Study On Microwave-assisted Extraction Of Flavonoids From Cajanus Cajan Leaves And Antioxidant Activity

In the present study, efficient and rapid microwave-assisted extraction of orientin and luteolin was established, and the process parameters were system systematically optimized. Moreover, the antioxidant activities of extracts from different extraction methods and orientin and luteolin were determined.The results as follow:1. A RP-HPLC method for determination of orientin and luteolin was developed as follow:The chromatographic column:HIQ sil C18W (5μm,250mm×4.6mm i.d.,5μm); gradient program of mobile phase A (formic acid/water,0.1:99.9, v/v) and mobile phase B (formic acid/methanol,0.1:99.9, v/v):0～15min,33%～33%B;15～40min,33%～75%B;40～45min,75%～-33%B; flow rate:1mL/min; column temperature:30℃; injection volume:10μL; and detection wavelength:330nm for orientin,254nm for luteolin.The developed method above showed good linearity in the range from13.50to270.00μg/mL for orientin, from17.00to340.00μg/mL for luteolin, and presented high reproducibility and precision with R.S.D. of less than5%. The recovery yield was98.16%～102.35%and the R.S.D was less than4%.2. Microwave-assisted extraction of orientin and luteolin from pigeon pea leaves was established, and the main parameters influencing the recovery were studied. The optimum extraction process was as follows:Particle size:50mesh Extraction solvent:80%ethanolRatio of liquid/solid:20mL/g Extraction temperature:60℃Number of extraction cyeles:4times Extraction time:10minRadiation powe:500WUnder the above optimized conditions, the extraction yieldS of orientin and luteolin were4.42±0.01mg/g and0.10±0.01mg/g, respectively.Compared microwave-assisted extraction with conventional heat reflux, ultrasound-assisted extraction and soaking extraction, the microwave-assisted extraction significantly improved the yields of orientin and luteolin in pigeon pea the leaves, and greatly shorten the extraction time. This significantly reduced the decomposition of thermal flavonoids under high temperature for a long time, maximizely retenting the efficacy of active ingredient.3. The antoxidant activities of extracts and orientin and luteolin were investigated. Among the extracts tested, the extract from microwave-assisted extraction showed the best antoxidant activity (IC50=0.26mg/mL). At the concentration of2mg/mL, four extracts could scavenge more than80%free radical. Luteolin had excellent antoxidant activity with IC50of0.035mg/mL which was close to IC50of BHT (0.014mg/mL).