A New C-Glycosylflavone from the Rhizomes of Cyperus rotundus

Abstract

Cyperus rotundus. Its chemical structure was elucidated on the basis of UV, IR, MS, and NMR spectroscopic analyses. Compound 1 showed moderate inhibitory activity against MRB in the test, with an IC 50 value of approximately 56.03 PM. Keywords: Cyperus rotundus, flavonoid, macrophage respiratory burst.The rhizome of Cyperus rotundus is an important traditional Chinese medicine, which is widely used in folk medicine as an anti-inflammatory, antidepressant, antipyretic, analgesic, and antiemetic remedy for dysentery and womencs diseases [1]. Iridoid glycosides, flavonoids, glycosides, and some novel sesquiterpenoids have been reported from Cyperus rotundus [2][3][4][5][6][7]. In this paper we describe a new flavone C-glycoside, 5,7-dihydroxy-4c-methoxy-8-C-[2cc-(2ccc-methylbutyryl)]-E-Dglucopyranosyl flavone, obtained by systematic extraction and isolation from the rhizomes of Cyperus rotundus based on bioactivity-guided analysis.Compound 1 was isolated as a pale yellow amorphous powder. Its molecular formula, C 27 H 30 O 11 , was deduced by HR-EI-MS (calcd m/z 531.1904; found 531.1872, [M + H] + ). The UV spectrum exhibited absorption maxima at 266 nm (band II) and 340 nm (band I), which are characteristic absorption bands of a flavone skeleton. The IR spectrum of 1 displayed absorptions at 3346 (hydroxyl), 1736 (ester), and 1643 cm -1 (D,E-unsaturated ketone). The occurrence of a flavone skeleton in the molecule could be easily deduced from the 1 H NMR spectrum, which showed the signals for an exchangeable proton at G 13.58 (1H, s, 5-OH), a sharp one-proton singlet at G 6.87 (1H, s, H-3) on the C-ring, and AAcBBc-type aromatic protons at G 8.10 (2H, d, J = 8.0 Hz, H-2c, 6c) and G 6.93 (2H, d, J = 8.0 Hz, H-3c, 5') on the B-ring, together with one broad singlet at G 6.08 (1H, s, H-6) on the A-ring [8,9]. The above NMR spectroscopic data revealed the presence of a trisubstituted A-ring and a p-substituted B-ring in 1. In addition, the 1 H NMR spectrum showed a series of signals between G 3.50 and 4.90 indicative of a sugar moiety. The coupling constant (J = 10.0 Hz) of the anomeric proton [G 4.88 (1H, d)] is consistent with the presence of a E-C-glucoside in 1 [10], a fact supported further by the 13 C NMR signals (G 70.6, 71.4, 75.2, 70.4, 82.5, and G 61.1) of the sugar unit [11]. The 1 H and 13 C NMR spectrum also displayed the presence of signals attributable to a 2ccc-methylbutyryl unit [G H 0.61 (3H, t, J = 7.2 Hz, H-4ccc), 0.68 (3H, t, J = 7.2 Hz, 2ccc-CH 3 ), 1.11 (2H, m, H-3ccc), and 1.99 (1H, m, H-2ccc); G C 11.0 (C-4ccc), 16.3 (2ccc-Me), 25.6 (C-3ccc), 40.3 (C-2ccc), 174.4 (C-1ccc)], which was confirmed by long-range correlations from H- (Fig. 1). The observed 13 C NMR chemical shift of the C-glycosylated carbon (G 104.3, C-8) of ring A revealed the presence of a C-8 glycosylated flavonoid skeleton in 1. The presence of the C-8 glycosyl moiety was supported further by the HMBC correlations observed between the anomeric proton [G 4.88 (1H, d, J = 10.0 Hz,] and the quaternary carbons C-7, C-8, and C-8a of r...

Recent Advances on Natural Aryl-C-glycoside Scaffolds: Structure, Bioactivities, and Synthesis—A Comprehensive Review

“…Compound 68 , isolated from the rhizomes of Cyperus rotundus , showed moderate inhibitory activity against MRB, with an IC 50 value of approximately 56.03 µM [ 15 ]. Nervilifordin J ( 94 ), isolated from a 60% EtOH extract of the aerial parts of Nervilia fordii , showed interesting inhibitory effects on nitric oxide production in lipopolysaccharide-activated RAW264.7 macrophages, with EC 50 values of 14.80 µM [ 17 ].…”