以反應曲面法探討不同萃取條件對薏仁麩皮機能性成分的影響

Abstract

薏仁 (Coix lachryma-jobi L.var. ma-yuen Stapf.)，為禾本科一年生草本作物，自古即被認為是藥食兼用的材料，能抑制腫瘤細胞生長、抗發炎。薏仁麩皮 (adlay bran, AB)占糙薏仁的7%，是加工過程重要的副產物。AB富含蛋白質、脂質、膳食纖維，和一些具有生物活性的化合物，如酚類化合物和植物固醇。然而，具有多種價值的AB卻當成廢棄物處理，不曾善加利用。因此本研究目的欲尋找萃取AB酚類化合物的最適條件。 利用反應曲面法 (response surface methodology, RSM)，探討總萃取率、總酚含量及總類黃酮含量來評估萃取 AB 酚類化合物的最適條件。根據預實驗的結果，萃取溫度和乙醇濃度為影響萃取機能性成分的重要因素，並利用旋轉式中心組合設計 (rotatable central composite design, RCCD) 訂出13組萃取條件，其中五組條件為中心點，接著使用二階模式探討不同萃取條件下對萃取率、總酚含量、總類黃酮含量的影響。實驗結果發現，薏仁麩皮乙醇萃取物1 (adlay bran ethanolic extract 1, ABE1) 的萃取率、總酚含量、總類黃酮含量都能符合所建立的迴歸模式，且能解釋的變異程度超過78%。綜合萃取結果，最適的萃取條件為55%乙醇、50℃的萃取溫度。經高效能液相層析儀 (high-performance liquid chromatography, HPLC) 定量得知，薏仁麩皮乙醇萃取物1的乙酸乙酯區分層 (ethyl acetate fraction of adlay bran ethanolic extract 1, ABE1-Ea) 的酚類化合物含量依序為對羥基苯甲酸 (p-hydroxybenzoic acid, 114.9 μg/g sample)、香草醛 (vanillin, 63.7 μg/g sample) 和阿魏酸 (ferulic acid, 61.6 μg/g sample)。本研究結果顯示，薏仁麩皮經萃取有助於提升機能性及加工利用性，具有開發成保健素材的潛力。

Adlay ( Coix lachryma-jobi L. var. ma-yuen Stapf ) is an one year grass crop that has long been used as a traditional Chinese medicine (TCM) to treat tumor and inflammation. In addition, adlay bran (AB) is an important byproduct of the milling process, representing 7% of the dehulled adlay. AB is rich in proteins, lipids, dietary fibers and bioactive compounds, such as phenolic compounds and phytosterols. However, AB which contains considerable amounts of valuable compounds is dealt as agricultural waste without properly utilization. The aim of this study is to search optimization extraction conditions of phenolic compounds from AB. The extraction of phenolic compounds from AB was optimized by the simultaneous maximization of the yield in adlay bran extract, total phenolics (TP), total flavanoids (TFA), using the response surface methodology (RSM). According to the preliminary results, extraction temperature and ethanol concentration were selected as the most affective factors for extracting. A rotatable central composite design (RCCD) consisting of 13 experimental runs with five replicates at the center point was then applied and a second-order polynomial model was used to describe the experimental data regarding the yield in adlay bran extract 1 (ABE1), TP and TFA. The experimental results fitted well to the model and more than 78% of the variability was explained. The optimized conditions were 55% ethanol and 50℃. Based on the high-performance liquid chromatography (HPLC) analysis, the more abundant phenolic compounds in ethyl acetate fraction of adlay bran ethanolic extract 1 (ABE1-Ea) in orders are p-hydroxybenzoic acid (114.9 μg/g sample), vanillin (63.7 μg/g sample), and ferulic acid (61.6 μg/g sample). In conclusion, extraction process may improve the processing, ulization and function of AB so that AB shows functional ingredients potential.