Integrated Chemical Profiling and Biological Assessment of Melittis melissophyllum L. (Lamiaceae): Antioxidant, Antimicrobial and Cytotoxic Activities

Background/Objectives: Melittis melissophyllum L. (bastard balm) is a perennial herb belonging to the Lamiaceae family. This study investigated the phytochemical composition, antioxidant properties, antimicrobial activity, and cytotoxic effects of a 50% (v/v) ethanol–water extract of M. melissophyllum. Methods: The phytochemical profiles were characterized by spectrophotometric analysis, while individual polyphenolic compounds were identified and quantified using LC–MS. Antioxidant activity was assessed using the DPPH radical scavenging and FRAP assays. The cytotoxic effects were evaluated in normal human foreskin fibroblasts (BJ) and two human cancer cell lines, HCT-116 (colorectal carcinoma) and OVCAR-3 (ovarian adenocarcinoma). The antimicrobial efficacy of M. melissophyllum extracts was assessed against a panel of Gram-positive and Gram-negative bacterial strains, as well as a representative yeast species. Results: The results revealed a high content of polyphenolic compounds in the tested extract. Cytotoxicity assays demonstrated good tolerability toward normal cells while indicating inhibitory effects on tumor-derived cell lines. In addition, the extract exhibited limited but measurable strain-dependent antimicrobial activity. Conclusions: Collectively, these findings suggest that M. melissophyllum represents a promising source of bioactive compounds with potential medicinal applications.