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.