Identification of Three New Flavonoids from the Peels of Citrus unshiu, Jin Pi

Abstract

Aurantii Nobilis Pericarpium is the dried peels of mature fruits of Citrus unshiu Marcow, which is used as traditional medicine for treating coughing, dyspepsia, and relieving exhaustion. Many compounds such as flavonoids and limonoids with anti-allergic, anti-viral, and anti-inflammatory activities were previously isolated from C. unshiu. From this study, the extract of the peels of C. unshiu was investigated and a total of six compounds were isolated from the C. unshiu for the first time. Three new flavonoids, 3,6,7,8,2',5'-hexa-methoxyflavone (2), 5,6,7,8,3',4'-hexamethoxy-homoflavone (3), 5,6,7,8,4'-tetramethoxy-homoflavone (4) were isolated, with three known compounds, 6,7,8,4',-tetramethoxyflavone (1), 3,6,7,8,2',5'-hexamethoxyflavone (6), and scopoletin (5). To the best of our knowledge, flavonoids 1 and 6 were never been isolated from natural resources although they were reported as the synthetic compounds. The structures of 2, 3 and 4 were elucidated on the basis of spectroscopic evidences, including 1D and 2D NMR analysis.;진피(Aurantii Nobilis Pericarpium)는 귤나무(Citrus unshiu Marcow)의 성숙한 과일 껍질을 말린 것으로 기침, 소화불량증 등에 사용되었다. C. unshiu에서 flavonoid와 limonoid류가 분리 보고된 바 있으며, 이들은 항알러지, 항바이러스, 항염증 작용 등을 함유하고 있음을 관련 문헌을 통해 확인할 수 하였다. 본 연구에서는 C.unshiu 알코올 추출물의 분획 중 에틸 아세테이트 분획물의 성분을 연구하였다. C. unshiu로부터 3개의 새로운 플라보노이드 구조들, 3,6,7,8,2',5'-hexa-methoxyflavone (2), 5,6,7,8,3',4'-hexamethoxyhomoflavone (3), 5,6,7,8,4'-tetramethoxyhomoflavone (4)이 분리되었다. 합성물질로는 알려졌으나 식물에서는 처음 분리되는 2개의 물질들, 6,7,8,4'-tetramethoxyflavone (1), 3,6,7,8,2',5'-hexamethoxyflavone (6)도 분리되었다. 추가적으로 여러 식물에서 이미 분리된 바 있는 scopoletin (5)도 진피에서는 처음 분리되었다.