Effect of simultaneous ultrasonic/microwave assisted extraction on the antioxidant and antibacterial activities of burdock leaves

Abstract

The effects of different extraction methods on the antioxidant and antibacterial activities of burdock leaves extracts were first investigated. The extracts of burdock leaves were prepared by 10 h maceration extraction (ME) and simultaneous ultrasonic/microwave assisted extraction (UMAE) with a significantly short operation time of 30 s. The UMAE extract exhibited 50.60% inhibition of lipid peroxidation, 51.22% scavenging of DPPH radical at 0.8 mg/ml, 55.21 and 79.80% scavenging of hydroxyl and superoxide anion radicals at 2.5 mg/ml. These activities were much higher than those of ME extract. Moreover, the UMAE extract was more effective against Gram-positive and Gram-negative bacteria than ME extract. The MIC values ranged from 1.5 to 2.5 mg/ml. Among the phenolic compounds identified in the extracts, the occurrence of o-hydrobenzoic acid and ferulic acid in burdock leaves is reported for the first time. The results indicated UMAE to be a new, fast and efficient alternative for preparation of antioxidant and antibacterial agents.   Key words: Antibacterial activity, antioxidant activity, burdock leaves, phenolic compounds, simultaneous ultrasonic/microwave assisted extraction.