Antimicrobial Activity of Quercus mongolica Leaf Ethanol Extract and Organic Acids against Food-borne microorganisms

식중독균에 대한 신갈나무 잎 추출물과 유기산의 항균효과

This study was conducted to determine the optimal extraction condition of temperatures and kinds of extraction solvent, and antimicrobial activity of ethanol extract of Quercus mongolica leaf and organic acid against foodborne microorganisms. The antimicrobial activity of ethanol extract at $60^{\circ}C$ for 6 hour against foodborne microorganisms was stronger than those at $30^{\circ}C\;and\;90^{\circ}C$. Also, the ethanol extract showed stronger antimicrobial activity than those of water and methanol extract. The minimal inhibitory concentrations of the ethanol extract of Quercus mongolica leaf against B. cereus and L. monocytogenes, was $62.5{\sim}125\;{\mu}g/mL$ but, the minimal inhibitory concentration was $250\;{\mu}g/mL$ against S. typhimurium and P. aeruginosa and over $500\;{\mu}g/mL$ against E. coli O157:H7, respectively. The minimal inhibitory concentrations of the lactic, citric, acetic acid and the ethanol extract of Quercus mongolica leaf against B. cereus and L. monocytogenes was 2500, 5000, 1250 and $125\;{\mu}g/mL$, respectively. The combined effect of each organic acid and the ethanol extract against B. cereus was not observed but, synergistic effect was observed against L. monocytogenes. In the meantime, when the ethanol extract was combined with each organic acid at sub-lethal concentration, the combination did not increase the inhibitory effect of the most active single compound alone against E. coli O157:H7, respectively.

신갈나무 잎 추출물의 항균력은 추출 온도별로는 $60^{\circ}C$에서 추출시 $30^{\circ}C$와 $90^{\circ}C$에 추출하는 것보다 약간 더 높은 활성을 나타내었으며 추출 용매별로는 에탄올로 추출한 경우가 물 또는 메탄올 추출물보다 대체로 높은 항균활성을 나타내었다. 신갈나무 잎 에탄올 추출물은 그람양성균인 B. cereus, S. aureus 그리고 L. monocytogenes균에 대하여 $62.5{\sim}125\;{\mu}g/mL$ 범위에서 최소저해농도를 나타내었으나 그람음성균인 S. typhimurium과 P. aeruginosa 균은 $250\;{\mu}g/mL$, E. coli O157:H7 균에 대하여는 $500\;{\mu}g/mL$ 이상에서 최소저해농도를 나타내었다. B. subtilis ATCC 6633균과 L. monocytogenes ATCC 19111균에 대한 젖산, 구연산, 초산 및 신갈나무 잎 에탄올 추출물의 최소저해농도는 두균모두 각각 2,500, 5,000, 1,250 및 $125\;{\mu}g/mL$이었으며 이들의 병용처리시 B. subtilis ATCC 6633균에는 효과가 없었으나 L. monocytogenes ATCC 19111균에 대하여는 상승항균효과를 나타내었다. 한편, 각각의 sub-lethal 농도에서 E. coli O157:H7 0019균에 대한 신갈나무 잎 에탄올 추출물과 유기산들과의 병용처리시 두 물질간에는 상승효과는 없는 것으로 나타났다.