Ethanol extract of lemon balm (Melissa officinalis L.) leaves: Response Surface Optimization (RSM) of antioxidant activity and evaluation of antibacterial and anticancer effects

Lemon balm (Melissa officinalis L.) is among the plants used by humans for various purposes. This study aimed to determine the total phenolic content and evaluate the antibacterial, antioxidant, and anticancer activities of the ethanolic leaf extract of M. officinalis naturally growing in Elazığ (Türkiye). The extract was prepared by ultrasonic-assisted extraction, and antioxidant activity was optimized using Response Surface Methodology (RSM). Antibacterial activity was tested using the agar well diffusion method, antioxidant capacity was evaluated by DPPH and CUPRAC assays, and anticancer effects were assessed on A549, U2OS, and HUVEC cell lines using the MTT assay. The extract exhibited a high total phenolic content (129.0±3.0 mg GAE/mL). No antibacterial activity was observed against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, or Bacillus cereus. Antioxidant activity increased in a concentration-dependent manner, reaching 51.0% DPPH scavenging and 1.144 CUPRAC absorbance at 60 µg/mL. Cytotoxicity also increased in a dose- and time-dependent manner, with the strongest effect observed in A549 cells at 200 µg/mL after 48 h (cell viability: 56.6%). RSM modeling showed excellent predictive performance (R² = 0.9704). These findings indicate that M. officinalis from Elazığ is a rich phenolic source with notable antioxidant potential and moderate cytotoxic activity, and that RSM can effectively optimize extraction conditions for enhanced antioxidant performance.