Evaluation of bioactive compounds in leaf and root of five beetroot varieties

Abstract

Natural compounds are essential in modern nutrition for preventing chronic diseases in the human body. The bioactive substances in 5 beetroot cultivars' leaves and roots were evaluated in the experiment, providing an answer to which stage (60th, 85th, and 105th) of the vegetation is most suitable for fresh consumption. The results show that the polyphenol, flavonoid, and FRAP levels in the leaf and root samples varied throughout the vegetation period. The 60-day old leaf samples of ‘Libero’ had the highest total polyphenol content. The flavonoid content showed a similar trend. Furthermore, the highest FRAP value was found in leaf samples from ‘Libero’ and ‘Pablo F1’ that were 60 days old. In 85-day-old plants, the polyphenol content of the leaves was significantly reduced. On day 85, however, a value was slightly higher in the roots. These findings support the nutritional value of the 85-day-old beetroot (leaves and 3–5 cm diameter roots). At the 85-day stage, the leaf and root had a relatively low nitrate content (10–70 mg/kg). However, higher nitrate content was detected at the end of the growing period (105 days). The experiment demonstrated that beet leaves can be used as a component of fresh salads on the 60th day of the growing season because the amount of bioactive substances (polyphenols, flavanoids) is highest at that time. By the 85th day of growth, the root had grown to 4–5 cm in diameter, and the tissue structure of the leaves is edible (it can be eaten raw), making it ideal for batch sales. By the end of the growing season (day 105), the root has been strengthened, and its bioactive substances have been reduced by up to 1/3 compared to the previous state (85 days), resulting in a decrease in the amount of bioactive substances. • The growing period can determine the amount of bioactive compound in beetroot. • The beetroot leaves have the highest polyphenol and flavonoid content at the stage of 60-day, which proved that the younger leaves are more nutritious and suitable for a fresh salad. • For the root, higher bioactive compounds and lower nitrate content was measured on the 85th day of the vegetation period by sowing time on March 30 (springtime). • The harvested plants with healthy leaves and roots (4–5 cm diameter) are suitable for fresh consumption, which was confirmed with the high content of bioactive compounds.