Subcritical water extraction of flavonols myricetin, quercetin, and kaempferol from plants

국문 초록 (Abstract)

플라보노이드는 식물의 꽃, 잎, 뿌리, 열매 등에서 유래되는 불용성 물질로서 강력한 항산화 및 항균효과를 나타내는 물질이다. 본 연구에서는 플라보노이드와 같은 비극성 물질 추출에 있어 친환경적이며 자동화된 추출기술로 각광 받고 있는 아임계수 추출 방법을 이용하여 플라보놀 (flavonol)의 –OH기 (hydroxyl group) 개수의 차이에 따른 추출 조건을 확립하고, 아임계수 추출과 유기용매 추출 효율을 비교 분석하였다. 홍차, 샐러리, 인삼 잎으로부터 flavonol myricetin, quercetin, 그리고 kaempferol을 추출하였다. 아임계수 추출을 위하여 추출용매로 순수한 물을 이용하였으며 추출 온도 (110-200℃) 및 시간 (5-15분)의 변화를 주었다. 시료 1 g과 규조토 3 g을 혼합한 후 아임계수 추출장치 (DIONEX, Accelerated Solvent Extractor, ASE350)를 이용하여 추출하였고, HPLC를 이용하여 분석하였다. Myricetin은 170℃/15분에 (686.38±60.1 mg/kg celery), quercetin 역시 170℃/15분에 (1179.42±206 mg/kg black tea), kaempferol은 200℃/15분에 (2770.6±71.9 mg/kg black tea) 가장 많은 플라보놀이 추출되었다. 이는 에탄올, 메탄올 그리고 열수 추출과 비교할 경우 훨씬 높은 효율을 나타내며, 기존 유기용매 추출의 대체기술로서 아임계수 추출법의 우수성을 보여준 결과라 할 수 있다. 또한 아임계수 추출법은 물의 온도 및 시간을 변화함으로써 식물로부터 화학적 구조가 다른 flavonol을 선택적으로 추출하는데 있어 매우 적합한 방법임을 확인하였다. 더 나아가 다양한 플라보노이드의 화학적 구조와 추출 최적화를 통해 식물 유래 생리활성 물질의 신속하고 안전한 선택적 추출에 대한 활용 가능성이 기대되는 바이다.

다국어 초록 (Multilingual Abstract)

Plants contain numerous bioactivity compounds, of which especially flavonoids are known for their biological functionalities such as prevention of diseases and antioxidant activities. One kind of flavonoids, flavonols, are present in a wide variety of fruits and vegetables, and are compounds that include hydroxyl (–OH) groups at the 3-position of flavones. This study was designed to identify any change in extraction behavior according to the number of hydroxyl groups in flavonols. Therefore, myricetin, quercetin, and kaempferol—which may only be differentiated as flavonols using the number of hydroxyl groups—were subjected to the experiment. Also, this study compared the efficiencies of using subcritical water, hot water, and organic solvents to extract flavonols from black tea, celery, and ginseng leaf. Subcritical water extraction (SWE) was conducted using an accelerated solvent extractor, and the effect of key operating conditions was determined by varying the temperature (110–200°C), extraction time (5–15 min), and pressure (90–110 atm). The extracts were analyzed quantitatively using high-performance liquid chromatography. The yields of myricetin, quercetin, and kaempferol from plants were maximal at extraction temperatures of 170°C, 170°C and 200°C, respectively, and they seemed to be dependent on the number of hydroxyl groups included in the chemical structure of the flavonols, with more of those with fewer hydroxyl groups attached being extracted at higher temperatures. The results also showed that the yields of quercetin by SWE were two- to four-, two- to five-, and two- to twenty seven-fold higher than those obtained using the ethanol, methanol, and water-at-boiling-point extraction methods, respectively. This study shows that water at the subcritical state can be used as an efficient solvent for extracting flavonol such as myricetin, quercetin, and kaempferol from plants. SWE is not only effective and ecofriendly, but is also a highly selective and rapid method for extracting flavonol from plants.

목차 (Table of Contents)

• Ⅰ. INTRODUCTION 1
• Ⅱ. MATERIALS AND METHODS 13
• A. Sample preparation 13
• B. Chemicals 13
• C. SWE 14
• D. Traditional extraction methods 16
• E. HPLC analysis method 16
• F. Analysis of general components 17
• Ⅲ. RESULTS AND DISCUSSION 20
• A. Chemical compositions of samples and its SW extracts 20
• B. Solid yields of SW extracts from plants 25
• C. Quality and quantity analyses of flavonol obtained by SWE of plants 27
• 1. HPLC chromatograms 27
• 2. Change of flavonol concentrations according to different numbers of hydroxyl groups from SW extracts 30
• D. Comparison of flavonol concentrations with traditional extraction methods 41
• Ⅳ. SUMMARY AND CONCLUSIONS 47
• REFERENCES 49
• 국문초록 58