6-hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydro-1-benzof uran-2(4H)

Journal of Medicinal Plants Research Vol. 5(4), pp. 613-625, 18 February, 2011
Available online at http://www.academicjournals.org/JMPR
ISSN 1996-0875 ©2011 Academic Journals
Full Length Research Paper
Isolation and characterization of (6S,9R)
6-hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydro-1-benzof
uran-2(4H)-one from Scutellaria barbata
Tieshan Wang 1 , Zhaoyu Wang 2 , Lijing Chen 1 , Shengtan Zhang 1 and Jingming Lin 1 *
1 Department of Pharmacy, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, People’s Republic of
China.
2 College of Life Science and Bio-Pharmaceutical, Guangdong Pharmaceutical University, Guangzhou 510006, People’s
Republic of China.
Accepted 29 December, 2010
The ethanol extract of the aerial parts of Scutellaria barbata used variously in ethno medicinal
treatments in Korea and southern China was studied. A silica gel column chromatography of the ethanol
extract using petroleum ether-acetone eluted a white slice crystal which was identified purely by
spectral analyses as (6S, 9R)6-hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydro-1-benzofuran-2(4H)-one. The
compound was firstly isolated from the genus S. barbata.
Key words: Scutellaria barbata, (6S, 9R)6-hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydro-
1-benzofuran-2(4H)-one, chromatography, spectral analyses.
INTRODUCTION
Scutellaria barbata D. Don (Lamiaceae) as a popular
traditional medicinal herb “Ban-Zhi-Lian” listed in the
Chinese Pharmacopoeia has a therapeutic history
extending back over thousands of years, and is still
currently attracting attention worldwide. As a perennial
herb, S. barbata D. Don is distributed natively throughout
Korea and southern China. In the clinic, the herb has
been used in the treatment of digestive system cancers,
hepatoma, lung cancer, breast cancer, and other
diseases (Lee et al., 2004; Goh et al., 2005; Cha et al.,
2004; Suh et al., 2007). In recent years, more than fifty
flavanoids, over thirty neo-clerodane type diterpenoids
and alkaloids have been reported from the plant (Dai et al.,
2006, 2007, 2008, 2009; Lee et al., 2010). However,
numerous constituents of this herb are still unknown. In
the course of our seeking for more new compounds, we
started phytochemical research on the air-dried aerial
parts of S. barbata and isolated of (6S,9R)
6-hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydro-1-benzofur
*Corresponding author. E-mail: linjm1231@21cn.com. Tel:
86-20-61643557. Fax: 86-20-61643010.
an-2(4H)-one. The present paper reports the isolation and
structure identification of the compound from S. barbata.
MATERIALS AND METHODS
Plant material
S. barbata was collected in Queshan County, Henan Province,
China, in September 2009, and identified by Prof. Shouyao Zhang,
Department of Pharmacy, Zhujiang Hospital, Southern Medical
University, Guangdong, China. A voucher specimen, number
090912, was deposited there. The collected sample was air-dried,
pulverized using a mill hammer and stored in polythene bags for
use.
Extraction and isolation
The air-dried aerial parts of S. barbata (25.6 kg) was finely cut and
soaked in acid ethanol (12 mol/L HCl-95% EtOH, 2:100, v/v) for 72 h
at room temperature, then extracted three times (1 h × 3) in an
ultrasonic bath with acid ethanol (40 l × 3). After evaporating of the
solvent under reduced pressure, the extract (2.15 kg) was dissolved
and suspended in 2% HCl (8.0 l), stood overnight and filtrated. The
acidic solution was basified to pH 10 with NH4OH (25%) and
exhaustively extracted with CHCl3 (6 l × 5). The organic fractions
were combined, and the solvent was evaporated under vacuum to

614 J. Med. Plant. Res.
Figure 1. The EI-MS of the compound.
yield the CHCl3 alkaloidal fraction (19.8 g). The alkaloidal fraction
was initially subjected to column (3.0 × 80 cm) chromatography on
silica gel (200 to 300 mesh, 160 g), eluted with petroleum
ether-acetone [95:5 (3.0 l), 90:10 (5.0 l), 85:15 (5.0 l), 80:20 (7.0 l),
75:25 (7.0 l), 70:30 (7.0 l), 60:40 (5.0 l), 50:50 (5.0 l), 40:60 (5.0 l)] to
give nine fractions. Fraction 2 yielded crude crystalline solid, which
afforded a white slice crystal (83 mg) after recrystallization with
petroleum ether–acetone (9:1, v/v).

Figure 2. Proposed fragmentation pathway of the compound.
RESULTS AND DISCUSSION
The compound was isolated as a white slice crystal. The
molecular formula was established as C11H16O3 by
elemental analysis and Electron Impact-Mass
Spectrogram (EI-MS) (Figure 1), which showed a
molecular ion at 196 [M + ]. Other prominent peaks
obtained were as shown below: EI-MS, m/z:
111,135,140,153,163,178. The fragmentation pathway
was shown in Figure 2. The IR spectrum (Figure 3)
showed absorption bands at 3435, 1720, 1621,1177,
1099, 1026 cm -1 , which were indicative of the hydroxyl,
conjugated carbonyl, and α, β-unsaturated γ-lactone
moieties.
The 1 H and 13 C-NMR were shown in Figures 4 and 5,
Wang et al. 615
respectively. The 1 H and 13 C NMR spectral data were
shown in Table 1. The 1 H-NMR spectrum revealed the
presence of the following fragments: three tertiary methyl
groups at δ1.25 (3H, s, H-10), 1.46 (3H, s, H-11), 1.73 (3H,
s, H-9), an α, β-unsaturated γ-lactone moiety at δ 5.67
(1H, s, H-2), a hydroxyl proton at δ 4.13 (1H, d, J= 4.1Hz).
Detailed examination of the 1 H– 1 H COSY spectrum
(Figure 6) further indicated the presence of a spin system,
which included the signals of two methylenes (δ1.53, dd,
J=4.6, 17.9Hz, Ha-5; 1.97, dt, J=3.25, 17.9Hz, Hb-5),
(δ1.70, dd, J=4.9, 16.8 Hz, Ha-7; 2.38, dt, J=16.8, 3.25Hz,
Hb-7), a methine (δ4.27, m, H-6).Thus, H-6 coupled with
the signals of H2-7 and H2-5. In addition, the long-range
couplings (HMQC shown in Figure 7 and HMBC shown in
Figure 8) between H3-9/C-8, H3-10/C-4, H3-11/C-4,

616 J. Med. Plant. Res.
Figure 3. The IR spectrum of the compound.
Tansmittance [%]

Figure 4. 1 H-NMR spectrum of the compound.
H2-5/C-4, as well as H2-7/C-8 ascertained hydroxyl proton
at C-6. The relative stereochemistry of the chiral centers
was resolved by a combination of NOESY 1D spectrum
Wang et al. 617
(Figure 9), NOE difference spectrum (Figure 10) and an
analysis of the specific rotation value. In the NOE
difference spectrum, the resonance of H3-11, Hb-5 and

618 J. Med. Plant. Res.
Figure 5. 13 C-NMR spectrum of the compound.
Hb-7 and hydroxyl proton were obviously enhanced by
irradiation of H3-9; In the NOESY 1D spectrum, the
resonance of H3-10, H3-9 and Hb-5 and hydroxyl proton
were obviously enhanced by selective irradiation of H3-11.
Thus, hydroxyl proton and H3-9 were on the same
molecular face. In addition, the specific rotation value was

Figure 6. 1 H- 1 H COSY spectrum of the compound.
Wang et al. 619

620 J. Med. Plant. Res.
Figure 7. HMQC spectrum of the compound.

Figure 8. HMBC spectrum of the compound.
Wang et al. 621

622 J. Med. Plant. Res.
Figure 9. NOESY 1D spectrum by selective irradiation of H3-11 of the compound.

Figure 10. NOE difference spectrum by irradiation of H3-9 of the compound.
determined to be [ ] 30
α D -93.6(c 0.06, MeOH). Based on
the above analysis, the structure of this compound was
confirmed as shown in Figure 11.
ACKNOWLEDGEMENTS
Wang et al. 623
This research was supported by Guangdong natural
science fund (Project No. 10151051501000029). The

624 J. Med. Plant. Res.
Figure 11. (6S,9R) 6-hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydro-1-benzofuran-
2(4H)-one Molecular formula. C11H16O3. anal. C 67.16%, H 8.27%, O24.57%.
Physical description: white slice crystal (petroleum ether–acetone, 9:1, v/v). Melting
point: 151-153°C.
Table 1. 1 H and 13 C NMR spectral data of the compound (500 and 125 MHz, in Acetone) a, b).
Position δ δ
H
C
1 171.6 s
2 5.67 (s, 1H) 113.3 d
3 183.4 s
4 36.6 s
5 1.53 (dd, 17.9, 4.6, Ha-5) 46.4 t
1.97 (dt, 17.9, 3.25, Hb-5)
6 4.27 (m, 1H) 66.8 d
7 1.70 (dd, 16.8, 4.9, Ha-7) 47.9 t
2.38 (dt, 16.8, 3.25, Hb-7)
8 87.0 s
9 1.73 (s, 3H) 27.5 q
10 1.25 (s, 3H) 31.0 q
11 1.46 (s, 3H) 26.9 q
6-OH 4.13 (d, 4.1)
Dept
(a) Chemical shift values were in ppm and J values (in Hz) were presented in parentheses, (b) The
assignments were based on HMQC, HMBC, and 1 H– 1 H COSY experiments.
authors would like to thank Ms. Xiaoyan Li, Huimin Deng,
Yafei Zhu and Mr. Hanhui Wen (Testing Center, Sun
Yat-sen University) for the measurement of elemental
analysis, IR, NMR spectra and EI-MS, respectively.
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