어성초(H. cordata Thunb) 건조 분말(0.05 g)을 10 mL의 증류수와 함께 스테인리스 용기에 넣고 밀봉한 후 여러 온도(50, 100, 200, $300^{circ}C$)에서 10, 30, 60분간 추출하였다. 추출온도와 시간은 어성초 추출물의 중요 성분, 항산화 활성, acetylcholinesterase 저해 활성에 크게 영향을 미쳤다. $300^{circ}C$에서 30분간 처리한 어성초 추출물에서 가장 높은 페놀 함량($33.34{pm}0.96;{mu}g$ gallic acid equivalents/mL), quercetin 함량($15.75{pm}0.20;{mu}g/mL$), DPPH 라디칼 소거능($44.07{pm}2.65%$), acetylcholinesterase 저해 활성($36.53{pm}1.14%$)이 나타났다. 플라보노이드 함량은 $100^{circ}C$ 10분 추출물에서 $2.55{mu}g$ quercetin equivalents/mL로 가장 높게 측정되었다. $100^{circ}C$ 이상의 고온에서 밀폐된 증류수는 높은 압력에서 아임계수 형태로 존재하는데 이러한 아임계수는 고품질의 어성초 추출물을 제조하는데 매우 유용하였다.
Houttuynia cordata Thunb powder (0.05 g) was placed in a stainless vessel containing 10 mL of water, and subcritical water (SCW) extraction was carried out at various temperatures (50, 100, 200, and $300^{circ}C$) for 10, 30, and 60 min. SCW treatment significantly affected physiologically important compounds, antioxidant activity, and acetylcholinesterase inhibitory activity of H. cordata Thunb extracts. H. cordata Thunb extracted at $300^{circ}C$ for 30 min had the highest quercetin content, DPPH radical scavenging activity, total phenolic content, and acetylcholinesterase inhibitory activity, whereas the extract at $100^{circ}C$ for 10 min possessed the highest flavonoid content. The highest ABTS radical scavenging activity was found in H. cordata Thunb extracted at 200 and $300^{circ}C$ for 60 min. These results indicate that SCW extraction might be a useful processing method for obtaining valuable materials from H. cordata Thunb.
