Effect of extraction condition with two ultrasonic methods on phenolic, flavonoids and DPPH free radical scavenging of Celtis australis extract

Plants are rich source of phenolic compounds (phenolic acids, flavonoids and tannins) that are most important natural antioxidants. In the present study two ultrasonic methods including probe and bath were used for the extraction of phenolic and flavonoid compounds from Celtis australis. The effects of different extraction time including 30, 60 and 90 min (bath method) and 5, 10 and 20 min (probe method) on extraction of phenolic and flavonoid compounds were evaluated and then the ability of extracts to scavenge DPPH free radical were evaluated using three extraction solvent of water, 80% methanol and 70% ethanol. The results showed that in the probe method of ultrasonic, the highest phenolic compound (8.906±0.017 milligrams gallic acid/ g dry sample), the flavonoid (3.35±0.056 mg of quercetin/g of dry sample) and DPPH radical scavenging activity (94.723±1.127 mg of quercetin/g of dry sample) and DPPH radical scavenging activity (94.74%) were obtained using 70% ethanol within 20 minutes extraction. The minimum extraction of phenolic compounds was obtained using water for 5 minutes with 4.315±0.184 milligrams gallic acid/ g dry sample. In the ultrasound bath, the highest extraction rate of phenolic compounds (8.816±0.015 mg gallic acid equivalent/ g dry sample) was extracted using 70% ethanol for 90 minutes. The ethanol 70-90 minutes with 2.536±0.02 mg of quercetin/ g of dry sample showed the highest extraction rate of flavonoid compounds between all treatments. The minimum extraction of phenolic, flavonoid, DPPH radical scavenging activity was obtained using water -30 minutes (for ultrasonic Bath) and water - 5 minutes (for ultrasonic probe). Results showed that two methods of ultrasound had different effect on extraction of bioactive compound from Celtis australis. In each extraction method, the extraction rate of phenolic and flavonoid compounds were solvent-dependent.