牛蒡，是一種富含豐富胺基酸與多酚類的蔬菜。這種蔬菜，已在中國被視為日常生活飲品數百年，並引進日本和台灣。在這個研究中，利用了熱風乾燥與冷凍乾燥牛蒡根，分別測定了其總酚類含量、抗氧化活性、游離胺基酸及多酚類化合物。熱風乾燥與冷凍乾燥牛蒡之水和80％酒精萃取物其總酚含量沒有顯著差異（p＝0.31，0.9）。而經過水萃取的冷凍乾燥牛蒡其抗氧化活性明顯高於熱風乾燥牛蒡（p＝0.00034）。牛蒡之主要游離胺基酸，為精胺酸3858.76 mg/100g dry weight（DW）、脯胺酸1533.86 mg/100g DW、天門冬醯胺586.86 mg/100g DW，在熱風乾燥加熱後，分別明顯下降至919.02，774.60和229.44 mg/100g DW。利用LC-MS-MS鑑定出牛蒡根含有Chlorogenic acid（氯原酸）、Caffeic acid（咖啡酸）和Quercetin（槲皮酮）三個多酚類化合物，由結果得知熱風乾燥的過程會使咖啡酸和氯原酸，分別從0.032增加至0.33和9.11至10.88 μg/g DW，而只有熱風乾燥牛蒡含有槲皮酮3.92 × 10-4 μg/g DW。這些結果表明，加熱過程中可能會導致牛蒡根之游離胺基酸含量減少，而多酚類化合物的含量及有機酸、揮發性成份經由加熱過程則增加。 Burdock (Arctium lappa) is an amino acid and polyphenol riched vegetable and has been consumed as a vegetable and beverage in Taiwan, Japan, and China for many years. The total phenolic content, antioxidant activity, free amino acid, and polyphenolic compound profiles of the hot air and freeze dried burdock root powders were determined in this study. There were no significant differences for the total phenolic content of the water and 80% alcoholic extracts between the hot air and freeze dried burdock roots（p＝0.31, 0.9）. However, the antioxidant activity of the water extracts of freeze dried burdock roots was significant higher than the hot air dried burdock（p＝0.00034）. The major free amino acids of burdock root determined by Amino Acid Analyzer were arginine（3858.76 mg/100 g DW）, proline（1533.86mg/100 g DW）, and aspargine（586.86mg/100 g DW）that were decreased to 919.02, 774.60, and 229.44 mg/100 g DW after hot air drying, respectively. Three polyphenolic compounds（chlorogenic acid, caffeic acid, and quercetin）in the 80% alcoholic extracts of burdock roots were identified by LC-MS-MS. The hot air drying process causes the increasing of caffeic acid and chlorogenic acid from 0.032 to 0.33 and 9.11 to 10.88μg/g DW. Only 3.92 ×10-4 μg/g DW of quercetin was detected in hot air dried burdock roots. These results suggest that heating process may cause the decrease of free amino acid content of burdock roots, whereas, the amount of polyphenolic compounds in burdock roots were increased after heating process.
