α-Tetralone glycosides from the green walnut husks of Juglans mandshurica Maxim. and their cytotoxic activities

Article abstract of DOI:10.1080/14786419.2018.1561681

Five new α-tetralone glycosides, juglanbiosides A-E (1–5), together with an α-tetralone derivative (15) and nine known 1,4-naphthoquinones (6–14) were isolated from the 95percent EtOH extract of green walnut husks of Juglans mandshurica Maxim. Their structures were elucidated by comprehensive spectroscopic methods (¹H, ¹³C NMR, DEPT, HSQC, HMBC, CD, HR-ESI-MS). In vitro cytotoxicities of all the isolated compounds were evaluated against BGC-823, HCT-15 and K562 cancer cell lines. (Figure presented.).

Full text of DOI:10.1080/14786419.2018.1561681

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: https://www.tandfonline.com/loi/gnpl20
α-Tetralone glycosides from the green walnut
husks of Juglans mandshurica Maxim. and their
cytotoxic activities
Yuan-Yuan Zhou, Shuang Guo, Ying Wang, Hong-Juan Song, Hui-Rui Gao,
Xiao-Juan Zhang, Yan-Ping Sun, Yan Liu, Bing-You Yang & Hai-Xue Kuang
To cite this article: Yuan-Yuan Zhou, Shuang Guo, Ying Wang, Hong-Juan Song, Hui-Rui Gao,
Xiao-Juan Zhang, Yan-Ping Sun, Yan Liu, Bing-You Yang & Hai-Xue Kuang (2019): α-Tetralone
glycosides from the green walnut husks of Juglansꢀmandshurica Maxim. and their cytotoxic
activities, Natural Product Research, DOI: 10.1080/14786419.2018.1561681
To link to this article: https://doi.org/10.1080/14786419.2018.1561681
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NATURAL PRODUCT RESEARCH
https://doi.org/10.1080/14786419.2018.1561681
a-Tetralone glycosides from the green walnut husks of
Juglans mandshurica Maxim. and their cytotoxic activities
Yuan-Yuan Zhoua, Shuang Guoa, Ying Wanga, Hong-Juan Songa, Hui-Rui Gaoa,
Xiao-Juan Zhangb, Yan-Ping Suna, Yan Liua, Bing-You Yanga and Hai-
Xue Kuanga
b
aCollege of Pharmacy, Heilongjiang University of Chinese Medicine, Harbin, China; Academic
research department, Heilongjiang University of Chinese Medicine, Harbin, China
ABSTRACT
ARTICLE HISTORY
Received 4 October 2018
Accepted 13 December 2018
Five new a-tetralone glycosides, juglanbiosides A-E (1–5), together
with an a-tetralone derivative (15) and nine known 1,4-naphtho-
quinones (6–14) were isolated from the 95% EtOH extract
of green walnut husks of Juglans mandshurica Maxim. Their struc-
tures were elucidated by comprehensive spectroscopic methods
(1H, 13C NMR, DEPT, HSQC, HMBC, CD, HR-ESI-MS). In vitro cytotox-
icities of all the isolated compounds were evaluated against
BGC-823, HCT-15 and K562 cancer cell lines.
KEYWORDS
The green walnut husks
Juglans mandshurica
Maxim.; a-tetralone
glycosides; 1,4-
naphthoquinones; cytotoxic
activities
1. Introduction
Juglans mandshurica Maxim is a deciduous tree, which belongs to the Juglandaceae
family, and widely distributed in the Korea, Far East Russia and northeast of China
(Zhao et al. 2018). The kernels of the nuts are edible. The green walnut husks of J.
mandshurica, as a kind of Chinese folk medicines, has been used to treat dermatosis,
uterine prolapse and leukopenia. In addition, modern researches have shown that the
CONTACT Hai-Xue Kuang
hxkuang@yahoo.com; Bing-You Yang
ybywater@163.com
Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2018.1561681.
ß 2019 Informa UK Limited, trading as Taylor & Francis Group

2
Y.-Y. ZHOU ET AL.
Figure 1. Structures of compounds 1–5.
herb possesses extensive pharmacological activities, such as anti-tumor (Lou et al.
2018; Lou et al. 2017), antioxidant (Meshkini and Tahmasbi 2017), anti-inflammatory
(Dong and Yuan 2018) and antimicrobal effects (Wianowska et al. 2016). Previous
phytochemical studies on the green walnut husks of J. mandshurica led to the isola-
tion of chemical constituents including naphthoquinones (Jiang et al. 2018), diarylhep-
tanoids (Jin et al. 2015), triterpenoids (Zhou et al. 2015b) and phenolic acids (Huo
et al. 2017), etc. It is well to be mentioned that the derivates of 1,4-naphthoquinone
and a-tetralone possess the capacity of killing cancer cells (Chen et al. 2015; Guo et al.
2015). To discover hit or lead compounds possessing anticancer activity from trad-
itional Chinese medicine herbs, we carried out the investigation concerning 1,4-naph-
thoquinones and a-tetralones of the green walnut husks of J. mandshurica, which
resulted in the isolation of 15 compounds, including 5 new a-tetralone glycosides
(Figure 1). In addition, the antitumour activity of compounds 1–15 in vitro was eval-
uated using MTT assay on the BGC-823, HCT-15, K562 human cancer cells.
2. Results and discussion
Compound 1 was obtained as a yellow amorphous powder. Its molecular formula,
C22H30O13, was determined by analyzing the peak at m/z 525.2070 [M þ Na]þ in the
1
HR-ESI-MS, which indicating 8 degrees of unsaturation. H NMR spectrum of 1 showed

NATURAL PRODUCT RESEARCH
3
two methylene protons in the high field at dH 2.26 (2H, m, H-3), 3.00 (1H, ddd,
J ¼ 17.0, 12.4, 5.6 Hz, H-2a) and 2.51 (1H, brd, J ¼ 17.0 Hz, H-2b), and an oxymethine at
1
dH 5.33 (1H, brs, H-4). Besides, H NMR also displayed three protons of an ABC spin
system at dH 7.58 (1H, brd, J ¼ 8.0 Hz, H-6), 7.45 (1H, t, J ¼ 8.0 Hz, H-7) and 7.66 (1H,
brd, J ¼ 8.0 Hz, H-8), indicating the presence of a tri-substituted benzene ring. The 13C
NMR spectrum, in combination with HMBC and HSQC spectrum (Figures S7 and S8)
showed signals for a carbonyl carbon at dC 200.0 (C-1), two methylene carbons at dC
30.7 (C-3), 33.7 (C-2) and a tertiary carbon with hydroxyl group at dC 61.4 (C-4). All the
analysis mentioned above indicated that compound 1 was a derivative of a-tetralone
(Wu et al. 2010). The substituent position of the hydroxyl group was deduced to be C-
5 through the correlations between dH 5.33 (H-4) and dC 156.9 (C-5) in HMBC spectra.
1
In sugar region of H NMR spectrum, two doublets at dH 4.98 (1H, d, J ¼ 7.5 Hz, H-10)
and 4.37 (1H, d, J ¼ 7.6 Hz, H-100) belonging to the anomeric glucose protons were
appeared and pointed out a b-configuration of glycosyl linkages. The former signal
gave cross-peak in the HMBC experiment (Figure S2) with C-5 (dC 156.9) which was an
evidence confirming that the sugar moiety was attached at position 5 of aglycone.
The cross-peaks between dH 4.18 (1H, brd, J ¼ 11.6 Hz, H-60a) and dC 104.8 (C-100), dH
4.37 (H-100) and dC 69.9 (C-60) in the HMBC spectrum indicated that the connection
type of glucopyranose was 1!6. The absolute configurations of two glucoses were
both determined as D-form by acid hydrolysis, derivatization and GC analysis.
Furthermore, the CD spectrum of its aglycone was measured to determine the abso-
lute configuration of the chiral center at C-4. It was identified to be S configuration by
comparing its CD spectrum data with those of the references (Machida et al. 2005),
where a positive Cotton effect at 227 nm was observed (Figure S3). Accordingly,
the structure of 1 was determined to be 4(S)-4,5-dihydroxy-a-tetralone 5-O-b-D-
glucopyranosyl(l’’!6’)-b-D-glucopyranoside, named as juglanbioside A.
Compound 2 was obtained as a yellow amorphous powder, which assigned the
molecular formula to be C22H30O14 according to HR-ESI-MS data at m/z 541.1979
[M þ Na]þ (calcd for 541.1954), and the unsaturation was same as for 1. A comparison
of its NMR data with those of 1 indicated that an aromatic proton at C-8 in 1 was sub-
stituted by a hydroxyl group at the same position in 2. Thus, the AB-type aromatic
proton signals at dH 7.58 (1H, d, J ¼ 9.2 Hz, H-6) and 6.91 (1H, d, J ¼ 9.2 Hz, H-7) were
observed in place of ABC-type in the aryl ring. The remaining substructure of 2 was
elucidated to be identical to that of 1 by detailed analysis of HMQC and HMBC NMR
spectrum of 2. Accordingly, the structure of 2 was elucidated to be 4(S)-4,5,8-trihy-
droxy-a-tetralone 5-O-b-D-glucopyranosyl(l’’!6’)-b-D-glucopyranoside, and named as
juglanbioside B.
Juglanbioside C (3), yellow amorphous powder, possessed a molecular formula of
C21H28O13 determined by positive HR-ESI-MS at m/z 511.1886 ([M þ Na]þ, calcd for
511.1894), indicating 8 degrees of unsaturation. By comparison of its NMR data with
that of 2 revealed that their structures were the same, except for one of the glucopyr-
anosyl unit replaced by arabinofuranosyl unit in sugar moiety, and the absolute
configuration of arabinofuranosyl unit and glucopyranosyl unit in 3 were determined
D-form and L-form respectively by acid hydrolysis, derivatization and GC analysis.
1
The H NMR spectrum showed b-anomeric configuration for glucopyranosyl unit due

4
Y.-Y. ZHOU ET AL.
to the large terminal constant values of the proton at dH 4.78 (1H, d, J ¼ 7.6 Hz, H-10),
and the a orientation of the anomeric configuration for arabinofuranosyl unit was
deduced from the small coupling constant of the anomeric proton at dH 4.93 (1H, d,
J ¼ 1.2 Hz, H-100). Accordingly, the structure of 3 was assigned to be 4(S)-4,5,8-trihy-
droxy-a-tetralone 5-O-a-L-arabinopyranosyl(l’’!6’)-b-D-glucopyranoside.
Compound 4 was obtained as a yellow amorphous powder and determined to
have the molecular formula C22H30O13 based on its HR-ESI-MS data at m/z 525.2047
[M þ Na]þ (calcd for 525.2064), corresponding to 8 degrees of unsaturation. A detailed
comparison of NMR data revealed that 4 is differed from 1 mainly at C-4 and C-5. The
chemical shift of H-6 (dH 7.10, 1H, dd, J ¼ 7.9, 1.1 Hz) of 4 was shifted upfield by
ꢀ0.48 ppm, and C-4 at dC 69.5 was shifted down field by 8.1 ppm than that of 1,
respectively. It was also clearly determined by the long range correlation between dH
4.57 (1H, d, J ¼ 7.9 Hz, H-1’) and dC 69.5 (C-4), dH 5.43 (1H, t, J ¼ 3.0 Hz, H-4) and dC
103.7 (C-1’) in the HMBC spectra (Figure S2), together with the NMR data as described
above, suggesting the position of glycosylation at C-4 (dC 69.5) in 4 and the hydroxyl
located at C-5 (dC 156.9). Accordingly, the structure of 4 was established to be 4(S)-
4,5-dihydroxy-a-tetralone 4-O-b-D-glucopyranosyl(l’’!6’)-b-D-glucopyranoside, and
named as juglanbioside D.
Juglanbioside E (5), a yellow amorphous powder, was assigned the same molecular
formula, C22H30O13, as 1 and 4 by HR-ESI-MS at m/z 525.1993 [M þ Na]þ (calcd for
525.2026). Comparison of the NMR and HR-ESI-MS data of 5 with those of 4 revealed
the only difference was that the substitution site of a hydroxyl group at C-5 in 4 was
replaced by C-8 in 5. A group of obvious ABC-type aromatic proton signals at dH 7.18
(1H, dd, J ¼ 8.0, 0.8 Hz, H-5), 7.50 (1H, t, J ¼ 8.0 Hz, H-6) and 6.89 (1H, dd, J ¼ 8.0, 0.8 Hz,
1
H-7) were comfirmed by HNMR of compound 5. Meanwhile the aromatic carbon at C-
4 (dC 74.7) had HMBC correlation signals with H-5 (dH 7.18), and it clearly indicated
that the C-5 has not been substituted. Thus, it indicated the substituted position of
the hydroxyl group was at C-8 (dC 163.9) on the aromatic ring. Accordingly, the struc-
ture of
5
was established to be 4(S)-4,8-dihydroxy-a-tetralone 4-O-b-D-
glucopyranosyl(l’’!6’)-b-D-glucopyranoside, and named as juglanbioside E.
The five new a-tetralone glycosides were named as juglanbiosides A-E (1-5). The
known compounds were identified as juglone (6) (Yamashita et al. 2009), 5-methoxy-
1,4-naphthoquinone (7) (Dong et al. 2011), 2-hydroxy-1,4-naphthoquinone (8) (Zhou
et al. 2015a), 3-methoxy juglone (9) (Lee et al. 2016), 2-ethoxy juglone (10) (Li et al.
2006), 3-ethoxy juglone (11) (Li et al. 2006), 5,8-dihydroxy-1,4-naphthoquinone (12)
(Dong et al. 2011), 2,5-dihydroxy-1,4-naphthoquinone (13) (Zhou et al. 2015a), 3,5-
dihydroxy-1,4-naphthoquinone (14) (Dong et al. 2011) and (S)-regiolone (15) (Lee et al.
2016) (Figure S1).
Several 1,4-Naphthoquinone and a-tetralone derivatives from J. mandshurica have
been reported to have cytotoxic properties in various cancer cell lines (Yao et al.
2014). Therefore we evaluated for the cytotoxic activities of compounds 1-15 against
three human cancer cell lines (BGC-823, HCT-15 and K562) (Table S1) with cisplatin as
a positive control of MTT assay. The IC50 values were expressed as the means SD
based on three independent experiments. The aglycones isolated from the CH2Cl2
extract layer showed varying degrees of cytotoxicity, of which compound 6 showed

NATURAL PRODUCT RESEARCH
5
extremely strong activities with IC50 values of 9.6 2.35, 27.8 2.66 and 35.5 5.11 lM.
And we found that any changes in the structure resulted in significantly reduced cyto-
toxicity. Moreover, these a-tetralone glycosides isolated from the n-butanol layer had
no activities (IC50 ꢁ 100 lM). It is reported that the antineoplastic activity of a-tetra-
lone homologues appeared to be much less efficacy than 1,4-naphthoquinones (Yang
et al. 2018). And this conclution is basically consistent with our experimental findings.
3. Experimental section
3.1. General
Optical rotations were determined with a JASCO P2000 digital polarimeter (Jasco,
Tokyo, Japan). Circular dichroism (CD) spectra were performed on an Applied
Photophysics Spectropolarimeter (Agilent, USA). HR-ESI-MS spectra were acquired on a
micromass LCT spectrometer (Waters, Milford, USA). The NMR spectra were measured
with a Bruker DPX 400 spectrometer (Bruker, Rheinstetten, Germany), using TMS as an
internal standard. Silica gel H (200-300 mesh) (Qingdao Haiyang Chemical Co. Ltd.,
Qingdao, China), C18 reversed-phase (RP-18) silica gel (50 lm, YMC Ltd., Kyoto, Japan)
and sephadex LH-20 (Amersham Pharmacia Biotech, Uppsala, Sweden) were used for
open column chromatography. Thin-layer chromatography (TLC) was performed on
precoated silica gel GF254 (Qingdao Haiyang Chemical Co. Ltd., Qingdao, China). HPLC
chromatograms were obtained with an Agilent Technologies 1260 infinity HPLC sys-
tem (Agilent Technologies, Germany) and SunFire C18 column (Waters, 150 ꢂ 4.6 mm,
5 lm, USA). Semi-preparative HPLC (Waters, 515-2414, Milford, MA, USA) was carried
out with a Hypersil-ODS II column (300 ꢂ 20 mm i.d., 10 lm, Ylite, Dalian, China). All
solvents were used of analytical grade (Tianjin Chemical Reagents Company Ltd.,
Tianjin, China).
3.2. Plant material
The green walnut husks of JM were collected from Changbai Mountain, Jilin Province,
China in 2016, and identified by Professor Bingyou Yang of College of Pharmacy of
the Heilongjiang University of Chinese Medicine. The voucher specimen (No.
20160902) was preserved in the Herbarium Laboratory of Heilongjiang University of
Chinese Medicine.
3.3. Extraction and isolation
The air-dried powdered green walnut husks of Juglans mandshurica (10.0 kg) were
extracted with 95% EtOH at room temperature three times, seven days each time. The
solvent was evaporated to dryness, and then yielded a crude extract (684.3 g). The
extract was suspended in H2O and partitioned successively with CH2Cl2 (3 ꢂ 1.5 L),
EtOAc (3 ꢂ 1.5 L) and n-butanol (3 ꢂ 1.5 L), respectively. The CH2Cl2 part (97.0 g) was
fractionated by silica gel column chromatography (CC) with a gradient of pet. ether-
EtOAc (1:0!0:1, v/v) to obtain eleven fractions (Fr.A-Fr.K). Fr.C (5.6g) was further sepa-
rated by silica gel CC with pet. ether-EtOAc (50:1!1:1, v/v) to yield six subfractions

6
Y.-Y. ZHOU ET AL.
(Fr.C1-C6). The compound 6 (80.5 mg) was crystallized from Fr.C1 (201.6 mg). Fr.C2
(215.6 mg) was further purified by silica gel CC eluted with pet. ether-EtOAc (30:1, v/v)
to yield 7 (12.7 mg), 8 (8.4 mg), 9 (7.5 mg), 10 (7.2 mg) and 11 (5.6 mg). Fr.C3(262.9 mg)
was purified by preparative TLC developed with pet. ether-EtOAc (25:1, v/v) to yield
15 (6.6 mg). Fr.E (3.2 g) was purified by the silica gel CC eluting with CH2Cl2-MeOH
(35:1!0:1, v/v) to afford five subfractions (Fr.E1-E5). Fr.E2 (118.0 mg) was purified by
preparative TLC eluting with CH2Cl2-MeOH (25:1, v/v) to give 12 (6.3 mg), 13 (5.4 mg)
and 14 (7.1 mg). The n-butanol part (148.0 g) was subjected by silica gel CC with a gra-
dient of CH2Cl2-MeOH (1:0!0:1, v/v) to afford five fractions (Fr.L-Fr.P). Fr.N (8.6 g) was
fractionated by ODS CC eluting with MeOH-H2O (2:8!10:0, v/v) to offer nine subfrac-
tions (Fr.N1-Fr.N9). Fr.N6 (766.3 mg) was purifed by Sephadex LH-20 CC eluting with
MeOH-H2O (40:60, v/v) to yield six subfracions (Fr.N6-1-Fr.N6-6). Fr.N6-2 (99.6 mg) was
finally purifed by semi-preparative HPLC eluting with MeOH-H2O (30:70, v/v) to give 4
(4.7 mg, tR ¼ 22 min), 1 (6.9 mg, tR ¼ 25 min). Fr.N6-3 (152.0 mg) was separated by
semi-preparative HPLC eluting with MeOH-H2O (25:75, v/v) to offer 3 (6.0 mg, tR
¼
26 min) and 5 (3.4 mg, tR ¼ 30 min). Compound 2 (7.9 mg, tR ¼ 33 min) was then
obtained from Fr.N6-4 (212.0 mg) by semi-preparative HPLC eluted with MeOH-H2O
(20:80, v/v).
3.3.1. Juglanbioside A (1)
Yellow amorphous powder; [a]2D5-30.2 (c 0.10, MeOH); CD (c 1.15 ꢂ 10ꢀ5, MeOH) ᭝e
(nm): þ9.60 (227), -1.12 (287); HR-ESI-MS m/z 525.2070 [M þ Na]þ (calcd for
1
C22H30O13Na, 525.2096). H NMR and 13C NMR data see the supplementary material.
3.3.2. Juglanbioside B (2)
Yellow amorphous powder; [a]2D5-28.6 (c 0.10, MeOH); CD (c 1.02 ꢂ 10ꢀ5, MeOH) ᭝e
(nm): þ6.65 (212), -2.45 (340); HR-ESI-MS m/z 541.1979 [M þ Na]þ (calcd for
1
C22H30O14Na, 541.1954). H NMR and 13C NMR data see the supplementary material.
3.3.3. Juglanbioside C (3)
Yellow amorphous powder; [a]2D5-12.2 (c 0.10, MeOH); CD (c 1.37 ꢂ 10ꢀ5, MeOH) ᭝e
(nm): þ7.05 (215), -1.85 (341); HR-ESI-MS m/z 511.1886 [M þ Na]þ (calcd for
1
C21H28O13Na, 511.1894). H NMR and 13C NMR data see the supplementary material.
3.3.4. Juglanbioside D (4)
Yellow amorphous powder; [a]2D5-22.9 (c 0.10, MeOH); CD (c 1.28 ꢂ 10ꢀ5, MeOH) ᭝e
(nm): þ8.94 (224), -2.18 (284); HR-ESI-MS m/z 525.2047 [M þ Na]þ (calcd for
1
C22H30O13Na, 525.2064). H NMR and 13C NMR data see the supplementary material.
3.3.5. Juglanbioside E (5)
Yellow amorphous powder; [a]2D5-18.7 (c 0.10, MeOH); CD (c 1.85 ꢂ 10ꢀ5, MeOH) ᭝e
(nm): þ12.17 (211), -3.30 (265); HR-ESI-MS m/z 525.1993 [M þ Na]þ (calcd for
1
C22H30O13Na, 525.2026). H NMR and 13C NMR data see the supplementary material.

NATURAL PRODUCT RESEARCH
7
3.4. Acid hydrolysis
Compounds 1-5 (each about 1.5 mg) were treated with 4.0 N TFA (trifluoroacetic acid,
aqueous solution, 3 mL) at 95 ꢃC for 6 h. After cooling to room temperature, the reac-
tion mixture was extracted with CH2Cl2 (5 mL ꢂ 3). The aqueous phases were evapo-
rated to dryness. The residue was analyzed by TLC, with silica gel G as adsorbents,
10% H2SO4 in 95% EtOH as detection reagent for spraying, followed by heating the
plate to develop the colors, and with CH2Cl2-MeOH-HOAc-H2O (25:10:2:2) as solvent
systems for the development of sugars. The Rf values of D-glucose and L-arabinose
were determined, by interactive comparison with the authentic D-glucose and L-ara-
binose, in the order of 0.24 and 0.53, respectively. Subsequently, the residues were dis-
solved in pyridine. And then 0.5 mL hexamethyldisilane and 0.3 mL
trimethylchlorosilane were added, followed by heating at 60 ꢃC for 2 h. Finally, the
thiazolidine derivative was analysed by GC (Lin et al. 2018), and the retention times of
D-glucose and L-arabinose were 14.525, 10.687 min, respectively.
3.5. In vitro antitumor activities assay
The human gastric cancer (BGC-823), colorectal cancer (HCT-15) and erythroleukemic
(K562) cell lines were obtained from the Institute of Biochemistry and Cell Biology
(Shanghai, China) and cultured in Dulbecco’s Modified Eagle’s Medium (DMEM) supple-
mented with 5% fetal bovine serum (Gibco, New York, USA) and 1% antibiotic mixture
comprising penicillin-streptomycin (Sigma, Missouri, USA). Three cell lines were seeded
at 4 ꢂ 103 cells per well in 96-well culture plates and allowed to incubate for 24 h in a
humidified environment containing 5% CO2 at 37 ꢃC. The cells were then treated with
various concentrations of compounds (10 lL) for 48 h. Cisplatin was used as a positive
control. The concentrations of cisplatin and the test compounds were 0.04, 0.2, 1.0, 5,
25 and 125 lM in medium, respectively. At the end of the incubation, MTT (10 lL,
5 mg/mL) solution was added into each well. Plates were further incubated another
4 h under the above conditions. After decanting the MTT solution, the formazan crys-
tals were dissolved by 100 lL DMSO with gently shaking of 5 min at room tempera-
ture. The optical density (OD) was measured at 490 nm using a multiscan microplate
reader (Thermo Labsystems, Helsinki, Finland). All the experiments were performed
independently in triplicate. The antitumor activities were expressed as the 50% inhib-
ition concentration (IC50 value).
4. Conclusion
In this study, we mainly reported the isolation, structure elucidation and cytotoxicities
of five new compounds, named juglanbiosides A-E (1–5), together with ten known
compounds 6–15. The cytotoxic activities of the isolated compounds were evaluated
against three human cancer cell lines. In the meantime, we preliminarily summarized
the structure-activity relationship of them. The information rendered by structure-activ-
ity relationship may lead to a better understanding of structural requirements of anti-
tumor activity and maybe also can help in the design of novel potent
antitumor activity.

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Y.-Y. ZHOU ET AL.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the National Science Foundation [grant number 81202890]; China
Postdoctoral Science Foundation funded project [grant number 2013M530164 and 2014T70374];
Heilongjiang Postdoctoral Fund [grant number LBH-Z13195 and LBH-Q16207]; Harbin city youth
science and technology innovation talents [grant number 2013RFQXJ052].
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