Pharmacognostic, Phytochemical, and Antioxidant Characterization of Linaria vulgaris Mill. Aerial Parts from Central Kazakhstan

Linaria vulgaris Mill. (common toadflax; Plantaginaceae) is a medicinal plant whose pharmacognostic characteristics, chemical composition, and biological activity remain poorly documented. This study aimed to evaluate the aerial parts of L. vulgaris growing in Central Kazakhstan (Karaganda Region; collected in July–August 2024) and to provide a scientific basis for the standardization of this medicinal plant material. Resource assessment, pharmacognostic analysis, radiochemical and elemental analyses, HPLC, GC-MS, and in vitro antioxidant assays were performed. The highest raw material yields (232 and 225 kg/ha) were recorded near Molodezhnoye village and in the Karkaraly Mountains, respectively. The main quality parameters were established: loss on drying (6.35 ± 0.07%), total ash (7.37 ± 0.05%), acid-insoluble ash (0.65 ± 0.02%), and extractive content with 70% ethanol (11.34 ± 0.18%). The contents of 137Cs and 90Sr were below the national regulatory limits, and the analyzed elements showed no substantial contamination; however, a complete safety assessment would also require the determination of mercury, pesticide residues, microbial contamination, and mycotoxins. Phytochemical analysis revealed amino acids and flavonoids, with linarin as the predominant flavonoid (3.91%), indicating its potential as a marker compound for standardization. GC-MS analysis of the essential oil (yield 0.04%) tentatively identified 22 constituents (52.52% of the total peak area), with hexahydrofarnesyl acetone, phytol, palmitic acid, and benzaldehyde as the major ones. The 70% ethanolic extract showed concentration-dependent reducing and DPPH radical-scavenging activities. These findings provide new data on L. vulgaris raw material from Central Kazakhstan and support further studies on its quality, standardization, and biological activity in cell-based and in vivo models.