Research of yield, essential oil and flavonoid content in the aboveground part of Mentha longifolia L. (Huds.)) and the possibilities of exogenous ways of their regulation

Mentha longifolia is a promising source of medicinal raw materials with a wide range of antimicrobial and fungicidal activity. The aim of the work is quantitative estimation of flavonoids content calculated as luteolin, the yield of the aboveground mass and the content of essential oil, as well as to assess the effect of micronutrient fertilization on these indicatorsin the raw material Menthalongifolia. Material and methods. The research was carried out in 2017–2020. The material for the study was the plant raw material of Menthalongifolia of the second year of vegetation from the biocollection of the All-Russian Research Institute of Medicinal and Aromatic Plants. To increase the yield of the aerial part and stimulate the accumulation of essential oil in the leaves of Menthalongifolia, foliar treatments were used at the at the beginning of vegetation and at the beginning of budding of a binary mixture for organic mineral fertilizer EcoFus (1 l / ha) and micronutrient fertilizer Siliplant (0.5 l / ha). Harvesting was carried out 5–7 days after treatment: at the beginning of vegetation, at the beginning of butonization, in the phase of mass butoniza-tion, mass flowering and after re-regrowth. The content of essential oil was determined in air-dry raw materials by hydrodistillation. The extraction of flavonoids was carried out with 70% ethyl alcohol. The quantitative assessment of the content of the sum of flavonoids calculated as luteolinwas carried out by the method of spectrophotometry after the reaction of complexation with aluminum chloride. Results. As a result of the research, it was revealed that the content of the sum of flavonoids calculated as luteolin in the raw material increased from the period of vegetative growth tomass butonization (from 3.60 to 4.35%) and sharply decreased by the beginning of mass flowering to 2.55%, respectively. The phase of mass butonization is optimal for harvesting raw materials due to the maximum content of phenolic compounds and essential oil (4.35 and 1.92%, respectively). Conclusion. The use of a binary mixture of micronutrients leads to an increase in the yield of raw materials and the content of essential oil in it; however, it leads to a decrease in the content of flavonoids by 34.4% in the phase of mass butonization phase.