The aerial parts of Valeriana collina and Valeriana stolonifera are considered a promising source of bioactive compounds with antimicrobial and hepatoprotective properties; however, their pharmacological characteristics have not been sufficiently studied.

The aim of the work. To comprehensively evaluate the antimicrobial / antifungal potential, acute toxicity, and hepatoprotective activity of thick extracts from the herbs of V. collina and V. stolonifera.

Materials and methods. Antimicrobial activity was determined by the agar diffusion method (well method). Acute toxicity was evaluated in Wistar rats according to OECD guidelines. Hepatoprotective activity was studied in a paracetamol-induced hepatitis model by measuring alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) levels; silymarin was used as the reference drug.

Results. Both extracts exhibited a broad spectrum of antimicrobial activity; V. stolonifera was more effective against P. aeruginosa (p = 0.0113), while V. collina showed higher activity against C. albicans (p = 0.0080). Both samples were classified as low-toxicity (GHS Category 5). In the hepatitis model, V. stolonifera significantly reduced ALT, AST, and ALP levels, being not inferior – and in the case of ALP, superior – to silymarin.

Conclusions. Both thick extracts of V. collina and V. stolonifera demonstrated pronounced antimicrobial activity against gram-positive and gram-negative bacteria as well as C. albicans. V. stolonifera was more effective against P. aeruginosa, whereas V. collina showed higher activity against C. albicans. These differences may be associated with variations in the ratios of biologically active compounds within the extracts, supporting the need for further chemical and pharmacological studies to elucidate mechanisms of action. A 20 % aqueous solution of the thick extract of V. collina administered intragastrically can be classified as toxicity class 5, with an LD50 ranging from 2000–5000 mg/kg. The solution of the thick extract of V. stolonifera caused no mortality in rats, classifying it as a substance with low acute toxicity (GHS Category 5, LD50 ≥5000 mg/kg). Further testing of the studied samples is not recommended unless specifically required for regulatory purposes. The studied valerian extracts, especially V. stolonifera, exhibited an expressed hepatoprotective effect in a paracetamol-induced hepatitis model in rats. The paracetamol-induced hepatitis led to marked biochemical and morphological signs of liver damage in rats. The V. stolonifera extract demonstrated a clear hepatoprotective effect, evidenced by reduced ALT, AST, and ALP levels and a decrease in the necrotic area of the liver. The effectiveness of the V. stolonifera extract exceeded that of the reference drug, silymarin.