Discovery of Undescribed Triterpenoids and Flavonoids From the Fruits of Syzygium attopeuense With Their α‐Glucosidase and α‐Amylase Inhibitory Activity

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The fruits of Syzygium attopeuense were extracted and isolated by using various chromatographic methods to obtain 13 compounds (1–13). Three of them, 2α,3β,6β‐trihydroxy‐24‐nor‐urs‐4(23),12,20(30)‐trien‐28‐oic acid 28‐O‐β‐D‐glucopyranoside (1), 3β,6β,23‐trihydroxyurs‐12‐en‐28‐oic acid 28‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐β‐D‐glucopyranoside (2), and (2R,3R)‐5,7,3ʹ,4ʹ‐tetrahydroxyflavanone 3‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐β‐D‐glucopyranoside (3) were verified by CAS SciFinder as previously undescribed compounds. Their structures were determined by using infrared, electronic circular dichroism, high‐resolution‐electrospray ionization‐mass spectrometry, and one‐dimensional and two‐dimensional nuclear magnetic resonance methods. Moreover, Compounds 1, 2, 4–7, and 12 inhibited significantly α‐glucosidase with minimum inhibitory concentration (IC50) values ranging from 18.3 to 147.5 µM, while compounds 1, 4, 5, and 12 significantly inhibited α‐amylase with IC50 values of 98.5, 176.0, 131.6, and 184.5 µM, respectively.