Effects of Gamma Irradiation on the Properties of Bioactive Compounds of Bee Pollen

Extended Abstract Background: Bee pollen is used in human and animal nutrition and is rich in bioactive compounds, such as flavonoids and polyphenols. It has a wide range of therapeutic properties and plays an important role in preventing diseases related to free radicals. The use of unprocessed bee pollen in human nutrition can be harmful due to the presence of allergenic compounds and contamination of the product. Bee pollen is a natural product and fungal contamination is possible during collection by insects or improper storage. Gamma irradiation can remove microbial contamination, increase protein bioavailability, change their function, and be used for bee pollen processing by changing the structure of allergenic compounds. This research aimed to study the effects of gamma irradiation on the properties of bioactive compounds, including protective effects against tissue damage, digestive system health, and anti-inflammatory and anti-allergenic effects of gamma-irradiated bee pollen. Methods: Raw and gamma-irradiated bee pollen with a dose of 25 kGy of gamma rays in 2% of the basic diet was fed to 96 adult male Wistar rats. Experimental diets included no use of pollen, using raw bee pollen, and using gamma-irradiated bee pollen with a dose of 25 kGy. Sodium fluoride (1 g/kg of diet) was used to cause poisoning and tissue damage. After 42 days, the effects of pollen nutrition in preventing sodium fluoride toxicity were studied using histological studies and liver enzymes. The effects of pollen feeding on the microbial flora of the digestive tract, intestinal morphology, and villus growth were studied by sampling intestinal tissue and contents. Interleukin-4 was measured to study the antiallergic effects of pollen by the ELISA method. Experimental data were analyzed in a completely randomized experimental design using SAS statistical software.  Means were compared with Duncan's test at the level of 5%. Results: The total protein and malondialdehyde contents in the irradiated samples were not different from the control sample (p > 0.05), but using bee pollen caused a decrease in serum alanine transferase (p < 0.05). There was a significant difference in the amount of blood cations in the sodium fluoride group. The use of bee pollen improved the increase of sodium and potassium levels and the decrease of phosphorus in the sodium fluoride group (p < 0.05). No significant difference was observed in serum interleukin-4 concentration in different treatments of raw and radiation-processed pollen with a dose of 25 kGy (p > 0.05). The results of measuring the antimicrobial properties of gamma-irradiated pollen showed that irradiation did not affect the antimicrobial properties of bee pollen (p < 0.05). The antimicrobial properties of bee pollen on Gram-positive bacteria are more than Gram-negative bacteria. Bee pollen has more antimicrobial activity against Gram-positive bacteria than Gram-negative bacteria and fungi. Bee pollen destroys Gram-positive and Gram-negative bacteria, but the sensitivity of Gram-positive bacteria is higher than that of Gram-negative bacteria due to the nature of the cell membrane layer. The use of pollen decreased the population of Gram-positive and Gram-negative bacteria in the intestine (p < 0.05). The decrease in the population of intestinal bacteria can be due to the antimicrobial effects of pollen or changes in the morphology of the intestinal wall, which plays a role in bacterial attachment and establishment and prevents the destruction and damage of the intestinal epithelial cells. The histological results showed that the diet containing raw and irradiated bee pollen reduced sodium fluoride damage, including bleeding of  the testicles and digestive tract, hyperemia, and swelling of hepatocytes, and kidney damage. The morphological characteristics of the intestines of rats fed with pollen were significantly different from those fed with a pollen-free diet (p < 0.05). In the experimental group of raw and processed pollen, the ratio of villus height to crypt depth and villus height increased in the duodenum, jejunum, and ileum (p < 0.05). Diets containing sodium fluoride caused a decrease in villus length and crypt depth along the intestine, but the reduction percentage was lower in pollen-containing diets. There was a significant difference in the intestinal morphological characteristics of rats fed with both raw and processed pollens (p < 0.05). The effect of raw pollen was greater in the duodenum and jejunum, but processed pollen increased the length of the villi in the ileum, though the depth of the ileal crypt was not different (p > 0.05). The use of pollen caused an increase in the relative volume of the epithelium and a decrease in the connective tissue of the jejunum, along with increases in the villi length and the jejunum crypt depth. These results show the growth-stimulating effect of pollen on intestinal villi. The use of pollen increased the height of the villi and the depth of the intestinal crypt of the tested rats. Bee pollen gamma irradiation did not change this property of pollen, and it caused better functioning of the digestive system in cases such as the length of ileal villi. Conclusion: According to the results of this research, a dose of 25 kGy of gamma radiation without negative effects on the properties of the bioactive compounds of bee pollen can be used for the radiation processing of bee pollen.