Seven new glycosides from the leaves of Datura metel L.

Article abstract of DOI:10.1080/14786419.2020.1779713

Seven new glycosides (1–7) and seventeen known analogues (8–24) were isolated from the leaves of Datura metel L. The structures of these compounds were all elucidated by detailed spectroscopic analyses and comparison with literature values. All isolates were evaluated for cytotoxicity against Hela, MGC-803, Ishikawa cell lines and compounds 6, 7, 14–17 and 24 exhibited different degrees of antiproliferative effects.

Full text of DOI:10.1080/14786419.2020.1779713

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: https://www.tandfonline.com/loi/gnpl20
Seven new glycosides from the leaves of Datura
metel L.
Jin-Yan Tan, Yan Liu, Yan-Gang Cheng, Yan-Ping Sun, Xiao-Mao Li, Wei Guan,
Juan Pan, Bing-You Yang & Hai-Xue Kuang
To cite this article: Jin-Yan Tan, Yan Liu, Yan-Gang Cheng, Yan-Ping Sun, Xiao-Mao Li, Wei
Guan, Juan Pan, Bing-You Yang & Hai-Xue Kuang (2020): Seven new glycosides from the leaves
of Daturaꢀmetel L., Natural Product Research
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NATURAL PRODUCT RESEARCH
https://doi.org/10.1080/14786419.2020.1779713
Seven new glycosides from the leaves of Datura metel L.
ꢀ
ꢀ
Jin-Yan Tan , Yan Liu , Yan-Gang Cheng, Yan-Ping Sun, Xiao-Mao Li, Wei Guan,
Juan Pan, Bing-You Yang and Hai-Xue Kuang
Key Laboratory of Chinese Materia Medica, Ministry of Education of Heilongjiang University of
Chinese Medicine, Harbin, China
ABSTRACT
ARTICLE HISTORY
Received 25 February 2020
Accepted 30 May 2020
Seven new glycosides (1–7) and seventeen known analogues
(8–24) were isolated from the leaves of Datura metel L. The struc-
tures of these compounds were all elucidated by detailed spectro-
scopic analyses and comparison with literature values. All isolates
were evaluated for cytotoxicity against Hela, MGC-803, Ishikawa
cell lines and compounds 6, 7, 14–17 and 24 exhibited different
degrees of antiproliferative effects.
KEYWORDS
Leaves of Datura metel L.;
allopyranoside; glycosides;
cytotoxicity
1. Introduction
Datura metel L., one kind of traditional Chinese medicine from Solanaceae family, con-
tains various types of natural products (Yang et al. 2008; Yang et al. 2007; Javaid et al.
2010). Up to now, plenty of chemical constituents have been isolated from D. metel
including steroids, sesquiterpenes and alkaloids (Yang et al. 2010a; Liu et al. 2019;
Yang et al. 2010b; Guo et al. 2019). Because of the structural diversity and excellent
activities, previous phytochemical studies of D. metel was mostly focussed on the ste-
roids and sesquiterpenes. Glycosides as essential natural products which have received
more and more attention due to their pharmacological activities such as cytotoxicity,
anti-inflammatory and antiviral (Yang et al. 2017; Liu et al. 2017; Li et al. 2020; Wang
et al. 2019).
In this article, we reported on some glycosides from the n-BuOH-soluble fraction of
D. metel leaves as a part of our ongoing research for searching new biologically active
Bing-You Yang
ybywater@163.com;CONTACT Hai-Xue Kuang
hxkuang@yahoo.com
ꢀ
Jin-Yan Tan and Yan Liu have contributed equally to this work.
Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2020.1779713.
ß 2020 Informa UK Limited, trading as Taylor & Francis Group

2
J.-Y. TAN ET AL.
Figure 1. Structures of daturglycosides A–G (1–7) from the leaves of Datura metel L.
compounds. Seven previously undescribed glycosides, daturglycosides A–G (1–7)
(Figure 1), along with seventeen known ones were isolated by several chromato-
graphic methods (Figure S2). Their structures were established by 1D/2D NMR, as well
as HR-ESI-MS analysis, and by comparison of their spectral data with previous
literatures. Here, the detail isolations and structural elucidations for daturglycosides
A-G (1–7) were provided in this manuscript, and the cytotoxicity of all isolates was
evaluated on Hela, MGC-803 and Ishikawa cell lines.
2. Results and discussion
2.1. New compound structure elucidation
Daturglycoside A (1) gave the molecular formula C17H32O11 as established by
1
HR-ESI-MS at m/z 435.1844 [M þ Na]þ. The H NMR spectrum of 1 showed the signals
for two methyl groups at both of dH 0.93 (6H, d, J ¼ 4.4 Hz) and one anomeric proton
of b-glucose at dH 4.39 (1H, d, J ¼ 7.8 Hz). In addition, the triplet of H-300 with a small J
value (J ¼ 2.9 Hz), combined with the larger coupling constant of H-100 (J ¼ 7.8 Hz), and
the splitting patterns of H-200 to H-500 indicated that 1 had a b-allopyranoside moiety
(Shen et al. 2019; Lu et al. 2019). The 13C-NMR spectrum of 1 revealed 17 carbon
signals, which corresponded to two methyl groups (both of dC 23.1), two methylenes
[one oxygenated (dC 69.5)], one methine (dC 26.0) and two sugar moieties,
1
respectively. The H-1H COSY correlations of 1 led to the establishment of aglycone to
be a 3- methylbutan-1-ol as depicted in bold-red lines in Figure S1. Furthermore, the
key HMBC correlations of H-100/C-20 and H-10/C-1 indicated that the b-allopyranoside
moiety was attached to C-20 of the b-glucopyranose and the b-glucopyranose moiety
was attached to C-1. The absolute configurations of the b-glucose and b-allose were
further determined to be both of D after acid hydrolysis (Liu et al. 2017).
Therefore, the structure of 1 was determined as 3-methylbutan-O-b-D-allopyranosyl-
(100!20)-b-D-glucopyranoside.
The molecular formula of daturglycoside B (2) was assigned as C18H32O11 by HR-
1
ESI-MS at m/z 447.1842 [M þ Na]þ. The H NMR spectrum of 2 revealed the presence
of one methyl group [dH 0.98 (3H, t, J ¼ 7.5 Hz)], two olefinic protons [dH 5.41 (1H, m);

NATURAL PRODUCT RESEARCH
3
5.45 (1H, m)] and two anomeric protons [dH 4.42 (1H, d, J ¼ 7.8 Hz); 4.94 (1H, d,
J ¼ 8.0 Hz)]. The 13C-NMR spectrum of 2, coupled with the DEPT spectrum showed 18
carbon signals, including one methyl group (dC 14.7), three methylenes of which one
was oxygenated (dC 70.5) and two olefinic carbons (dC 125.9, 134.5). A comparison of
the 1 D NMR spectroscopic data of 2 with those of 1 indicated that these two
compounds were closely related in structure except for the aglycone. Comparison
with literature values, together with 1H-1H COSY and key HMBC correlations
(Figure S1) established the aglycone of 2 to be a (Z)-3-hexenyl (Liu et al. 2017). The
absolute configurations of glycosyl groups were determined by GC analysis. Thus, 2
was established as (Z)-3-hexenyl-O-b-D-allopyranosyl-(100!20)-b-D-glucopyranoside.
Daturglycoside C (3) possessed the molecular formula of C18H32O11 according to
1
the HR-ESI-MS at m/z 447.1852 [M þ Na]þ. The H-NMR spectrum of 3 showed charac-
teristic signals of glycosyls at dH 4.05 (2H, t, J ¼ 2.9 Hz), 4.63 (1H, d, J ¼ 7.9 Hz) and 4.72
(1H, d, J ¼ 7.9 Hz), assigned two b-allopyranoside moieties. A comparison of 1H and
13C NMR spectroscopic data of 3 with those of 2 suggested that these two
compounds were closely related in structure, except for the sugar moiety. The HMBC
correlation between C-60 and H-100 suggested that the attachment position of C-60 of
one b-allopyranoside was at C-100 of another b-allopyranoside (Figure S1). The absolute
configurations of the b-allose were determined to be both of D by GC analysis
after acid hydrolysis. From the above data, the structure of 3 was elucidated as
(Z)-3-hexenyl-O-b-D-allopyranosyl-(100!60)-b-D-allopyranoside.
Daturglycoside D (4) had the molecular formula of C17H32O9 as deduced by analysis
of HR-ESI-MS at m/z 403.1947 [M þ Na]þ. Comparison of the 1 D NMR data of 4 with
those of known (3 R,5R)-3-O-b-D-mannosyl-3,5-dihydroxydecanoic acid revealed a high
similarity, except for the sugar moiety and the presence of an additional methoxy moi-
ety (Dang et al. 2014). A larger coupling constant of H-10 (J ¼ 8.0 Hz) and the triplet of
H-30 with a small J value (J ¼ 3.0 Hz) indicated 4 had a b-allopyranoside moiety (Lu
et al. 2019). Furthermore, the position of the extra methoxy group was determined
due to the key HMBC correlation from H-OMe [dH 3.68 (3H, s)] to C-1 (dC 174.0) (Figure
S1). The absolute configuration of the b-allose was determined to be D by GC after
acid hydrolysis (Liu et al. 2017). Hence, the structure of 4 was defined as 3-O-b-D-
allopyranosyl-3,5-dihydroxydecanoic acid methyl ester.
The molecular formula of daturglycoside E (5) was determined as C17H30O9 by HR-
1
ESI-MS at m/z 401.1787 [M þ Na]þ. The H and 13C NMR data of 5 exhibited a close
resemblance to 4, and the only difference was the presence of an additional olefin
bond between C-7 and C-8 in 5. The Z geometry of D7 was deduced by the key
NOESY correlation between H-6 (dH 2.23) and H-9 (dH 2.07). Thus, 5 was eventually
identified as (Z)-3-O-b-D-allopyranosyl-3,5-dihydroxydecanoic acid methyl ester.
Daturglycoside F (6) possessed a molecular formula of C19H32O9 based on HR-ESI-
1
MS at m/z 409.1840 [M þ Na-H2O]þ. The H NMR spectrum of 6 revealed the signals
for three tertiary methyls [dH 0.97 (3H, s); 1.19 (3H, s); 1.21 (3H, s)], one carbomethoxy
group [dH 2.29 (3H, s)] and two protons of a trans-disubstituted double bond [dH 6.19
(1H, d, J ¼ 15.8 Hz); 7.17 (1H, d, J ¼ 15.8 Hz)]. In addition, an anomeric proton [dH 4.69
(1H, d, J ¼ 8.0 Hz)] and a characteristic proton signal of b-D-allose-H-3 at dH 4.04 (1H, t,
J ¼ 3.0 Hz) were also observed in 1H NMR spectrum. The 13C-NMR (DEPT-135) data

4
J.-Y. TAN ET AL.
showed 19 carbon resonances assignable to four methyl carbons, three methylenes
(one oxygenated), eight methines and four quaternary carbons (two oxygenated and
one carbonyl), suggestive of a glycoside with a C13-norisoprenoid structure. The 1 D
NMR data of 6 was found to be similar to those of known 5b,6a-dihydroxy-3b-(b-D-
glucoyranosyloxy)-7-megastigmen-9-one, except for the sugar moiety (Zhang et al.
2012). The assignments of the NMR data were completed by the HSQC, HMBC and
1H-1H COSY spectra (Figure S1). The relative configurations of 6 were deduced from
the NOESY experiment. H-3 showed NOE correlations with H-2a, H-2b, H-4a and H-4b,
suggesting the equatorial position of it in a chair conformation of cyclohexane.
Furthermore, the NOE correlations from Me-12 and Me-13 to H-2a, H-2b, H-4a and
H-4b indicated that Me-12 and Me-13 also adopted equatorial positions. The relative
configurations of H-3 and Me-13 were determined as a-orientations on the basis of
the key NOE correlations of Me-12/H-3 and Me-12/Me-13. Next, the NOE cross-peaks
of Me-11/H-8, Me-10/H-7 and Me-10/H-8 placed them in b-orientations (Zhang
et al. 2012). All these NOESY features resembled those of 5b,6a-dihydroxy-3b-(b-D-
glucoyranosyloxy)-7-megastigmen-9-one, suggesting that 6 possessed the same
relative configurations as it. Therefore, the structure of 6 was assigned as 5b,6a-
dihydroxy-3b-(b-D- allopyranosyl)-7-megastigmen-9-one.
Daturglycoside G (7) was purified with the molecular formula of C16H18O9 based on
1
HR-ESI-MS at m/z 377.0849 [M þ Na]þ. The H NMR data of 7 revealed one anomeric
proton [dH 5.39 (1H, d, J ¼ 7.9 Hz)], two aromatic protons [dH 7.17 (1H, s); 7.21 (1H, s)],
one methoxy group [dH 3.91 (3H, s)] and two olefinic protons [dH 6.31 (1H, d,
J ¼ 9.5 Hz); 7.90 (1H, d, J ¼ 9.5 Hz)]. The 13C-NMR data of 7 revealed 16 carbon signals,
corresponding to a 1,2,4,5-substituted aromatic (dC 110.8, 152.1, 148.3, 105.1, 150.7,
114.4), one methoxy group (dC 57.1), a b-D-allopyranoside moiety (dC 100.2, 71.9, 73.0,
68.5, 76.0, 62.7), one carbonyl group (dC 163.6) and two olefinic carbons (dC 114.5,
145.7). The 1 D and 2 D NMR spectra of 7 resembled known isoscopoletin, with the
major difference at the presence of an extra sugar moiety (Xu et al. 2019). The key
HMBC correlations of H-10/C-6 indicated that the b-D-allopyranosyl was attached to
C-6 (Figure S1). Thus, 7 was established as isoscopoletin-O-b-D-allopyranoside.
The seventeen known compounds were identified as butyl-b-D-glucopyranoside (8)
(Tian et al. 2015), foliachinenoside I (9) (Nakamura et al. 2011), (Z)-3-hexenyl-b-D-
glucopyranoside (10) (Liu et al. 2017), (Z)-3-hexenyl-O-a-arabino- pyranosyl-(1!6)-O-
b-D-glucopyranoside (11) (Iha et al. 2012), (Z)-3-hexenyl-O-b- D-glucopyranosyl-
(100!20)-b-D-glucopyranoside (12) (Lee et al. 2014), nicglycoside C (13) (Liu et al.
2017), 40-dihydrophaseic acid b-glucopyranose ester (14) (Amakura et al. 2013), corch-
oionoside C (15) (Yoshikawa et al. 1997), (6S,9R)-roseoside (16) (Yoshikawa et al. 1997),
citroside A (17) (Zhang et al. 2010), 4-(4-hydroxyphenyl)- 2-butanone 40-O-b-D-gluco-
pyranoside (18) (Fan et al. 2000), benzyl primeveroside (19) (Mosad et al. 2017), ben-
zyl-O-a-L-rhamnopyranosyl-(1!6)-b-D-glucopyr- anoside (20) (Fang et al. 2018),
cuminyl-glucopyranoside (21) (Fujita et al. 1995), 2-phenylethyl b-D-glucopyranoside
(22) (Xia et al. 2013), phenethanol-b-vicianoside (23) (Ma et al. 2001) and juglanoside
B (24) (Liu et al. 2004), respectively. Their structures were established by 1D/2D NMR,
as well as HR-ESI-MS analysis, and by comparison of their spectral data with previous
literatures (Table S1).

NATURAL PRODUCT RESEARCH
5
2.2. Cytotoxicity activity
All isolated compounds (1–24) were evaluated for antiproliferative effects against
three human cancer cell lines, including Hela, MGC-803 and Ishikawa. As shown in
Table S2, compounds 6, 7, 14–17 and 24 exhibited different degrees of antiprolifera-
tive effects on Hela, MGC-803 and Ishikawa, while the remaining compounds were
regarded to be inactive. For the compounds with the same mother nucleuses (1–3,
8–13), new compounds 1–3 showed similar antiproliferative effects to others, which
indicated that a b-allopyranoside moiety had little effect on cytotoxicity activity.
Furthermore, compounds 6 and 14–17 belonged to the megastigmane glycosides, dis-
played moderate inhibitory effects against Hela, MGC-803 and Ishikawa cell lines (IC50
values from 7.82 to 44.18 lM).
3. Experimental
3.1. General experimental procedures
NMR spectra were recorded on Bruker DRX 400-MHz or AV 600-MHz spectrometers
(Bruker, Karlsruhe, Germany). TMS was used as an internal standard. HR-ESI-MS spectra
were performed on Thermo Scientific Orbitrap FusionTM LumosTM TribridTM mass spec-
trometer or Triple TOFTM 5600 MS/MS system from Applied AB Sciex. GC-MS analysis
was performed on an Agilent 7890 A system. Optical rotations were recorded on a
JASCO P-2000 polarimeter (Jasco, Tokyo, Japan). Semi-preparative HPLC was performed
on
a Shimadzu CBM-Semi-preparative liquid chromatograph series (Shimadzu
Corporation, Japan, CBM-20A) using a Waters SunFireTM C18 column (250 ꢁ 10 mm,
5 lm; Waters). Silica gel (200–300 mesh, Qingdao Marine Chemical Ltd., Qingdao,
China) and octadecylsilyl silica gel (ODS, YMC Company Ltd., Japan) were used for col-
umn chromatography. All the solvents were of analytical grade (Tianjinfuyu Company
Ltd, Tianjin, China).
3.2. Plant material
The dry leaves of D. metel were harvested from Shuangcheng district of Heilongjiang
Province, China, in September 2017, which was identified by Prof. Rui-Feng Fan of
Heilongjiang University of Chinese Medicine. The voucher specimen (Herbarium No.
20170901) had been deposited in the School of Pharmacy, Heilongjiang University of
Chinese Medicine, Harbin, China.
3.3. Extraction and isolation
The dry leaves of D. metel (10.0 kg) were extracted with 70% aqueous ethanol under
reflux for triple (60 L, 2 h each). The extracts were filtered and concentrated under
reduced pressure by rotary evaporators. The residues (2.41 kg) were suspended in H2O
and then sequentially partitioned with petroleum ether (PE), ethyl acetate (EtOAc) and
n-butyl alcohol (n-BuOH) to obtain 465.2, 502.1 and 443.5 g of extracts, respectively.
The crude n-BuOH extract (200 g) was submitted to column chromatography (silica

6
J.-Y. TAN ET AL.
gel, CH2Cl2/MeOH) to give ten fractions (Fr. a-j). Fr. c was chromatographed on ODS to
afford Fr. c-1 to Fr. c-15 (H2O/MeOH, 1:0 to 0:1). Fr. c-5 was purified with semi-prepara-
tive HPLC to afford compounds 1 (4.2 mg), 2 (8.2 mg) and 8 (3.3 mg). Fr. c-6 was separ-
ate by semi-preparative HPLC to obtain compounds 9 (2.8 mg) and 22 (7.3 mg). Fr. c-
11 was separated by semi-preparative HPLC to afford compounds 6 (5.7 mg), 14
(9.4 mg) and 15 (5.8 mg). Fr. c-13 was purified by semi-preparative HPLC to obtain
compounds 16 (7.4 mg), 17 (6.2 mg) and 24 (4.7 mg). Fr. d was chromatographed on
ODS to give eleven subfractions (d1-d11). Fr. d-3 was purified by semi-preparative
HPLC to yield compounds 18 (4.2 mg) and 19 (3.6 mg). Fr. d-5 was further separated
by semi-preparative HPLC to yield compounds 20 (3.9 mg) and 21 (7.7 mg). Fr. e was
separated by ODS chromatography, eluted with (H2O/MeOH, 1:0 to 0:1) to afford Fr. e-
1 to Fr. e-11. Fr. e-4 was further fractionated by semi-preparative HPLC to afford com-
pounds 4 (7.1 mg) and 5 (3.5 mg), Fr. e-5 was further separated by semi-preparative
HPLC to afford compounds 3 (3.4 mg), 10 (8.8 mg), 11 (5.1 mg) and 12 (6.3 mg). Fr. e-6
was purified by semi-preparative HPLC to obtain compounds 7 (5.3 mg) and 13
(5.2 mg). and. Fr. f was separated on ODS to obtained eight subfractions (f1-f10). Fr. f-
4 was further purified by HPLC to obtain compound 23 (3.2 mg).
20
Daturglycoside A (1): White amorphous powder. ½aꢂD ¼ ꢃ16 (c 0.1, MeOH); HR-ESI-
1
MS: m/z 435.1844 [M þ Na]þ (calcd for C17H32O11Na, m/z 435.1843). H NMR (600 MHz,
in MeOH-d4): dH 3.97 (1H, m, H-1a), 3.42 (1H, m, H-1b), 1.52 (2H, m, H-2), 1.77 (1H, m,
H-3), 0.93 (6H, d, J ¼ 4.4 Hz, H-4, H-5), 4.39 (1H, d, J ¼ 7.8 Hz, H-10), 3.42 (1H, m, H-20),
3.54 (1H, m, H-30), 3.32 (1H, m, H-40), 3.27 (1H, m, H-50), 3.87 (1H, dd, J ¼ 2.2, 11.8 Hz,
H-60a), 3.68 (1H, m, H-60b), 4.95 (1H, d, J ¼ 7.8 Hz, H-100), 3.36 (1H, m, H-200), 4.07 (1H, t,
J ¼ 2.9 Hz, H-300), 3.53 (1H, m, H-400), 3.70 (1H, m, H-500), 3.82 (1H, m, H-600a), 3.68 (1H,
m, H-600b). 13C NMR data (150 MHz, in MeOH-d4): dC 69.5 (C-1), 39.6 (C-2), 26.0 (C-3),
23.1 (C-4), 23.1 (C-5), 103.1 (C-10), 82.7 (C-20), 77.8 (C-30), 71.4 (C-40), 77.9 (C-50), 62.7 (C-
60), 102.6 (C-100), 73.3 (C-200), 72.7 (C-300), 68.6 (C-400), 75.8 (C-500), 63.0 (C-600).
20
Daturglycoside B (2): White amorphous powder. ½aꢂD -22 (c 0.1, MeOH). HR-ESI-MS:
1
m/z 447.1842 [M þ Na]þ (calcd for C18H32O11Na, m/z 447.1843). H NMR (400 MHz, in
MeOH-d4): dH 3.89 (1H, m, H-1a), 3.59 (1H, m, H-1b), 2.39 (2H, m, H-2), 5.41 (1H, m, H-
3), 5.45 (1H, m, H-4), 2.09 (2H, m, H-5), 0.98 (3H, t, J ¼ 7.5 Hz, H-6), 4.42 (1H, d,
J ¼ 7.8 Hz, H-10), 3.42 (1H, dd, J ¼ 7.8, 8.9 Hz, H-20), 3.53 (1H, m, H-30), 3.33 (1H, m, H-40),
3.27 (1H, m, H-50), 3.87 (1H, m, H-6’a), 3.67 (1H, m, H-60b), 4.94 (1H, d, J ¼ 8.0 Hz, H-100),
3.37 (1H, dd, J ¼ 2.8, 8.0 Hz, H-200), 4.07 (1H, t, J ¼ 2.8 Hz, H-300), 3.54 (1H, m, H-400), 3.72
(1H, m, H-500), 3.82 (1H, m, H-600a), 3.68 (1H, m, H-600b). 13C NMR data (100 MHz, in
MeOH-d4): dC 70.5 (C-1), 28.8 (C-2), 125.9 (C-3), 134.5 (C-4), 21.6 (C-5), 14.7 (C-6), 103.1
(C-10), 83.0 (C-20), 77.8 (C-30), 71.4 (C-40), 77.8 (C-50), 62.7 (C-60), 102.8 (C-100), 73.4 (C-200),
72.7 (C-300), 68.6 (C-400), 75.9 (C-500), 63.0 (C-600).
20
Daturglycoside C (3): White amorphous powder. ½aꢂD -19 (c 0.1, MeOH). HR-ESI-MS:
1
m/z 447.1852 [M þ Na]þ (calcd for C18H32O11Na, m/z 447.1843). H NMR (600 MHz, in
MeOH-d4): dH 3.85 (1H, m, H-1a), 3.52 (1H, m, H-1b), 2.37 (2H, m, H-2), 5.39 (1H, m, H-
3), 5.45 (1H, m, H-4), 2.08 (2H, m, H-5), 0.97 (3H, t, J ¼ 7.5 Hz, H-6), 4.63 (1H, d,
J ¼ 7.9 Hz, H-10), 3.33 (1H, m, H-20), 4.05 (1H, t, J ¼ 2.9 Hz, H-30), 3.61 (1H, dd, J ¼ 2.9,
9.7 Hz, H-40), 3.84 (1H, m, H-50), 4.14 (1H, dd, J ¼ 1.9, 11.3 Hz, H-6’a), 3.75 (1H, dd,
J ¼ 5.1, 11.3 Hz, H-60b), 4.72 (1H, d, J ¼ 7.9 Hz, H-100), 3.33 (1H, m, H-200), 4.05 (1H, t,

NATURAL PRODUCT RESEARCH
7
J ¼ 2.9 Hz, H-300), 3.49 (1H, dd, J ¼ 2.9, 9.6 Hz, H-400), 3.69 (1H, m, H-500), 3.84 (1H, m, H-
600a), 3.66 (1H, m, H-600b). 13C NMR data (150 MHz, in MeOH-d4): dC 70.6 (C-1), 28.8 (C-
2), 125.9 (C-3), 134.5 (C-4), 21.5 (C-5), 14.6 (C-6), 102.0 (C-10), 72.4 (C-20), 72.8 (C-30),
68.7 (C-40), 74.5 (C-50), 70.1 (C-60), 102.4 (C-100), 72.3 (C-200), 72.8 (C-300), 68.9 (C-400), 75.5
(C-500), 63.1 (C-600).
20
Daturglycoside D (4): White amorphous powder. ½aꢂD -126 (c 0.1, MeOH). HR-ESI-MS:
1
m/z 403.1947 [M þ Na]þ (calcd for C17H32O9Na, m/z 403.1944). H NMR (400 MHz, in
MeOH-d4): dH 2.79 (1H, dd, J ¼ 6.7, 15.7 Hz, H-2a), 2.60 (1H, dd, J ¼ 5.6, 15.7 Hz, H-2b),
4.25 (1H, m, H-3), 1.76 (1H, m, H-4a), 1.67 (1H, m, H-4b), 3.75 (1H, m, H-5), 1.46 (2H, m,
H-6), 1.45 (1H, m, H-7a), 1.33 (1H, m, H-7b), 1.33 (2H, m, H-8), 1.34 (2H, m, H-9), 0.92
(3H, t, J ¼ 6.9 Hz, H-10), 4.71 (1H, d, J ¼ 8.0 Hz, H-10), 3.23 (1H, dd, J ¼ 3.0, 8.0 Hz, H-20),
4.02 (1H, t, J ¼ 3.0 Hz, H-30), 3.45 (1H, dd, J ¼ 3.0, 9.6 Hz, H-40), 3.66 (1H, m, H-50), 3.80
(1H, dd, J ¼ 1.8, 11.3 Hz, H-60a), 3.63 (1H, dd, J ¼ 5.8, 11.3 Hz, H-60b), 3.68 (3H, s, 1-
OMe). 13C NMR data (100 MHz, in MeOH-d4): dC 174.0 (C-1), 42.1 (C-2), 77.9 (C-3), 43.3
(C-4), 70.7 (C-5), 38.8 (C-6), 26.3 (C-7), 33.1 (C-8), 23.7 (C-9), 14.4 (C-10), 102.0 (C-10),
72.4 (C-20), 72.9 (C-30), 68.9 (C-40), 75.3 (C-50), 63.3 (C-60), 52.1 (1-OMe).
20
Daturglycoside E (5): White amorphous powder. ½aꢂD -26 (c 0.1, MeOH). HR-ESI-MS:
1
m/z 401.1787 [M þ Na]þ (calcd for C17H30O9Na, m/z 401.1788). H NMR (400 MHz, in
MeOH-d4): dH 2.78 (1H, dd, J ¼ 6.7, 15.6 Hz, H-2a), 2.58 (1H, dd, J ¼ 5.6, 15.6 Hz, H-2b),
4.24 (1H, m, H-3), 1.70 (2H, m, H-4), 3.81 (1H, m, H-5), 2.23 (2H, t, J ¼ 6.4 Hz, H-6), 5.40
(1H, m, H-7), 5.47 (1H, m, H-8), 2.07 (2H, m, H-9), 0.97 (3H, t, J ¼ 7.5 Hz, H-10), 4.72 (1H,
d, J ¼ 8.0 Hz, H-10), 3.24 (1H, dd, J ¼ 3.0, 8.0 Hz, H-20), 4.03 (1H, t, J ¼ 3.0 Hz, H-30), 3.45
(1H, dd, J ¼ 3.0, 9.6 Hz, H-40), 3.62 (1H, m, H-50), 3.79 (1H, m, H-6’a), 3.63 (1H, m, H-6’b),
3.67 (3H, s, 1-OMe). 13C NMR data (100 MHz, in MeOH-d4): dC 174.0 (C-1), 42.2 (C-2),
77.9 (C-3), 42.6 (C-4), 70.7 (C-5), 36.4 (C-6), 125.8 (C-7), 134.7 (C-8), 21.7 (C-9), 14.4 (C-
10), 102.1 (C-10), 72.4 (C-20), 72.9 (C-30), 68.9 (C-40), 75.3 (C-50), 63.3 (C-60), 52.1 (1-OMe).
20
Daturglycoside F (6): White amorphous powder. ½aꢂD -34 (c 0.1, MeOH). HR-ESI-MS:
1
m/z 409.1840 [M þ Na-H2O]þ (calcd for C19H32O9Na, m/z 409.1838). H NMR (400 MHz,
in MeOH-d4): dH 1.75 (1H, m, H-2a), 1.41 (1H, dd, J ¼ 10.2, 13.0 Hz, H-2b), 3.91 (1H, m,
H-3), 2.42 (1H, ddd, J ¼ 1.3, 5.0, 14.6 Hz, H-4a), 1.80 (1H, dd, J ¼ 8.4, 14.6 Hz, H-4b), 7.17
(1H, d, J ¼ 15.8 Hz, H-7), 6.19 (1H, d, J ¼ 15.8 Hz, H-8), 2.29 (3H, s, Me-10), 0.97 (3H, s,
Me-11), 1.21 (3H, s, Me-12); 1.19 (3H, s, Me-10), 4.69 (1H, d, J ¼ 8.0 Hz, H-10), 3.24 (1H,
dd, J ¼ 3.0, 8.0 Hz, H-20), 4.04 (1H, t, J ¼ 3.0 Hz, H-30), 3.49 (1H, dd, J ¼ 3.0, 9.7 Hz, H-40),
3.68 (1H, m, H-50), 3.84 (1H, m, H-60a), 3.66 (1H, m, H-60b). 13C NMR data (100 MHz, in
MeOH-d4): dC 36.0 (C-1), 45.3 (C-2), 72.6 (C-3), 38.3 (C-4), 68.4 (C-5), 71.1 (C-6), 145.3 (C-
7), 133.8 (C-8), 200.3 (C-9), 27.5 (C-10), 25.5 (C-11), 29.5 (C-12), 20.2 (C-13), 100.4 (C-10),
72.3 (C-20), 73.0 (C-30), 68.9 (C-40), 75.4 (C-50), 63.1 (C-60).
20
Daturglycoside G (7): White amorphous powder. ½aꢂD -64 (c 0.1, MeOH). HR-ESI-MS: m/z
1
377.0849 [M þ Na]þ (calcd for C16H18O9Na, m/z 377.0849). H NMR (400 MHz, in MeOH-d4):
dH 6.31 (1H, d, J¼ 9.5 Hz, H-3), 7.90 (1H, d, J¼ 9.5Hz, H-4), 7.21 (1H, s, H-5), 7.17 (1H, s, H-
8), 5.39 (1H, d, J¼ 7.9 Hz, H-10), 3.69 (1H, m, H-20), 4.16 (1H, t, J¼ 2.8 Hz, H-30), 3.62 (1H, dd,
J¼ 2.8, 9.7 Hz, H-40), 3.93 (1H, m, H-50), 3.89 (1H, m, H-60a), 3.70 (1H, m, H-60b), 3.91 (3H, s,
7-OMe). 13C NMR data (100 MHz, in MeOH-d4): dC 163.6 (C-2), 114.5 (C-3), 145.7 (C-4), 110.8
(C-5), 152.1 (C-6), 148.3 (C-7), 105.1 (C-8), 150.7 (C-9), 114.4 (C-10), 100.2 (C-10), 71.9 (C-20),
73.0 (C-30), 68.5 (C-40), 76.0 (C-50), 62.7 (C-60), 57.1 (7-OMe).

8
J.-Y. TAN ET AL.
3.4. Acid hydrolysis and GC analysis
The newly isolated glycosides (1–7, each 2 mg) were acid hydrolysed according to the
earlier (Liu et al. 2017). And then the hexane layer (reaction products) were analysed
by an Agilent 7890 A GC system using a DM-5 column (30 m ꢁ 0.25 mm, 0.25 lm). The
absolute configurations were determined by comparing retention times with deriva-
tives prepared in the same way from standard sugars (The details were found in
Supplementary material, Figure S54).
3.5. Cytotoxicity
The isolated glycosides (1–24) were evaluated for their cytotoxicity against three
human cancer cell lines, including Hela, MGC-803 and Ishikawa, using the MTT assay
according to the earlier (Sun et al. 2016). Briefly, all the cells were cultured in DMEM
medium (Hyclone, USA), supplemented with 10% fetal bovine serum (FBS, BI) (37 ꢄC,
5% CO2). Cells were cultivated at densities of 1 ꢁ 104 cell/wells in 96-well for 12 h and
continuously exposed to different concentrations of test compounds. After 24 h, 20 lL
of MTT solution was added to each well which was incubated for another 3 h. Then
DMSO was added to each well to dissolve the formed formazan crystals, and the OD
values were recorded at 570 nm by a microplate reader. Fluorouracil (5-FU) was used
as a positive control. Cell viability was detected and cytotoxic activity was calculated
as the IC50 value.
4. Conclusion
In conclusion, seven new and seventeen known glycosides were isolated and identi-
fied from the leaves of D metel. At the same time, all the isolates were evaluated for
their cytotoxic activities against Hela, MGC-803 and Ishikawa cell lines. Some of them
possessed moderate antiproliferative effects, and 40-dihydrophaseic acid b-glucopyra-
nose ester (14) was the best, with the IC50 values as 13.14, 7.82 and 21.71 lM on Hela,
MGC-803 and Ishikawa cell lines, respectively.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was financially supported by National Natural Science Foundation of China (NSFC)
(81773883 and 81903781), China Postdoctoral Science Foundation (2018M631978), Excellent
Youth Project of Heilongjiang Natural Science Foundation (YQ2019H029) and Heilongjiang
Postdoctoral Science Foundation (LBH-Z18245), Heilongjiang university of Chinese medicine
Founds (2018pt01 and 2018bs03).

NATURAL PRODUCT RESEARCH
9
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