Production of an antioxidant naphthoquinone pigment by Comamonas testosteroni during growth on naphthalene

Abstract

A cell bound red pigment was synthesized by an indigenous petroleum contaminated soil isolate, Comamonas testosteroni, during growth on naphthalene as a sole source of carbon and energy. Ferric ion supplementation in the medium inhibited the pigment production. UV-visible spectrum of the pigment in ethanol showed absorption maxima at 251, 289, 318, 328, 333 and 362 nm and a broad peak at 479 nm. Ethanolic solution of pigment showed development of crystals on storage. Chemical analysis, FTIR and NMR spectroscopy studies revealed it as a novel isoprenoid quinone, a 2-methyl naphthoquinone with phytyl side chain. Ferric reducing/antioxidant power assay proved its in vitro antioxidant activity. Both pigment and ferric ions are proposed to have protective role against superoxide radical generated through intense activity of flavin containing naphthalene dioxygenase during naphthalene metabolism.