Bioactivity-guided isolation of anti-hepatitis B virus active sesquiterpenoids from the traditional Chinese medicine: Rhizomes of Cyperus rotundus

摘要

Ethnopharmacological relevance: The rhizome of Cyperus rotundus (C. rotundus) is a well-known traditional Chinese medicine to cure hepatitis in many formulae, but the active components responsible for hepatitis have not been elucidated. According to our bioassay on HepG2.2.15 cell line in vitro, the ethanol extract of C. rotundus demonstrated potent anti-HBV activity. This current study was designed to isolate and identify the anti-HBV active constituents from the rhizomes of C. rotundus. Material and methods: Bioactivity and LC-MS guided fractionation on the extract of C. rotundus using various chromatographic techniques including open-column, Sephadex LH-20 and semi-preparative high performance liquid chromatography led to the isolation and identification of thirty-seven sesquiterpenoids. Structural elucidation of the isolates was carried out by extensive spectroscopic analyses (UV, IR, HRMS, 1D- and 2D -NMR). The anti-HBV activity and cytotoxicity were evaluated on the HBV-transfected HepG2.2.15 cell line in vitro. The cytotoxicity effects of the isolates were assessed by a MTT assay. The secretions of HBsAg and HBeAg in the culture medium were detected by ELISA method, and the load of HBV DNA was quantified by real-time fluorescent PCR technique. Results: Five new patchoulane-type sesquiterpenoids, namely cyperene-3, 8-dione (1), 14-hydroxy cyperotundone (2), 14-acetoxy cyperotundone (3), 3β-hydroxycyperenoic acid (4) and sugetriol-3, 9-diacetate (5), along with 32 known sesquiterpenoids were isolated from the active fractions of C rotundus. Compounds 2 and 3 were the first cyperotundone-type sesquiterpenoids with a hydroxyl group at C-14 position. Nine eudesmane-type sesquiterpenoids (15-21 and 23-24) significantly inhibited the HBV DNA replication with IC_(50) values of 42.7 ± 5.9, 22.5 +1.9,13.2 ± 1.2,10.1 ± 0.7,14.1 ± 1.1,15.3 ± 2.7, 13.8 ± 0.9,19.7 + 2.1 and 11.9 + 0.6 μM, respectively, of which, compounds 17, 21, 23 and 24 possessed high SI values of 250.4,125.5, >259.6 and 127.5, respectively. Two patchoulane-type sesquiterpenoids (4 and 7) effectively suppressed the secretion of HBsAg in a dose-dependent manner with 1C_(50) values of 46.6 + 14.3 (SI=31.0) and 77.2 + 13.0 (Sl=1.7) |iM, respectively. Compounds 2, 8, 12, 15, 17 and 25 possessed moderate activities against HBeAg secretion with IC_(50) values of 162.5 + 18.9 (SI=13.3), 399.2 + 90.0 (SI = 10.6), 274.7 + 70.8 (SI=5.2), 313.9 + 87.5 (SI=7.2), 334.0 + 70.4 (SI=9.9) and 285.3 + 20.9 (SI=15.5) ^iM, respectively. Conclusions: This is the first study to reveal the anti-HBV constituents of C. rotundus, demonstrating that the eudesmane-type sesquiterpenoids might contribute to the anti-HBV activity of the rhizomes of C rotundus.