Research On Synthesis And Biological Activity Of Luteolin And Its Metal Complexes

Luteolin was a representative natural flavonoid with a variety of biological activity, such as anti-inflammatory, anti-allergic, anti-tumor, anti-bacterial, anti-viral and so on. What’s more, Luteolin could react with trace metal elements to form luteolin metal complexes, it not only could improve the physical and chemical properties of luteolin and promote human’s absorption and utilization, but also enhance its physiological and biochemical function, even generate some new biological activity through synergistic effect. At the same time, luteolin metal complexes played a very important role in the absorption, transport and metabolism of trace metal elements. In this paper, luteolin was synthesized through semi-synthetic methods, luteolin metal complexes were prepared and their biological activity were studied. The main contents and results were as follows:(1) Preparation of luteolin. The raw material that hesperidin adopted Semi-synthesis approach to scueessfully synthesize hesperetin, eriodictyol luteolin by glycoside hydrolysis, demethylation, dehydrogenation reaction steps. And their structure were characterized by infrared spectroscopy, UV spectroscopy, mass spectrometry and NMR spectrometry, reaction mechanism was discussed. The results showed that the final product was luteolin, comprehensive yield 45.84%, content 95.76%.(2) Preparation of luteolin-Zn complex and luteolin-Mn complex. The effects of different conditions on the luteolin’s yield were analyzed, and the complexes formation between luteolin and metal ions Zn2+ and Mn2+ were examined under UV–visible, infra-red spectroscopy, TGDSC and elemental analysis techniques. The results indicated that the optimum conditions is reaction time 4h, pH 4, reaction temperature 60 ℃ and molar ratio 2:1 and luteolin react with Zn2+ and Mn2+ through 4-carbonyl-5-hydroxy chelation site in the two luteolin molecule.(3) Biological activity of luteolin and its complexes. Antioxidant activity, antibacterial activity and the inhibition of xanthine oxidase were studied between luteolin and its complexes. The results indicated that the complexes have a better antioxidant ability, antibacterial ability and inhibition ability of xanthine oxidase than luteolin. In the antioxidant activity experiment, luteolin and its complexes showed ability to scavenge free radicals such as DPPH radical, ? OH radical and O2- ? radical. In the antibacterial activity experiment, luteolin and its complexes showed antibacterial ability for pathogens such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Listeria monocytogenes.Through enzyme kinetic analysis, luteolin and its complexes belonged to competitive reversible inhibition on the inhibition type of xanthine oxidase. Effects of luteolin and its complexes on HepG2 cells proliferation and glucose consumption ability were studied. Through the establishment of dexamethasone-induced insulin resistance in HepG2 cells model, effects of different concentrations of the test sample on relative cell viability and glucose consumption ability of HepG2 cells were analyzed. The results showed that luteolin-Zn complex and luteolin-Mn complex have stronger toxicity on HepG2 cells luteolin. Besides, luteolin-Zn complex exhibited the highest glucose consumption ability and low toxicity to HepG2 cells, followed by luteolin-Mn complex. And luteolin could not promote glucose consumption in HepG2 cells at the concentration in the range of 0~100 μg/m L.