Investigation of antioxidant and antimicrobial properties of various extracts from houttuynia cordata thunb

Abstract

The extraction of Houttuynia cordata Thunb. (H. cordata) is carried out by two methods: pressurized solvent extraction (PSE) and percolation with different solvents such as methanol, ethanol, hexane and ethyl acetate. This study mainly focused on percentage yield, total phenolic content, total flavonoid content, antioxidant capacity and antimicrobial activity of various extracts from the two methods. Overall, the conventional method had lower yield than PSE, but the antioxidant capacity of extracts between two methods were not significantly different across corresponding solvents. Meanwhile, methanol was the most efficient solvent showing the highest percentage yield (8.66±2.38), total phenolic and flavonoid contents (3.34±0.69 mg GAE/g DS and 2.68±0.11 mg QE/g DS), and the lowest IC50 value – the concentration needed to decrease 50% concentration of free radical in fixed DPPH solution (0.87±0.053 mg/mL). In terms of scavenging capacity, methanol extract was 111 times weaker than ascorbic acid followed by ethyl acetate extract with 143 times, ethanol extract with 161 times and hexane extract with 248 times. Because ethanol was always applied in pharmaceutical industry as it is relatively safe for consumption, ethanol was used for subsequent optimization in SpeedExtractor – PSE machine. At optimum temperature at 70℃ in this machine, ethanol extract reached 12.44±1.67 in percentage yield, 75.25±7.72 mg GAE/g DS in total phenolic content, 17.00±1.10 mg QE/g DS in total flavonoid content and 0.486±0.037 mg/mL in IC50 value. At this point, talking to antioxidant capacity, ethanol extract was 62 times weaker than ascorbic acid, proven to be strong scavenger. Finally, all extracts did not show any antimicrobial activities on three strains bacteria including Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Keywords: Houttuyia cordata Thunb., pressurized solvent extraction, conventional extraction, methanol, ethanol, hexane, ethyl acetate, temperature optimization, antioxidant activity, antimicrobial activity.