In Vitro Cytotoxicity of Secondary Metabolites Extracted from Pseudomonas aeruginosa BS25 Strain

Pseudomonas includes ubiquitous, opportunistic, pathogenic bacteria known to produce a variety of bioactive compounds. Objective of present study was to evaluate bioactive secondary metabolites produced by novel Pseudomonas aeruginosa BS25 strain. The bacterium isolated from patient’s wound was identified via 16S rRNA sequencing. To prepare extracts, nonpolar to polar solvents, i.e., hexane [H], ethyl acetate [E], acetone–ethyl acetate [AE] and water [W], were used. Cytotoxicity screening was performed against three cancer cell lines: HeLa, HepG2 and SHSY5Y. The effect on cell proliferation and mitochondrial activity was measured in HepG2 and Leishmania major. Furthermore, induction of apoptosis, necrosis, singlet oxygen release, lipid peroxidation and DNA binding were evaluated. For chemical composition colorimetric methods, TLC, HPLC and GC–MS analysis were performed. Extract [H] was effective against all cancer cell lines (relative viability: HeLa = 42.97 ± 3.46%, HepG2 = 41.54 ± 4.26%, SHSY5Y = 49.18 ± 2.98%). It strongly inhibited cell proliferation and mitochondrial activity (HepG2 IC₅₀: 168.93 µg/ml), inducing apoptosis (apoptotic cells: 150 µg/ml = 24.89 ± 1.7%, 200 µg/ml = 43.83 ± 2.92%). Furthermore, [H] induced oxidative stress (Φ_Δ = 0.5 ± 0.17) and generated TBARs (150 µg/ml = 1.81 ± 0.02 and 200 µg/ml = 2.1 ± 0.2) and DNA degradation. On the other hand, IC₅₀ for L. major was 94.2 µg/ml. Chemical composition analysis indicated the presence of flavonoids, whereas TLC and HPLC revealed two major fractions, and GC–MS showed similarity with l-(+)-ascorbic acid 2,6-dihexadecanoate and 7,9-di-tertbutyl-1-oxaspiro (4,5) deca-6,9-diene-8-one. [H] of BS25 strain exhibits strong biological activity including ROS production, DNA damage and induction of apoptosis. Further investigations on normal cells and in vivo effects are required to fully understand its therapeutic potential.