جستجوی مقالات مرتبط با کلیدواژه « antioxidant activity » در نشریات گروه « کشاورزی »

In this study, anthocyanin and phenolic compounds were extracted from pomegranate peel powder with supercritical CO2 and Lepidium perfoliatumseed gum and maltodextrin were used as the nanoencapsulation wall. The nanoencapsulation extract was dried with a freeze dryer. Color stability and antioxidant activity of nanoencapsulation extract were evaluated. The levels of anthocyanin and phenolic compounds were evaluated by differential pH and Folin-Ciocalteu method, respectively. Particle size, nanoencapsulation efficiency of anthocyanin,nanoencapsulation phenol, color stabilityat different temperatures and pH as well as antioxidant activity were evaluated by DPPH. The amount of anthocyanin and phenol extracted in this method was 3.943±0.133 mg/g of pomegranate peel powder and 504.521±2.537 mg/g of gallic acid per 100 g, respectively. Nanoencapsulation efficiency was higher for anthocyanin than phenols. The release of anthocyanin at different pHs was different, so that anthocyanin behaved differently at different pHs. Polymerization and color increased with increasing temperature. The antioxidant activity of the fine-grained extract by DPPH method increased with increasing concentration and its IC50 was equivalent to 1.092± 0.024 m /ml.

This study aimed to investigate the chemical composition, antioxidant properties, and antimicrobial activity of Tanacetum balsamita L. essential oil. The essential oil was extracted using the water distillation method, and then the total phenolic content (using the Folin-Ciocalteu method), total flavonoid content (using the aluminium chloride colorimetric method), antioxidant activity (using DPPH and ABTS free radical scavenging methods), and antimicrobial activity (using disk diffusion agar, well diffusion agar, minimum inhibitory concentration, and minimum bactericidal concentration methods) were evaluated. The total phenolic and flavonoid contents of the essential oil were found to be 29.50 mg gallic acid equivalent per gram and 14.90 mg quercetin equivalent per gram, respectively. The essential oil exhibited significant antioxidant activity, with the ability to scavenge 50.40% and 53.55% of free radicals DPPH and ABTS, respectively. According to the results of disc diffusion agar method, Bacillus subtilis and Salmonella typhi were the most sensitive and resistant bacterial strains, respectively, with zone of inhibition diameters of 16 mm and 10.50 mm. The zone of inhibition diameters for these bacteria in the well diffusion agar method were obtained as 16.30 mm and 10.80 mm, respectively. The minimum inhibitory concentration and minimum bactericidal concentration for B. subtilis were determined as 4 mg/mL and 32 mg/mL, respectively, and for S. typhi, they were 64 mg/mL and greater than 512 mg/mL, respectively. According to the results, T. balsamita essential oil can be used as a natural antioxidant and antimicrobial agent in food products.

Kefir is a dairy that contains lactic acid, carbon dioxide, and other volatile aromatics traditionally produced by the activity of kefir dunkers (Gaware et al., 2011). One of the constituent components of kefir grain are mucoid substances that are produced by the microbial flora of this grain, and exopolysaccharide called kefiran is one of them. Radhouani et al. (2018) showed that kefir is a suitable material for use in the field of biomaterials production, film and tissue formation. The most prominent biodegradable biopolymers used in food packaging from the group of biopolymers produced by microorganisms are bacterial cellulose and kefir (Rhim et al., 2013 and Sabatino et al., 2020). Kefiran is able to produce transparent films with relatively good mechanical resistance. Recently, the antimicrobial effect of postbiotics has attracted the attention of researchers. Postbiotics are actually a byproduct of the fermentation process done by probiotics (Moradi et al., 2019). Silver nanoparticle is one of the nanomaterials that has been mentioned in many studies for its antimicrobial effect as well as the effect of improving the mechanical and barrier properties of biodegradable films (Ajitha et al., 2021; Blosi et al., 2021; Li et al., 2023). One of the new methods in the production of biopolymer films that has recently attracted the attention of researchers is the electrospinning method. Electrospinning is a process in which continuous polymer fibers with diameters in the sub-micrometer range are produced through the action of a high-voltage electric field applied to a solution.

To cultivate kefir seeds, kefir grains were first cultured in fresh cow's milk for activation and growth. In order to increase the activation speed, greenhouse was used at a temperature of 27°C. To extract kefir from kefir grains, kefir grains were mixed with distilled water at a ratio of 1:10 at a temperature of 81°C and then the resulting mixture was centrifuged at a temperature of 20°C for 20 minutes. Then, kefirs using 96% ethanol were centrifuged at a temperature of 4°C for 20 minutes, and the obtained precipitates were mixed with distilled water at a temperature of 80°C in a ratio of 1:5. This washing step was repeated twice until a white deposit of kefir was obtained and then, was dried.In order to extract the postbiotic extract, first, 5 g of kefir seeds were inoculated in the milk culture medium and placed in a greenhouse at 35°C for 48 hours. Then the culture medium was centrifuged and the supernatant was filtered with a needle filter. In this study, a concentration of 4% kefir was used to produce electrospun nanofibers. In this way, 0.04 g of kefir was added to 10 ml of postbiotic extract and electrospuned (Ethnaashri et al. 2024). To prepare the next treatments, three levels of silver nanoparticles (1, 2.5, and 4% by weight of kefir) were added to the previous solution and treated with an ultrasonic probe for 5 minutes (40 kHz, 100W).Also, in order to study the properties of the nanofibers, FTIR, XRD, DSC and SEM analysis were performed and the contact angle, antioxidant activity and antimicrobial activity of them were studied.

This research was designed and implemented with the aim of developing an active electrospun nanofiber substrate for use in food preservation. Kefiran nanofibers containing kefir postbiotics in constant concentration and silver nanoparticles in different concentrations were prepared and their structural, morphological and functional properties were evaluated. Comparison of FTIR spectra of nanofibers containing nanosilver shows that the addition of nanoparticles had no effect on the chemical structure of nanofibers. Due to the small amount of nanosilver in the formulation of nanofibers, the peak related to the nanoparticles itself was not observed. The lack of change in the spectrum of kefir chemical groups due to the addition of nanosilver means that the nanoparticles are physically bound in the polymer network of kefir nanofibers. SEM images show tha nanofibers had a uniform cylindrical shape with a smooth surface and no knots. The average diameter of kefiran nanofibers without nanosilver was about 245 nm. Also, by increasing the concentration of silver nanoparticles to 2.5%, the size of nanoparticle clusters on the surface of nanofibers increased and the average diameter of kefir nanofibers decreased to 205 nm. XRD analisys of kefiran nanofibers showed a sharp peak at the angle of 2θ=44.5°. The results indicate the semi-crystalline nature of kefir nanofibers. With the increase of silver nanoparticles, there is no change in the intensity and location of the main peak at the angle of 44.5°, but a new peak is created at the angle of 2θ = 1.38° and the highest intensity is observed in the sample containing 4% nanosilver. The control nanofibers of kefir containing postbiotics showed three ranges of changes in the DSC test. The main melting peak of this nanofiber was observed at 73°C. By adding silver nanoparticles, the thermal properties of kefir nanofibers were weakened. The results show that silver nanoparticles affected the thermal properties of kefir and reduced its resistance to temperature. The contact angle of nanofibers by adding of silver nanoparticles at a concentration of 1%, shwed no significant change (p>0.05). But when the amount of silver nanoparticles reached 2.5% and 4%, the contact angle decreased significantly (p<0.05) and in fact the hydrophilic property of nanofibers increased. The antibacterial activity of electrospun kefir nanofibers containing postbiotics and nanosilver was investigated against E. coli and S. aureus. By increasing the amount of silver nanoparticles, the antimicrobial property increased and the sample containing 4% nanosilver showed the highest antibacterial activity against both bacteria. In this research, kefir nanofibers containing postbiotic showed an antioxidant activity of 5.65%, which is due to the low amount of postbiotic in the nanofiber formulation. By increasing the concentration of silver nanoparticles, the antioxidant activity increased significantly, and the highest inhibitory activity was observed at a concentration of 4% with a power of 59.21%.

The results of the FTIR test proved the physical connection and the lack of chemical bonding between silver nanoparticles and nanofibers. Good and uniform surface morphology was observed in kefir nanofibers in SEM test, but silver nanoparticles were observed in aggregated form. The XRD test showed no effect of nanosilver on the structure of kefiran nanofibers, but in the DSC test, the weakening of the thermal properties of kefiran nanofibers was reported with an increase in the concentration of nanosilver. The control nanofibers of kefirs that had only postbiotics also had antioxidant and antimicrobial properties, but these functional properties were enhanced by increasing the concentration of silver nanoparticles, and nanofibers containing 4% nanosilver showed the best antimicrobial and antioxidant properties. In general, the results of this study showed that kefir nanofibers containing postbiotic kefir and silver nanoparticles have favorable physical and functional characteristics and can be used as active food packaging and can be used for the purposes of increasing the shelf life of food and preventing microbial and oxidative spoilage.

Seeds and nuts have received increasing attention due to their nutritional value and the high therapeutic properties of their bioactive compounds. Most of the seeds are used as nuts, and some of them are considered agricultural waste. Pumpkin seeds have a high content of protein (30–40% in terms of dry matter). Proteins are among the vital health-giving components that provide nitrogen, essential amino acids and energy necessary for normal cells. Pumpkin seeds are a good source of amino acids such as valine, histidine, isoleucine, leucine, threonine and methionine. Protein hydrolysate is a mixture of peptides and amino acids that can show antioxidant, antimicrobial, anticancer, antidiabetic and antihypertensive properties. During hydrolysis, proteins are broken into small peptides and amino acids. Since enzymatic hydrolysis is performed in relatively mild conditions and no amino acid damage occurs, this type of hydrolysis is preferred over acid and alkaline hydrolysis. Hydrolysates obtained from pumpkin seed protein have bioactive properties, especially antioxidant activity. Pretreatment of proteins before enzymatic hydrolysis acts to improve the release of bioactive peptides from different proteins. Pretreatment can facilitate the unfolding the structure of proteins and thus increase the access of enzymes to peptide bonds. The main properties of microwaves usually show three characteristics: penetration, reflection and absorption. Microwave assisted enzymatic hydrolysis can shorten the time  and improve the speed of the reaction. The purpose of this research was to investigate the antioxidant activity of pumpkin seed protein hydrolysates (Cucurbita maxima L.) by alcalase enzyme in two conditions: without pretreatment and using microwave pretreatment.

In this study, Pumpkin (Cucurbita maxima L.) was purchased from the local market of Astane Ashrafieh in Gilan province. The seeds were scooped manuallyand then dried in an oven at 50°C for 72 hours. After the production of protein concentrate from pumpkin seeds, the chemical properties of the concentrate, such as the amount of fat, protein, ash and moisture, were measured. The isolated pumpkin seed solution was exposed to microwave energy with a power of 450-900 watts for 30–90 seconds and was used as a substrate solution in enzymatic hydrolysis experiments. It should be noted that after measuring the total antioxidantactivityr for different powers and times of microwave pretreatment, the power of 600 watts for 60 seconds was selected  and applied before enzymatic hydrolysis. Enzymatic hydrolysis was done by alcalase enzyme with a concentration of 0.5 to 2.5% compared to the protein substrate during 20 to 190 minutes, and the optimum temperature and pH of alcalase were determined in order to produce hydrolysates with antioxidant activity. Antioxidant activity was measured by using DPPH free radical inhibition, total antioxidant activity and iron chelation activity methods.

Bioactive peptides produced by the enzymatic hydrolysis of proteins have significant antioxidant properties. Pumpkin seeds can be used as a rich source of nutrients and bioactive compounds in various food industries. The results showed that the maximum amount of antioxidant activity without pre-treatment was achieved in 165 minutes with a 2.2% ratio of E/S by using DPPH free radical scavenging activity (40.5%), total antioxidant power (0.79), and iron chelation activity (96.2%) methods. By using microwave pre-treatment, the maximum amount of antioxidant activity was achieved in a shorter time and with less enzyme (105 minutes and E/S ratio 1.5%) using DPPH free radical scavenging (52%), total antioxidant power (0.711), and iron chelation activity (93%). Therefore, it can be concluded that using microwave assisted enzymatic hydrolysis , in addition to achieving hydrolysates with proper antioxidant activity, is a suitable method to save time and reduce enzyme concentrations used in enzymatic hydrolysis.

Herbal bioactive compounds are secondary metabolites of plants that are produced in response to environmental stress and to protect the plant against harsh conditions. These compounds have both health effects on humans and also have preservative effects in food products. The conditions for extracting active compounds have a significant effect on their functional activities, and conventional and new methods have been used to extract bioactive compounds from plants. The aim of this study was to compare the extraction methods of bioactive compounds of Persian Golnar extract (PGE). In this research three methods of ohmic (temperatures of 45 °C and 60 °C for 40 and 60 min), ultrasonic (temperatures of 40 °C, 50 °C and 60 °C for 20 and 40 min) and perculation (for 24, 48 and 72 h) were used to prepare PGE, and the best extract was selected based on the extraction yield, total phenol content (TPC), total anthocyanin content (TAC) and antioxidant activity (DPPH radical scavenging). The results showed that there was no significant difference between the extraction yields of all three methods (p>0.05). The ohmic method had the same TPC as the ultrasonic method, but showed a higher TAC and antioxidant activity and was chosen as the best method. The optimal treatment in this stage included ohmic method, 60 °C and 40 min, and the extract obtained under these conditions contained 109.74 mg GAE/g of TPC, 373.26 mg/g of TAC and 81.11% antioxidant activity.

The genetic diversity of plant species and their relationship with wild species is very important to improve the yield of crops..The first step in the improvement of medicinal plants is to identify and collect endemic genotypes.Endemic genotypes are very important in the selection of cultivars due to their adaptability to the climate of the region. Mentha longifolia is one of the important endemic medicinal plants of Iran, which is used in various pharmaceutical, food and cosmetic industries. Essential oil, phenolic compounds, flavonoids and other compounds such as steroids and ceramides are important chemical compounds in oregano plant. In this study, morphological diversity, essential oil and antioxidant activity of 20 Mentha longifolia genotypes in West and East Azerbaijan provinces were investigated. The aim of this research, on the one hand, is to know the potential and range of diversity of Menta longifolia genotypes in its natural habitats in West Azarbaijan and East Azarbaijan provinces. On the other hand, the introduction of regions with superior genotypes in terms of these traits is for use in breeding programs.

The collection of plant samples from some areas of two northwestern provinces of Iran (West Azerbaijan and East Azerbaijan) was done in the spring of 2022. In order to evaluate the morphological traits of the plant in the flowering season, 11 quantitative traits of the plant including plant height, inflorescence length, crown diameterstem diameter, internode length, leaf length, leaf width, number of leaves, number of inflorescences, fresh weight, dry weight and the number of sub-branches were evaluated. After drying the plant samples, essential oil extraction was done using a clonger, and the essential oil samples were transferred to Urmia University Jihad to identify compounds by gas chromatography. Extraction of plant samples was done by ultrasonic method .Antioxidant activity was evaluated by DPPH method. All the obtained data were analyzed with three repetitions and based on a completely random design using SPSS software .LSD test was used to compare the mean data. Data clustering was done based on Ward's method and Euclidean distance square measure. Principal component analysis was performed on the data .Also, in this study, correlation between studied traits was done by R software.

The results of analysis of variance showed that the genotypes collected from different regions have significant differences in terms of plant height, inflorescence length, crown diameterstem diameter, internode length, leaf length, leaf width, number of leaves, number of inflorescences, fresh weight, dry weight and the number of sub-branches are investigated (P < 0.01). The results of the analysis of the percentage and chemical composition of the essential oil showed that the type of genotype had a significant effect on the amount of these compounds in different genotypes of Mentha longifolia (P < 0.01). Among the studied genotypes, the highest percentage of essential oil and the amount of Trans-Caryophyllene and Germacrene D compounds were found in G18 of Iranq region of Tabriz, also the highest amount of Alpha-Terpineol and Spathulenol was found in G16 of Aghajari region of Maragheh. Also, there was a significant difference between different genotypes of mint in terms of antioxidant activity. The maximum amount of antioxidant activity (80.81%) was observed in G3 of Hachesu area in Shahindej. Based on Ward's cluster analysis, the genotypes were divided into three main groups. G1 alone was placed in a separate group due to the high content of Spathulenol and high antioxidant activity. The second group, which includes most of the genotypes (G2, G3, G5, G16, G19, G17, G20, G12, G14, G4, G6, G8, G11, G13, G9, G7 and G10), has a moderate amount of morphological traits, essential oil components and antioxidant activity. G15 and G18 genotypes were placed in the third group. The prominent features of these genotypes were high values of length and number of inflorescences, length and width of leaves, number of leaves, fresh and dry weight of the plant, number of sub-branches, percentage of essential oil, alpha-Humulene, trans-Caryophyllene and GermacreneD and antioxidant activity.Using principal component analysis, 21 primary variables were determined in the form of two principal components.The first component explained 40% and the second component 19% of the total variance. The results of correlation analysis showed that there was a positive and significant correlation between the percentage of essential oil and some morphological traits, the percentage of essential oil and the amount of Germacrene D, trans-Caryophyllene, beta-Farnesene and isomenthon, as well as antioxidant activity and morphological traits.

The findings of this study showed that G15 belonging to Maragheh with an altitude of 1776 m had the highest number of leaves, length and width of leaves, fresh weight, dry weight and number of sub-branches, internode length and number of inflorescences compared to other genotypes.Therefore, it can be said that this genotype has priority for breeding, domestication and crop cultivation projects and is suitable for its introduction to the market as a medicinal plant.In addition, the results showed that the highest percentage of essential oil and the amount of compounds such as Germacrene D, Trans-Caryophyllene, Spathulenol, Beta-Farnesene, Alpha-Terpineol were obtained in genotypes with high altitudes.

The use of safe ingredients to preserve food is steadily increasing. The high time and cost of production and approval of synthetic food additives and the reduction of public acceptance of these compounds have caused serious problems in their utilization. Excessive use of synthetic preservatives, which some of them are suspected to be toxic, has completely eliminated these additives and led to the use of natural alternatives to preserve or extend the shelf life of food products. Many plant-based bioactive compounds are good alternatives to synthetic antimicrobial and antioxidant supplements. Plant extracts have significant biological activity including antioxidant, antibacterial, and antifungal properties, which has increased their use in food products. In addition, plant-derived antimicrobial compounds have been considered in the pharmaceutical industry to control microbial pathogens. Natural antioxidant and antimicrobial compounds are receiving a lot of research and industrial attention in food preservation technologies. In the last 2 decades, the use of herbal medicines rich in bioactive molecules (including polyphenols, carotenoids and flavonoids) with medicinal and health effects such as delaying the onset of some diseases such as cardiovascular disorders, diabetes, and cancer have increased.The plant Prosopis farcta grown in arid and semi-arid regions. In Iran, it is found in the southern regions of the country. In traditional medicine, this plant is used to prevent hyperlipidemia and hyperglycemia, to treat hemorrhoids, intestinal diseases and diarrhea, and leprosy, and to reduce abortion. In addition, antimicrobial and antioxidant properties of various species of Prosopis have been reported. Accordingly, in this study, after examining the of total phenols and flavonoids concentrations, the antioxidant and antimicrobial properties of ethanolic extract of Prosopis farcta were determined. 

The ethanolic extract of P. farcta was obtained maceration method. Total phenol content (by Folin-Ciocalteu reagent method), total flavonoid content (by aluminum chloride method), antioxidant activity (by DPPH and ABTS free radical scavenging and beta-carotene bleaching methods), and antimicrobial effect against Escherichia coli, Shigella dysentery, Staphylococcus aureus, and Bacillus subtilis (by disk diffusion agar, well diffusion agar, minimum inhibitory concentration, and minimum fungicidal concentration) of the extract were evaluated. 

farcta ethanolic extract showed high phenol content (145.58 ± 1.30 mg GAE/g), while its total flavonoid content was 72.37 ± 1.48 mg QE/g. Antioxidant activity of ethanolic extract of melon root using different methods of DPPH and ABTS free radical scavenging and beta-carotene bleaching inhibition were 62.60, 71.82 and 54.50%, respectively. Antibacterial activity of P. farcta ethanolic extract against Escherichia coli, Shigella dysentery, Staphylococcus aureus, and Bacillus subtilis according to disk diffusion agar and well diffusion agar methods showed that the antimicrobial activity of the extract was concentration dependent and Shigella dysentery and Staphylococcus aureus were the most resistant and sensitive bacterial strains to the extract respectively. The minimum inhibitory concentrations of ethanolic extract of P. farcta root for Escherichia coli, Shigella dysentery, Staphylococcus aureus, and Bacillus subtilis were 8, 8, 4 and 4 mg/ml, respectively; while the minimum bactericidal concentrations for these bacteria were 128, 256, 32 and 64 mg/ml, respectively. 

In the present study, ethanolic extract obtained from the roots of P. farcta was identified as a rich source of phenolic and flavonoid compounds. The ethanolic extract showed effective antimicrobial and antioxidant properties. The results greatly indicated the promising effect of P. farcta root extract against Gram-positive and Gram-negative bacterial species. As the microbial resistance is constantly increasing, ethanolic extract of P. farcta root can be considered as a suitable complementary option to tackle this problem. In addition, the identification of individual components of P. farcta ethanolic extract and their biological functions or their combination with common antioxidant and antimicrobial agents could be the subject of future research.

Drought stress is the most critical factor limiting agricultural and medicinal plants' performance in arid and semi-arid areas. Silybum Marianum L. is a medicinal plant with antioxidant properties. In addition to the plant's genetic nature, flavonolignan production and accumulation are affected by various environmental conditions. The accumulation of secondary metabolites under drought stress was studied concerning the antioxidant defense system at the biochemical level. The purpose is to evaluate the secondary metabolites of milk thistle under non-stress conditions and different levels of drought stress and different growth conditions, as well as to identify the best level of moisture stress and the time of harvesting the plant to increase the effective compounds. Milk thistle seeds were disinfected and transferred to a Petri dish containing filter paper and placed in a germinator at 25°C for germination. The germinated seeds were transferred to the pots and put under controlled temperature and humidity in the greenhouse of Hirmand city, Shandel village, located 25 km from Zabul city, Sistan, and Baluchistan province. Evaluation of the effect of drought stress at four different levels of irrigation (25, 50, 75, and 100% of water requirement respectively severe stress, moderate stress, mild stress, and non-stress) and in 3 growth stages (6, 13 and 20 weeks after planting) on biochemical traits including proline content (PC), carbohydrates content (CC), total phenol content (TPC), total flavonoid content (TFC), antioxidant activity and activity of antioxidant enzymes such as catalase (CA), ascorbate peroxidase (AP), guaiacol peroxidase (GP), superoxide dismutase (SOD) and polyphenol oxidase (PO) was carried out. The experiment was done as a factorial based on a completely randomized design with three replications. Data and errors were examined for normality. After confirming the normality of the data and errors, analysis of the variance of the traits and comparing the mean of the traits (LSR) was done at the 5% level. The variance analysis of traits showed that the effect of different levels of irrigation, harvest time, and their interaction on all traits was significant. Comparison of the average interaction effect of irrigation treatment and harvest time of traits: proline content, carbohydrates content, phenol and flavonoid content, and antioxidant activity increased in all growth stages and the lowest and highest values were respectively observed in the growth stage 6 weeks after planting in 100 Percentage of water requirement and growth stage 20 weeks after harvesting in the condition of 25% water requirement. Therefore, the drought stress factor can be used to improve the effective substances of this plant. In addition, the final growth stage is the most appropriate time to harvest this plant due to the accumulation of secondary metabolites at this stage. The interaction effect of irrigation treatment and harvest time was not significant for the activity of guaiacol peroxidase enzyme, and for other antioxidant enzymes it showed that the highest activity of catalase enzyme was at the growth stage 6 weeks after planting in conditions of 25 and 50% water requirement, for ascorbate peroxidase enzyme, it belonged to the growth stage 6 weeks after planting in the condition of 100% water requirement, and for polyphenol oxidase and superoxide dismutase enzymes, it belonged to the growth stage 20 weeks after planting in the condition of 25% water requirement. These results indicate that antioxidant enzymes act differently at different growth stages and under various moisture stress conditions. The evaluation results of milk thistle in 4 irrigation regimes and three growth stages showed that most biochemical traits increased under stress conditions. This indicates that the milk thistle plant responds to drought stress through an enzymatic and non-enzymatic antioxidant defense system. Milk thistle plants had the highest total phenolic and flavonoid content at the final development stage (20 weeks after planting). Therefore, the best time to harvest is at the final stage of development, which has the most polyphenolic compounds.

Nowdays, because of human industrial activities, ozone layer depletion increases the amount of ultraviolet (UV) irradiation that reaches Earth’s surface; creating problems for living organisms. Since plants always need sunlight, the effects of UV radiation on plants are inescapable. The present study was conducted to evaluate the physiological, phytochemical and chlorophyll fluorescence responses and stomatal characteristics of three cornflower cultivars to UV radition in 2018.

The experiment was performed as a split plot in a completely randomized design. Ultraviolet light was considered as the first factor in four levels (control, ultraviolet A, ultraviolet B and ultraviolet A + B) and three cornflower cultivars as the second factor. When seedlings had four real leaves, the UV treatments were started by ultraviolet lamps made by Q-Lab company of the USA. At the end of experiment, physiological and phytochemichal traits including relative water content, electrolyte leakage, lipid peroxidation, chlorophyll a and b, carotenoid content, catalase and peroxidase activity, stomatal gurad cell length and width, stomatal index, stomatal density, chlorophyll fluorescence, phenol and flavonoid contents, anthocyanin, and antioxidant activity of extract were assayed. The analysis of variance was done using Minitab software according to the experimental desing. Mean comparison was performed using LSD test method at 0.05.

The results showed that the amount of malondialdehyde, electrolyte leakage and antioxidant enzymes activity was increased under UV-B radiation. UV-B radiation decreased leaf chlorophyll content, but increased carotenoids. UV A had no significant effect on chlorophyll, while, increased carotenoids. Maximum fluorescence, variable fluorescence and maximum quantum efficiency of photosystem ІІ were reduced under UV treatment. In contrast, UV radiation increased the minimum of fluorescence. UV-B and UV-A+B radiation increased width of stomatal gurad cell, and stomatal index and density, but decreased length of stomatal gurad cell in cornflower. The amount of flavonoids, total phenol, anthocyanin and antioxidant activity of cornflowers increased by UV radiation. Among the cornflower cultivars studied, Kornblume blau cultivar had shown the highest values of total phenol, total flavonoids and anthocyanins as well as antioxidant activity.

In the present study, UV-B radiation and simultaneous UV-A+B radiation led to more extensive physiological and phytochemical responses in cornflower cultivars. Based on the results obtained in this study, it can be concluded that UV-B has more destructive effects than UV-A on cornflower. In the comparison between cultivars, it was found that Kornblume blau cultivar is more suitable for medicinal use due to its higher phytochemical compounds and biological activity.