Phytochemical Characterization, Antioxidant, Antimicrobial and Cytotoxic Activities of Seseli transcaucasicum (Schischk.) Pimenov & Sdobnina

Species belonging to the genus Seseli have long been known to be used as herbal remedies in traditional medicine for various purposes such as colds, inflammation, pain, and gastrointestinal disorders. Therefore, in this study, the flower parts of Seseli transcaucasicum (Schischk.) Pimenov & Sdobnina were extracted using methanol and acetone to investigate their phytochemical composition and antioxidant, antimicrobial, and cytotoxic activities. For this purpose, total phenolic content (TPC), DPPH free radical scavenging activity (RSA), phenolic component (PCs) profile, volatile component composition, antimicrobial effect, and cytotoxic potential on the HT29 human colorectal adenocarcinoma cell line were evaluated. When the results were examined, HPLC analysis of phenolic components revealed that both extracts contained particularly high levels of rosmarinic acid, catechin, and quercetin. Among these, rosmarinic acid was detected in the highest amount, with 15.195 mg/g in the methanol extract and 14.929 mg/g in the acetone extract. The volatile components of this plant were determined by GC-MS, and a total of 29 volatile compounds were identified. Among these, β-pinene (220.792 mg/kg), Δ3-carotene (81.898 mg/kg), α-sedrene (63.331 mg/kg), elixen (44.535 mg/kg), sabinene (40.822 mg/kg), and D-limonene (38.422 mg/kg) were identified as the most dominant compounds. It was observed that the methanol extract had a higher total phenolic content (77.389 ± 1.389 mg gallic acid equivalent/g extract) and higher free radical scavenging activity (40.933 ± 0.067 mg trolox equivalent/g extract) compared to the acetone extract. Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans strains were used to determine the antimicrobial activities of plant extracts, and moderate inhibitory effects were observed against these microorganisms. The highest antimicrobial activity was determined by the 16 mm inhibition zone created against S. aureus by the methanol extract at a concentration of 100 mg/mL. The cytotoxic activity of the plant was determined by measuring its dose-dependent antiproliferative effect on HT29 cells. When the difference between solvents was examined, it was observed that the acetone extract at a concentration of 500 µg/mL reduced cell viability by 18.03%, while the methanol extract at the same concentration reduced viability by 30.56%. According to the results, S. transcaucasicum is rich in phenolic and terpenic compounds and exhibits antioxidant, antimicrobial, and cytotoxic effects. Therefore, this plant species is considered a promising resource for the development of naturally occurring biologically active compounds.