介質研磨甘藷葉之理化性質及其葉黃素生物分布

Abstract

甘藷葉 (Ipomoea batatas leaves) 富含膳食纖維、維生素、礦物質、抗氧化物質等機能性成分，為國人常食用的葉菜類蔬菜。根據我國國民飲食資料庫估算，由蔬果獲得之抗氧化活性成分中，甘藷葉約佔1/3。文獻指出，甘藷葉富含葉黃素 (lutein)，與預防罹患老年性黃斑部病變 (age-related macular degeneration, AMD)、白內障 (cataracts) 等眼部疾病有關；葉菜類中葉黃素會與蛋白質形成複合物存在於細胞壁內，藉由加熱或細磨得以釋放。介質研磨 (media milling) 可使生物材料微細化，粒徑分布落在0.1 ~ 1 μm次微米 (sub-micron) 等級，有利於活性成分釋放，增加生物利用率。本研究以介質研磨製備甘藷葉懸浮液，探討TNG57、TNG71、CYY98-63、CYY100-01四個品種之冷風、冷凍乾燥甘藷葉於研磨前後，其理化性質及葉黃素、總類胡蘿蔔素含量之變化，並以Wistar大鼠為動物模式，探討給予大鼠富含葉黃素之甘藷懸浮液四週後，分析其血漿及肝臟中葉黃素之含量，以了解葉黃素之生物分布，以利作為開發視力保健產品之參考。結果顯示，不同品種甘藷葉研磨兩小時後，懸浮液體積平均粒徑從56-117.77 m大幅下降至7-27 m，數量上99.8%微粒為次微米級 (< 1 m)；界面電位低於-30 mV，顯示懸浮液穩定性高；pH值介於5.1 ~ 5.86之間偏弱酸性，隨研磨時間增加有先升後降的趨勢，但變化度皆小於0.5，其中pH值又以CYY98-63 (紫葉品種) 為最低 (5.1 ~ 5.4)；黏度方面，相較於未研磨懸浮液黏度 (994 ~ 3732 cP)，研磨後上升為 (3357 ~ 12410)，增加2 ~ 8倍，且研磨90分鐘時達最高值；色澤上，隨研磨時間增加，亮度 (L值) 皆有上升趨勢，a值負值增加，b值正值增加，表示樣品經研磨後趨向黃綠色；生物活性成分上，乾燥條件上，不論葉黃素或總類胡蘿蔔素，冷凍乾燥組別皆高於冷風乾燥；品種上，葉黃素含量以CYY98-63 (紫葉品種)為最高，每克乾重含0.84 ~ 0.97毫克，大鼠動物試驗上，肝臟部分，介入組別含葉黃素者，都高於無葉黃素介入的控制組。

Sweet potato (Ipomoea batatas L.) leaves, a common vegetable in Taiwan, are rich in dietary fiber, minerals, antioxidants and other bioactive compounds. According to National Food Consumption Database, sweet potato leaves are important sources for antioxidant components obtaining from fruits and vegetables. Sweet potato leaves are rich in lutein which are associated with preventing eye diseases such as age-related macular degeneration (AMD) and cataracts. In leafy vegetables, lutein is present in the cell wall, formed a complex with protein which can be released by heating or fine grinding. Media milling can reduce the particle size distribution into the sub-micron scale, 0.1 to 1 μm, facilitating the release of bioactive compounds and the increase of bioavailability. In this study, we explored the effects on physicochemical properties and the content of lutein, total carotenoid of different varieties and drying conditions sweet potato leaves using media-milling process. Biodistribution of lutein was evaluated using Wistar rats as animal models by analyzing the lutein content of plasma and liver after administering lutein-containing sweet potato suspension for four weeks. The results showed that the volume-mean diameter of sweet potato suspension particle decreased sharply from 56 ~ 117.77 m to 7 ~ 27 m, and the percentage of particle smaller than submicron (<1 m) was 99.9% after two hours milling. The zetapotential were higher than 30 mV or lower than -30 mV, indicating the high stability of the suspensions were obtained. The pH values of suspensions were ranged 5.1 ~ 5.86, which were weak acidity. The viscosity of suspensions were reached the highest value after media-milled for 90 minutes. The viscosity of media-milled suspensions (3357 to 12410 cP) were 8 folds higher than without media-milled suspensions (994 ~ 3732 cP). With the increase of milling time, the color of suspensions were tended to yellowish green. The lutein content and total carotenoid content of freeze-dried group were higher than that of cool-dry. The lutein content of CYY98-63 (purple leaf varieties) was the highest (0.84 ~ 0.97 mg per gram dry basis). Biodistribution results showed that the lutein content in liver of lutein intervention group was higher than that of control group without intervention of lutein.