Melanogenesis-inhibitory and cytotoxic activities of diarylheptanoids from acer nikoense bark and their derivatives

Article abstract of DOI:10.1002/cbdv.201200024

Nine cyclic diarylheptanoids, 1-9, including two new compounds, i.e., 9-oxoacerogenin A (8) and 9-O-β-D-glucopyranosylacerogenin K (9), along with three acyclic diarylheptanoids, 10-12, and four phenolic compounds, 13-16, were isolated from a MeOH extract of the bark of Acer nikoense (Aceraceae). Acid hydrolysis of 9 yielded acerogenin K (17) and D-glucose. Two of the cyclic diarylheptanoids, acerogenin A (1) and (R)-acerogenin B (5), were converted to their ether and ester derivatives, 18-24 and 27-33, respectively, and to the dehydrated derivatives, 25, 26, 34, and 35. Upon evaluation of compounds 1-16 and 18-35 for their inhibitory activities against melanogenesis in B16 melanoma cells, induced with α-melanocyte-stimulating hormone (α-MSH), eight natural glycosides, i.e., six diarylheptanoid glycosides, 2-4, 6, 9, and 12, and two phenolic glycosides, 15 and 16, exhibited inhibitory activities with 24-61% reduction of melanin content at 100 μM concentration with no or almost no toxicity to the cells (88-106% of cell viability at 100 μM). In addition, when compounds 1-16 and 18-35 were evaluated for cytotoxic activity against human cancer cell lines, two natural acyclic diarylheptanoids, 10 and 11, ten ether and ester derivatives, 18-22 and 27-31, and two dehydrated derivatives, 34 and 35, exhibited potent cytotoxicities against HL60 human leukemia cell line (IC₅₀ 8.1-19.3 μM), and five compounds, 10, 11, 20, 29, and 30, against CRL1579 human melanoma cell line (IC₅₀ 10.1-18.4 μM). Copyright

Full text of DOI:10.1002/cbdv.201200024

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Melanogenesis-Inhibitory and Cytotoxic Activities of Diarylheptanoids from
Acer nikoense Bark and Their Derivatives
by Toshihiro Akihisa*, Ayano Takeda, Hiroyuki Akazawa, Takashi Kikuchi,
Satoru Yokokawa, Motohiko Ukiya, Makoto Fukatsu, and Kensuke Watanabe
College of Science and Technology, Nihon University; 1-8-14 Kanda Surugadai, Chiyoda-ku,
Tokyo 101–8308, Japan
(fax: þ81-3-3293-7572; e-mail: akihisa.toshihiro@nihon-u.ac.jp)
Nine cyclic diarylheptanoids, 1–9, including two new compounds, i.e., 9-oxoacerogenin A (8) and 9-
O-b-d-glucopyranosylacerogenin K (9), along with three acyclic diarylheptanoids, 10–12, and four
phenolic compounds, 13–16, were isolated from a MeOH extract of the bark of Acer nikoense
(Aceraceae). Acid hydrolysis of 9 yielded acerogenin K (17) and d-glucose. Two of the cyclic
diarylheptanoids, acerogenin A (1) and (R)-acerogenin B (5), were converted to their ether and ester
derivatives, 18–24 and 27–33, respectively, and to the dehydrated derivatives, 25, 26, 34, and 35. Upon
evaluation of compounds 1–16 and 18–35 for their inhibitory activities against melanogenesis in B16
melanoma cells, induced with a-melanocyte-stimulating hormone (a-MSH), eight natural glycosides, i.e.,
six diarylheptanoid glycosides, 2–4, 6, 9, and 12, and two phenolic glycosides, 15 and 16, exhibited
inhibitory activities with 24–61% reduction of melanin content at 100 mm concentration with no or
almost no toxicity to the cells (88–106% of cell viability at 100 mm). In addition, when compounds 1–16
and 18–35 were evaluated for cytotoxic activity against human cancer cell lines, two natural acyclic
diarylheptanoids, 10 and 11, ten ether and ester derivatives, 18–22 and 27–31, and two dehydrated
derivatives, 34 and 35, exhibited potent cytotoxicities against HL60 human leukemia cell line (IC50 8.1–
19.3 mm), and five compounds, 10, 11, 20, 29, and 30, against CRL1579 human melanoma cell line (IC50
10.1–18.4 mm).
Introduction. – The bark of the Japanese maple tree, Acer nikoense Maxim.
(Aceraceae; Japanese name, Megusurino-ki) has been used as a folk medicine for the
treatment of hepatic disorders and eye disease [1]. The bark has been reported to
contain various diarylheptanoids and phenolic compounds [2–4] possessing several
biological properties including inhibitory effects on degranulation in RBL-2 H3 cells
[5], on nitric-oxide (NO) production in lipopolysaccharide-activated macrophages [6],
and on expression of Naþ-glucose co-transporter in COS-1 cells [7], as well as
hepatoprotective effects [8]. In our search for potential bioactive compounds from
natural sources, we have demonstrated that the diarylheptanoid and phenolic
constituents of the extract of A. nikoense stem bark exhibited inhibitory effects against
12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation in mice [9],
against Epstein–Barr virus early antigen (EBV-EA) activation induced by TPA [9],
and against melanogenesis in B16 melanoma cells [10][11], in addition to free radical-
scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical [10]. In a
continuing study on the constituents of A. nikoense bark extract, we have isolated
twelve diarylheptanoids, 1–12, including two new compounds, 8 and 9, along with four
ꢀ 2012 Verlag Helvetica Chimica Acta AG, Zꢁrich

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phenolic compounds, 13–16, from the extract. In addition, we have prepared 18
derivatives, 18–35, from two cyclic diarylheptanoids, acerogenin A (1) and (R)-
acerogenin B (5). Here, we describe structure elucidation of the two new compounds, 8
and 9, and evaluation of compounds 1–16 and 18–35 for their inhibitory activities
against melanogenesis in B16 melanoma cells induced with a-melanocyte-stimulating
hormone (a-MSH), and cytotoxic activities against two human cancer cell lines.
Results and Discussion. – Isolation, Identification, and Characterization. The
MeOH extract of A. nikoense bark was fractionated into AcOEt, BuOH, and H2O-
soluble fractions. Nine cyclic diarylheptanoids, 1–9, three acyclic diarylheptanoids, 10–
12, and two phenolic compounds, 13 and 14, from the AcOEt-soluble fraction, and two
phenolic glycosides, 15 and 16, from the BuOH-soluble fraction were isolated. Two
compounds, 9-oxoacerogenin A (8) and 9-O-b-d-glucopyranosyl acerogenin K (9),

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among the 16 compounds were new ones, and their structures were elucidated on the
basis of spectroscopic data and comparison with literature.
The molecular formula of 8 was determined as C19H20O4 on the basis of its HR-ESI-
MS (m/z 335.1303 ([MþNa]þ , C19H20NaO4þ ; calc. 335.1259)). The 13C-NMR spectrum
of 8 (Table 1) exhibited 19 signals assignable to two benzene rings (five singlets and
seven doublets), five CH2 groups, a C¼O group, and an CHꢀO C-atom. These findings,
in combination with its IR spectrum which showed absorption bands at 3403, 1705,
1504, and 1055 cmꢀ1 assignable to OH, C¼O, aromatic ring, and ether functions, and its
UV spectrum which exhibited an absorption at 276 nm (log e 3.52), suggested that 8 is a
diphenyl ether-type cyclic diarylheptanoid [2][3][9]. Compound 8 was shown to
possess a b-ketol system at C(9) (C(9)¼O) and C(11)
in the heptyl chain
based on the observation of 13C,1H long-range couplings from HꢀC(4) and HꢀC(6) to
C(7), from HꢀC(7) to C(9), from HꢀC(11) to C(9) and C(13), and from HꢀC(13) to
C(14) and C(15), in the HMBC spectrum (Table 1 and Fig.). Furthermore, the
presence of a OH group at C(2) was evidenced by 13C,1H long-range couplings from
HꢀC(3), HꢀC(4), and HꢀC(6) to C(2) observed in the HMBC spectrum of 8. The
1
above findings coupled with analysis of H,1H-COSY (Fig.), HMQC, and HMBC
(Table 1, Fig.) data indicated that 8 possesses the structure of 4,12-dihydroxy-2-
oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexaen-10-one, which has been named 9-
oxoacerogenin A. The configuration at C(11) of compound 8 remained undetermined.
Figure. 1H,1H-COSY (—) and major HMBC (H!C) correlations for compounds 8 and 9
The molecular formula of 9 was determined as C25H32O8, based on its HR-ESI-MS
(m/z 483.1984 ([MþNa]þ , C25H32NaO8þ ; calc. 483.1994)). In the UV spectrum of 9,
absorption maxima were observed at 217, 256, and 297 nm, suggesting a biphenyl-type
cyclic diarylheptanoid structure [2][4][12]. The IR spectrum of 9 showed absorption
bands at 3397, 1506, and 1075 cmꢀ1, ascribable to OH, aromatic ring, and ether
functions [12]. Acid hydrolysis of 9 with 1m HCl/MeOH 1:1 furnished compound 17
and d-glucose, of which the latter was identified by GLC analysis of its trimethylsilyl
thiazolidine derivative [13]. The 13C- and 1H-NMR of 9 evidenced the presence of two

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1479
benzene rings (six singlets and six doublets in the 13C-NMR), six CH2 groups (six triplets
in the 13C-NMR), an CHꢀO group (d(C) 67.4 (d), d(H) 4.29 (t)), and a b-
glucopyranosyl moiety (d(H) 5.78 (d, J¼7.8, HꢀC(1’))) (Table 1). The NMR signals
of aglycone moiety were very similar to those of acerogenin K (17) [4], suggesting that
9 possesses an acerogenin K structure as an aglycone moiety. The HMBC cross-
correlation observed for HꢀC(9) with C(1’) indicated that the sugar moiety is located at
1
C(9) in 9 (Table 1 and Fig.). The above evidences, coupled with analysis of H,1H-
COSY, HMQC, and HMBC spectra, indicated that 9 has the structure 3,17-
dihydroxytricyclo[12.3.1.12,6]nonadeca-1(18),2,4,6(19),14,16-hexaen-9-yl b-d-glucopyr-
anoside (¼ 9-O-b-d-glucopyranosylacerogenin K). The configuration at C(9) of
compounds 9 and 17 remained undetermined.
Identification of 14 known compounds, i.e., acerogenin A (1) [7][14], aceroside I
(2) [9][14], aceroside III (3) [15], aceroside VI (4) [15], (R)-acerogenin B (5) [6][7],
aceroside B1 (6) [6], acerogenin I (7) [4], acerogenin G (10) [16], (–)-centrolobol (11)
[17], aceroside VIII (12) [17], raspberry ketone (13) [18], (þ)-rhododendrol (14) [19],
apiosylepirhododendrin (15) [20], and kelampayoside A (16) [21], was achieved by
comparison of their MS and 1H-NMR data with those in the literature. Among these,
compounds 10 and 16 were isolated from this plant for the first time in this study.
Preparation of Acerogenin A (1) and (R)-Acerogenin B (5) Derivatives. Acerogenin
A (1) and (R)-acerogenin B (5) were obtained from aceroside I (2) and aceroside B1
(6), respectively, by acid hydrolysis. Methylation of 1 with CH2N2 [14] yielded 2-O-
methylacerogenin A (18). Acetylation of 1 and 18 with Ac2O gave 2,11-di-O-
acetylacerogenin A (21) and 11-O-acetyl-2-O-methylacerogenin A (19), respectively.
On the other hand, treatment of 1 with TsOH in AcOEt yielded 11-O-acetylacerogenin
A (20), which was considered to be formed by transesterification with the solvent
AcOEt. Esterification of 1 with crotonic acid and trans-cinnamic acid in the presence of
O,O-di(pyridin-2-yl)thiocarbonate (DPTC) and 4-(dimethylamino)pyridine (DMAP)
[22] yielded 2,11-di-O-crotonylacerogenin A (22) and 2,11-di-O-cinnamoylacerogenin
A (23), respectively. Esterification of 1 with succinic anhydride in the presence of
DMAP gave 11-O-succinylacerogenin A (24). Dehydration of 1 with thionyl chloride
(SOCl2) [23] yielded (10E)-10,11-dehydro-11-deoxyacerogenin A (25) and (11E)-
11,12-dehydro-11-deoxyacerogenin A (26). Treatment of compound 5 with the
reagents as described above yielded 2-O-methylacerogenin B (27), 9-O-acetyl-2-O-
methylacerogenin B (28), 9-O-acetylacerogenin B (29), 2,9-di-O-acetylacerogenin B
(30), 2,9-di-O-crotonylacerogenin B (31), 2,9-di-O-cinnamoylacerogenin B (32), 9-O-
succinylacerogenin B (33), (8E)-8,9-dehydro-9-deoxyacerogenin B (34), and (9E)-
9,10-dehydro-9-deoxyacerogenin B (35), respectively. The structures of these deriv-
1
atives were elucidated based on their ESI-MS, HR-ESI-MS, and H-NMR data. In
addition, the assigned structures of four dehydration products, 25, 26, 34, and 35, were
1
confirmed by H,1H-COSY spectra.
Melanogenesis Inhibitory Activity. Sixteen compounds, 1–16, isolated from A.
nikoense, and 18 derivatives, 18–35, synthesized from 1 and 5 were evaluated for their
melanogenesis inhibitory activities on a-MSH-stimulated B16 melanoma cells [24], as
well as their cytotoxic activities by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-
2H-tetrazolium bromide (MTT) assay (Table 2). At a concentration of 10 mm, eleven
natural compounds, 2–6, 8, 9, 12, and 14–16, from A. nikoense and three semi-

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synthesized compounds, 19, 27, and 33, showed inhibition of melanogenesis (melanin
content 58.3–92.5%) with no or almost no toxicity to the cells (cell viability 90.7–
111.2%). Their inhibitory activities against melanogenesis were superior to a known
melanogenesis inhibitor, arbutin (melanin content 98.4% and cell viability 99.4% at the
same concentration), which has been recognized as a useful depigmentation compound
for skin whitening in the cosmetic industry [25]. Among the above, eight glycosides, i.e.,
five cyclic diarylheptanoid glycosides, 2–4, 6, 9, one acyclic diarylheptanoid glycoside,
12, and two phenolic glycosides, 15 and 16, exhibited no or almost no toxicity to the cells
(cell viability 87.9–106.2%) even at a high concentration (100 mm), while these showed
inhibition of melanogenesis (melanin content 39.4–76.2%) almost equivalent to or
more superior to reference arbutin (melanin content 73.6% and cell viability 88.9% at
the same concentration). High melanogenesis inhibitory activity without significant
effect on the cell proliferation of three diarylheptanoid glycosides, 2, 3, and 6, was
observed also in our previous study, in which they were evaluated in B16 melanoma

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cells without a-MSH-stimulation [10]. From the results of the anti-melanogenesis test
in B16 melanoma cells in this and in our recent studies [10], it appears that some of the
glycosidic diarylheptanoids and phenolic compounds from the bark of A. nikoense may
be valuable as potential skin-whitening agents.
Cytotoxic Activity. The cytotoxic activities of compounds 1–16 and 18–35, and two
reference chemotherapeutic drugs, cisplatin and 5-fluorouracil, against two human
cancer cell lines, HL60 (leukemia) and CRL1579 (melanoma), were determined by
means of MTT assay, and the results are compiled in Table 2. Two acyclic diaryl-
heptanoids, 10 and 11, from A. nikoense, and ten esters, 18–22 and 27–31, and two
dehydroderivatives, 34 and 35, of compounds 1 and 5 exhibited cytotoxic activities with
IC50 values in the range of 8.1–19.3 mm, although these were less active than reference
cisplatin (IC50 1.9 mm) and 5-fluorouracil (IC50 9.5 mm) against HL60. On the other
hand, two acyclic diarylheptanoids, 10 and 11, and three esters derivatives, 20, 29, and
30, exhibited cytotoxicity against CRL1579 with IC50 values in the range of IC50 10.1–
18.4 mm, indicating higher activities than reference cisplatin (IC50 21.1 mm) and 5-
fluorouracil (IC50 >100 mm). On the basis of the results presented in Table 2, the
following conclusions can be drawn about the structure–activity relationship of the
compounds evaluated: i) Deglycosylation of cyclic diarylheptanoid glycosides, 1 vs. 2–4
and 5 vs. 6, and acyclic diarylheptanoid glycoside, 11 vs. 12, increased the activity
against both HL60 and CRL1579 cells, which is consistent with the observation of the
cytotoxicity against B16 melanoma cells described above. ii) Acyclic diarylheptanoids
(i.e., 10 and 11) are more cytotoxic than cyclic diarylheptanoids (i.e., 1, 5, 7, and 8). iii)
Methylation of the phenolic OH group (i.e., 18, 19, 27, and 28), and acetylation and
crotonylation of the phenolic (i.e., 21, 22, 30, and 31) and heptyl-chain OH groups (i.e.,
20–22 and 29–31) of cyclic diarylheptanoids (i.e., 1 and 5) increased the activity
significantly. iv) Cinnamoylation on both the phenolic and heptyl-chain OH groups
(i.e., 23 and 32) and succinylation on the heptyl-chain OH group (i.e., 24 and 33) of
cyclic diarylheptanoids (i.e., 1 and 5) reduced or exerted almost no influence on the
activity. v) Dehydration of the heptyl-chain OH group of 1 and 5 into (E)-8,9- and (E)-
9,10-dehydro derivatives 34 and 35, respectively, increased the activity while that into
(E)-10,11- and (E)-11,12-dehydro derivatives 25 and 26, respectively, exerted almost
no influence or reduced the activity. It may be suggested that acyclic diarylheptanoids
and structural modification of natural cyclic diarylheptanoids are useful to develop
effective antitumor drugs.
Experimental Part
General. Column chromatography (CC): silica gel (SiO2, 230–400 mesh; Merck), Diaion HP-20
(Mitsubishi Chemical Co., Tokyo, Japan), and octadecyl silica gel (ODS; Chromatorex-ODS, 100–200
mesh; Fuji Silysia Chemical, Ltd., Aichi, Japan). Reversed-phase (RP) prep. HPLC was carried out on
an ODS column (Pegasil ODS-II 5 mm column (Senshu Scientific Co., Ltd., Tokyo, Japan), 25 cmꢁ
10 mm i.d.) at 258 with MeCN/H2O/AcOH 45 :55 :0.1 (HPLC system I; flow rate 2.0 ml/min), MeOH/
H2O/AcOH 55 :45 :0.1 (HPLC system II; flow rate 2.0 ml/min), or MeOH/H2O/AcOH 20 :80 :0.1
(HPLC system III); 30 :70 :0.1 (HPLC system IV), or 75 :25 :0.1 (HPLC system V; flow rate 3.0 ml/min)
as mobile phase. Gas-liquid chromatography (GLC): Shimadzu GC-17A instrument on a DB-17 fused
silica glass cap. column (Agilent Technologies, Inc., Santa Clara, CA, USA; 30 mꢁ0.32 mm i.d.; column
temp. 2008; injection and detector temp. 2708; N2 flow rate 1.8 ml/min; split ratio 1:34). Crystallizations

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were performed in MeOH. M.p.: Yanagimoto Micro Mp apparatus; uncorrected. Optical rotations:
JASCO P-1020 digital polarimeter. UV Spectra: JASCO V-630Bio spectrophotometer; lmax (log e) in nm.
IR Spectra: JASCO FTIR-300E spectrometer; n in cmꢀ1. 1D- and 2D-NMR spectra: JEOL ECX-400
(1H, 400 MHz; 13C, 100 MHz) or JEOL ECX-500 (1H, 500 MHz; 13C, 125 MHz) spectrometer at r.t.;
C5D5N or CDCl3 soln.; d in ppm rel. to Me4Si as internal standard, J in Hz. ESI-, and HR-ESI-MS:
Agilent 1100 LC/MSD TOF (time-of-flight) system (positive-ionization mode, cap. voltage 3000 V,
fragmentor voltage 225 V).
Chemicals and Materials. The stem bark obtained from a 25-year-old tree of Acer nikoense in the
summer of 2007 was purchased from Sirakami Fruit Park (Gunma, Japan). The plant was authenticated
by Mr. Hiroshi Sato (Sirakami Fruit Park), and voucher specimen has been deposited with the authorsꢂ
laboratory (Coll. Sci. Technol., Nihon Univ.). The chemicals were purchased as follows: 5-fluorouracil
from Nacalai Tesque, Inc. (Kyoto, Japan), fetal bovine serum (FBS), RPMI-1640 medium, antibiotics
(100 units/ml penicillin and 100 mg/ml streptomycin), and non-essential amino acid (NEAA) from
Invitrogen Co. (Carlsbad, CA, USA), Eagleꢀs minimal essential medium (MEM), and MTT from Sigma-
Aldrich Japan Co. (Tokyo, Japan), arbutin (4-hydroxyphenyl b-d-glucopyranoside), diazo(trimethylsi-
lyl)methane (Me3SiCHN2; 10% in hexane), TsOH, 4-(dimethylamino)pyridine (DMAP), and O,O-
di(pyridin-2-yl)thiocarbonate (DPTC) from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan), crotonic
acid, (E)-cinnamic acid, succinic anhydride, cisplatin, l-glucose, and TMS-HT kit (hexamethyldisil-
azane-trimethylchlorosilane (HMDS-TMCS) in anh. pyridine) from Wako Pure Chemical Industries Ltd.
(Osaka, Japan), d-glucose, l-cysteine methyl ester hydrochloride, and molecular sieves (3 ꢃ 1/16) from
Kanto Chemical Co., Inc. (Tokyo, Japan), and Amberlite MB-4 from Organo Co. (Tokyo, Japan). All
other chemicals and reagents were of anal. grade.
Cell Cultures. Cell lines HL60 (leukemia), CRL1579 (melanoma), and B16 A45 (murine melanoma)
were obtained from Riken Cell Bank (Tsukuba, Ibaraki, Japan). Two cell lines, HL60 and CRL1579, were
grown in RPMI-1640 medium. The medium was supplemented with 10% FBS and antibiotics. B16 Cells
were cultured in MEM supplemented with 5% FBS and antibiotics. Cells were incubated at 378 in a 5%
CO2 humidified incubator.
Extraction and Isolation. The dried stem bark of A. nikoense (1799 g) was finely cut and extracted
with hexane (reflux, 3 h, 3ꢁ ) which yielded the extract (9.6 g) containing fatty constituents. The defatted
residue was then extracted with MeOH (reflux, 3 h, 3ꢁ ) to give the extract (205.8 g), which was
partitioned in an AcOEt/H2O mixture. The aq. layer was extracted with BuOH, and removal of the
solvent under reduced pressure from the AcOEt-, BuOH-, and H2O-soluble portions yielded 78.2, 84.6,
and 30.9 g of the residue, resp.
CC on SiO2 (990 g) of a portion (57.7 g) of the AcOEt-soluble fraction eluted with hexane/AcOEt
1:1, AcOEt, and then with AcOEt/MeOH 7:3 gave eight fractions, Frs. 1 (1.14 g), 2 (4.02 g), 3 (0.26 g), 4
(1.06 g), 5 (8.13 g), 6 (1.71 g), 7 (28.55 g), and 8 (7.78 g). A portion (1.00 g) of Fr. 2 was further separated
by CC (SiO2 (100 g); hexane/AcOEt gradient 1:0!0 :1) to furnish six fractions, Frs. 3-1–3-6. Prep.
HPLC (system I) of Fr. 3-2 (105 mg) yielded compounds 5 (22.3 mg; tR 33.0 min) and 13 (22.3 mg; tR
11.3 min). Fr. 3-3 (707 mg) was further subjected to CC (SiO2 (50 g); hexane/AcOEt gradient 1:0!0 :1)
which yielded seven fractions, Frs. 3-3a–3-3g. Prep. HPLC (system I) of Fr. 3-3e (417 mg) yielded
compounds 1 (57.0 mg; tR 22.0 min), 8 (2.1 mg; tR 19.3 min), 10 (5.8 mg; tR 18.8 min), and 14 (258.0 mg; tR
6.3 min). In addition, prep. HPLC (system I) of Fr. 3-3g (99 mg) yielded 11 (68.1 mg; tR 14.3 min). Fr. 4
was subjected to CC (SiO2 (53 g); hexane/AcOEt gradient 1:1!0 :1) to yield purified Fr. 4 (580 mg),
which, upon prep. HPLC (system I), yielded compound 7 (5.8 mg; tR 41.3 min). A portion (23.86 g) of
Fr. 7 was subjected to CC (SiO2 900 g); AcOEt/MeOH gradient 19 :1!0 :1) to yield nine fractions,
Frs. 7-1–7-9. Further CC on SiO2 (37 g) of a portion (1.25 g) of Fr. 7-1 (10.14 g) yielded four fractions,
Frs. 7-1a–7-1d. Prep. HPLC (system II) of Fr. 7-1a (322 mg), 7-1b (103 mg), and 7-1d (559 mg) yielded
compounds 2 (100.4 mg; tR 23.0 min) and 6 (202.3 mg; tR 29.6 min), compounds 4 (10.8 mg; tR 23.0 min)
and 9 (21.4 mg; tR 39.7 min), and compounds 3 (155.5 mg; tR 34.8 min) and 12 (154.6 mg; tR 26.0 min),
resp. A portion (52.6 g) of the BuOH-soluble fraction was chromatographed on a Diaion HP-20 (500 g)
column (MeOH/H2O gradient 1:9!10 :0) to yield seven fractions, Fr. B1–B7. Fr. B2 (5.58 g) was
further chromatographed on ODS (250 g) column (MeOH/H2O gradient 0 :1!1:0) to yield seven
fractions, Fr. B2-1–B2-7. Prep. HPLC (system III) of Fr. B2-4 (328 mg) yielded 16 (15.4 mg; tR 24.6 min).

CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
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On the other hand, further CC (SiO2 (75 g); CHCl3/MeOH gradient 1:0!0 :1) of a portion (1.50 g) of
Fr. B2-5 (2.86 g) yielded five fractions, Fr. B2-5a–B2-5e. Prep. HPLC (system IV) of Fr. B2-5a (201 mg)
yielded 15 (143.4 mg; tR 16.7 min). The physical characteristics and spectral data of two new compounds,
8 and 9, are given below.
(11x)-9-Oxoacerogenin A (¼4,12-Dihydroxy-2-oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hex-
aen-10-one; 8). Fine needles. M.p. 147–1508 (MeOH). [a]2D5 ¼ þ0.5 (c¼0.36, EtOH). UV (MeOH): 276
(3.52). IR (KBr): 3403 (OH), 1705 (C¼O), 1504 (arom. C¼C), 1231, 1055 (CꢀOꢀC). 1H- and 13C-NMR:
Table 1. HR-ESI-MS: 335.1303 ([MþNa]þ , C19H20NaO4þ ; calc. 335.1259).
(9x)-9-O-b-d-Glucopyranosylacerogenin
K
(¼ 3,17-Dihydroxytricyclo[12.3.1.12,6]nonadeca-
1(18),2,4,6(19),14,16-hexaen-9-yl b-d-Glucopyranoside; 9). Fine needles. M.p. 166–1698 (MeOH).
[a]2D5 ¼ ꢀ71.1 (c¼0.34, EtOH). UV (MeOH): 217 (4.03), 256 (3.45), 297 (3.15). IR (KBr): 3397 (OH),
1506 (aromatic C¼C), 1075. 13C- and 1H-NMR: Table 1. HR-ESI-MS: 483.1984 ([MþNa]þ
,
C25H32NaOþ8 ; calc. 483.1994).
Acid Hydrolysis of 9 and Sugar Identification. A soln. of 9 (12.3 mg) in 1m HCl/MeOH 1:1 (12 ml)
was heated under reflux for 2 h. The mixture was diluted with H2O and extracted with AcOEt (3ꢁ ). The
AcOEt extract was passed through CC (SiO2 (5 g); hexane/AcOEt) to yield acerogenin K (17) (5.0 mg).
The aq. layer was neutralized by passing through an Amberlite MB-4, and the eluate was concentrated.
The residue (3.7 mg) was dissolved in pyridine (0.5 ml) and stirred with l-cysteine methyl ester (5 mg)
for 1.0 h at 608. The trimethylsilylation reagent HMDS-TMCS (0.3 ml) was added, and warming at 608
was continued for another 30 min. The mixture was centrifuged, and a portion (1 ml) of the filtrate was
analyzed by GLC. The GLC afforded a peak with tR 18.3 min which was identical with that of authentic
d-glucose (tR 18.2 min). Authentic l-glucose eluted with tR 16.0 min under the same GLC condition.
(9x)-Acerogenin K (¼ Tricyclo[12.3.1.12,6]nonadeca-1(18),2,4,6(19),14,16-hexaene-3,9,17-triol; 17).
1
[a]2D4 ¼ ꢀ9.0 (c¼1.52, EtOH). H-NMR (400 MHz; C5D5N): 1.44 (sept., J ¼ 6.0, HaꢀC(11)); 1.70–1.80
(m, HbꢀC(11)); 1.74–1.83 (m, HaꢀC(8)); 1.89 (dd-like, J ¼ 12.1, 12.1, HaꢀC(10)); 1.93–2.05 (m,
HbꢀC(8), HaꢀC(12)); 1.98–2.10 (m, HbꢀC(10)); 2.43 (dt, J ¼ 2.5, 15.6, HbꢀC(12)); 2.49 (dt, J ¼ 3.6, 13.4,
HaꢀC(7)); 2.88 (br. d, J ¼ 17.0, HbꢀC(7)); 3.00 (dt, J ¼ 2.4, 17.4, HaꢀC(13)); 3.34 (ddd, J ¼ 2.3, 13.3, 16.2,
HbꢀC(13)); 4.47 (br. t, J ¼ 9.6, HꢀC(9)); 7.14 (dd, J ¼ 2.3, 8.2, HꢀC(5)); 7.19 (br. s, HꢀC(15), HꢀC(16));
7.25 (br. d, J ¼ 8.2, HꢀC(4)); 7.47 (br. s, HꢀC(19)); 7.57 (br. s, HꢀC(18)). 13C-NMR (100 MHz; C5D5N):
23.5 (C(11)); 27.2 (C(8)); 27.6 (C(13)); 30.4 (C(7)); 35.8 (C(12)); 40.7 (C(10)); 68.0 (C(9)); 116.9 (C(4),
C(16)); 127.4 (C(2)); 127.5 (C(1)); 129.9 (C(5)); 130.0 (C(15)); 131.1 (C(6)); 131.6 (C(14)); 134.7
(C(19)); 135.2 (C(18)); 152.7 (C(3), C(17)). The structure of 17 was supported by its 1H,1H-COSY,
HMQC, and HMBC spectra. The 1H- and 13C-NMR signal assignments for HꢀC(7), HꢀC(8), HꢀC(12),
and HꢀC(13) reported in [4] were revised as described above. ESI-MS: 321 ([MþNa]þ , C19H22NaO3þ ).
Acid Hydrolysis of 2 and 6. A soln. of 2 (300 mg) in 1m HCl/MeOH (1:1; 24 ml) was heated under
reflux for 2 h. After cooling, the mixture was poured into ice-H2O, and extracted with AcOEt. The
AcOEt extract, after usual workup, yielded 1 (185 mg). In a similar procedure of acid hydrolysis, 6
(400 mg) yielded 5 (175 mg).
Acerogenin A (¼(12R)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexaene-4,12-diol; 1).
[a]2D0 ¼ þ59.9 (c¼0.49, EtOH) (lit. [2]: [a]D ¼ þ57.3). 1H-NMR (400 MHz; CDCl3): 0.78–0.85 (m,
HaꢀC(9)); 0.90–0.97 (m, HaꢀC(10)); 0.98–1.06 (m, HbꢀC(9)); 1.04–1.12 (m, HbꢀC(10)); 1.18–1.27 (m,
HaꢀC(8)); 1.42–1.52 (m, HbꢀC(8)); 1.62 (dddd, J¼4.1, 5.5, 9.6, 10.1, HaꢀC(12)); 1.88 (dq, J¼14.2, 4.1,
HbꢀC(12)); 2.37–2.49 (m, CH2(7)); 2.68 (dt, J ¼ 2.8, 12.8, HaꢀC(13)); 2.98 (dt, J¼13.3, 3.7, HbꢀC(13));
3.25 (tt, J¼5.0, 5.0, HꢀC(11)); 5.62 (d, J¼1.8, HꢀC(6)); 5.72 (br. s, OHꢀC(2)); 6.59 (dd, J¼1.8, 8.0,
HꢀC(4)); 6.83 (d, J¼8.0, HꢀC(3)); 6.92 and 7.14 (dd, J¼2.8, 8.2, each 1 H, HꢀC(16), HꢀC(18)); 7.19 and
7.28 (dd, J¼2.3, 8.2, each 1 H, HꢀC(15), HꢀC(19)). ESI-MS: 321 ([MþNa]þ , C19H22NaO3þ ).
(R)-Acerogenin B (¼(10R)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexaene-4,10-diol; 5).
[a]2D0 ¼ ꢀ76.4 (c¼0.49, EtOH) ([2][6]: [a]D ¼ ꢀ95.0). 1H-NMR (400 MHz; CDCl3): 0.74–0.82 (m,
HaꢀC(10)); 0.95–1.05 (m, HaꢀC(11)); 1.18–1.28 (m, HbꢀC(10)); 1.25–1.35 (m, HbꢀC(11)); 1.45–1.53 (m,
CH2(8)); 1.50–1.58 (m, HaꢀC(12)); 1.76 (sept.-like, J¼7.2, HbꢀC(12)); 2.52–2.62 (m, HaꢀC(7)); 2.55–
2.67 (m, HbꢀC(7), HaꢀC(13)); 2.80 (ddd, J¼4.4, 6.0, 13.2, HbꢀC(13)); 3.02–3.11 (m, HꢀC(9)); 5.57 (d,
J¼1.8, HꢀC(6)); 6.63 (dd, J¼1.8, 8.2, HꢀC(4)); 6.84 (d, J¼8.2, HꢀC(3)); 6.93 and 7.13 (2dd, J¼2.5, 8.2,

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CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
each 1 H, HꢀC(16), HꢀC(18)); 7.23 and 7.30 (2dd, J¼2.1, 8.2, each 1 H, HꢀC(15), HꢀC(19)). ESI-MS:
321 ([MþNa]þ , C19H22NaOþ3 ).
CH2N2 Methylation of 1 and 5. To a soln. of 1 (10.4 mg) in AcOEt/MeOH (2 :1; 3.0 ml), Me3SiCHN2
(10% in hexane; 0.2 ml) was added, and the mixture was stirred at r.t. for 1 h. Removal of the solvent
under reduced pressure yielded 18 (10.3 mg). Similarly, methylation of 5 (9.7 mg) yielded 27 (9.9 mg).
2-O-Methyl Acerogenin A (¼(12R)-4-Methoxy-2-oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-
hexaen-12-ol; 18). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 3.23–3.31 (m, HꢀC(11)); 3.93 (s,
MeO). ESI-MS: 335 ([MþNa]þ , C20H24NaO3þ ).
2-O-Methyl Acerogenin B (¼(10R)-4-Methoxy-2-oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-
hexaen-10-ol; 27). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 3.02–3.11 (m, HꢀC(9)); 3.93 (s,
MeO). ESI-MS: 335 ([MþNa]þ , C20H24NaO3þ ).
Acetylation of 1, 5, 18, and 27 by Ac2O. To a soln. of 1 (10.4 mg) in pyridine (0.5 ml), Ac2O (0.5 ml)
was added, and the mixture was left overnight at r.t. The mixture was then poured into ice-H2O, and
extracted with Et2O. The Et2O extract, after washing with dil. HCl soln. (HCl/H2O 1:9) and with sat.
NaHCO3 aq. soln. followed by usual workup, yielded 21 (10.4 mg). Similarly, acetylation of 5 (5.2 mg), 18
(5.1 mg), and 27 (4.2 mg) yielded 30 (5.1 mg), 19 (5.6 mg), and 28 (4.8 mg), resp.
11-O-Acetyl-2-O-methyl Acerogenin A (¼(12R)-4-Methoxy-2-oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),
15,17,18-hexaen-12-yl Acetate; 19). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 1.97 (s, AcOꢀC(11));
3.88 (s, AcOꢀC(2)); 4.32–4.38 (m, HꢀC(11)). ESI-MS: 377 ([MþNa]þ , C22H26NaO4þ ).
2,11-Di-O-acetyl Acerogenin A (¼(12R)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexaene-
1
4,12-diyl Diacetate; 21). Amorphous solid. H-NMR (400 MHz; CDCl3): 2.02 (s, AcOꢀC(11)); 2.37 (s,
AcOꢀC(2)); 4.32–4.38 (m, HꢀC(11)). ESI-MS: 405 ([MþNa]þ , C23H26NaO5þ ).
9-O-Acetyl-2-O-methyl Acerogenin B (¼(10R)-4-Methoxy-2-oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),
15,17,18-hexaen-10-yl Acetate; 28). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 1.90 (s, AcOꢀC(9));
3.88 (s, MeOꢀC(2)); 4.38 (ddd, J¼3.6, 7.2, 13.8, HꢀC(9)). ESI-MS: 377 ([MþNa]þ , C22H26NaO4þ ).
2,9-Di-O-acetyl Acerogenin B (¼(10R)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexaene-
1
4,10-diyl Diacetate; 30). Amorphous solid. H-NMR (400 MHz; CDCl3): 1.94 (s, AcOꢀC(9)); 2.27 (s,
AcOꢀC(2)); 4.37 (ddd, J¼3.2, 7.6, 13.2, HꢀC(9)). ESI-MS: 405 ([MþNa]þ , C23H26NaO5þ ).
Acetylation of 1 and 5 by AcOEt in the Presence of TsOH. A soln. of 1 (17.4 mg) and TsOH (17.7 mg),
along with a few pieces of molecular sieves in AcOEt (5.0 ml), was heated under reflux for 7 h. The
mixture was filtered, and the usual workup of the filtrate yielded a residue (16.0 mg) which, upon CC
(SiO2; hexane/AcOEt gradient 9 :1!7:3), yielded 20 (5.4 mg). The similar acetylation of 5 (10.5 mg)
yielded 29 (3.4 mg).
11-O-Acetyl Acerogenin A (¼(12R)-4-Hydroxy-2-oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-
1
hexaen-12-yl Acetate; 20). Amorphous solid. H-NMR (400 MHz; CDCl3): 1.97 (s, AcOꢀC(11)); 4.31
(tt, J¼4.0, 6.8, HꢀC(11)), ESI-MS: 363 ([MþNa]þ , C21H24NaO4þ ).
9-O-Acetyl Acerogenin B (¼(10R)-4-Hydroxy-2-oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexa-
en-10-yl Acetate; 29). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 1.97 (s, AcOꢀC(9)); 4.38 (ddd, J¼
3.0, 7.2, 14.0, HꢀC(9)). ESI-MS: 363 ([MþNa]þ , C21H24NaO4þ ).
Esterification of 1 and 5 with Crotonic Acid. To a soln. of 1 (20.4 mg) in toluene (3.0 ml), crotonic
acid (20.8 mg), DMAP (15.5 mg), and DPTC (30.7 mg) were added, and the mixture was stirred at r.t.
for 48 h under N2. The mixture was poured into H2O, and extracted with Et2O. The Et2O extract
(26.2 mg) was passed through CC (SiO2; hexane/AcOEt gradient 9 :1!1:1) to afford 22 (2.8 mg).
Similarly, the esterification of 5 (20.5 mg) with crotonic acid yielded 31 (2.7 mg).
2,11-Di-O-crotonyl Acerogenin A (¼(12R)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexa-
ene-4,12-diyl Bis[(2E)-but-2-enoate]; 22). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 1.88 (dd, J ¼
1.8, 6.9, Me(4’’)); 1.98 (dd, J ¼ 1.8, 6.9, Me(4’)); 4.43 (ddd, J¼3.7, 7.3, 10.6, HꢀC(11)); 5.84 (dq, J¼15.6,
1.4, HꢀC(2’’)); 6.15 (dq, J¼15.6, 1.8, HꢀC(2’)); 6.91–6.98 (m, HꢀC(3’’)); 7.23–7.29 (m, HꢀC(3’)). ESI-
MS: 457 ([MþNa]þ , C27H24NaO4þ ).
2,9-Di-O-crotonyl Acerogenin B (¼(10R)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexa-
ene-4,10-diyl Bis[(2E)-but-2-enoate]; 31). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 1.86 (dd,
J ¼ 1.8, 6.9, Me(4’’)); 1.98 (dd, J ¼ 1.8, 6.9, Me(4’)); 4.45 (dq, J¼3.2, 7.8, HꢀC(9)); 5.76 (dq, J¼15.1, 1.4,

CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
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HꢀC(2’’)); 6.15 (dq, J¼15.6, 1.8, HꢀC(2’)); 6.85–6.91 (m, HꢀC(3’’)); 7.23–7.29 (m, HꢀC(3’)). ESI-MS:
457 ([MþNa]þ , C27H24NaOþ4 ).
Esterification of 1 and 5 with (E)-Cinnamic Acid. To a soln. of 1 (20.5 mg) in toluene (2.0 ml), (E)-
cinnamic acid (20.6 mg), DMAP (15.8 mg), and DPTC (30.6 mg) were added and stirred at r.t. for 24 h
under N2. The mixture was poured into H2O, and extracted with Et2O. The Et2O extract (30.4 mg) was
subjected to CC (SiO2; hexane/AcOEt gradient 9 :1!1:1) to afford 23 (17.8 mg). Esterification of 5
(19.5 mg) with (E)-cinnamic acid as described above yielded 32 (11.4 mg).
2,11-Di-O-cinnamoyl Acerogenin A (¼(12R)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexa-
ene-4,12-diyl Bis[(2E)-3-phenylprop-2-enoate; 23). Amorphous solid. 1H-NMR (400 MHz; CDCl3):
4.49–4.56 (m, HꢀC(11)); 6.44 (dt-like, J¼15.6, 2.3, HꢀC(2’’)); 6.75 (d, J¼16.0, HꢀC(2’)); 7.39 (t-like, J¼
3.0, HꢀC(6’’), HꢀC(7’’), HꢀC(8’’)); 7.42 (t-like, J¼3.0, HꢀC(6’), HꢀC(7’), HꢀC(8’)); 7.51–7.55 (m,
HꢀC(5’’), HꢀC(9’’)); 7.59–7.63 (m, HꢀC(5’), HꢀC(9’)); 7.68 (dd-like, J¼1.8, 16.0, HꢀC(3’’)); 7.95 (d, J¼
16.0, HꢀC(3’)). ESI-MS: 581 ([MþNa]þ , C37H34NaO5þ ).
2,9-Di-O-cinnamoyl Acerogenin B (¼(10R)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexa-
ene-4,10-diyl Bis[(2E)-3-phenylprop-2-enoate]; 32). Amorphous solid. 1H-NMR (400 MHz; CDCl3):
4.54 (ddd, J¼2.8, 8.0, 13.2, HꢀC(9)); 6.34 (dt-like, J¼16.0, HꢀC(2’’)); 6.74 (d, J¼16.0, HꢀC(2’)); 7.39 (t-
like, J¼3.0, HꢀC(6’’), HꢀC(7’’), HꢀC(8’’)); 7.42 (t-like, J¼3.0, HꢀC(6’), HꢀC(7’), HꢀC(8’)); 7.49 (dd,
J¼2.0, 6.0, HꢀC(5’’), HꢀC(9’’)); 7.59 (dd, J¼2.0, 6.0, HꢀC(5’), HꢀC(9’)); 7.60 (d, J¼16.0, HꢀC(3’’));
7.94 (d, J¼16.0, HꢀC(3’)). ESI-MS: 581 ([MþNa]þ , C37H34NaO5þ ).
Esterification of 1 and 5 with Succinic Anhydride. To a soln. of 1 (20.8 mg) in pyridine (10.0 ml),
succinic anhydride (21.0 mg) and DMAP (10.6 mg) were added, and the mixture was refluxed for 7 h.
The mixture was poured into H2O and extracted with AcOEt. The AcOEt extract was washed with dil.
HCl and then with H2O. The mixture obtained (23.2 mg) was subjected to CC (SiO2; hexane/AcOEt
gradient 8 :2!0 :1) to afford 24 (2.2 mg). Esterification of 5 (21.0 mg) with succinic anhydride as
described above yielded 33 (2.2 mg).
11-O-Succinyl Acerogenin
A
(¼ Butanedioic Acid Mono[(12R)-4-hydroxy-2-oxatricyclo-
[13.2.2.13,7]icosa-3,5,7(20),15,17,18-hexaen-12-yl] Ester; 24). Amorphous solid. 1H-NMR (400 MHz;
C5D5N): 2.86–2.97 (m, CH2(2’), CH2(3’)); 4.60–4.8 (m, HꢀC(11)). ESI-MS: 421 ([MþNa]þ
,
C23H26NaOþ6 ).
9-O-Succinyl Acerogenin B (¼ Butanedioic Acid Mono[(10R)-4-hydroxy-2-oxatricyclo[13.2.2.13,7]-
icosa-3,5,7(20),15,17,18-hexaen-10-yl] Ester; 33). Amorphous solid. 1H-NMR (400 MHz; C5D5N): 2.80–
2.95 (m, CH2(2’), CH2(3’)); 4.70–4.79 (m, HꢀC(9)). ESI-MS: 421 ([MþNa]þ , C23H26NaO6þ ).
Dehydration of 1 and 5. A soln. of 1 (100.6 mg) in pyridine (5.0 ml) was treated with SOCl2 (0.5 ml),
and the mixture was stirred at 08 for 5 h. The mixture was poured into ice-H2O and extracted with
AcOEt. The AcOEt extract was washed with sat. aq. NaHCO3 and brine, and then worked up as usual to
yield a residue (96.5 mg), which, upon CC (SiO2; hexane/AcOEt gradient 9 :1!7:3), afforded a
fraction containing dehydration products. Prep. HPLC (system IV) of this fraction yielded 25 (6.3 mg; tR
46.0 min) and 26 (3.4 mg; tR 49.6 min). The procedure as described above for 5 (100.3 mg) yielded 34
(9.8 mg; tR 50.4 min) and 35 (1.7 mg; tR 48.8 min).
11-Deoxy-10(11)E-dehydroacerogenin A (¼(11E)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),11,
15,17,18-heptaen-4-ol; 25). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 1.47 (dt, J¼12.0, 6.4,
CH2(8)); 1.77 (dd, J¼5.7, 12.1, CH2(9)); 2.25 (dd, J¼7.1, 12.7, CH2(12)); 2.44 (dd, J¼6.4, 6.4, CH2(7));
2.78 (dd, J¼6.4, 6.4, CH2(13)); 4.90 (dt, J ¼ 15.4, 5.9, HꢀC(10)); 5.09 (dt, J¼14.9, 7.7, HꢀC(11)); 5.41 (d,
J¼1.7, HꢀC(6)); 5.52 (br. s, HOꢀC(2)); 6.57 (dd, J¼2.1, 8.2, HꢀC(4)); 6.82 (d, J¼8.3, HꢀC(3)); 7.00 (dt,
J ¼ 8.5, 2.0, HꢀC(16), HꢀC(18)); 7.08 (dt, J ¼ 8.3, 2.0, HꢀC(15), HꢀC(19)). HR-ESI-MS: 303.1364
([MþNa]þ , C19H20NaOþ2 ; calc. 303.1361).
11-Deoxy-11(12)E-dehydroacerogenin A (¼(12E)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),12,
15,17,18-heptaen-4-ol; 26). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 1.09–1.17 (m, CH2(9));
1.28–1.37 (m, CH2(8)); 1.91 (ddd, J¼1.2, 6.4, 10.8, CH2(10)); 2.46 (t, J¼6.0, CH2(7)); 3.29 (dd, J¼2.0,
5.2, CH2(13)); 4.48 (dtt, J ¼ 14.9, 1.6, 6.4, HꢀC(11)); 5.75 (dtt, J¼15.6, 1.6, 5.2, HꢀC(12)); 5.60 (br. s,
HOꢀC(2)); 5.69 (d, J¼1.7, HꢀC(6)); 6.58 (dd, J¼1.2, 8.0, HꢀC(4)); 6.82 (d, J¼8.3, HꢀC(3)); 7.07 (dt,
J ¼ 8.5, 2.0, HꢀC(16), HꢀC(18)); 7.22 (dt, J ¼ 8.3, 2.0, HꢀC(15), HꢀC(19)). HR-ESI-MS: 303.1369
([MþNa]þ , C19H20NaOþ2 ; calc. 303.1361).

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9-Deoxy-8(9)E-dehydroacerogenin B (¼(9E)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),9,15,17,18-
1
heptaen-4-ol; 34). Amorphous solid. H-NMR (400 MHz; CDCl3) : 1.09–1.19 (m, CH2(11)); 1.47–1.55
(m, CH2(12)); 1.85 (dd, J¼7.2, 12.8, CH2(10)); 2.63 (dt, J¼10.8, 6.0, CH2(13)); 3.00 (d, J¼7.2, CH2(7));
5.18 (dt, J ¼ 14.8, 7.6, HꢀC(8)); 5.34 (d, J¼1.6, HꢀC(6)); 5.39 (dt, J¼14.8, 7.6, HꢀC(9)); 5.57 (br. s,
HOꢀC(2)); 6.59 (dd, J¼1.6, 8.0, HꢀC(4)); 6.82 (d, J¼7.6, HꢀC(3)); 7.02 (dt, J ¼ 8.3, 2.2, HꢀC(16),
HꢀC(18)); 7.21 (dt, J ¼ 8.3, 2.2, HꢀC(15), HꢀC(19)). HR-ESI-MS: 303.1385 ([MþNa]þ , C19H20NaO2þ ;
calc. 303.1361).
9-Deoxy-9(10)E-dehydroacerogenin
B
(¼(10E)-2-Oxatricyclo[13.2.2.13,7]icosa-3,5,7(20),10,
15,17,18-heptaen-4-ol; 35). Amorphous solid. 1H-NMR (400 MHz; CDCl3): 1.77–1.85 (m, CH2(12));
2.05–2.15 (m, CH2(11), CH2(8)); 2.50 (dt, J¼10.8, 5.6, CH2(7)); 2.74 (t, J¼6.3, CH2(13)); 4.83 (dtt, J ¼
16.0, 1.2, 5.6, HꢀC(10)); 5.00 (dtt, J¼15.6, 1.6, 6.4, HꢀC(9)); 5.54 (br. s, HOꢀC(2)); 6.04 (d, J¼2.4,
HꢀC(6)); 6.54 (dd, J¼2.0, 8.0, HꢀC(4)); 6.79 (d, J¼8.0, HꢀC(3)); 7.00 (dt, J ¼ 8.8, 2.0, HꢀC(16),
HꢀC(18)); 7.28 (dt, J ¼ 8.8, 2.0, HꢀC(15), HꢀC(19)). HR-ESI-MS: 303.1380 ([MþNa]þ , C19H20NaO2þ ;
calc. 303.1361).
Cell Lines and Culture Conditions. B16 4A5 (mouse melanoma), HL60 (human leukemia), and
CRL1579 (human melanoma) cell lines were purchased from Riken Cell Bank (Tsukuba, Ibaraki,
Japan). B16 Cells were cultured in D-MEM medium, while HL60 and CRL1579 cells were grown in
RPMI-1640 medium. The medium was supplemented with 10% FBS and antibiotics (100 units/ml
penicillin and 100 mg/ml streptomycin). Cells were incubated at 378 in a 5% CO2 humidified incubator.
The cells were cultured according to the method described in [24][26][27].
Cytotoxicity Assay. Cytotoxicity assay was performed according to the method described in
[24][26][27].
Assay of Melanin Content. Melanogenesis inhibition assay in the a-MSH-stimulated B16 melanoma
cells was performed according to the method described in [27].
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Received January 23, 2012