For the first time, the component composition of the low-molecular-weight metabolome of perfoliate pondweed (Potamogeton perfoliatus L., family Potamogetonaceae), which grows in the Astrakhan region (lower zone of the Volga river delta), has been investigated. Low molecular weight organic compounds (LMWOCs) in the composition of essential oil were obtained from dried plants by steam hydrodistillation using the Clevenger apparatus. The qualitative and quantitative compositions of the LMWOCs were investigated using gas chromatography-mass spectrometry (GC/MS complex TRACE ISQ (Thermo Scientific) with a quadrupole mass analyzer). The low molecular weight metabolome of P. perfoliatus contained 164 components, of which 151 were identified. Major LMWOCs were carboxylic acids – tetradecanoic (69.7%) and hexadecanoic (10.1%), as well as phytol (3.4%) and phyton (1.4%), characterized by diverse biological activities. The antioxidant activity of an aqueous-alcoholic extract of P. perfoliatus was investigated by a photometric method based on the reaction of DPPH (2,2-diphenyl-1-picrylhydrazyl) dissolved in ethanol with an antioxidant sample. It has been shown that P. perfoliatus extract has more pronounced antioxidant properties than the tested drugs (ascorbic acid and emoxipine). P. perfoliatus from the lower zone of the Volga River delta can be considered as a naturally renewable resource for obtaining raw materials for creating effective composites of new generation algicides to combat cyanobacterial "bloom", as well as for obtaining valuable natural forms of LMWOCs of plant origin for various types of application in pharmacology, medicine, cosmetology, food industry, and other industries.

Plants contain many natural compounds that have antimicrobial and antioxidant activity. In recent years, there has been an increased interest in natural antimicrobials, especially those derived from plants. The growing resistance of pathogenic microorganisms to antibiotics leads to the search for potential alternatives – plant extracts. Plant extracts seem to be a promising solution to the problem of increasing resistance to microorganisms, and can also provide antioxidant protection for agro-food safety. One of the most promising and interesting plants is the black nightshade (Solanum nigrum L.). Studies have been conducted to identify the antioxidant and antimicrobial activity of this plant. The results revealed a high antioxidant capacity of the black nightshade leaves, and also showed an antimicrobial effect against some microorganism.