Reductive Metabolism of Ellagitannins in the Young Leaves of Castanopsis sieboldii スダジイ新葉におけるエラジタンニンの還元的代謝

The leaves of Castanopsis sieboldii (Fagaceae) contain characteristic hexahydroxydiphenoyl (HHDP) esters of 28-O-glucosyl 2α,3β,23,24-tetrahydroxyolean- and urs-12-en-28-oic acids. In this study, uncharacterized substances were detected in the young leaves, which are not observed in the mature leaves. Preliminary HPLC analyses indicated that the substances had dehydro-HHDP (DHHDP) ester groups; however, the esters were unstable and decomposed during extraction. Therefore, the compounds were isolated as their stable phenazine derivatives by extracting the young leaves with acidic aqueous EtOH containing o-phenylenediamine. The structures of the phenazine derivatives indicated that the unstable metabolites of the young leaves were 3,24-DHHDP esters of the abovementioned triterpenes. Extraction of the young leaves with 80% acetonitrile containing reducing agents, ascorbic acid or dithiothreitol afforded the corresponding HHDP esters. Furthermore, heating of the young leaves in 80% acetonitrile also yielded the same HHDP esters as the reduction products. The results suggested that the HHDP esters are reductively produced from DHHDP esters in the young leaves. In addition, the structures of five previously reported triterpene HHDP esters were revised.

長崎大学学位論文 学位記番号:博(医歯薬)甲第1235号 学位授与年月日:令和2年3月19日

Author: HatsumiWakamatsu, Sumire Tanaka, Yosuke Matsuo , Yoshinori Saito, Koyo Nishida and Takashi Tanaka

Citation: Molecules, 24(23), art.no.4279; 2019

Nagasaki University (長崎大学), 博士(薬学) (2020-03-19)

http://hdl.handle.net/10069/39933

長崎大学学位論文 [学位記番号]博（医歯薬）甲第1235号 [学位授与年月日]令和2年3月19日

(2020-03-19)