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A new protostane-type triterpenoid, 5β,29-dihydroxy alisol A (1) was isolated from Alisma plantago-aquatica subsp. orientale (Sam.) Sam. as well as 12-deoxyphorbol-13α-pentadecanoate (2). We first report the presence of compound 2 in the genus Alisma. Their structures were established on the basis of 1D and 2D NMR, and HRESIMS spectroscopic analyses. All the isolated compounds were assayed for their inhibitory effects against human carboxylesterase 2 (HCE-2). Compounds 1 and 2 displayed inhibitory activities against HCE-2 with IC 50 values of 29.2 and 4.6 μM, respectively. The interaction mechanisms of HCE-2 with compounds 1 and 2 were investigated by molecular docking, respectively.

The chemical constituent investigation of Alisma plantago - aquatica subsp . orientale has led to isolation and identification of thirteen compounds, including one new sesquiterpene, (10 S )-11-hydroxy- β -cyperone ( 1 ), three sesquiterpenes ( 2 - 4 ), five phenylpropanoids ( 5 - 9 ), and four alkaloids ( 10 - 13 ). We report herein, for the first time, the presence of compounds 2 - 13 in the genus Alisma . Their structures were established using 1D and 2D NMR and HRESIMS spectroscopic analyses. All the isolated compounds were assayed for their inhibitory activities against nitric oxide production in LPS-induced RAW 264.7 cells and antioxidant activities by DPPH scavenging assay. Compounds 1 - 13 displayed significant inhibitory effects against NO production at a certain concentration, while compound 5 showed antioxidant activity with IC 50 of 55.28 μM. The interactions of compounds 1 , 5 , and 11 with iNOS were investigated using molecular docking.

Two new protostane-type triterpenoids, 17-epi alisolide (1) and 24-epi alismanol D (2), were isolated from Alisma orientalis together with one known compound. Their structural elucidations were conducted by NMR, UV and HRESIMS spectroscopic analyses, and comparison with the literature data. All the isolated compounds were evaluated for inhibitory effects on HCE-2. Compound 2 displayed moderate inhibitory activity against HCE-2 with IC 50 value of 23.1 μM.