A new ent-atisane diterpenoid from the aerial parts of Euphorbia antiquorum L.

Abstract

A new ent-atisane diterpenoid, ent-3-acetoxy-1,16,17-trihydroxyatisane (1), along with four known compounds, 3,3′,4′-tri-O-methylellagic acid (2), (R)-(+)-lasiodiplodin (3), taraxerol (4), and syringic acid (5) were isolated from the aerial parts of Euphorbia antiquorum L. The structure of compound 1 was identified by interpretation of their spectroscopic data and comparison with those reported in the literature.

Alpha-Glucosidase Inhibitory Diterpenes from Euphorbia antiquorum Growing in Vietnam

“…Compounds 1-4, 6, and 7 were evaluated for their alpha-glucosidase inhibition (Table 1). All tested compounds showed stronger activity than the positive control, acarbose (IC 50 332.5 µM), similar to previously reported ent-atisane [10]. Among them, compound 3 showed the highest alpha-glucosidase inhibition (IC 50 69.62 µM), indicating the important role of the acetonide moiety at C-16 and C-17.…”

“…Indeed, NOESY correlations of H-1/H-2a, H-3/H-2a, H-2a/H-20, H-20/H-13, and H-20/H-14 indicated the co-facial of all mentioned protons. The orientation of 16-OH was validated by NOESY correlations of H-17/H-9 and H-9/H-5 (Figure 3 and Supplementary Materials Figure S2), supported by the NMR comparison of the previously reported ent-atisanes, isolated from the same bio-source [3,10]. Altogether, the chemical structure of 1 was established as shown, namely ent-1α,3α,16β,17-tetrahydroxyatisane.…”

“…Isolates were assayed for their alpha-glucosidase inhibition. [3,10,16], further supported by the key heteronuclear multiple bond correlation (HMBC) correlations (Figure 2 and Supplementary Materials Figure S1). Detailed comparison of nuclear magnetic resonance (NMR) data of 1, ent-1β,3β,16β,17-tetrahydroxyatisane and ent-1β,3α,16β,17-tetrahydroxyatisane [16] indicated that they shared the same planar structure.…”

“…After evaporation of the extracts, the residue (757.2 g) was dissolved in ethanol, suspended in water then successfully partitioned with n-hexane, n-hexane-EtOAc (1:1, v/v), and EtOAc to give n-hexane, n-hexane-EtOAc (1:1, v/v), and EtOAc extracts. The EtOAc extract (180.7 g) was purified by silica gel column chromatography (CC) using n-hexane-EtOAc-Acetone (1:1:2, v/v/v) as an eluent, to afford seven major fractions, labelled A-E. Fractions B and C were investigated in our previous reports [10]. Fractions D were selected for further isolation.…”

“…Those isolated compounds showed various biological activities including cytotoxic, antiinflammatory, anti-HIV activities, and the inhibition of nitric oxide (NO) production [9]. As a continuation of our discovery of alpha-glucosidase inhibitory metabolites from E. antiquorum [10], the further investigation on the Vietnamese plant E. antiquorum L. was performed. In this paper, the isolation and structural elucidation of seven diterpenoids, ent-1α,3α,16β,17tetrahydroxyatisane (1), ethyl ent-3,4-seco-4,16β,17-trihydroxyatisane-3-carboxylate (2), entatisane-3-oxo-16β,17-acetonide (3) [11], ent-3α-acetoxy-16β,17-dihydroxyatisane (4) [12], ent-16β,17-dihydroxyatisane-3-one (5) [13], calliterpenone (6) [14], and ingol 12-acetate (7) [15] (Figure 1) from the most bioactive fraction of the title plant are reported.…”