본 실험에서는 지황의 주요성분인 catalpol의 함량 및 항산화 특성을 비교하였다. 실험에 사용한 지황은 고강, 수원 10호, 수원11호, 지황1호, 고려지황이었으며 수분함량은 각각 77.6, 77.4, 78.4, 75.8, 78.1%를 나타내었다(p<0.05). Catalpol은 표준품을 사용하였으며, 동결건조 한 고강, 수원 10호, 수원11호, 지황1호, 고려의 catalpol 함량은 각각 108.15, 84.21, 85.21, 85.59, 144.88 mg/g으로, 고려지황의 catalpol 함량이 가장 높았다(p<0.05). 총 phenol은 각각 0.446, 0364, 0.358, 0.440, 0.459 mg/g, $IC_{50}$으로 계산된 DPPH radical 소거능은 각각 240.6, 270.2, 355.7, 245.3, 205.8 mg/g, hydroxyl radical 소거능은 각각 46.7, 67.4, 63.5, 44.8, 38.8 mg/g을 나타내었다. 항산화 활성에서는 고려지황이 가장 좋은 것으로 사료된다. 또한 지황의 유효성분 및 항산화성이 좋은 고려지황을 이용하여 기능성식품 및 의약품으로의 개발이 필요할 것으로 판단된다.
This study was to investigate catalpol content and antioxidant activities in five cultivars (Kokang, Suwon 10, Suwon 11, Jiwhang 1 and Korea) of Rehmannia Radix. Catalpol content was analysed by HPLC using $C_{18}$ column ($150{ imes}4.6;mm$, $5{mu}m$), 1% acetonitrile and a UV detector. The standard curve was found to be a linear regression of y=0.0483x-0.0841 ($R^2$=0.999). The catalpol content ranged from 85.2 mg/g to 144.9 mg/g, of which the Korea was the highest among cultivars. The total phenol content in Rehmannia Radix was 0.358~0.459 mg/g, of which the Korea was the highest among cultivars. The antioxidant activities determined by DPPH and hydroxyl radical scavenging activities were the highest in Korea with $IC_{50}$ of 205.8 mg/g for DPPH radical scavenging activity and $IC_{50}$ of 38.8 mg/g for hydroxyl radical scavenging activity. Based on these results, the Korea among Rehmannia Radix cultivars was suggested to be a potent medicinal plant material for antioxidant activities.
