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

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)-5,7,3',4'-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.