A trehalose ester from Lancea tibetica

Article abstract of DOI:10.1080/14786419.2014.930859

A phytochemical study of the 95% ethanolic extract of the whole plant of Lancea tibetica Hook. f. et Thoms. led to the isolation of a new trehalose ester, 6-O-undecanoyl-α,β-trehalose (1), along with 23 known compounds (2-24), of which compounds 2-17 were isolated from this plant for the first time. The structures of these compounds were established on the basis of spectroscopic methods. Compound 1 was evaluated for their in vitro anti-proliferative activities against MCF-7, NCI-H460 and Hep-G2 tumour cell lines. Compound 1 exhibited potent inhibitory activity against NCI-H460 cell growth, in contrast to moderate cytotoxic activity against MCF-7 and Hep-G2 cells.

Full text of DOI:10.1080/14786419.2014.930859

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A trehalose ester from Lancea tibetica
Shi-Jun Liuab, Zhi-Xin Liaoab, Chao Liua & Yan-Bo Qua
a Department of Pharmaceutical Engineering, School of Chemistry
and Chemical Engineering, Southeast University, Nanjing 211189,
P.R. China
b Jiangsu Province Hi-Tech Key Laboratory for Bio-medical
Research, Southeast University, Nanjing 211189, P.R. China
Published online: 26 Jun 2014.
To cite this article: Shi-Jun Liu, Zhi-Xin Liao, Chao Liu & Yan-Bo Qu (2014) A trehalose ester from
Lancea tibetica, Natural Product Research: Formerly Natural Product Letters, 28:19, 1613-1618,
DOI: 10.1080/14786419.2014.930859
To link to this article: http://dx.doi.org/10.1080/14786419.2014.930859
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Natural Product Research, 2014
Vol. 28, No. 19, 1613–1618, http://dx.doi.org/10.1080/14786419.2014.930859
A trehalose ester from Lancea tibetica
Shi-Jun Liua,b, Zhi-Xin Liaoa,b*, Chao Liua and Yan-Bo Qua
aDepartment of Pharmaceutical Engineering, School of Chemistry and Chemical Engineering, Southeast
University, Nanjing 211189, P.R. China; Jiangsu Province Hi-Tech Key Laboratory for Bio-medical
Research, Southeast University, Nanjing 211189, P.R. China
b
(Received 30 March 2014; final version received 1 June 2014)
A phytochemical study of the 95% ethanolic extract of the whole plant of Lancea
tibetica Hook. f. et Thoms. led to the isolation of a new trehalose ester, 6-O-
undecanoyl-a,b-trehalose (1), along with 23 known compounds (2–24), of which
compounds 2–17 were isolated from this plant for the first time. The structures of these
compounds were established on the basis of spectroscopic methods. Compound 1 was
evaluated for their in vitro anti-proliferative activities against MCF-7, NCI-H460 and
Hep-G2 tumour cell lines. Compound 1 exhibited potent inhibitory activity against
NCI-H460 cell growth, in contrast to moderate cytotoxic activity against MCF-7 and
Hep-G2 cells.
Keywords: Lancea tibetica; trehalose ester; triterpenoid; flavone; anti-tumour activity
1. Introduction
The genus Lancea (Scrophulariaceae) is represented in China by only two species (Lancea
tibetica and Lancea hirsuta Bonati) (Hou 1982). L. tibetica, a perennial herb, is used as a
traditional Tibetan medicine for the treatment of leukaemia, intestinal angina, heart disease and
cough (Chinese Herbs editor 2002). Previous phytochemical studies on L. tibetica have revealed
that it is a rich source of lignans (Su et al. 1999; Li et al. 2008). To ascertain its chemical
composition and medicinal value, the 95% ethanol extract of the whole plant of L. tibetica was
investigated.
2. Results and discussion
The ethanolic extract of L. tibetica has afforded a new trehalose ester, 6-O-undecanoyl-a,b-
trehalose (1), along with 23 known compounds, viz. betulinic acid (2) (Siddiqui et al. 1988); (3b)-
lup-20(29)-en-3-yl stearate (3) (Silva de Miranda et al. 2007); 2a,3a-dihydroxyolean-12-en-28-oic
acid (4) (Lahlou et al. 1999); dillenic acid B (5) (Nick et al. 1994); chrysoeriol (6) (Jia et al. 1986);
luteolin (7) (Miyazawa & Hisama 2003); selagin (8) (Voirin et al. 1976); tricin (9) (Jiao et al. 2007);
5-hydroxy-40-methoxyflavone (10) (Boltenkov et al. 2005); 7-O-(200-O-glucuronosyl) glucurono-
syltricin (11) (Kim et al. 2008); 6000-sinapoylsaponarin (12) (Ohkawa et al. 1998); 1-hydroxy-8-
methoxyxanthone (13) (Gengan et al. 2003); menthalactone (14), (Villasenor & Sanchez 2009);
(2)-phillygenin (15) (Messiano et al. 2008); myo-inositol (16) (Yoo et al. 2002); lycopene (17);
oleanolic acid (18) (Hu et al. 2011); sylvatesmin (19) (Banerji & Pal 1982); phillyrin (20) (Rahman
etal. 1990);simplocosin(21)(Suetal.1999);lantibesideB(22)(Lietal. 2008);sesamin(23)(Zhang
etal. 1987) and sucrose (24). Thestructure ofknowncompoundswasconfirmedbycomparisonwith
*Corresponding author. Email: zxliao@seu.edu.cn
q 2014 Taylor & Francis

1614
S.-J. Liu et al.
spectral data available with us and in the literature. However, the structure of compound 1 was
established as 6-O-undecanoyl-a,b-trehalose based on spectroscopic data (IR, NMR and MS
spectra) in combination with chemical degradation.
20
Compound 1 was obtained as a white powder. ½aꢀD ¼ þ114 (c ¼ 0.20, MeOH). m.p. 142–
1
1438C. The molecular formula was deduced to be C23H42O12 based on the H, 13C NMR data
and the quasi-molecular ion peak at m/z 509.2593 [M–H]2 (calcd for C23H41O12: 509.2597) in
the HR-ESI-MS. The IR (KBr) absorptions at 3466 (br) and 1731 cm21 suggested the presence
of hydroxyl and ester groups. The assignment of 1H and 13C NMR signals was confirmed with
the aid of 2D NMR (HSQC, HMBC and ROESY) spectra.
The 1H NMR spectrum displayed 21 signals between 6.65 and 2.90 ppm appropriate for two
pyranose residues, signals for the 21 lipid chain protons (d 2.26, t, 2H; 1.50, m, 2H; 1.23, br s,
14H; 0.83, t, 3H). The 13C NMR spectrum (Table S1) displayed the appropriate signals for the 12
carbons in the two sugar residues, signals for a long lipid chain and one ester carbonyl. A
ROESY experiment (Figure 1) assisted by an HSQC experiment clearly identified the two
pyranose residues as one a-glucose and one b-glucose residues, as indicated by the coupling
constants of the relevant protons. The coupling constants of the two anomeric protons (4.89 and
4.29 ppm) are 3.7 and 6.1 Hz, respectively, indicating that both glucose units have the a
configuration and b configuration at the anomeric centres, respectively. The a and b
configurations are also consistent with the 13C NMR shifts of the two anomeric carbons (92.2
and 96.8 ppm) (Yang et al. 2007).
The connectivities between the two glucose residues and the undecanoyl chain were
established by a HMBC experiment (Figure 1). The long-range H–C correlations from H-1
(4.89 ppm) to C-10 (96.8 ppm) indicated that the two glucose residues were connected at C-l–C-
10 through a glycosidic linkage to form an a,b-trehalose moiety. The correlations from both H-
6a (4.28 ppm), H-6b (3.96 ppm) and H-200 (2.26 ppm), H-300 (1.50 ppm) to the ester carbonyl at
172.9 ppm suggested that the lipid chain was attached to the oxygen on C-6. The 1H NMR data
(from H-200 to H-1100), 13C NMR data (from C-100 to C-1100) and the quasi-molecular ion peak at
m/z 509.2593 [M 2 H]2 (calcd for C23H41O12: 509.2597) indicated that the two main fragments
of compound 1 are trehalose and undecanoyl.
The identities of the two main fragments of compound 1, trehalose and undecanoyl, are also
supported by the results of alkaline hydrolysis. The major non-volatile products of alkaline
hydrolysis of compound 1 are identified as a,b-D-trehalose and undecanoic acid, identical with
authentic samples (TLC, IR, [a ]D and NMR). On the basis of the above analysis, compound 1
was identified as 6-O-undecanoyl-a,b-trehalose.
The cytotoxic activity of compound 1 was evaluated in vitro. Compared with cisplatin,
compound 1 was found to show potent cytotoxicity in NCI-H460 cell lines with IC50 value of
16.2 mM (cisplatin: 29.6 mM) and weak cytotoxic activity in MCF-7 (32.8 mM) (cisplatin:
(a)
O
(b)
O
(c)
O
11″
CH2CH2CH2CH2CH2CH2CH2CH2CH2CH3
H
CH2CH2CH2CH2CH2CH2CH2CH2CH2CH3
(CH2)9CH3
1″
6
O
O
O
5
O
4
HO
HO
H
1
2
H
3
H
O
O
H
HO
HO
HO
HO
HO
HO
O
HO
6′
5′
HO
HO
HO
O
HO
HO
HO
HO
HO
HO
O
O
4′
O
O
2′
1′
3′
OH
OH
OH
Figure 1. (a) Structure of 1. (b) Key HMBC (H ! C) correlations of 1. (c) Key ROESY correlations of 1.

Natural Product Research
1615
26.2 mM) and Hep-G2 (20.6 mM) (cisplatin: 15.8 mM). Cisplatin was used as a positive control
(Table 1).
3. Experimental
3.1. General experimental procedures
Optical rotations were measured on a Perkin Elmer-343 spectropolarimeter (Perkin-Elmer,
Waltham, MA, USA). IR spectra were recorded on a NICOLET IR200 FT-IR spectrophotometer
1
(Thermo Electron, Waltham, MA, USA). H NMR spectra were scanned on a Bruker Avance
1
DRX-500 spectrometer (Bruker Co., Fallanden, Switzerland) at 500 MHz ( H). 13C NMR
¨
¨
spectra were obtained on a Bruker Avance DRX-300 spectrometer (Bruker Co., Fallanden,
Switzerland) at 75 MHz (13C). HR-ESI-MS was carried on an Agilent Technologies 6224 TOF
LC-MS apparatus (Agilent Technologies, Santa Clara, CA, USA). Column chromatography
(CC) was performed using silica gel (200–300 mesh, Qingdao Marine Chemical, Inc., Qingdao,
Shandong Province, China). MCI GEL CHP20p (75–150 mm, Mitsubishi Kasei Corporation,
Chiyoda-ku, Tokyo, Japan) was also used for CC. TLC was conducted on silica gel GF254 plates
(10–40 mm; Qingdao Marine Chemical, Inc., Qingdao, Shandong Province, China). Petroleum
ether, ethyl acetate, n-BuOH and other reagents were purchased from Nanjing Wanqing reagent,
Inc., Nanjing, Jiangsu Province, China. Spots were observed by UV light as well as by spraying
with 10% H2SO4–EtOH followed by heating. Tumour cells were incubated in an HF-212UV
CO2 incubator and observed under an OLYMPUS CKX41 (Olympus, Japan) inverted
microscope. Optical density values were read under a BIO-RAD Model 680 (Bio-Rad Company,
Hercules, CA, USA) microplate reader.
3.2. Plant material
The dried whole plant of L. tibetica Hook. f. et Thoms. was purchased in April 2013 from
‘Jiukang’ Tibetan medicine market in Xining of Qinghai Province, China. It was identified by
Prof. Xue-Feng Lu of the Northwest Institute of Plateau Biology, Chinese Academy of Sciences,
Xining, China, and a voucher specimen (No. 13-01-03) has been deposited at the laboratory of
Zhi-Xin Liao, Southeast University, Nanjing, China.
3.3. Extraction and isolation
The dried and powdered plant material (5.0 kg) of L. tibetica was percolated four times with 95%
ethanol at room temperature. The filtrates were consolidated and evaporated in vacuum to give a
concentrate. The crude extract was subsequently suspended in H2O (5000 mL) and extracted
with petroleum ether (4 £ 2000 mL), ethyl acetate (4 £ 2000 mL) and n-BuOH (4 £ 2000 mL),
successively. After the removal of the solvents, three separate residues were obtained. The
petroleum ether fraction was first purified over MCI GEL eluted with 80% ethanol to remove the
Table 1. Cytotoxicity of compound 1 (mean ^ SD, n ¼ 5).
Median inhibitory rate (IC50) (mM)
Sample
MCF-7a
Hep-G2a
NCI-H460a
1
32.8 ^ 0.5
26.2 ^ 0.4
20.6 ^ 0.4
15.8 ^ 0.3
16.2 ^ 0.3
29.6 ^ 0.5
Cisplatinb
a Clinical strain.
b Positive control.

1616
S.-J. Liu et al.
pigments. The remaining material was evaporated for further isolation, which was separated by
repeated silica gel CC eluted with petroleum ether–ethyl acetate to yield 23 (20.0 mg), 2
(18.0 mg), 3 (15.0 mg), 19 (105 mg), 4 (26.0 mg), 5 (32.0 mg), 18 (5.60 g), 17 (2.00 mg), 14
(15.0 mg) and 1 (20.0 mg). The ethyl acetate fraction was subjected to silica gel CC eluted with a
gradient system of petroleum ether–ethyl acetate to give 15 (16.5 g), 10 (15.0 mg), 13 (20.0 mg),
6 (30.0 mg), 9 (5.00 mg), 7 (18.0 mg) and 8 (308 mg). The n-BuOH extract fraction was
fractionated by CC over silica gel by repeating with the gradient system of increasing polarity
(chloroform–methanol) to give 20 (10.8 g), 12 (30.0 mg), 11 (16.0 mg), 22 (18.0 mg), 21
(15.3 g), 16 (20.0 mg) and 24 (10.0 mg).
3.4. 6-O-Undecanoyl-a,b-trehalose (1)
20
White powder; m.p. 142–1438C, Rf ¼ 0.48; petroleum ether–ethyl acetate, 1:1; ½aꢀD þ 114
(methanol, c ¼ 0.20); IR (KBr) vmax (cm21): 3466, 2920, 2850, 1731; HR-ESI-MS: m/z
1
509.2593 [M 2 H]2 (calcd. for C23H41O12: 509.2597); H NMR (DMSO-d6, 500 MHz): 0.83
(3H, t, J ¼ 6.9 Hz, H-1100), 1.23 (14H, br s, H-400-1000), 1.50 (2H, m, H-300), 2.26 (2H, t,
J ¼ 6.9 Hz, H-200), 2.90 (1H, m, H-20), 3.03 (1H, m, H-40), 3.04 (1H, m, H-3), 3.12 (1H, m, H-2),
3.12 (1H, m, H-30), 3.31 (1H, m, H-5), 3.42 (1H, m, H-50), 3.76 (1H, m, H-4), 3.94 (1H, m, H-
60b), 3.96 (1H, m, H-6b), 4.24 (1H, m, H-60a), 4.28 (1H, m, H-6a), 4.29 (1H, d, J ¼ 6.1 Hz, H-10),
4.89 (1H, d, J ¼ 3.7 Hz, H-1); 13C NMR (DMSO-d6, 75 MHz): 13.9 (C-1100), 22.0 (C-1000), 24.4
(C-300), 28.6 (C-500), 28.7 (C-600), 28.9 (C-700), 29.0 (C-800), 29.0 (C-900), 31.2 (C-400), 33.4 (C-200),
63.8 (C-6), 63.8 (C-60), 69.1 (C-4), 70.1 (C-3), 70.5 (C-40), 72.1 (C-2), 72.8 (C-50), 73.5 (C-5),
74.6 (C-20), 76.4 (C-30), 92.2 (C-1), 96.8 (C-10), 172.9 (C-100); for 1H and 13C NMR data (DMSO-
d6), see Table S1. For ROESY and HMBC correlations, see Figure 1.
3.5. Alkaline hydrolysis of compound 1
A solution of compound 1 (10 mg) in 95% EtOH (2 mL) and 5% NaOH (2 mL) was refluxed for
3 h. After cooling, the mixture was diluted to 10 mL, acidified to pH 5 with dilute HCl and
extracted with CHCl3. Concentration of the CHCl3 extract yielded undecanoic acid (2.60 mg,
95%), which was identical with the authentic sample. The aqueous solution was concentrated to
dryness and acetylated with Ac2O/pyridine/DMAP to produce a,b-D-trehalose octaacetate,
which was also identical with the authentic sample (TLC, IR, [a]D and NMR).
3.5.1. Undecanoic acid
White solid; Rf ¼ 0.52; petroleum ether–ethyl acetate, 10:1. IR (KBr) vmax (cm21): 2922, 2853,
2673, 1710, 1464, 1411, 1377, 1364, 1286, 1240, 1221, 936, 720, 624, 480; 13C NMR (CDCl3,
75 MHz): 14.0, 22.7, 24.2, 29.1, 29.2, 29.3, 29.4, 29.7, 31.0, 34.0, 179.2.
3.5.2. a,b-D-Trehalose octaacetate
20
White powder; Rf ¼ 0.42; petroleum ether–ethyl acetate, 8:1; ½aꢀD þ 64 (CHCl3, c ¼ 0.20); IR
(KBr) vmax (cm21): 2924, 2858, 1245, 1053, 969, 898, 845; 13C NMR (CDCl3, 75 MHz): 20.3,
20.3, 20.4, 20.5, 20.5, 20.5, 20.6, 20.6, 60.5, 61.9, 66.9, 68.3, 68.4, 69.8, 71.1, 71.8, 72.4, 72.9,
89.8, 95.2, 169.4, 169.5, 169.6, 170.2, 170.2, 170.4, 170.8, 171.2.
3.6. In vitro cytotoxic assay
IC50 values for compound 1 were determined as described previously (Lu et al. 2013). The anti-
tumour activities of compound 1 against NCI-H460, MCF-7 and Hep-G2 cells were tested using

Natural Product Research
1617
the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) MTT assay, and cisplatin
was used as a positive control. IC50 values of compound 1 and cisplatin were determined using
average data over five replicates. The cell suspensions were distributed into 96-well cell culture
plates and cultured at 36–378C in a 5% CO2 incubator for 24 h. Cell viability was measured by
the MTT method after 48 h of incubation. Experiments were conducted in quintuplicate.
Cytotoxicity was expressed as the concentration of compound inhibiting cell growth by 50%
(IC50). Origin 7.5 computer program (Data Analysis and Graphics Software, Origin 7.5,
Northampton, MA, USA) was used to determine the median inhibitory rate (IC50), and the
results are shown in Table 1.
4. Conclusion
6-O-Undecanoyl-a,b-trehalose (1), a new trehalose ester, has been isolated from the genus
Lancea for the first time. Its structure was determined using spectroscopic methods. a,b-
Trehalose skeleton of 1 was rarely reported in the literature. Cisplatin was used as a positive
control. Compared with cisplatin, compound 1 was found to show potent cytotoxicity in NCI-
H460 cell lines with IC50 value of 16.2 mM (cisplatin: 29.6 mM) and weak cytotoxic activity in
MCF-7 (32.8 mM) (cisplatin: 26.2 mM) and Hep-G2 (20.6 mM) (cisplatin: 15.8 mM) (Table 1).
Compounds 2–17 were isolated from this plant for the first time.
Supplementary material
Supplementary material relating to this article is available online, alongside Table S1 and
Figures S1–S6.
Acknowledgement
We thank Prof. Xue-Feng Lu of the Northwest Institute of Plateau Biology, Chinese Academy of Sciences,
Xining, China, for the identification of the plant material.
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