Diploma work antioxidant properties of dihydroquercetin. Fundamental research
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Antioxidants (AO)- substances that prevent oxidation. In a living organism, the leading factor in oxidation is the formation of free radicals; therefore, the action of antioxidants in biological systems is considered mainly from the standpoint of preventing the oxidation of organic substances by free radicals.
Currently, there are a large number of different methods for determining antioxidants: photometric, chemical, electrochemical, etc. However, many of them have significant drawbacks that make it difficult to understand and further use the results obtained by these methods. The most common disadvantages include the following:
- Artificial or uncharacteristic for biological systems conditions for measuring the antioxidant effect are used. For example, instead of biological free-radical reactions, purely chemical redox reactions are used, or the ability of a substance to donate / accept electrons when exposed to an electric current is measured. The results of measurements obtained under such conditions do not allow us to say that the test substance will exhibit the same "antioxidant" effect in the body.
- Determination of the antioxidant action is carried out by measuring the amount of accumulated oxidation products (oxidation markers). Thus, it is indeed possible to determine the amount of antioxidant in the test sample, but very important information about the activity of the antioxidant is missed. Ignoring the activity of an antioxidant, in turn, can lead to significant errors in determining its amount, for example, for "weak" antioxidants that act slowly but for a long time.
Chemiluminescent method is the most informative method for studying antioxidants and has a number of significant advantages:
- Direct determination of antioxidant activity- the direct action of antioxidants on free radicals is recorded. The chemiluminescent method uses a chemical free radical generation system that produces a control chemiluminescent glow. Then an antioxidant is added to such a system, which neutralizes free radicals, which leads to the suppression of control chemiluminescence.
A significant advantage of this approach is the possibility of using various chemical systems for the generation of free radicals, which makes it possible to additionally determine the specificity of antioxidants and the localization of their action. - Measurement of quantitative and qualitative characteristics of antioxidants- the chemiluminescent method allows characterizing any compound with an antioxidant effect by two independent indicators:
- Anti-Oxidant Capacity (AOE)- the total amount of free radicals that can neutralize the compound contained in the sample of a certain volume.
- Antioxidant Activity (AOA)- the rate of neutralization of free radicals, i.e. the number of radicals neutralized per unit of time.
Chemiluminescent method
gives an important understanding that the action of antioxidants must be evaluated by two indicators - quantitative (AOE) and qualitative (AOA).
The following figure shows this position:
Influence of different antioxidants on chemiluminescence
(the numbers next to the graphs indicate the concentration of the antioxidant):
on the left - a "strong" antioxidant, on the right - a "weak" antioxidant.
Antioxidants differ significantly in their activity. There are "strong" antioxidants, ie. antioxidants with high activity, which inhibit free radicals at a high rate and completely inhibit chemiluminescence. Such antioxidants have a maximum effect already at low concentrations and are quickly consumed. On the other hand, there are "weak" antioxidants, ie. antioxidants with low activity, which inhibit free radicals at a low rate and suppress chemiluminescence only partially. Such antioxidants have a significant effect only in high concentrations, but they are slowly consumed and act for a long time.
The chemiluminescent method can be used to determine antioxidant parameters:
- biological fluids (plasma, saliva, urine);
- pharmacological preparations and biologically active additives;
- beverages and food additives;
- cosmetics and care products;
- and etc.
- Chemiluminometer Lum-100- provides temperature control and registration of chemiluminescence of 1 sample.
- Chemiluminometer Lum-1200- provides temperature control and simultaneous registration of chemiluminescence up to 12 samples.
The invention relates to the food industry and can be used to determine the total antioxidant activity. The method is carried out as follows: the analyte interacts with the reagent 0.006 M Fe(III) - 0.01 M o-phenanthroline. Ascorbic acid (AA) interacts with the same reagent, which is added in a ratio of 1:100. Then incubated for at least 90 minutes and photometered at 510±20 nm. After that, the dependence of the value of the analytical signal on the amount of substance is established and the value of the total AOA is calculated. The presented method allows less time-consuming and more reliable determination of the total antioxidant activity of plant materials and food products based on it. 2 w.p. f-ly, 1 ill., 5 tab.
The invention relates to analytical chemistry and can be used in determining the total antioxidant activity (AOA) of plant materials and food products based on it.
Known coulometric method for determining the total AOA of tea, based on the interaction of aqueous extracts of the product with electrically generated bromine compounds (I.F. Abdulin, E.N. Turova, G.K. Budnikov. Chemistry, 2001, vol. 56, no. 6, pp. 627-629). The choice of electrogenerated bromine compounds as a titrant is due to their ability to enter into various reactions: radical, redox, electrophilic substitution and addition by multiple bonds. This makes it possible to cover a wide range of biologically active tea compounds with antioxidant properties. The disadvantages of the method are the possibility of the bromination reaction with substances that are not antioxidants, and the expression of the resulting value of the total AOA in units of the amount of electricity (kC/100 g), which makes it difficult to evaluate the results.
A known voltammetric method for determining the total antioxidant activity by the relative change in the current of oxygen electroreduction in the potential range from 0.0 to -0.6 V (rel. sat. c.s.e.) on a mercury-film electrode (Pat. 2224997, Russia IPC 7 G 01 N 33/01 Voltammetric method for determining the total activity of antioxidants / E. I. Korotkova, Yu. The disadvantage of this method is the occurrence of side electrochemical reactions, which reduces the efficiency of the determination of antioxidants, which leads to a decrease in the reliability of the results.
A known method for controlling the total AOA of prophylactic and therapeutic antioxidant agents for lipid peroxidation to malonic aldehyde with spectrophotometric or chemiluminescent detection (Pat. 2182706, Russia, IPC 7 G 01 N 33/15, 33/52. funds / Pavlyuchenko I.I., Basov A.A., Fedosov S.R. - No. 2001101389/14; application 01/15/2001; publ. 05/20/2002). At the same time, antioxidant activity is inversely proportional to the level of lipid peroxidation products. The disadvantage of this method can be considered a limited range of analyzed objects, since under these conditions, antioxidants of only one group, lipids, are determined.
A known method for determining the total AOA of a plant extract, which consists in incubating the extract with linetol and iron (II) sulfate, initiating the oxidation reaction by UV irradiation and subsequent interaction with thiobarbituric acid in the presence of triton X-100 (Application 97111917/13, Russia, IPC 6 G 01 N 33/00 Method for determining the total antioxidant activity / Rogozhin VV - Appl. 08.07.1997; publ. 10.06.1999). When carrying out spectrophotometry, a mixture of ethanol and chloroform in a ratio of 7:3 is used. The AOA value of a biological material is determined by the ratio of the accumulation of the reaction product - malondialdehyde in a sample containing an extract to a sample with a prooxidant. The disadvantage of this method lies in the possibility of side reactions during UV irradiation, which reduces the reliability of the results of the analysis.
The listed methods for determining the total AOA have a number of disadvantages: high labor intensity, low reliability, the measured value of the total AOA is not related and is not comparable with any conventional substance.
The closest analogue to the claimed invention is a method for determining the total AOA of medicinal plants by measuring the chemiluminescence that occurs when reacting with luminol in the presence of an oxidizing agent hydrogen peroxide (M.Kh. canary grass by chemiluminescence // Journal of Analytical Chemistry, 2004, V.59, No. 1, P.84-86). For a quantitative assessment of the total AOA, the reducing ability of the extract of medicinal raw materials and the activity of a potent antioxidant - ascorbic acid in the amount of 25-110 μg were compared. Compared with the above methods, in the prototype, hydrogen peroxide is used as an oxidizing agent, which interacts with a wide range of antioxidants, and the measured value of the total AOA of the object is determined and expressed relative to ascorbic acid, which is a common antioxidant, which makes it possible to obtain reliable results while maintaining other disadvantages. The disadvantages also include the complexity of the equipment used in the method.
The technical objective of the claimed invention is the development of a less time-consuming and reliable method for determining the total antioxidant activity of plant materials and food products based on it.
To solve the technical problem, it is proposed to interact the analyte with the reagent 0.006 M Fe (III) - 0.01 M o-phenanthroline, and ascorbic acid (AA) with the same reagent, which is added in a ratio of 1:100, incubated for at least 90 minutes, photometered at 510±20 nm, followed by establishing the dependence of the analytical signal on the amount of substance and calculating the total AOA. In particular, the calculation can be carried out according to formula (I), derived from the equation of quantitative correspondence between the object under study and ascorbic acid:
where a, b are the coefficients in the regression equation for the dependence of the analytical signal on the amount of AA;
a", c" - coefficients in the regression equation for the dependence of the analytical signal on the amount of the object under study;
x sun. - mass of the studied reducing agent (sample), mg.
The use of the proposed reagent under these conditions allowed us to expand the linear range and reduce the lower limit of the determined amounts of ascorbic acid. The proposed set of essential features allows you to determine the total AOA of a wide range of plant materials and food products based on it.
Quantitative correspondence equations connect the dependence of the analytical signal on the amount of ascorbic acid and the dependence of the analytical signal on the amount of the object under study, provided that the antioxidant activity is equal.
After processing the results of photometric measurements of the magnitude of the analytical signal by the least squares method (K. Derffel Statistics in analytical chemistry. - M .: "Mir", 1994. S. 164-169; A.K. Charykov Mathematical processing of the results of chemical analysis - L .: Chemistry, 1984. S.137-144) these dependencies were described by a linear regression function: y=ax+b, where a is the regression coefficient, b is a free member. The coefficient a in the regression equation is equal to the tangent of the slope of the straight line to the x-axis; coefficient b - distance along the y-axis from the origin (0,0) to the first point (x 1 , y 1).
The coefficients a and b are calculated by the formulas:
The regression equation for the dependence of AS on the amount of ascorbic acid at a given time has the form:
y AK \u003d a x AK (mg) + b,
regression equation for the dependence of AS on the amount of the object under study (reducing agent):
y VOST \u003d a "x VOST (mg) + b",
where for AK, for VOST is the optical density of the photometric solution;
x AK (mg), x VOST (mg) - concentration of ascorbic acid (reducing agent) in solution;
then, by equating the values of the functions, we obtain formula (I) for calculating the antioxidant activity of the object under study in units of the amount (mg) of ascorbic acid.
The drawing shows the dependence of the analytical signal on the amount of reducing agent.
The optical density of the analyzed solutions was measured on a KFK-2MP photoelectric colorimeter.
It is known (F. Umland, A. Yasin, D. Tirik, G. Vunsch Complex compounds in analytical chemistry - M.: Mir, 1975. - 531 p.) that o-phenanthroline forms a water-soluble chelate with iron (II) red-orange color, which is characterized by an absorption maximum at λ=512 nm. Therefore, in the proposed method, photometry is carried out at λ=510±20 nm.
The optimization of the composition of the reagent and its amount introduced into the reaction was carried out on the basis of the results of multifactorial planning of the experiment using the Latin Square method, which consisted in changing all the studied factors in each experiment, and each level of each factor only once meets different levels of other factors. This allows you to identify and evaluate the effect caused by each factor under study separately.
The following factors were used: the amounts of Fe(III), o-phenanthroline, and the volume of the reagent introduced into the reaction. The combination of factors should provide a wide range of analytical signal (AS) linearity with sufficient sensitivity, on the one hand, and stability of the reagent over time, on the other. This made it possible to single out the following levels for each factor:
the amount of Fe(III): 0.003 M (A 1); 0.006 M (A 2); 0.009 M (A 3);
amount of o-phenanthroline: 0.01 M (B 1); 0.02 M (B 2); 0.03 M (B 3);
reagent volume: 0.5 ml (C 1); 1.0 ml (C 2); 2.0 ml (C 3) (Table 1).
To select the optimal combination of factor levels, calibration dependences of AS on the amount of ascorbic acid were obtained in the range from 10 to 150 μg (which is necessary to confirm the linearity of the function), the regression equation of the obtained dependence was calculated, and then the value of AS at a given amount (120 μg) of ascorbic acid. Thus, for each composition of the reagent (factors A, B), the volume (factor C) was selected, at which the AC value is maximum. This made it possible to reduce the number of considered combinations to nine (Table 2).
Comparing the total AS for each level, the amounts with the maximum value were identified: ΣA 2 (0.991); ΣB 1 (1.066); ΣC 2 (1.361). This made it possible to conclude that the reagent composition is optimal: 0.006 M Fe (III) - 0.01 M o-phenanthroline with its volume introduced into the reaction, 1.0 ml per 100 ml of solution.
At the optimal concentration of the reagent, we studied the change in the dependence of AS on the concentration of ascorbic acid and some reducing agents common in natural objects (tannin, rutin, quercetin) at different incubation times of the reaction mixture (30, 60, 90, 120 min). It was found that for all the studied reducing agents, the dependence of AS on their content is linear in the range of 10-150 μg (see drawing) and the AS value depends on the incubation time (table 3).
It can be seen from the drawing that the change in AC under the action of rutin is insignificant, tannin approaches, and quercetin exceeds the same dependence for ascorbic acid. When considering the change in AC from the time of incubation for all the studied reducing agents (Table 3), it was found that the stabilization of the analytical signal over time is observed from 90 minutes.
| Table 3 Change in AS of reducing agents over time |
|||||
| Test substance | m substances, mg / cm 3 | Analytical signal | |||
| Time of incubation of the reaction mixture, min | |||||
| 30 | 60 | 90 | 120 | ||
| Vitamin C | 10 | 0,038 | 0,042 | 0,044 | 0,044 |
| 100 | 0,340 | 0,352 | 0,360 | 0,363 | |
| Tannin | 10 | 0,029 | 0,037 | 0,042 | 0,043 |
| 100 | 0,280 | 0,295 | 0,303 | 0,308 | |
| Rutin | 10 | 0,013 | 0,016 | 0,019 | 0,019 |
| 100 | 0,150 | 0,166 | 0,172 | 0,175 | |
| Quercetin | 10 | 0,031 | 0,044 | 0,051 | 0,053 |
| 100 | 0,420 | 0,431 | 0,438 | 0,442 |
To prove the summing nature of the determined AOA value, the effect of the reagent Fe (III) - o-phenanthroline on model solutions, which included reducing agents: tannin, rutin, quercetin, and ascorbic acid in various ratios, was studied. Table 4 presents the results of the analysis of model mixtures.
| Table 4 Results of the analysis of model mixtures (P=0.95; n=3) |
|||||||||
| The number of components in the mixture | Total AOA, calculated, mcgAA | Total AOA, found, mcgAA | |||||||
| introduced | in terms of AK | ||||||||
| AK | Tannin | Rutin | Quercetin | AK | Tannin | Rutin | Quercetin | ||
| - | 20 | 20 | 20 | - | 16,77 | 9,56 | 32,73 | 59,06 | 57,08 |
| - | 10 | 10 | 10 | - | 8,35 | 4,77 | 16,41 | 29,53 | 26,95 |
| - | 50 | 10 | 10 | - | 42,02 | 4,77 | 16,41 | 63,20 | 55,04 |
| - | 10 | 50 | 10 | - | 8,35 | 23,93 | 16,41 | 48,69 | 50,06 |
| - | 10 | 10 | 50 | - | 8,35 | 4,77 | 81,70 | 94,82 | 91,61 |
| - | 30 | 10 | 10 | - | 25,19 | 4,77 | 16,41 | 46,37 | 39,24 |
| - | 10 | 30 | 30 | - | 8,35 | 14,35 | 49,06 | 71,76 | 73,47 |
| 20 | 20 | 20 | 20 | 20 | 16,77 | 9,56 | 32,73 | 79,06 | 96,29 |
| 50 | 10 | 10 | 10 | 50 | 8,35 | 4,77 | 16,41 | 87,95 | 93,07 |
| 10 | 50 | 10 | 10 | 10 | 42,02 | 4,77 | 16,41 | 73,20 | 78,15 |
| 10 | 10 | 50 | 10 | 10 | 8,35 | 23,93 | 16,41 | 58,69 | 78,74 |
| 10 | 10 | 10 | 50 | 10 | 8,35 | 4,77 | 81,70 | 104,82 | 121,45 |
| 30 | 30 | 10 | 10 | 30 | 25,19 | 4,77 | 16,41 | 76,37 | 84,59 |
| 10 | 10 | 30 | 30 | 10 | 8,35 | 14,35 | 49,06 | 81,76 | 103,31 |
The calculation of the theoretical value of the total AOA was carried out according to the equations of quantitative correspondence characterizing the antioxidant capacity of the studied reducing agent with respect to ascorbic acid, under conditions of equal antioxidant activity: .
The value of the experimental (found) AOA was calculated using the averaged regression equation for the dependence of AS on the amount of ascorbic acid. From the results presented in Table 4, it can be seen that the experimentally obtained AOA values agree satisfactorily with the theoretically calculated ones.
Thus, the determined value of AOA is a total indicator, and the determination of its value using the equations of quantitative correspondence is correct.
The proposed method has been tested on real samples. To determine the total AOA of a real sample or its extract, calibration dependences of AS on the amount of analyte and ascorbic acid were obtained at an incubation time of the reaction mixture of at least 90 minutes. The calculation of the total AOA was carried out according to formula (I) and expressed in mg of ascorbic acid per gram of the test object (mgAA/g).
To confirm the correctness of the proposed method, these samples were tested according to known methods, evaluating the content of ascorbic acid (GOST 24556-89 Processed products of fruits and vegetables. Methods for determining vitamin C) and the predominant reducing agents: in tea - tannin (GOST 19885-74 Tea. Methods for determining the content tannin and caffeine), in rosehips - the amount of organic acids (GOST 1994-93 Rosehips. Specifications) (table 5).
1 Milentiev V.N. 2Sannikov D.P. 3Kazmin V.M. 21 Oryol State Institute of Economics and Trade
2 Federal State Budget Institution "Center for Chemicalization and Agricultural Radiology "Orlovsky"
3 Federal State Budgetary Educational Institution of Higher Professional Education "State University - Educational, Scientific and Industrial Complex"
The possibility of using chemiluminescence to assess the antioxidant activity of food substances was studied. The proposed method is based on the chemiluminescence of luminol in an alkaline medium, the intensity of which depends on the amount of peroxides in the chemiluminescent sample. Chemiluminescence was recorded using a developed setup containing a dosing pump, a light-tight chamber, a glass vacuum photomultiplier tube, and a computer system. To enhance chemiluminescence, a solution of potassium ferricyanide was added to luminol. Changes in the intensity of chemiluminescence were recorded at the moment of introduction of the analyzed sample into the luminol solution. Dandelion extract obtained by dry low-temperature distillation was used as the analyzed sample. It contains phenolic compounds known for their high antioxidant activity. It has been established that the chemiluminescence method can be used to determine the antioxidant properties of various food compounds.
chemiluminescence
antioxidant activity
peroxides
nutrients
1. Vasiliev R.F. Chemical glow // Chemistry and chemists, 21.01.10. – URL: http://chemistry-chemists.com. (date of access: 22.08.13).
2. Vladimirov Yu.A. Free radicals and antioxidants // Vestn. RAMN. - 1998. - No. 7. - P. 43-51.
3. Kondrashova E.A. Chemiluminescence as the most sensitive method of enzyme immunoassay and its application. Clinical laboratory diagnostics. - 1999. - No. 9. - P. 32.
4. Lyubimov, G.Yu. Chemiluminescent analysis // Immunology. - 1991. - No. 1. - P. 40–49.
5. Mayansky A.N., Nevmyatullin A.L., Chebotar I.V. Reactive chemiluminescence in the phagocytosis system // Microbiology. - 1987. - No. 1. - S. 109–115.
6. Sherstnev M.P. Calcium-dependent and calcium-independent pathways of cell chemiluminescence generation. Chemiluminescence Issues. - 1991. - No. 2. - S. 1–4.
Today, chemiluminescence is a large area of science located at the interface between chemistry, physics and biology. With chemiluminescence, there is a direct conversion of chemical energy into the energy of electromagnetic oscillations, i.e. into the world. Using chemiluminescence, one can learn about how the reaction proceeds, what is its mechanism, which is necessary for the efficient and rational conduct of technological processes. If the technological process of obtaining any chemical product is accompanied by chemiluminescence, then its intensity can serve as a measure of the speed of the process: the faster the reaction, the brighter the glow. During the chemiluminescence reaction, energy-rich products are obtained, which then give off energy by emitting light, i.e., chemical energy is converted into electromagnetic radiation energy.
The aim of the study was to explore the possibility of using chemiluminescence to assess the antioxidant activity of food substances.
Research results and discussion
The problem of assessing the antioxidant activity of food substances is very relevant. The use of the term "antioxidant activity" in order to show the usefulness of a particular product is often done without any chemical and biochemical argument. As a rule, the antioxidant activity of any substance refers to the effectiveness of reducing the peroxide value. The very concept of peroxide value also does not fully reveal its chemical essence, since it does not fully correspond to the kinetics and thermodynamics of the stages of metabolism of a particular food product. In addition, this value is used to characterize lipids in the form of fats. However, the processes of oxidation and the formation of peroxides in the body occur not only with the use of fats, but also with other products. In other words, the content of peroxide in a particular product can be said to be “weighed” on a kind of balance, where the “reference weight” is a unit of concentration in an acidic environment of the iodide ion oxidized by peroxides, as a result of which molecular iodine is formed:
I- - e → I; (one)
I + I → I20. (2)
When molecular iodine is titrated with a solution containing sodium thiosulfate, its concentration is established and, consequently, the amount of oxidizers of iodide ions is determined, i.e. peroxide compounds, which is actually called peroxide number. Determining the peroxide value using this kind of "weighing" is based on the reaction shown in fig. one.
Rice. 1. Determination of peroxide value using sodium thiosulfate
Thus, the concentration of peroxides is determined from the equation
С(I2) = ϒ(C[-O-O-]), (3)
where ϒ is the correlation coefficient between the concentration of molecular iodine and the concentration of peroxides.
The proposed method for determining peroxides in products is based on the chemiluminescence of luminol (C[lm]) in an alkaline medium, the intensity (Ichl) of which depends on the concentration of peroxides (C[-O-O-]), in a chemiluminescent sample:
IHL. = Ϧchl ω, (4)
where Ϧchl is the quantum yield of chemiluminescence; ω - reaction rate involving peroxides:
khlC[-O-O-] C[lm] = ω, (5)
where kchl is the reaction rate constant or at:
C[lm] kchl Ϧchl = K, (6)
IХЛ = K C[-O-O-]. (7).
The amount of peroxides (-O-O-) is determined by the light sum (S):
The value of S depends on the degree of completeness of peroxide consumption in the chemiluminescent reaction.
To determine the constant K, a calibration curve is constructed for the dependence of the light sum S on the concentration of peroxide, which is determined by titration:
S = f(C[-O-O-]). (9)
Hydrogen peroxide H2O2 is used as peroxides.
Then the data obtained from equation (3) and (9) are compared. Based on the comparison of ϒ and K, a conclusion is made about the agreement of the reaction mechanisms underlying the determination of peroxides by these methods. It was found that in this range of peroxide concentrations ϒ and K indeed agree with each other and therefore they can be used to determine the peroxide value .
Chemiluminescence was observed in an alkaline medium containing luminol (5-amino-1,2,3,4-tetrahydro-1,4-phthalazinedione, 3-aminophthalic hydrazide, H2L). It was recorded using a chemiluminescent setup, including a glass vacuum photomultiplier. The photomultiplier is powered by a high-voltage rectifier (7) coupled to a block (9) that amplifies the photomultiplier signal, which is recorded on the computer monitor display (5).
Rice. 2. Registration of chemiluminescence of the analyzed product: 1 - dosing pump; 2 - lightproof chamber; 3 - mirror; 4 - cuvette; 5 - computer system; 6 - photomultiplier; 7 - high voltage rectifier; 8 - a device that allows you to determine the spectral region of chemiluminescent radiation; 9 - block amplifying the photomultiplier signal
A dosing pump (1) is required to introduce the analyzed sample into a cuvette (4) containing a chemiluminescent solution of luminol. This dispenser acts as a stirrer for the injected sample with a chemiluminescent solution. To enhance the reaction rate and intensity of chemiluminescence, a solution of potassium ferricyanide was added to luminol. Mixing is carried out by air bubbles obtained by pumping air through the solution liquid with a pump. The mirror (3) located in the light-tight chamber (2) serves for better light collection of chemiluminescent radiation incident on the photo-cathode of the photomultiplier (6) mounted in the light-tight chamber. The dispenser allows you to enter the desired components of the liquid into the cuvette without opening the light-tight chamber (2) during the experiments. In this case, these liquids enter the cuvette (4) through glass or plastic tubes. The computer system allows you to register the dependence of the luminescence intensity I on time t, that is, the chemiluminescence kinetics:
The computer system reflects the rise and fall constants in the function I = f(t), which are conjugated with the rate constants of the reactions that cause chemiluminescence, that is, with their kinetics. A device (8) is included in the chemiluminescent chamber, which makes it possible to determine the spectral region of chemiluminescent radiation, that is, the dependence:
I = f1(λ). (eleven)
This block is a cassette in the form of a disk, in which boundary filters are mounted. The change of light filters is carried out by turning the disc cassette about the horizontal axis connecting the centers of the plane of the light filters and the plane of the photocathode of the photomultiplier.
The measurement process is carried out as follows:
1. The response of the photomultiplier to changes in its supply voltage and to changes in the intensity of the reference light source that falls on its cathode is set.
2. The cuvette is filled with a solution of luminol in an alkaline medium.
3. The dispenser is filled with the analyzed sample.
4. The dependence of the intensity of chemiluminescence on time t is recorded. Chemiluminescence is monitored until the time t1, at which the change in I1 from time t is minimal: I1 = f1(t).
5. A portion of the analyzed solution is fed using a dispenser.
6. Chemiluminescence of the analyzed sample is observed, the kinetics of which is I = f(t).
On fig. Figure 3 shows a graph of the dependence of functions (I1 = f1(t)), conjugated with a graph (I = f(t)), after the introduction of the analyzed solution.
As can be seen from fig. 3, the intensity of chemiluminescence of luminol changes: a sharp rise is followed by a sharp decrease in luminescence after the addition of the analyzed sample.
Since the enhancement of chemiluminescence during the oxidation of luminol is associated with the formation of peroxides, the decrease in the intensity of chemiluminescence after the introduction of the analyzed sample indicates a decrease in their number. Therefore, we can speak about the presence of antioxidant activity in the compounds that make up the analyzed sample.
It should be noted that the dandelion extract obtained by dry low-temperature distillation, which contains phenolic compounds known for their high antioxidant activity, was used as the analyzed sample.
Rice. Fig. 3. Dependence graph of functions (I1 = f1(t)), conjugated with the graph (I = f(t)), after the introduction of the analyzed solution
In addition, during the experiment it was found that using chemiluminescence it is possible to determine the amount of peroxides in superdilute systems, which is important for assessing the onset of oxidation of products, for example, during their storage.
Thus, the conducted studies have shown that the method for determining peroxides in products, based on the chemiluminescence of luminol in an alkaline medium, makes it possible to evaluate the antioxidant activity of food substances and can be used to establish the antioxidant properties of various food compounds.
Reviewers:
Litvinova E.V., Doctor of Technical Sciences, Professor of the Department of Technology, Organization and Food Hygiene, OrelGIET, Orel;
Kovaleva O.A., Doctor of Biological Sciences, Director of INITs, FSBEI HPE "Oryol State Agrarian University", Orel.
The work was received by the editors on November 08, 2013.
Bibliographic link
Panichkin A.V., Bolshakova L.S., Milentiev V.N., Sannikov D.P., Kazmin V.M. USE OF CHEMILUMINESCENCE FOR EVALUATION OF ANTIOXIDANT PROPERTIES OF NUTRIENTS // Fundamental Research. - 2013. - No. 10-11. – S. 2436-2439;URL: http://fundamental-research.ru/ru/article/view?id=32810 (date of access: 12/17/2019). We bring to your attention the journals published by the publishing house "Academy of Natural History"
