title: Putative structure and characteristics of a red water-soluble pigment secreted by Penicillium marneffei.
abstract: The dimorphic fungus, Penicillium marneffei, produces and secretes a brick red pigment, during growth at temperatures below 30 degrees C. It generally diffuses into commonly used media like Sabouraud dextrose agar and malt extract agar. The pigment was purified by reverse-phase liquid chromatography and subjected to structural determination by elemental and spectral analysis using atomic absorption (AAS), ultra violet and visible (UV-VIS), fluorescence, infra red (IR), nuclear magnetic resonance (NMR) and tandem mass spectrometry (MS-MS). The pigment showed a buffering ability in aqueous solutions, maintaining an alkaline pH of 8.0. It behaved as a colorimetric pH indicator over a wide acidic and alkaline pH range, with discoloration occurring ostensibly through hydrolysis of key chemical groups at extremely acidic pH ( approximately 2.0). The pigment was found to have some structural resemblance with the copper-colored pigment (herquinone) produced by Penicillium herquei as both pigments contain the phenalene carbon framework. The notable differences between herquinone and the pigment produced by P. marneffei are (i) the latter's apparent dimerization through a sulphur-sulphur (disulfide) bond and (ii) the presence of 1,1,3,3-tetramethyl-2,3-dihydropyrrole moiety in the latter instead of 2,3,3-trimethyl-2,3-dihydrofuran moiety found in the former. The delineation of the structure of the pigment produced by Penicillium marneffei may help in understanding certain aspects of the biology of this pathogenic fungus.
authors.affiliation: Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Sonia
authors.initials: S
authors.lastname: Bhardwaj
authors.forename: Anshuman
authors.initials: A
authors.lastname: Shukla
authors.forename: Sourav
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Swati
authors.initials: S
authors.lastname: Sharma
authors.forename: Purnananda
authors.initials: P
authors.lastname: Guptasarma
authors.forename: Asit K
authors.initials: AK
authors.lastname: Chakraborti
authors.forename: Arunaloke
authors.initials: A
authors.lastname: Chakrabarti
mesh_terms: D002853:Chromatography, Liquid; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010407:Penicillium / Q000145:classification / Q000378:metabolism*; D010860:Pigments, Biological / Q000737:chemistry / Q000378:metabolism; D012995:Solubility; D013054:Spectrophotometry, Atomic; D013329:Structure-Activity Relationship; D053719:Tandem Mass Spectrometry
chemical_list: D010860:Pigments, Biological