Three new phenol compounds from Iris dichotoma PALL

Article abstract of DOI:10.1002/hlca.201100492

Three new phenolic compounds, irisdichototins D, E, and F (1 - 3, resp.) were isolated from the stems of Iris dichotoma. The structures of the new compounds were elucidated by spectroscopic analyses, including 2D-NMR techniques.

Full text of DOI:10.1002/hlca.201100492

Helvetica Chimica Acta – Vol. 95 (2012)
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Three New Phenol Compounds from Iris dichotoma Pall.
by Long Huanga), Wenhui Mab), Yanze Liua), Yong Penga) and Peigen Xiao*a)
a) Institute of Medicinal Plant Development, Peking Union Medical College, Beijing 100193,
P. R. China (phone: þ 86-10-63011294; fax: þ 86-10-62894462; e-mail: xiaopg@public.bta.net.cn)
b) Shanghai Micronmr Infor Technology Co., Ltd., Shanghai 200437, P. R. China
Three new phenolic compounds, irisdichototins D, E, and F (1 – 3, resp.) were isolated from the stems
of Iris dichotoma. The structures of the new compounds were elucidated by spectroscopic analyses,
including 2D-NMR techniques.
Introduction. – Iris dichotoma Pa ll. (Iridaceae), a perennial herb, used as folk-
medicinal herb, is mainly distributed in the north of China. Its dried rhizomers, called
ꢀBai-Sheganꢁ in parts of China, are commonly used in Chinese folk medicine for
clearing heat and detoxifying, and to eliminate phlegm, swelling, and pain in the throat
[1]. Iridichototins A – C had been previously reported from the rhizomes of I.
dichotoma [2]. To find potential drug leads, the chemical constituents of I. dichotoma
were further investigated. Here, the isolation and structure elucidation of three new
phenolic compounds is described.
Results and Discussion. – Repeated column chromatography of the EtOH extract
from the rhizomes of I. dichotoma yielded irisdichototins D – F (1 – 3, resp.).
Irisdichototin D (1) was obtained as a white powder and assigned the molecular
formula C10H14O5 on the basis of HR-ESI-MS (m/z 237.0735 ([M þ Na]þ)). The
1H-NMR spectrum (Table 1) showed signals corresponding to two O-bearing CH
groups at d(H) 4.39 (d, J ¼ 6.0, HꢀC(1)) and 3.45 – 3.42 (m, HꢀC(2)), two H-atoms of
HOꢀCH2 at d(H) 3.31 (dd, J ¼ 6.0, 4.8, CH2(3)), three ABX aromatic H-atoms at d(H)
6.88 (d, J ¼ 1.2, HꢀC(2’)), 6.69 (d, J ¼ 8.4, HꢀC(5’)), 6.68 (dd, J ¼ 1.2, 8.4, HꢀC(6’)), and
one MeO group at d(C) 3.73 (s). The 13C-NMR data of 1 (Table 1), combined with
HSQC spectrum, exhibited ten C-atom signals comprising three signals of C-atoms of a
1
propanoid. Analyses of the H- and 13C-NMR data indicated that the structure of
compound 1 was similar to that of 4-O-methylguaiacylglycerol [3]. The main
ꢂ 2012 Verlag Helvetica Chimica Acta AG, Zꢃrich

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Helvetica Chimica Acta – Vol. 95 (2012)
Table 1. 1H- and 13C-NMR Data of 1 (at 600 and 150 MHz, resp., in CD3OD, d in ppm, J in Hz)
d(H)
d(C)
HꢀC(1)
HꢀC(2)
CH2(3)
C(1’)
4.39 (d, J ¼ 6.0)
3.45 – 3.42 (m)
3.31 (dd, J ¼ 6.0, 4.8)
72.83
75.98
62.62
134.33
110.97
145.31
147.00
114.74
119.05
HꢀC(2’)
6.88 (d, J ¼ 1.2)
C(3’)
C(4’)
HꢀC(5’)
HꢀC(6’)
HOꢀC(3’)
MeOꢀC(4’)
6.69 (d, J ¼ 8.4)
6.68 (dd, J ¼ 1.2, 8.4)
8.88 (br. s)
3.73 (s)
55.53
difference between the two compounds is that compound 1 contains a OH instead of an
MeO group at C(3’). The long-range HMBCs (Fig. 1) between the aromatic H-atoms
(d(H) 6.88 and 6.68) and C(4’) confirmed the position of the MeO group. Comparison
of the aforementioned data with those reported in [3] revealed that 1 is 1-(3-hydroxy-4-
methoxyphenyl)propane-1,2,3-triol, which is a new compound.
Fig. 1. Key HMBCs of 1
Compound 1 was assumed to be threo-configured on the basis of the J value of
6.0 Hz of the benzylic H-atom (HꢀC(1)) signal at d(H) 4.39 [4] and the CD spectrum
with Mo2(OAc)4 (positive effects at 302 nm) [5]. However, the absolute configuration
of 1 remains undetermined.
Irisdichototins E and F (2 and 3, resp.), white powder, were obtained as an epimeric
mixture (ca. 1:1 by 1H- and 13C-NMR). The molecular formula C14H18O9 was deduced
1
from HR-ESI-MS (m/z 353.0918 ([M þ Na]þ)). The H-NMR spectrum (Table 2) of
compound 2 exhibited signals corresponding to three ABM aromatic H-atoms at d(H)
7.68 (dd, J ¼ 1.2, 8.4), 7.55 (d, J ¼ 1.2), and 6.84 (dd, J ¼ 8.4), and a MeO group at d(H)
3.87 (s), which were very similar to those of vanillic acid [6]. On the other hand, twelve
H-atom signals were detected in the range of d(H) 3.0 – 4.0, together with the signal at
d(H) 5.28 (d, J ¼ 4.2) assigned to the anomeric H-atom, which suggested the presence
of a sugar moiety. In combination with the 13C-NMR spectrum, the signals of the C-
atoms of the glucosyl moiety (C(1) to C(6)) were observed at d(C) 92.10, 75.82, 74.18,
73.85, 69.70, and 63.47. In the HMBC spectrum of the compound (Fig. 2), the ester CO
C-atom signal at d(C) 168.7 was correlated with that of CH2(6) of the glucose at d(H)
4.54 (dd, J ¼ 4.8, 12.6), indicating an ester linkage between the COO group and
OꢀCH2(6) moiety of the glucose. Acid hydrolysis of 2 gave glucose, which was
identified by comparison with authentic sample. Based on these observations, the
structure of 2 was established as shown.

Helvetica Chimica Acta – Vol. 95 (2012)
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Table 2. 1H- and 13C-NMR Data of 2 and 3 (at 600 and 150 MHz, resp., in D2O, d in ppm, J in Hz)
2
3
d(H)
d(C)
d(H)
d(C)
HꢀC(1)
HꢀC(2)
HꢀC(3)
HꢀC(4)
HꢀC(5)
CH2(6)
C(1’)
5.28 (d, J ¼ 4.2)
3.25 – 3.47 (m)
3.25 – 3.47 (m)
3.25 – 3.47 (m)
3.25 – 3.47 (m)
92.10
74.18
73.85
69.70
75.82
4.74 (d, J ¼ 7.8)
3.25 – 3.47 (m)
3.25 – 3.47 (m)
3.25 – 3.47 (m)
3.25 – 3.47 (m)
96.08
73.74
75.61
69.86
77.54
4.50 – 4.54 (dd, J ¼ 4.8, 12.6)
63.47
4.46 – 4.50 (dd, J ¼ 5.4, 12.0)
63.47
168.65
116.82
113.00
148.91
156.37
116.63
125.34
55.90
168.65
116.82
113.00
148.91
156.37
116.63
125.34
55.90
C(1’’)
HꢀC(2’’)
7.55 (d, J ¼ 1.2)
7.55 (d, J ¼ 1.2)
C(3’’)
C(4’’)
HꢀC(5’’)
HꢀC(6’’)
MeOꢀC(3’’)
HOꢀC(4’’)
6.84 (d, J ¼ 8.4)
7.68 (dd, J ¼ 1.2, 8.4)
3.87 (s)
6.84 (d, J ¼ 8.4)
7.68 (dd, J ¼1.2, 8.4)
3.87 (s)
8.49 (s)
8.49 (s)
Fig. 2. Key HMBCs of 2 and 3
1
Comparison of the H- and 13C-NMR data of 3 with those of 2 indicated that the
small difference was that the b-glucose instead of a-glucose was attached to C(1’). The
1H-NMR of 3 showed the signal at d(H) 4.74 (d, J ¼ 7.8) together with those of six H-
atoms in the range of d(H) 3.0 – 4.0. In the HMBC spectrum of compound 3 (Fig. 2),
the CO C-atom signal at d(C) 168.7 correlated that of CH2(6) of the glucose at d(H)
4.50 (dd, J ¼ 5.4, 12.0), indicating the formation of an ester linkage between the COO
group and the OꢀCH2(6) moiety of the glucose. Therefore, the structure of 3 was
established as shown.
Experimental Part
General. Prep. HPLC: LabAlliance Series 1500 pump and a LabAlliance Model 500 variable-
wavelength detector with a reversed-phase (RP) column (Alltech Alltima C18, 5 mm, 10 ꢁ 250 mm, at
3.5 ml/min; detection at 260 nm). CD Spectra: JASCO J-815 spectrophotometer. 1H- and 13C-NMR
spectra (1 in (D6)DMSO and 2 in D2O): Bruker Avance-600 instrument, at 600 and 150 MHz, resp.,
chemical shifts d in ppm with TMS as internal standard, coupling constants J in Hz. Mass spectra: Thermo
LTQ ORBITRAP XL mass spectrometer (for ESI and HR-ESI).
Plant Material. The rhizomes of I. dichotoma were collected at Jiufeng mountain in Beijing, P. R.
China, in April 2009, and identified by P. X. , Institute of Medicinal Plant Development, Chinese
Academy of Medical Sciences and Peking Union Medical College. A voucher specimen (Bj090412) was
deposited with the Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and
Peking Union Medical College, Beijing, P. R. China.

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Helvetica Chimica Acta – Vol. 95 (2012)
Extraction and Isolation. The air-dried rhizomes of I. dichotoma (5 kg) were refluxed with 90%
EtOH (3 ꢁ 40 l, 2 h each). The extracts were concentrated under reduced pressure to syrup. The syrup
was suspended in H2O (6 l), followed by successive partitioning with petroleum ether (PE), AcOEt, and
BuOH. The BuOH extract (326.3 g) was subjected to column chromatography (CC; SiO2; CHCl3/
MeOH/H2O 100 :1:1 to 10 :5 :1) to afford twelve fractions, Frs. 1 – 12. Fr. 1 (18.2 g) was further subjected
to repeated CC (CHCl3/MeOH/H2O 99 :1:1 to 10 :3 :1), and then with prep. HPLC (Alltima C18, 5 mm,
10 mm ꢁ 250 mm; MeOH/H2O 43 :57; flow rate 3.6 ml/min) to give compound 1 (9 mg) and a mixture of
2/3 (11 mg).
Acid Hydrolysis. Compound 2 or 3 (1 mg) was heated at 1058 for 1 h in 1 ml of 2m HCl (H2O/
dioxane 1:1) separately and heated in a water bath at 808 for 2 h, then dioxane was evaporated, and the
aglycone was removed by extracting with AcOEt (5 ꢁ 2 ml). The aq. layer was neutralized with Ag2CO3,
centrifuged, and evaporated to dryness. The monosaccharide was identified as Glc by TLC (SiO2;
AcOEt/MeOH/H2O/AcOH 13 :2 :1:3) comparison with authentic sugars.
Irisdichototin D (¼ rel-(1R,2S)-1-(3-Hydroxy-4-methoxyphenyl)propane-1,2,3-triol; 1). White pow-
der. [a]2D5 ¼ þ9.02 (c ¼ 0.05, MeOH). UV (MeOH): 228. CD (c ¼ 0.01, DMSO þ Mo2(OAc)4): 302 (þ).
1
IR (KBr): 3420, 1621, 1509, 1450. H- and 13C-NMR: see Table 1. HR-ESI-MS: 237.0735 ([M þ Na]þ,
C10H14NaOþ5 ; calc. 237.0738).
Irisdichototins E and F (¼6-O-(4-Hydroxy-3-methoxybenzoyl)-a-d-glucopyranose and 6-O-(4-
Hydroxy-3-methoxybenzoyl)-b-d-glucopyranose; 2 and 3, resp.). White powder. UV (MeOH): 275. IR
(KBr): 3410, 1700, 1612, 1520, 1450. 1H- and 13C-NMR: see Table 2. HR-ESI-MS: 353.0918 ([M þ Na]þ,
C14H18NaOþ9 ; calc. 353.0920).
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Received December 7, 2011