不同生育期與乾燥方式對白芷產量和有效成分之探討

Abstract

白芷（Angelica dahurica）是常用的中藥材與機能性食品，另因具美白功效，可作為美白產品原料；本研究以臺灣栽培之白芷為材料，探討質量最佳之收穫生育期與乾燥法。白芷美白功效主因其根富含呋喃香豆素，本試驗鑑定出bergapten（佛手甘內酯）、 imperatorin（歐前胡素）、 isoimperatorin（異歐前胡素）、xanthotoxin（花椒毒素）、 oxypeucedanin（氧化前胡內酯） 和 phellopterin（珊瑚菜内酯）六種呋喃香豆素，前三者具美白功效；此外，抗氧化力亦是美白品質之指標，故分析總酚類含量與DPPH清除力。試驗分兩部分，最適收穫試驗，分析白芷三個生育階段，營養生長期、夏休眠期與抽苔期，結果營養生長期進入抽苔期白芷產量、有效成分皆下降；營養生長期進入夏休眠期，白芷產量、有效成分皆上升，但抗氧化力下降。綜合產量與有效成分含量結果，夏休眠期有效成分總量最高，營養生長期次之。乾燥試驗方面，以陰乾、冷凍乾燥、40˚C乾燥與70˚C乾燥四種方法處理白芷，結果顯示imperatorin、isoimperatorin平均含量在陰乾、冷凍乾燥、低溫熱風乾燥（40˚C）下無顯著差異；而陰乾與40˚C乾燥bergapten與總酚類含量較高，且DPPH清除力較佳；進一步分析，白芷莖、葉與種子皆含呋喃香豆素，而根部呋喃香豆素在皮層含量較髓部高。本篇試驗以夏休眠期為最佳之收穫期；40˚C 乾燥之品質較好。

Baizhi (Angelica dahurian) has been widely used as a traditional Chinese herbal medicine, functional food and ingredient of cosmetic product, mostly because of high furanocoumarin compounds in its root. This study was designed to determine the optimal harvest stage and postharvest handling of Baizhi to obtain the highest yield and productivity. Firstly, six furanocoumarin compounds were identified in Baizhi root by liquid chromatography, including bergapten, imperatorin, isoimperatorin, xanthotoxin, oxypeucedanin and phellopterin. The first three are believed to be the active compound for skin-depigmenting by blocking the tyrosinase synthesis, whose product accelerates skin-darkening. In addition, anti-oxidation activity of Baizhi roots, which revealed by either the total phenols or DPPH radical-scavenging activity, offers another process to block skin-darkening. For their role in blocking skin-darkening, the three compounds (bergapten, imperatorin and isoimperatorin) as well as the anti-oxidation activity were analyzed to reveal the quality of Baizhi. Four postharvest drying methods, in-the-shade-, 40℃-, 70℃- and freeze-drying, were applied to analyze Baizhi roots. The results showed that in-the-shade-, 40℃- and freeze-drying did not affect the contents of imperatorin and isoimperatorin. However, bergapten content, total phenols and DPPH radical-scavenging activity were obtained more efficiently by in-the-shade- and 40℃-drying methods than the others. Freeze-drying and 40℃-drying methods were used to analyze the productivities of vegetative, bolting and summer dormancy stages. The latter is a special trait of Baizhi that occurs in summer. Both the dry weight of Baizhi roots and active compounds within decreased at bolting stage. The highest dry weight and active compounds were obtained at dormancy stage, although the anti-oxidation activity was lower than the late vegetative stage. Further analyses indicate that in Baizhi roots, cortex yields more active compounds and more anti-oxidation activity then pith does. Taken together, it is suggested to harvest the Baizhi roots at dormancy stage and subsequently handled by 40℃-drying to obtain the highest production as the ingredient of skin-depigmenting products.