The effect of different growth conditions on the content of bioactive compounds and gross β-radioactivity of some wild edible plants in the Republic of Armenia

Background: Nowadays, people prefer using edible plants over synthetic drugs for the prevention and treatment of diseases. These plants are rich in bioactive compounds (BC), such as vitamins, carotenoids, proteins, carbohydrates, organic acids, flavonoids, tannins, and more. Humans have used them for thousands of years as both food and medicine. Through the rational use of edible plants, people aim to enhance the body’s immunity and prevent diseases. In this context, the need to obtain edible plants that are both rich in BC and radioecologically safe has become an urgent concern. Objective: To identify the optimal conditions for obtaining BC-rich radioecologically safe plant products, we studied the comparative characteristics of BC (protein, tannins, flavonoids) content and their gross β-radioactivity in several wild edible plants-WEP (sickleweed - Falcaria vulgaris Bernh., eryngium - Eryngium caucasicum Trautv., and rhubarb - Rheum rhabarbarum L.) under outdoor hydroponics and soil cultivation conditions. The research was conducted at the Institute of Hydroponics Problems (IHP) in the Ararat Valley; an area located within a 30 km radius of the Armenian Nuclear Power Plant (ANNP). Methods: Total protein content was assessed using the Kjeldahl method, and tannin content was determined using a titrimetric method, while the total flavonoid content was quantified using a spectrophotometric method. Gross β-radioactivity of samples was defined with radiochemical methods through the radiometer UMF-1500 with low background. Results: The cultivation method (hydroponics, soil) did not significantly affect the content of total flavonoids and tannins in sickleweed leaves. In hydroponics, the protein content in sickleweed increased by 1.3 times, while the flavonoid content in eryngium leaves and the tannin content were 1.2 times higher than those in soil-grown plants. The concentration of the nutrient solution (0.75N, 1.0N, 1.25N) significantly affected the flavonoid and tannin content in the petioles of rhubarb. The minimum flavonoid and tannin content in rhubarb petioles was recorded at 0.75N (0.2% and 2.1%, respectively), while the maximum content was observed at 1.25N (0.4% and 2.8%, respectively). Food plants, in order of gross β-radioactivity levels in hydroponics and soil, form the following descending order: sickleweed > eryngium > rhubarb. The gross β-radioactivity of plants varied between 780-910 Bq/kg in hydroponic systems, compared to 650-760 Bq/kg in soil. Novelty: This study is the first to integrate biochemical profiling of BC with radiological safety assessment in WEP (sickleweed, eryngium, and rhubarb) cultivated under hydroponic and soil conditions. It demonstrates that hydroponics not only enhances protein, flavonoid, and tannin yields but also ensures radio-ecological safety, confirming WEP as promising functional food ingredients and medicinal resources. Conclusion: In the raw materials of WEP, the content of certain BC in hydroponics exceeded that in soil. The raw materials of plants grown under different conditions are considered radio-ecologically safe because their gross β-radioactivity does not exceed the radio-ecological safety threshold set by the World Health Organization (< 1000 Bq/kg). Regardless of cultivation conditions, edible plants can be used as a functional food. Keywords: Falcaria vulgaris Bernh., Eryngium caucasicum Trautv., Rheum rhabarbarum L., protein, tannin, total flavonoids, radio-ecological safety.