Study On Bacteriostatic Activity And Light Stability Of Derivatives Of Orange Monascus Pigments

Monascus pigment is a kind of polyketone substance,which belongs to compound pigment,mainly including red,orange and yellow pigment.At present,there are two kinds of Monascus orange pigments whose chemical structures have been determined and are widely known,namely Rubropunctatin(O1)and Monascorubrine(O2).Since the two orange pigments O1 and O2 contain azaphilone structures,they are very easy to undergo ammoniation reaction with nitrogen-containing compounds to generate derivatives.In this paper,a variety of derivatives of Monascus orange pigments were prepared by using the characteristics of Monascus orange pigments,and their antibacterial activity,photostability and cytotoxicity were evaluated.The results are as follows:(1)The red yeast rice products with high orange pigment were screened from a variety of commercially available red yeast rice,and by optimizing the extraction solvent,the extraction efficiency of the orange pigment using dichloromethane was 29% higher than that of the national standard method.(2)Two kinds of Monascus orange pigments(O1,O2)were separated and purified by three separation methods: thin layer chromatography,silica gel column chromatography and preparative high performance liquid chromatography.The two kinds of orange pigments separated and prepared were tested by HPLC,and the purity reached more than99%,and the purity of single pigment was detected by thin-layer chromatography,and there was no fluorescent substance under ultraviolet light λ=365nm.(3)Two Monascus orange pigments(O1,O2)were reacted with sulfonamide to prepare two Monascus orange pigment derivatives RH1 and RH2.(4)Two kinds of Monascus orange pigments and eight kinds of derivatives of Monascus orange pigments were tested for the inhibition zone.Among them,only RB showed inhibitory effect on Staphylococcus aureus,and the diameter of the inhibition zone was 18.0 mm.Next,the minimum inhibitory concentration of RB against Staphylococcus aureus was determined,which was 46.9 μg/m L.(5)By measuring the absorbance values and L*,a*,b* values of two Monascus orange pigments and eight derivatives of Monascus orange pigments during the illumination process,the pigment preservation rate in a fixed period of time was calculated,and the results showed that 10 Among the Monascus pigments,R2 had the lowest pigment preservation rate,and R4 had the most stable pigment preservation rate.The hue results showed that the brightness of 10 kinds of Monascus pigments increased and the color became lighter during the illumination process.(6)The cytotoxicity of two Monascus orange pigments and eight derivatives of Monascus orange pigments were evaluated.MTT staining was used to detect the survival rate of Hep G2 cells after administration of different concentrations of Monascus pigment derivatives for 24 h.Of the ten pigments,two orange pigments had the lowest cytotoxicity.Compared with the cytotoxicity of Monascus orange pigment,the toxicity of Monascus orange pigment derivatives increased to different degrees.Among them,R3 has the lowest cytotoxicity,and RB has the highest cytotoxicity,with an IC50 value of 6.73 μg/mL.