Iridoids from the roots of Triosteum pinnatifidum

Abstract

A chemical investigation of the roots of Triosteum pinnatifidum led to the isolation of 10 iridoids, elucidated as triohimas A–C, naucledal, secologanin dimethyl acetal, grandifloroside, sweroside, loganin, vogeloside and (E)-aldosecologanin. Most of the compounds were derived from loganin or secologanin with a glucose moiety at C-1 position. The results indicate a close relationship between the two genera Triosteum and Lonicera, and support the viewpoint that the iridoids derived from loganin or secologanin could be the chemotaxonomic markers of the Caprifoliaceae family.

Full text

Iridoids from the roots of Triosteum pinnatifidum
Xin Chai
a
, Yan-Fang Su
a
,
b
,
*
, Yun-Hui Zheng
a
, Shi-Lun Yan
a
, Xiao Zhang
a
, Xiu-Mei Gao
b
a
School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, PR China
b
Tianjin Key Laboratory of TCM Chemistry and Analysis, Tianjin University of Traditional Chinese Medicine, Tianjin 300193, PR China
article info
Article history:
Received 16 September 2009
Accepted 31 December 2009
Keywords:
Triosteum
Triosteum pinnatifidum
Caprifoliaceae
Lonicera
Iridoids
Iridoid glucosides
abstract
A chemical investigation of the roots of Triosteum pinnatifidum led to the isolation of 10
iridoids, elucidated as triohimas A–C, naucledal, secologanin dimethyl acetal, grandi-
floroside, sweroside, loganin, vogeloside and (E)-aldosecologanin. Most of the compounds
were derived from loganin or secologanin with a glucose moiety at C-1 position. The
results indicate a close relationship between the two genera Triosteum and Lonicera, and
support the viewpoint that the iridoids derived from loganin or secologanin could be the
chemotaxonomic markers of the Caprifoliaceae family.
Ó2010 Elsevier Ltd. All rights reserved.
1. Subject and source
The genus Triosteum Linn. (Caprifoliaceae) is composed of about eight species mainly distributed in East Asia and North
America (Hsu et al., 1988). In traditional Chinese medicine the roots of Triosteum pinnatifidum Maxim., locally known as ‘‘Tian
Wang Qi’’, are used for the treatment of rheumatic disease, traumatic injury, dyspepsia and menoxenia (Guo et al., 2003).
Roots were collected from Mei County, Shaanxi province of China in August 2006 and authenticated by Prof. Zhen-Hai Wu,
Northwest A&F University. A voucher specimen (S200608007) was deposited in the herbarium, School of Pharmaceutical
Science and Technology, Tianjin University, China.
2. Previous work
To the best of our knowledge, no phytochemical investigations on T. pinnatifidum have been reported. There was only one
recent report on the isolation of three new iridoids, including triohimas A–C (Li et al., 2009) from the aerial parts of another
Triosteum species, Triosteum himalayanum Wall.
3. Present study
The air-dried powdered roots (20 kg) were refluxed with 95% EtOH and then with 60% EtOH twice, respectively. The
extract was suspended in water, and successively partitioned with petroleum ether (60–90

C), CHCl
3
, EtOAc and n-BuOH in
turn. The CHCl
3
extract (70 g) was subjected to silica gel column eluting with petroleum ether–Me
2
CO in a gradient manner,
and 57 fractions were collected. Fractions 9–12 were purified by silica gel column chromatographic process repeatedly to
*Corresponding author. School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, PR China. Tel.: þ86 22 27402885; fax:
þ86 22 27892025.
E-mail address: yfsuphd@yahoo.com (Y.-F. Su).
Contents lists available at ScienceDirect
Biochemical Systematics and Ecology
journal homepage: www.elsevier.com/locate/biochemsyseco
0305-1978/$ – see front matter Ó2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bse.2009.12.037
Biochemical Systematics and Ecology 38 (2010) 210–212

afford compound 1(850 mg). Fractions 26–38 were exposed to silica gel column chromatography and further purified by
Sephadex LH-20 (MeOH) to yield compound 3(660 mg). Fractions 20–25 were chromatographed over silica gel column
(CH
2
Cl
2
–Me
2
CO) and recrystallized with EtOAc to get compound 4(340 mg).
The petroleum ether extract (80 g) was subjected to silica gel column eluting with gradient petroleum ether–EtOAc
(10:0 /3:7), and 78 fractions were collected. Fractions 46–50 were purified by silica gel column chromatographic process
repeatedly to give compound 2(130 mg). Compound 1(3.2 g) was also obtained from fractions 51–71 by repeated silica gel
column chromatography.
The n-BuOH extract (1400 g) was chromatographed over D101 macroporousresin column, eluting with H
2
O and 30%, 50%,
70% and 95% EtOH. The 30% eluate (400 g) was exposed to silica gel column chromatography, eluting with EtOAc–MeOH–H
2
O
in a gradient manner. Fractions 19–24 were subjected to silica gel column using CHCl
3
–MeOH repeatedly to afford compounds
5(2 g) and 6(300 mg). Fractions 32–40 were purified by silica gel column chromatographic process repeatedly and further
O
OO
O
R
O
OO
O
O
10
45
6
7
8
9
1
2
311
12
13
10
45
6
7
8
9
1
2
3
11
12
1R=OMe
3 R=OH 2
O
O
OCHO
H
H
H
5
6
7
8
9
2
3
4
1
4
O
O
CO
2
Me
OMeMeO
H
H
O
OH
HO
HO
OH
5
O
O
CO
2
H
O
H
H
O
HO
HO
O
OH
HO
HO
OH
6
O
O
O
H
O
O
OH
HO
HO
OH
7
O
O
CO
2
Me
H
H
HO
O
OH
HO
HO
OH
8
O
O
O
H
H
OMeO
O
OH
HO
HO
OH
9
O
O
OHC
CO
2
MeMeO
2
C
O
H
H H
HO
10
O
OH
HO
HO
OH
O
HO
OH
OH
HO
Fig. 1. Structures of iridoids from the roots of Triosteum pinnatifidum.
X. Chai et al. / Biochemical Systematics and Ecology 38 (2010) 210–212 211

purified by ODS column (40% MeOH) to yield compounds 7(1 g), 8(130 mg) and 9(400 mg). Fractions 65–80 were exposed to
silica gel and ODS column (35% MeOH) to give compound 10 (1.5 g).
By a combination of spectroscopic methods (IR, MS,
1
H NMR,
13
C NMR, COSY, HSQC and HMBC), comparison with the
literature data and single crystal X-ray diffraction, the 10 compounds were identified as triohimas B (1)(Li et al., 2009),
triohimas A (2)(Li et al., 2009), triohimas C (3)(Li et al., 2009), naucledal (4)(Mclean and Murray, 1972), secologanin dimethyl
acetal (5)(Kakuda et al., 2000), grandifloroside (6)(Itoh et al., 2003), sweroside (7)(Cambie et al., 1990), loganin (8)(Mpondo
and Garcia, 1989), vogeloside (9)(Recio-Iglesias et al., 1992) and (E)-aldosecologanin (10)(Machida et al., 2002)(Fig. 1).
Impure compound 4was isolated from Nauclea diderrichii (Mclean and Murray, 1972), and we reported the
13
C NMR and
complete
1
H NMR spectroscopic data here for the first time.
Naucledal (4): colorless crystal, mp 115–116

C, [
a
]
21D
1.9

(c1.04, CHCl
3
). IR (KBr)
n
max
1722, 1697, 1616, 1415,1286, 1213,
1161, 110 4 c m
1
.
1
H NMR (CDCl
3
, 500 MHz)
d
9.87 (1H, d, J¼3.0 Hz, H-1), 2.33 (1H, ddd, J¼10.5, 10.0, 3.0 Hz, H-2), 4.18 (1H,
ddq, J¼10.0, 0.5, 6.5 Hz, H-3), 1.46 (3H, d, J¼6.5 Hz, H-4), 4.44 (1H, ddd, J¼11.5, 4.5 2.0 Hz, H-5a), 4.29 (1H, ddd, J¼11.5,13.0,
2.5 Hz, H-5b), 1.99 (1H, dddd, J¼13.5, 4.5, 2.5, 2.5 Hz, H-6a),1.58 (1H, dddd, J¼13.5, 12.5, 12.5, 4.5 Hz, H-6b), 2.93 (1H, dddd,
J¼12.5,10.5, 4.0, 2.0 Hz, H-7), 7.71 (1H, d, J¼2.0 Hz, H-9);
13
C NMR (CDCl
3
, 125 MHz)
d
200.7 (C-1), 55.9 (C-2), 73.3 (C-3), 19.5
(C-4), 67.9 (C-5), 27.5 (C-6), 31.7 (C-7),103.6 (C-8),155.9 (C-9), 165.2 (C-10). The assignments were accomplished on the basis
of COSY, HSQC, and HMBC spectra.
4. Chemotaxonomic significance
The Caprifoliaceae family consists of about 10 genera distributed in high altitude areas of the north temperate and tropic
regions. This family is well known for the components of iridoids mainly derived from loganin or secologanin with
a saccharide unit at C-1 position, which have been reported from Lonicera (Kakuda et al., 2000; Zeng et al., 2000; Qin et al.,
2008), Symphoricarpos (Makarevich et al., 2009) and Abelia (Tomassini et al., 2000). According to recent phylogenetic studies,
the genera Viburnum and Sambucus, formerly in Caprifoliaceae (Hsu et al., 1988), have been moved into Adoxaceae (Bell et al.,
2001; Zhang et al., 2003). In contrast to Caprifoliaceae, the iridoids reported from Viburnum (Tomassini et al., 2006; Wang
et al., 2008) and Sambucus (Gross et al., 1987) were mainly derived from the characteristic Valeriana-type structure (with
a sugar moiety at C-11 position and an isovaleroyl group at C-1 position).
The present work reported for the first time four iridoid aglycones (1–4) and six iridoid glucosides (5–10) with loganin or
secologanin skeleton from the title plant. High content compounds were triohimas B (1), triohimas C (3), secologanin
dimethyl acetal (5), sweroside (7) and (E)-aldosecologanin (10). Compounds 1–3are iridoids with an unusual
d
-lactone-
containing skeleton, isolated from T. himalayanum as new compounds. This may indicated that this kind of iridoid is
a characteristic constituent of the Triosteum genus. Compounds 5–10 with a glucose moiety at C-1 position were previously
isolated from the genus Lonicera (Kakuda et al., 2000; Machida et al., 2002; Qin et al., 2008). Compounds 5and 9were most
likely artifacts formed by reaction of secologanin and secologanic acid with MeOH during the isolation procedure (Tomassini
et al., 1995). Compound 4was first isolated as a pure natural compound, and the aglycone of compound 7could be converted
to compound 4(Purdy and Mclean, 1977). In conclusion, the iridoids from the roots of T. pinnatifidum indicate a close rela-
tionship between the two genera Triosteum and Lonicera, and our results support the viewpoint that the iridoids derived from
loganin or secologanin could be the chemotaxonomic markers of the Caprifoliaceae family.
Acknowledgements
Financial support from Tianjin Natural Science Foundation (No. 09JCYBJC13700) is gratefully acknowledged.
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