reconstructed from rhein-based natural fragrance in this invention for detecting the viscosity of wax emulsions in micro-regions, as shown below. Figure 1 As shown.

[0062] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0063] Example 1

[0064] 0.33g of veratral was mixed with methanol to obtain a natural fragrance solution with a concentration of 2mol / L; 25.42g of emodin was mixed with methanol to obtain an emodin solution with a concentration of 100mol / L.

[0065] At a temperature of 22℃ and a stirring speed of 600 r / min, a rhein solution was added dropwise to a natural fragrance solution at a rate of 3 mL / min. After the addition was completed, a dehydration condensation reaction was carried out at a temperature of 70℃ and a stirring speed of 1000 r / min for 24 h. After the reaction, the obtained sample was placed in a rotary evaporator and subjected to vacuum distillation at a pressure of -0.085 MPa. Then, extraction was performed (the extraction reagent contained ethyl acetate and water, with a volume ratio of 5:1). After extraction, the obtained organic phase was collected and subjected to vacuum distillation again at a pressure of -0.085 MPa. The obtained sample was then reacted with ethanol. The mixture was stirred until the solid content of the resulting solution was 20 mg / mL, and allowed to stand at 10°C for 18 h to complete precipitation. The precipitated solution was centrifuged in a centrifuge tube at 4000 r / min for 4.0 h. After centrifugation, the precipitate was collected and mixed with water until the solid content of the resulting solution was 10 mg / mL. The mixture was then centrifuged at 4000 r / min for 4.0 h. The precipitate was collected, and the process of mixing with water and centrifuging was repeated twice. The precipitate obtained by centrifugation was dried at -10°C for 30 h to obtain the molecular tool (labeled DDAD1) reconstructed from the rhein-based natural fragrance.

[0066] The DDAD1 prepared in this embodiment was weighed, and the mass of DDAD1 obtained in this embodiment was 0.73g. The yield was calculated, and the yield of DDAD1 obtained in this embodiment was 91%.

[0067] The relative molecular mass and chemical structure of DDAD1 prepared in this embodiment were analyzed, and the mass spectrum of DDAD1 in this embodiment was obtained, as shown below. Figure 2 As shown; the NMR spectrum of DDAD1 in this embodiment is as follows. Figure 3 As shown; from Figure 2 As can be seen from the data, the relative molecular mass of DDAD1 obtained in this embodiment is 402.11033, and the molecular mass of 3-(3,4-dimethoxystyryl)-1,8-dihydroxyanthracene-9,10-dione (C 24 H 18 The theoretical relative mass estimate of O6) is 402.14200, which shows that the obtained product DDAD1 is similar to C. 24 H 18 The relative molecular mass of O6 is consistent; from Figure 3 It can be seen from this that 13C NMR (101MHz, DMSO-d6) δ 188.22, 182.52, 163.10, 160.36, 149.73, 148.21, 140.52, 137.89, 134.58, 133.21, 131.83, 131.09, 128.25, 126.56, 120.80, 119.01, 116.10, 115.02, 112.10, 109.01, 56.38. The carbon skeleton shift in its molecular structure was confirmed, and it can be identified as the target product DDAD1.

[0068] Example 2

[0069] 0.17g of veratral and ethanol were mixed to obtain a natural fragrance solution with a concentration of 1mol / L; 0.25g of rhein and ethanol were mixed to obtain a rhein solution with a concentration of 1mol / L.

[0070] At 20℃ and 100 r / min, a rhein solution was added dropwise to a natural fragrance solution at a rate of 0.5 mL / min. After the addition was complete, a dehydration condensation reaction was carried out at 20℃ and 100 r / min for 80 h. After the reaction, the obtained sample was placed in a rotary evaporator and subjected to vacuum distillation at -0.090 MPa. Extraction was then performed (the extraction reagents included ethyl acetate and water, with a volume ratio of 1:1). After extraction, the obtained organic phase was collected and subjected to vacuum distillation again at -0.090 MPa. The sample was subjected to pressure distillation; then the obtained sample was mixed with ethanol to make the solid content of the mixed solution 1 mg / mL, and allowed to stand at 5 °C for 48 h to complete precipitation; the precipitated solution was centrifuged in a centrifuge tube at a speed of 1000 r / min for 8.0 h, and the precipitate was collected and mixed with water to make the solid content of the mixed solution 1 mg / mL, and then centrifuged at 1000 r / min for 8.0 h; the precipitate obtained by centrifugation was dried at -30 °C for 1 h to obtain the molecular tool (labeled DDAD2) reconstructed from the rhein-based natural fragrance.

[0071] The DDAD2 prepared in this embodiment was weighed, and the mass of DDAD2 obtained in this embodiment was 0.33g. The yield was calculated, and the yield of DDAD2 obtained in this embodiment was 82%.

[0072] The relative molecular mass and chemical structure of DDAD2 prepared in this embodiment were analyzed, and the relative molecular mass of DDAD2 obtained in this embodiment was also 402.11033, and its nuclear magnetic resonance spectrum was consistent with that of Example 1.

[0073] Example 3

[0074] 8.31g of veratral and propanol were mixed to obtain a natural fragrance solution with a concentration of 50mol / L; 1271.2g of rhein and propanol were mixed to obtain a rhein solution with a concentration of 300mol / L.

[0075] At a temperature of 25℃ and a stirring speed of 1200 r / min, a rhein solution was added dropwise to a natural fragrance solution at a rate of 3 mL / min. After the addition was completed, a dehydration condensation reaction was carried out at a temperature of 90℃ and a stirring speed of 1600 r / min for 1 h. After the reaction, the obtained sample was placed in a rotary evaporator and subjected to vacuum distillation at a pressure of -0.08 MPa. Then, extraction was performed (the extraction reagent contained ethyl acetate and water, with a volume ratio of 10:1). After extraction, the obtained organic phase was collected and subjected to vacuum distillation again at a pressure of -0.080 MPa. The obtained sample was then reacted with ethanol. The mixture was stirred until the solid content of the resulting solution was 50 mg / mL, and allowed to stand at 20°C for 1 h to complete precipitation. The precipitated solution was centrifuged in a centrifuge tube at 10000 r / min for 0.5 h. After centrifugation, the precipitate was collected and mixed with water until the solid content of the resulting solution was 30 mg / mL. The mixture was then centrifuged at 10000 r / min for 0.5 h. The precipitate was collected, and the steps of mixing with water and centrifugation were repeated 4 times. The precipitate obtained by centrifugation was dried at 0°C for 60 h to obtain the molecular tool (labeled DDAD3) reconstructed from the rhein-based natural fragrance.

[0076] The DDAD3 prepared in this embodiment was weighed, and the mass of DDAD3 obtained in this embodiment was 16.70 g. The yield was calculated, and the yield of DDAD3 obtained in this embodiment was 83%.

[0077] The relative molecular mass and chemical structure of DDAD3 prepared in this embodiment were analyzed. The relative molecular mass of DDAD3 obtained in this embodiment was also 402.11033, and its nuclear magnetic resonance spectrum was consistent with that of Example 1.

[0078] Performance testing

[0079] 2.01 mg of DDAD1 prepared in Example 1 was dissolved in a certain volume of paraffin to obtain a DDAD1 solution with a concentration of 5 mmol / L. Then, the DDAD1 solution was added to three wax emulsions of different viscosities to obtain mixed solutions of different viscosities (labeled as wax emulsion 1—viscosity 88.3 cP, wax emulsion 2—viscosity 298.2 cP, and wax emulsion 3—viscosity 648.3 cP). The concentration of DDAD1 in each mixed solution was 10 μmol / L. The test was conducted at room temperature with an external excitation light source wavelength of 440 nm. The spectra of DDAD1 obtained in Example 1 in mixed solutions of different viscosities were obtained, as shown below. Figure 4 As shown in Table 1, the test results of the optical signal intensity of mixed solutions with different viscosities are as follows.

[0080] Table 1. Test results of optical signal intensity of mixed solutions with different viscosities.

[0081] Sample Optical signal intensity (au) Viscosity (cP) Wax emulsion 1 2754 88.3 Wax emulsion 2 5495 298.2 Wax emulsion 3 7840 648.3

[0082] Depend on Figure 4 As shown in Table 1, the intensity differences of these three spectra are significant. This is due to the varying consistencies of the three wax emulsions. Specifically, wax emulsion 1 exhibits the lowest light signal intensity, indicating a relatively low viscosity; its viscosity is 88.3 cP. Wax emulsion 2 shows a moderate light signal intensity, indicating a slightly higher viscosity; its viscosity is 298.2 cP. Wax emulsion 3 shows a further increase in light signal intensity, exhibiting a paste-like consistency with a high viscosity of 648.3 cP. These test results demonstrate that the DDAD1 provided in Example 1 can emit light signals of varying intensities to wax emulsions of different consistencies, with a peak wavelength of 550 nm, which is typical green light, thus achieving a visual monitoring effect.

[0083] The viscosity sensitivity test of DDAD1 prepared in Example 1 was performed, specifically including the following steps: Glycerol and water were prepared in different proportions (the mass fraction of glycerol in the glycerol solution was 0%, 10%, 30%, 50%, 70%, and 99%, respectively) to obtain glycerol solutions of different viscosities. DDAD1 was added to each solution to ensure that the concentration of DDAD1 in each solution was 10 μmol / L. The test was conducted at room temperature, with an external excitation light source wavelength of 440 nm. The spectra of DDAD1 obtained in Example 1 in glycerol solutions of different viscosities were obtained, as shown below. Figure 5 As shown. From Figure 5 As can be seen, the intensity of the observable light signal gradually increases with the increase of the mass fraction of glycerol in the solution, reaching the maximum value in the glycerol solution with a mass fraction of 99%, which is up to 32 times higher than that of the pure water system.

[0084] Furthermore, after converting the aforementioned optical signal intensity and solution viscosity into logarithmic functions, they can be fitted to a straight line, which conforms to... -Hoffmann relation, specifically, the linear fitting graph between the optical signal intensity and viscosity of DDAD1 obtained in Example 1, as shown... Figure 6 As shown in Table 2; the logarithmic function values ​​of the optical signal intensity and viscosity of DDAD1 obtained in Example 1 are shown in Table 2 (I 550 This refers to the I value corresponding to a wavelength of 550 nm. Figure 6 As can be seen, the viscosity sensitivity coefficient of DDAD1 is 0.55, and the coefficient of determination is 0.98. The test results show that DDAD1 obtained in Example 1 has high viscosity sensitivity and can be used as a molecular-level tool for sensing the viscosity of wax emulsion micro-regions, providing a fast, efficient, and visualized way to adjust its consistency.

[0085] Table 2 shows the logarithmic function values ​​of the optical signal intensity and viscosity of DDAD1 obtained in Example 1.

[0086] Logarithm of viscosity (logη) 0.01 0.24 0.57 1.03 1.77 2.99 <![CDATA[Logarithm of fluorescence intensity (logI 550 )]]> 2.4 2.52 2.70 2.92 3.47 3.90

[0087] 4.02 mg of DDAD1 prepared in Example 1 was dissolved in paraffin to obtain a 10 mmol / L DDAD1 solution. For testing, the concentration was further diluted to 10 μmol / L with paraffin, and then added to solutions at different pH values ​​to verify its pH sensitivity. The test was conducted at room temperature with an external excitation light source wavelength of 440 nm. The spectra of DDAD1 obtained in Example 1 in solutions at different pH values ​​were obtained, as shown below. Figure 7 As shown. From Figure 7 As can be seen, the fluorescence intensity of DDAD1 does not change much in the pH range of 3 to 12, which is common in wax emulsions. It can exhibit good light signal release stability and is not easily affected by pH fluctuations, making it suitable for use in various wax emulsions with different pH values.

[0088] 0.80 mg of DDAD1 prepared in Example 1 was dissolved in paraffin to obtain a DDAD1 solution with a concentration of 2 mmol / L. For testing, the concentration was diluted to 10 μmol / L and added to water and glycerol respectively. The temperature was set to room temperature, and the external excitation light source wavelength was 440 nm. The change in light signal intensity over 60 min was measured. The photostability test results of DDAD1 obtained in Example 1 in glycerol and purified water are shown in the figure. Figure 8 As shown in Table 3, the photostability test data of DDAD1 obtained in Example 1 in glycerol and purified water are shown in Table 3.

[0089] Table 3. Photostability data of DDAD1 obtained in Example 1 in glycerol and purified water.

[0090] Time / min 0 10 20 30 60 Fluorescence intensity in purified water / au 251.0 248.1 245.2 241.3 234.1 Fluorescence intensity in glycerol / au 7983.0 7980.8 7965.1 7942.2 7916.0

[0091] from Figure 8 As shown in Table 3, DDAD1 maintains good light signal release intensity under continuous external light source irradiation, especially in high viscosity glycerol, where the light signal attenuation is less than 1%. This light signal stability indicates that it is suitable for micro-area viscosity response of wax emulsions and is not significantly affected even under long-term irradiation.

[0092] 1.21 mg of DDAD1 prepared in Example 1 was dissolved in paraffin to obtain a DDAD1 solution with a concentration of 3 mmol / L. For testing, the concentration was diluted to 10 μmol / L, and the solution was added separately to a mixed solution of water and glycerol, which have very low viscosity. The detection limit for viscosity was then tested. The above tests were conducted at room temperature, and a linear fitting graph of the detection limit for DDAD1 obtained in Example 1 was obtained, as shown below. Figure 9 As shown (I) 550 This refers to the I value corresponding to a wavelength of 550 nm. Figure 9 As can be seen from the data, in solutions with extremely low viscosity, the viscosity value of DDAD1 has a good linear relationship with the logarithm of the light signal emission intensity, with a fitting coefficient of determination of 0.99. Based on this linear relationship, the detection limit of DDAD1 is 1.23 cP, indicating that it is quite sensitive to changes in micro-region viscosity and is suitable for the regulation and monitoring of changes in the viscosity of wax emulsions.

[0093] As shown in the above embodiments, this invention provides a molecular tool for reconstructing rhein-based natural fragrances, its preparation method, and its application. This invention involves mixing a natural fragrance solution and a rhein solution, followed by a dehydration condensation reaction to obtain the molecular tool for reconstructing rhein-based natural fragrances. The rhein-based natural fragrance reconstructed molecular tool (DDAD) provided by this invention is a reconstructed combination of a natural fragrance, veratral, and a natural anthraquinone molecule, rhein, through conjugation coupling, exhibiting a structure with alternating single and double bonds. DDAD can exhibit different rotational states in solution atmospheres of varying viscosities, which are then converted into light signals and released, enabling rapid, efficient, and visual detection of the viscosity (thickness / dilution) of wax emulsion micro-regions. Various test results show that the rhein-based natural fragrance reconstructed molecular tool DDAD has a high sensitivity coefficient (x = 0.55), good pH stability, and maintains a good light signal and stable release even in wax emulsions with a wide pH range. Even after prolonged exposure to external light sources, its photostability in both dilute and viscous solutions remains high with minimal attenuation. Furthermore, the DDAD molecular tool reconstructed from natural fragrances exhibits a low detection limit, making it suitable for sensing subtle changes in the viscosity of wax emulsions. Moreover, this molecular tool is prepared via a simple one-step method, without the addition of any toxic catalysts or heavy metal ions, making it environmentally friendly and easy to operate. It also boasts a high yield, with abundant and cost-effective raw materials derived from natural products, resulting in controllable overall costs and suitability for large-scale industrial production applications.

[0094] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A molecular tool for reconstructing rhein-based natural fragrances, characterized in that, The structural formula of the molecular tool is: 。 2. The method for preparing the molecular tool reconstructed from rhein-based natural fragrance according to claim 1, characterized in that, Includes the following steps: A natural fragrance solution and a rhein solution were mixed and subjected to a dehydration condensation reaction to obtain the molecular tool for reconstructing the rhein-based natural fragrance. The natural fragrance in the natural fragrance solution is veratral.

3. The method for preparing the molecular tool reconstructed from rhein-based natural fragrance as described in claim 2, characterized in that, The solvent for the natural fragrance solution is an alcohol solvent, which includes one or more of methanol, ethanol, propanol, n-butanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol and 1,3-butanediol.

4. The method for preparing the molecular tool reconstructed from rhein-based natural fragrance as described in claim 3, characterized in that, The concentration of the natural fragrance solution is 1–50 mol / L.

5. The method for preparing the molecular tool reconstructed from rhein-based natural fragrance as described in claim 4, characterized in that, The solvent for the rhein solution is an alcohol solvent, which includes one or more of methanol, ethanol, propanol, n-butanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol and 1,3-butanediol.

6. The method for preparing the molecular tool reconstructed from rhein-based natural fragrance as described in claim 5, characterized in that, The concentration of the rhein solution is 1–300 mol / L.

7. The method for preparing the molecular tool reconstructed from rhein-based natural fragrance as described in claim 6, characterized in that, The molar ratio of veratral in the natural fragrance solution to chrysophanol in the rhein solution is 1:1 to 100.

8. The method for preparing the molecular tool reconstructed from rhein-based natural fragrance as described in claim 7, characterized in that, The temperature of the dehydration condensation reaction is 20–90°C, and the time of the dehydration condensation reaction is 1–80 h.

9. The application of the molecular tool reconstructed from rhein-based natural fragrance as described in claim 1 in the micro-area viscosity detection of wax emulsions.

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