ABSTRACT
ObjectiveTo study the chemical structure of gardenia blue pigment and its inhibitory activity against monoamine oxidase B （MAO-B）， in order to seek a potential feasible way for rational utilization and value enhancement of iridoids in Gardeniae Fructus. MethodIridoid glycosides in Gardeniae Fructus were hydrolyzed by cellulase to obtain their aglycones and reacted with amino acids. Then， the products were purified by column chromatography packed with D101 macroporous resin and preparative liquid chromatography to obtain gardenia blue pigments， and the gardenia blue pigments were identified by nuclear magnetic resonance （NMR） and mass spectrometry （MS）. Benzylamine was used as the reaction substrate of MAO-B and in vitro incubated with gardenia blue pigment monomers， high performance liquid chromatography （HPLC） was employed to determine the production of benzaldehyde for evaluating the inhibitory effect of gardenia blue pigments on MAO-B， the mobile phase was methanol （A） -50 mmol·L-1 potassium phosphate buffer （B， pH 3.2） （2∶3）， and the detection wavelength was 245 nm. ResultEight compounds of gardenia blue pigment A-H were synthesized and identified. In MAO-B inhibition test， compared with geniposide， the inhibitory activity of gardenia blue pigment D and E was significantly enhanced （P<0.05）. Compared with the 6β-hydroxygeniposide， the inhibitory activity of gardenia blue pigment G and H was significantly enhanced （P<0.05， P<0.01）. All the four gardenia blue pigments showed better MAO-B inhibitory activity than the prototype compounds. ConclusionGardenia blue pigment is a simple compound formed by one molecule of amino acid and one molecule of iridoid. Some gardenia blue pigments have better MAO-B inhibitory activity than the prototype compounds. The activity of gardenia blue pigment produced by different substrates is different， and the high-value gardenia blue pigment can be prepared based on experimental optimization， which can expand the application range of gardenia blue pigment and enrich the comprehensive utilization of iridoids from Gardeniae Fructus.