利用多酚類成分作為指標探討桑葉品質

Studies on the polyphenol constituents as markers for the quality assessment of mulberry leaves

Jerome Gilles Ganzon(Jerome Gilles Ganzon)

指導教授 ： 王靜瓊

臺北醫學大學/藥學院/藥學系(碩博士班)/博士(2018年)

摘要

桑葉（Morus alba L.）常用於驅散外感風熱型之喉嚨痛和咳嗽的藥材。然而，桑葉抗氧化的活性會受採集方式、環境因子及種別影響。因此本研究將利用清除DPPH自由基分析，追蹤分離50%甲醇市售桑葉萃取物中的天然物。首先利用逆相層析管柱Diaion HP20、Sephadex LH20、Lichroprep RP18、MCI CHP20及Oasis HLB之固定相，並以不同比例的甲醇水溶液當移動相。分離得到gastrodin (1)、5-O-caffeoylquinic acid (2)、4-O-caffeoylquinic acid (3)、rutin (4)、 isoquercetin (5)等五個多酚類(PCMs)，其對DPPH清除50%之濃度(SC50)分別為1412.24 μM、92.45 μM、32.19 μM、17.31 μM、22.88 μM。並利用此5個多酚類(PCMs)，分析桑枝頂部(0-10公分)、中間部(10-30公分)、底部(≧30公分)之葉子的含量。結果顯示：嫩葉的PCM含量高於成熟葉。且採集1-12月的葉片，其PCM的含量分佈具有顯著差異。於2015年1月和2月環境溫度 < 20 ºC、降雨量約50毫米、日曬時間約90±10小時，採集的桑葉PCM含量高於其他月份採集。此外，4-O-caffeoylquinic acid、rutin的含量與DPPH自由基清除能力間具有正相關性，因此建議可做為活性指標成分。此外，蠶桑(YS203)和果桑(GSM＃2)此兩種品系，含有PCMs且具抗氧化作用，建議可做為新資源。綜合而論，本研究利用分離得之多酚類(PCMs)的含量，評估全年的桑葉與DPPH自由基清除活性作用之關聯性，並首次發現桑葉中含有gastrodin。

關鍵字

mulberry ； leaves location ； 4-O-caffeoylquinic acid ； chemical markers ； antioxidant ； polyphenols ； harvest season ； gastrodin

並列摘要

Leaves of mulberry (Morus alba L.) is a commonly used traditional Chinese medicine for driving away exogenous wind heat which clinically presented as sore throat and cough. However, efficacy of the antioxidant activity of M. alba L. may possibly be influenced by way of leaves collection, environment conditions and even the varieties of the plant species. Thus, in this study, we firstly isolated compounds from the 50% aqueous methanol extract of commercial M. alba L. leaves following a bioassay-guided isolation scheme, using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The isolation process utilized a reversed-phase chromatographic column using various stationary phases (Diaion HP20, Sephadex LH20, Lichroprep RP18, MCI CHP20 and Oasis HLB) eluted with various proportions of methanol in water. This afforded polyphenolic compounds gastrodin (1), 5-O-caffeoylquinic acid (2), 4-O-caffeoylquinic acid (3), rutin (4) and isoquercetin (5) with 50% scavenging concentration potential (SC50) of 1412.24 µM, 92.45 µM, 32.19 µM, 17.31 µM and 22.88 µM, respectively. The isolated polyphenolic compounds 1-5 were employed as chemical markers (PCMs) that identified apical leaves, 0-10 cm, contained significantly higher PCMs than middle, 10-30 cm; and bottom,  30 cm leaves, located on a lateral branch from the apex. Furthermore, young leaves have higher PCMs content than older matured leaves. Harvesting season contributed significantly on the content distribution of PCMs in the 12-month methanol crude extract leaves samples. The months of January and February 2015 with relatively cold temperatures of less than 20 ºC, low precipitation about 50 mm monthly rain volume and a monthly sunshine exposure of about 90 ± 10 hrs provided M. alba L. leaves with higher PCMs content compared to leaves sampled in other months. Furthermore, there was a strong correlation between the content of 4-O-caffeoylquinic acid and rutin with the DPPH radical scavenging property and therefore suggested as markers for the activity. Moreover, the leaves from varieties YS203 (used for sericulture) and GSM#2 (grown for fruit production) contained PCMs and exhibited antioxidant activity comparable to commercial leaves, thus we suggested as new resource materials. In conclusion, this study showed correlation of content of the isolated PCMs with the DPPH radical scavenging activity in M. alba L. leaves for the period of one full year. Moreover, M. alba L. leaves contained gastrodin was firstly reported.

並列關鍵字

mulberry ； leaves location ； 4-O-caffeoylquinic acid ； chemical markers ； antioxidant ； polyphenols ； harvest season ； gastrodin

參考文獻

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