Purification and characterization of a new red pigment from Monascus purpureus in submerged fermentation

A metabolite was purified from Monascus perpureus culture broth with the aim of isolating economically viable new pigment having food coloring and therapeutic potential. Following optimization of physical and nutritional parameters of submerged fermentation the pigment was extracted using hexane, and purified by thin layer chromatography (TLC), column chromatography and semi-preparative HPLC. Based on UV–vis, IR, GC–MS and NMR analyses the pigment was chemically characterized as 9-(1-hydroxyhexyl)-3-(2-hydroxypropyl)-6a-methyl-9,9a-dihydrofuro[2,3-h]isoquinoline-6,8(2H,6aH)-dione with the molecular mass of m/z 375. The pigment presents numerous similarities with two classical red pigments, rubropunctamine and monascorubramine, but differs by the presence of hydroxy alkane substitutions at C-3 and C-9 positions. Antibacterial plate assay showed its inhibitory activity against Gram-positive bacteria. These results suggest the purified pigment is a new red pigment from Monascus purpureus with potential application in food coloring and antibacterial therapy.