Chemical Composition and Bioactivities of Turkish Leonurus Species (Lamiaceae) Extracts: Antioxidant, Antimicrobial, and Antiproliferative Potential

The genus Leonurus L. is renowned for its diverse secondary metabolites with significant pharmacological value; however, the chemical biodiversity and biological potential of its indigenous members in Türkiye remain largely unexplored. This study investigates four species (L. cardiaca, L. quinquelobatus, L. glaucescens, and L. persicus) to elucidate their phytochemical architecture and therapeutic capacities. Characterization of the ethanol, methanol, and aqueous (5% infusion) extracts via HPLC-MS/MS identified verbascoside, genkwanin, and caffeoylquinic acids as the major representative bioactive constituents across the studied Leonurus species. The extracts exhibited measurable biological activity, with L. cardiaca displaying the highest antioxidant profile (EC50 0.117 ± 0.01 mg/mL for DPPH, 2.731 ± 0.01 mM/Trolox for ABTS), correlating with its phenolic content. Notably, the extracts demonstrated notable anticandidal activity (MIC 0.1–1 mg/mL) and negligible to moderate antibacterial effects, alongside varying levels of susceptibility against breast (MCF7) and glioma (C6) cancer cell lines. These effects showed differentiation in toxicity compared to lung (A549) cells. This investigation provides scientific evidence supporting the traditional medicinal use of Leonurus species while highlighting their potential as standardized sources for the pharmaceutical and nutraceutical sectors. Our results lay a robust foundation for future bioactivity-guided isolation studies to further elucidate the molecular mechanisms behind their differential biological effects.