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薏仁麩皮富含酚類化合物萃取物之開發研究

A study on the development of phenolics-rich extracts from adlay bran

Advisor : 江文章

Abstracts


薏苡(Coix lachryma-jobi L.var. ma-yuen Stapf)為禾本科一年生草本植物,屬醫食同源的傳統中草藥。薏仁麩皮(adlay bran, AB)為薏苡籽實加工過程中所產生之副產物,含有豐富的蛋白質、脂質與植化素(phytochemical),薏仁麩皮乙醇萃取物(adaly bran ethanolic extract, ABE)更具有調節免疫、抗發炎和抑制腫瘤細胞生長等生理功能。過去研究發現薏仁麩皮的抗發炎成分在於酚類物質,且可藉由高效液相層析儀(high performance liquid chromatography, HPLC)定量出來。因此,本研究利用反應曲面法(response surface methodology, RSM)探討50℃下,不同萃取時間與乙醇濃度對ABE、ABE-Hex/EA區分層(n-hexane/ethyl acetate fractions from ABE)產率及其中24種酚類物質含量的影響,以尋找最適的萃取條件,並與25℃長時間萃取之結果做比較。結果顯示,ABE與ABE-EA (ethyl acetate fraction of ABE)區分層產率皆會隨乙醇濃度增加而減少,但乙醇濃度超過78%以上時,兩者產率皆會提升。進一步分析各萃取條件之ABE-EA層後,發現以80%以上之乙醇可萃取到的酚類化合物最多,且在50℃萃取1小時下可達飽和,若改以室溫萃取,經10天萃取後,酚類物質含量仍持續增加,而室溫長時間萃取所得之酚類化合物含量較相對高溫短時間多。另一方面,以氣相層析儀(Gas chromatography, GC)定量室溫萃取所得之ABE區分層中脂肪酸含量(mg/g ABE-Hex or ABE-EA)與植物固醇含量(μg/g ABE-Hex or ABE-EA),發現在25%乙醇萃取的結果中,無論是ABE-Hex (hexane fraction of ABE)或ABE-EA,皆含有較高量的棕櫚酸、油酸、硬脂酸及亞麻油酸。而植物固醇部份,則以95%乙醇所能萃取到的campesterol、stigmasterol、β-sitosterol及stigmastanol含量為多。總而言之,以高濃度乙醇萃取薏仁麩皮可獲得較多的酚酸/酚醛、類黃酮及植物固醇。此外,以皮爾森相關性分析檢定11種酚酸/酚醛物質與13種類黃酮物質間的相關性,並參考其抗發炎活性與在麩皮中的含量,進而挑選syringaldehyde、vanillin、vanillic acid、ferulic acid、caffeic acid、p-coumaric acid、 liquiritigenin、quercetin、naringenin、homoeriodictyol、5,7-dihydroxychromone及chrysoeriol作為薏仁麩皮中酚類化合物之指標性成分。以上結果可當作工廠大量生產與開發薏仁麩皮保健產品之參考。

Parallel abstracts


Adlay ( Coix lachryma-jobi L. var. ma-yuen Stapf )is an annual grass crop and has been used as a traditional Chinese medicine and nourishing food. Adlay bran (AB) is a byproduct of the milling process from dehulled adlay to polished adlay. AB is abundant in protein, lipid and phytochemicals. Adlay bran ethanolic extract (ABE) have immune-modulatory, anti-inflammatory and anti-tumor effects. Previous studies have demonstrated that different phenolic compounds from adlay might contribute to the anti-inflammatory activities. A high performance liquid chromatography (HPLC) analytical platform was developed to quantify these phenolic compounds. In the present study, response surface methodology (RSM) was employed to establish optimal extraction condition for phenolic-rich ABE extraction under 50℃. The effects of different extraction time and ethanol concentration on the yield of ABE, ABE-Hex/EA (n-hexane/ethyl acetate fractions from ABE) and 24 phenolic compounds were studied, and compared with the results obtained from long time extraction at 25℃. It was shown that the yield of ABE and ABE-EA decreased with increasing ethanol concentration, whereas both the yield increased when ethanol concentration was above 78%. The content of phenolic compounds (μg/g ABE-EA) under different extractive conditions were determined. According to the results, above 80% ethanol may be more suitable for obtaining the phenolic content in AB. The extraction for phenolic compounds achieved saturation within one hour at temperature of 50℃, however, it took more than ten days at 25℃. Longer extraction time at 25℃ has obtained more phenolic content than extractions done under 50℃ with shorter time period. Furthermore, we used gas chromatography (GC) to quantify fatty acid and phytosterol contents in ABE-Hex and ABE-EA which obtained from room temperature extractions. The results suggested that 25% ethanol is more appropriate for extraction of palmitic acid, oleic acid, stearic acid and linoleic acid. Conversely, 95% ethanol is more efficient for extracting campesterol, stigmasterol, β-sitosterol and stigmastanol. In conclusion, high ethanol concentrations might be a more appropriate choice for the extraction of AB. On the other hand, the correlation between 11 phenolic acids/phenolic aldehydes and 13 flavanoids was analyzed using Pearson’s correlation coefficients. Syringaldehyde, vanillin, vanillic acid, ferulic acid, caffeic acid, p-coumaric acid, liquiritigenin, quercetin, naringenin, homoeriodictyol, quercetin, 5,7-dihydroxychromone and chrysoeriol were chosen to be the representative phenolic compounds in AB, by taking into account the evaluation of correlation, anti-inflammatory capacity and content in AB. Hopefully this study may be applicable for plants employing solvent extraction processes and the development of health food in the future.

References


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