1
o-tolyl isothiocyanate revealed that 1 contained a
2
cordata, ongoing for many years, have revealed that this
8,9
5ꢀ7
13
D-galactose moiety. Analysis of C NMR spectroscopic
herb was rich in volatile oils,
flavonoids,
and
9ꢀ11
alkaloids.
data revealed that 1 possessed 33 carbons, including an
aldehyde [δ 9.90 (1H, s); δ 185.1], two tetrasubstituted
In a recent research effort aimed at the discovery of anti-
HSV active compounds from H. cordata, we investigated
the 50% aq. EtOH extract of the whole plant of H. cordata.
Bioassay-guided fractionation of the extract led to the
isolation of houttuynoids AꢀE (1ꢀ5), five novel flavo-
noids with unprecedented carbon skeletons, and their
presumably biosynthetic precursor hyperoside (6). Hout-
tuynoids AꢀE (1ꢀ5) are a new type of flavonoid with
houttuynin (3-oxododecanal) tethered to hyperoside.
Moreover, houttuynoids AꢀC (1ꢀ3) contain a stable
furano-type junction. In addition, they exhibited potent
anti-HSV activity in vitro. Below, we describe the isolation,
structure elucidation, and a possible biogenetic pathway of
these flavonoids, as well as their anti-HSV activity in vitro.
H
C
benzene rings [δ 6.23, 6.43 (each 1H, d, J = 1.9 Hz), 6.73
H
and 8.05 (each 1H, d, J = 8.3 Hz); δ 164.5, 161.3, 156.7,
C
144.8, 142.3, 128.9, 124.6, 113.7, 111.0, 104.5, 98.7, and
93.7], a hexose moiety [δ 5.23 (1H, d, J = 7.7 Hz) and
H
3.25ꢀ3.63 (6H, m); δ 102.2, 75.5, 73.1, 71.1, 67.7, and
C
60.0], and a nonyl group [δ 3.15 (2H, br. s), 1.74 (2H, m),
H
1.25ꢀ1.31 (12H, m), and 0.83 (3H, t, J = 6.7 Hz); δ 31.2,
C
1
13
28.8, 28.6 (ꢁ3), 27.7, 26.6, 22.1, and 13.9]. The H and
C
NMR resonances associated with fragment A (Supporting
1
3
Information) were very similar to those of hyperoside (6)
(Scheme 1).
According to the degree of unsaturation, the molecular
0
0
formula information, and the obvious downfield at C-3 ,
the two remaining quaternary carbons (δC 170.9 and
0
117.4) could be assigned as a bridge between 3 -O and
C-2 as part of a benzofuran ring system. In the HMBC
0
00
0
spectrum, correlations that existed between H-1 and C-2 /
0
0
00
00
00
00
C-3 /C-2 and between H-4 and C-2 /C-3 (see Support-
0
0
ing Information) revealed the aldehyde was linked to C-2
and the nonyl was attached to C-3 . Therefore, the struc-
0
0
0
00
ture of 1 was determined as a 5,7,4 -trihydroxy-2 -nonyl-
0
00
00 00
0
3
furanoflavonoid, and its assignment of the H and
-carboxaldehyde-[2 ,3 :2 ,3 ]-3-O-β-D-galactopyranosyl
1
13
C
1
1
NMR signals (Table 1) was aided by the results of Hꢀ H
COSY, HSQC, and HMBC experiments.
Houttuynoid B (2) was isolated as a brown amorphous
25
powder ([R]D ꢀ1.3 (c = 0.50, CH OH)). The molecular
3
formula of 2 was established as C H O by its HR-ESI-
38 12
32
þ
MS (m/z 637.2253 [M þ Na] , calcd for 637.2255). 2 also
contained a D-galactose moiety as evidenced by HPLC
analysis of products obtained from acid hydrolysis and
derivatization reactions by L-cysteine methyl ester and o-tolyl
isothiocyanate. The NMR spectroscopic data of 2 were
similar to those of 1, except for the lack of a signal associated
The air-dried powder of the whole plant (5.0 kg) of
Houttuynia cordata was refluxed with 50% (v/v) aqueous
ethanol toafford556 g ofcrudeextract, and the extractwas
separated continuously by column chromatography
over macroporous resin AB-8, ODS, HW-40, Sephadex
LH-20 and preparative HPLC to yield compounds 1
12
with an aldehyde group, which was supported by the HMBC
0
(132.4 mg), 2 (6.4 mg), 3 (83.2 mg), 4 (7.2 mg), 5 (7.8 mg),
and 6 (42.5 mg).
00
00
0
correlations between H-2 and C-3 /C-2 /C-3 . Thus, the
0
00
structure of 2 was assigned as a 5,7,4 -trihydroxy-2 -non-
0
Houttuynoid A (1) was obtained as a brown amorphous
2
00 00
0
yl-[2 ,3 :2 ,3 ]-3-O-β-D-galactopyranosyl furanoflavonoid
based on the results of 2D NMR experiments.
Houttuynoid C (3) was obtained as a brown amorphous
5
powder ([R] ꢀ1.1 (c = 0.50, CH OH)). It had the
D
3
molecular formula C H O determined by using
3
3
38 13
þ
HR-ESI-MS (m/z 665.2197 [M þ Na] , calcd. for 665.2205).
HPLC analysis of products obtained from acid hydrolysis
and derivatization reactions by L-cysteine methyl ester and
25
powder ([R]D ꢀ1.7 (c = 0.50, CH OH)). The molecular
3
formula of 3 was assigned as C H O based on HR-ESI-
3
3
38 13
þ
MS (m/z 665.2199 [M þ Na] , calcd for 665.2205). It is an
isomer of 1. HPLC analysisof products obtainedfrom acid
hydrolysis and derivatization reactions by L-cysteine
methyl ester and o-tolyl isothiocyanate indicated that 3
1
contained a D-galactose moiety. The similarity of the H
13
and C NMR spectroscopic data of 3 to those of 1
(5) Tutupalli, L. V.; Chaubal, M. G. Lloydia 1975, 38, 92–96.
(6) Lu, H. M.; Wu, X. J.; Liang, Y. Z.; Zhang, J. Chem. Pharm. Bull.
12
2
5
2
2
006, 54, 936–940.
7) Xu, Y. W.; Cai, Q. R.; Zhao, D.; Wu, W. J. Med. Plants Res. 2011,
, 3883–3886.
8) Choe, K. H.; Kwon, S. J.; Jung, D. S. Anal. Sci. Technol. 1991, 4,
85–288.
(
(
indicated that 3 possessed the same furanoflavonoid ske-
0
0
(
9) Chou, S. C.; Su, C. R.; Ku, Y. C.; Wu, T. S. Chem. Pharm. Bull.
leton with an anellated furan ring at the C-2 /C-3 positions
and a nonyl group. 3 contained a ketone (δ 195.0) rather
009, 57, 1227–1230.
C
(
10) Proebstle, A.; Neszmelyi, A.; Jerkovich, G.; Wagner, H.; Bauer,
R. Nat. Prod. Lett. 1994, 4, 235–240.
11) Kim, S. K.; Ryu, S. Y.; No, J.; Choi, S. U.; Kim, Y. S. Arch.
Pharm. Res. 2001, 24, 518–521.
12) Tanaka, T.; Nakashima, T.; Ueda, T.; Tomii, K.; Kouno, I.
(
(13) Hatano, T.; Yasuhara, T.; Yoshihara, R.; Ikegami, Y.; Matsuda,
M.; Yazaki, K.; Agata, I.; Nishibe, S.; Noro, T. Planta Med. 1991, 57,
83–84.
(
Chem. Pharm. Bull. 2007, 55, 899–901.
Org. Lett., Vol. 14, No. 7, 2012
1773