Prodigiosin derived from Serratia nematodiphila RR16 as Antioxidant agent

Red pigment is produced by microorganisms with extensive bioactivity, one of which is antioxidant activity. Antioxidants are essential to protect cells from damage caused by free radicals. The aim of this study was to investigate the antioxidant activity of red pigments from bacteria isolated from the rhizosphere soil of Rafflesia (Rafflesia arnoldii) plants, both in vitro and at the cellular level. The 16S rRNA gene analysis revealed that the isolate with code RR16 was Serratia nematodiphila. The chloroform extract of S. nematodiphila RR16 was found to have DPPH radical scavenging activity with an IC50 value of 111.18µg/mL. Pigment fractionation was performed by thin-layer chromatography (TLC) and bioautography to separate the extract components, while fraction isolation was performed by preparative TLC. The results showed that the red pigment fraction of S. nematodiphila RR16, with an Rf value of 0.29, had the strongest antioxidant activity, reaching a value of 140.31µg/mL. In addition, the red pigment extracts and fractions maintained cell viability and induced mitochondrial activity in the model organism Schizosaccharomyces pombe at concentrations of 100 and 140 µg/mL, respectively. The specific red pigment identified through a series of tests was prodigiosin, which was confirmed by the results of presumptive tests, UV-Vis absorption values, Fourier Transform Infrared (FTIR) characterization, ¹H Nuclear Magnetic Resonance (NMR), and the presence of the PigC gene, all of which exhibited characteristic features of prodigiosin. Therefore, this study is the first report on prodigiosin-derived pigments from S. nematodiphila that have antioxidant activity both in vitro and at the cellular level.