Microwave-assisted Extraction of Flavonoids from Rosemary and the Stability of Its Potassium-cyclodextrin Metal Organic Frameworks Inclusion Complex

Objective:To study the extraction process of rosemary flavonoids and the stability of its potassium-cyclodextrin metal organic frameworks inclusion complex (RF-K-CD-MOF). Methods:The conditions of microwave-assisted extraction of rosemary flavonoids were optimized by single factor experiments and response surface methodology. The extract was purified by D101 macroporous resin,and the purification effect was evaluated by HPLC method. RF-K-CD-MOF was synthesized by solvent method. Results:The optimal extraction conditions were as follows:Ethanol concentration 45%,ratio of liquid to solid 40:1 (mL:g),extraction temperature 77℃,initial microwave power 500 W,and extraction time 7 min. The yield of total flavonoids was 7.88% under these conditions and the purity of flavonoids was 30% in the extract. The purity of flavonoids increased from 30% to 70%. The flavonoids inclusion rate of RF-K-CD-MOF was 87.9%. The heat stability and acid-base resistance of rosemary flavonoids were both improved after embedding,keeping 70℃ for 9 days,the retention of total flavonoids increased from 20.9% to 60.6%. The effect on stability improvement was most significant in neutral environment,the retention of total flavonoids increased from 41.69% to 82.58%. Conclusion:The optimum extraction process of rosemary flavonoids by response surface methodology was convenient and effective,and the effect of macroporous resin for purification of flavonoids was significant. The heat stability and acid-base resistance of RF-K-CD-MOF were better than rosemary flavonoids extracts.