Journal of Agricultural and Food Chemistry
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1205, 1173 cm−1; 1H NMR (400 MHz, CDCl3) δ 7.67 (1H, d, J = 16.0
Hz, H-β), 7.35−7.51 (5H, m, H-2, 3, 4, 5, 6), 7.21−7.33 (5H, m, H-2′,
3′, 4′, 5′, 6′), 6.42 (1H, d, J = 16.0 Hz, H-α), 4.42 (2H, t, J = 7.2 Hz,
H-α′), 3.01 (2H, t, J = 7.2 Hz, H-β′); HRESIMS [M − H]− m/z
251.1067 (Calcd for C17H15O2, 251.1072).
Sinapic Acid Phenethyl Ester (11). The title compound was
prepared according to modified method A as light yellow oil (216 mg,
65.8% yield). IR (KBr) νmax 3419, 1704, 1633, 1514, 1283, 1218, 1153
cm−1; 1H NMR (400 MHz, CDCl3) δ 7.58 (1H, d, J = 16.0 Hz, H-β),
7.22−7.34 (5H, m, H-2′, 3′, 4′, 5′, 6′), 6.76 (2H, s, H-2, 6), 6.29 (1H,
d, J = 16.0 Hz, H-α), 4.43 (2H, t, J = 7.2 Hz, H-α′), 3.91 (6H, s, 3, 5−
OCH3), 3.02 (2H, t, J = 7.2 Hz, H-β′); HRESIMS [M − H]− m/z
327.1228 (Calcd for C19H19O5, 327.1232).
H-α), 3.45 (2H, t, J = 7.2 Hz, H-α′), 2.74 (2H, t, J = 7.2 Hz, H-β′);
HRESIMS [M − H]− m/z 298.1081 (Calcd for C17H16NO4,
298.1079).
Caffeic Acid 3,4-Dihydroxyphenethyl Ester (18). The title
compound was prepared according to method D as a white powder
(648 mg, 41.0% yield for Knoevenagel condensation). mp 118−120
°C; IR (KBr) νmax 3339, 1680, 1600, 1525, 1278, 1186 cm−1; 1H NMR
(400 MHz, CD3OD) δ 7.52 (1H, d, J = 16.0 Hz, H-β), 7.03 (1H, d, J =
2.0 Hz, H-2), 6.94 (1H, dd, J = 2.0, 8.0 Hz, H-6), 6.78 (1H, d, J = 8.0
Hz, H-5), 6.70 (1H, d, J = 2.0 Hz, H-2′), 6.70 (1H, d, J = 8.0 Hz, H-
5′), 6.58 (1H, dd, J = 2.0, 8.0 Hz, H-6′), 4.29 (2H, t, J = 7.2 Hz, H-α′),
2.84 (2H, t, J = 7.2 Hz, H-β′); HRESIMS [M − H]− m/z 315.0862
(Calcd for C17H15O6, 315.0869).
Caffeic Acid 4-Nitrophenethyl Ester (19). The title compound was
prepared according to method D as a light yellow powder (305 mg,
18.5% yield for Knoevenagel condensation). mp 172−174 °C; IR
(KBr) νmax 3418, 1691, 1596, 1507, 1340, 1277, 1167 cm−1; 1H NMR
(400 MHz, DMSO-d6) δ 9.55 (1H, s), 9.11 (1H, s), 8.17 (2H, d, J =
8.8 Hz, H-2′, 6′), 7.58 (2H, d, J = 8.8 Hz, H-3′, 5′), 7.44 (1H, d, J =
16.0 Hz, H-β), 7.03 (1H, d, J = 2.0 Hz, H-2), 6.98 (1H, dd, J = 2.0, 8.0
Hz, H-6), 6.76 (1H, d, J = 8.0 Hz, H-5), 6.21 (1H, d, J = 16.0 Hz, H-
α), 4.39 (2H, t, J = 6.4 Hz, H-α′), 3.11 (2H, t, J = 6.4 Hz, H-β′); 13C
NMR (100 MHz, DMSO-d6) δ 166.4, 148.5, 146.7, 146.3, 145.6,
145.4, 130.2, 125.4, 123.4, 121.4, 115.7, 114.9, 113.6, 63.5, 34.2;
HRESIMS [M − H]− m/z 328.0823 (Calcd for C17H14NO6,
328.0821).
Caffeic Acid 4-Aminophenethyl Ester (20). A mixture of caffeic
acid 4-nitrophenethyl ester (60 mg, 0.091 mmol), stannic chloride
dihydrate (123 mg, 0.55 mmol) and 5 mL of ethanol was heated to
reflux for 10 h before being cooled to room temperature. Ten
milliliters of saturated Na2CO3 was added, and the suspension was
extracted with ethyl acetate (10 mL × 3). The combined organic layer
was dried, evaporated and purified by column chromatography to give
the title compound as a light yellow powder (34 mg, 62.3% yield). mp
173−175 °C; IR (KBr) νmax 3432, 1692, 1598, 1515, 1280, 1175 cm−1;
1H NMR (400 MHz, DMSO-d6) δ 9.57 (1H, s), 9.12 (1H, s), 7.45
(1H, d, J = 16.0 Hz, H-β), 7.04 (1H, d, J = 2.0 Hz, H-2), 6.99 (1H, dd,
J = 2.0, 8.0 Hz, H-6), 6.91 (2H, d, J = 8.4 Hz, H-2′, 6′), 6.76 (1H, d, J
= 8.0 Hz, H-5), 6.50 (2H, d, J = 8.4 Hz, H-3′, 5′), 6.23 (1H, d, J = 16.0
Hz, H-α), 4.20 (2H, t, J = 7.2 Hz, H-α′), 2.75 (2H, t, J = 7.2 Hz, H-
β′); 13C NMR (100 MHz, DMSO-d6) δ 167.0, 148.9, 147.5, 146.0,
145.5, 129.7, 126.0, 125.1, 121.8, 116.2, 115.3, 114.5, 65.4, 34.3;
HRESIMS [M − H]− m/z 298.1075 (Calcd for C17H16NO4,
298.1079).
Caffeic Acid 3-Bromophenethyl Ester (12). The title compound
was prepared according to modified method A as white powder (42
mg, 11.6% yield). mp 120−122 °C; IR (KBr) νmax 3472, 3316, 1686,
1604, 1528, 1278, 1180 cm−1; 1H NMR (400 MHz, DMSO-d6) δ 9.59
(1H, s), 9.12 (1H, s), 7.52 (1H, m, H-2′), 7.44 (1H, d, J = 16.0 Hz, H-
β), 7.42 (1H, m, H-6′), 7.28 (2H, m, H-4′, 5′), 7.03 (1H, d, J = 2.0 Hz,
H-2), 6.98 (1H, dd, J = 8.0, 2.0 Hz, H-6), 6.75 (1H, d, J = 8.0 Hz, H-
5), 6.22 (1H, d, J = 16.0 Hz, H-α), 4.32 (2H, t, J = 6.8 Hz, H-α′), 2.95
(2H, t, J = 6.8 Hz, H-β′); 13C NMR (100 MHz, DMSO-d6) δ 166.4,
148.5, 145.6, 145.3, 141.1, 131.7, 130.5, 129.3, 128.1, 125.4, 121.6,
121.4, 115.7, 114.8, 113.7, 63.9, 34.0; HRESIMS [M − H]− m/z
361.0079 (Calcd for C17H14O4Br, 361.0075).
Caffeic Acid 2-Bromophenethyl Ester (13). The title compound
was prepared according to modified method A as white powder (68
mg, 18.7% yield). mp 137−139 °C; IR (KBr) νmax 3465, 3301, 1694,
1607, 1529, 1280, 1188 cm−1; 1H NMR (400 MHz, DMSO-d6) δ 9.59
(1H, s), 9.15 (1H, s), 7.61 (1H, dd, J = 7.6, 0.8 Hz, H-3′), 7.46 (1H, d,
J = 16.0 Hz, H-β), 7.41 (1H, dd, J = 7.6, 1.6 Hz, H-6′), 7.34 (1H, dt, J
= 7.6, 0.8 Hz, H-5′), 7.11 (1H, dt, J = 7.6, 1.6 Hz, H-4′), 7.04 (1H, d, J
= 2.0 Hz, H-2), 6.98 (1H, dd, J = 8.0, 2.0 Hz, H-6), 6.76 (1H, d, J = 8.0
Hz, H-5), 6.22 (1H, d, J = 16.0 Hz, H-α), 4.34 (2H, t, J = 6.8 Hz, H-
α′), 3.09 (2H, t, J = 6.8 Hz, H-β′); 13C NMR (100 MHz, DMSO-d6) δ
166.4, 148.5, 145.6, 145.3, 137.2, 132.6, 131.4, 128.8, 127.9, 125.4,
124.0, 121.4, 115.7, 114.8, 113.7, 62.7, 34.7; HRESIMS [M − H]− m/z
361.0073 (Calcd for C17H14O4Br, 361.0075).
Caffeic Acid Benzyl Ester (14). The title compound was prepared
according to method B as white powder (148 mg, 54.8% yield). mp
151−153 °C; IR (KBr) νmax 3466, 3327, 1689, 1601, 1535, 1277, 1177
cm−1; 1H NMR (400 MHz, CDCl3) δ 7.52 (1H, d, J = 16.0 Hz, H-β),
7.26−7.34 (5H, m, H-2′, 3′, 4′, 5′, 6′), 6.97 (1H, d, J = 1.2 Hz, H-2),
6.86 (1H, dd, J = 1.2, 8.0 Hz, H-6), 6.74 (1H, d, J = 8.0 Hz, H-5), 6.20
(1H, d, J = 16.0 Hz, H-α), 5.15 (2H, s, H-α′); HRESIMS [M − H]−
m/z 269.0810 (Calcd for C16H13O4, 269.0814).
p-Coumaric Acid Benzyl Ester (15). The title compound was
prepared according to method B as white powder (213 mg, 83.8%
yield). mp 90−92 °C; IR (KBr) νmax 3401, 1691, 1599, 1517, 1279,
1203, 1170 cm−1; 1H NMR (400 MHz, CDCl3) δ 7.60 (1H, d, J = 16.0
Hz, H-β), 7.34 (2H, d, J = 8.4 Hz, H-2, 6), 7.26−7.33 (5H, m, H-2′, 3′,
4′, 5′, 6′), 6.76 (2H, d, J = 8.4 Hz, H-3, 5), 6.27 (1H, d, J = 16.0 Hz,
H-α), 5.18 (2H, s, H-α′); HRESIMS [M − H]− m/z 253.0860 (Calcd
for C16H13O3, 253.0865).
3,4-Dihydroxyphenyl Propionic Acid Phenethyl Ester (21). To a
solution of caffeic acid phenethyl ester (50 mg, 0.176 mmol) in 10 mL
of ethyl acetate was added 10% Pd/C (5 mg) under nitrogen
atmosphere. The reaction flask was vacuumed and backfilled with
hydrogen and stirred at room temperature for 12 h. The mixture was
filtered and evaporated to give the titled compound as yellow gum (50
mg, 99.4% yield). IR (KBr) νmax 3400, 1709, 1605, 1519, 1352, 1282,
1
1192 cm−1; H NMR (400 MHz, CDCl3) δ 7.18−7.30 (5H, m, H-2′,
3′, 4′, 5′, 6′), 6.74 (1H, d, J = 8.0 Hz, H-5), 6.63 (1H, d, J = 2.0 Hz, H-
2), 6.57 (1H, dd, J = 2.0, 8.0 Hz, H-6), 4.28 (2H, t, J = 7.2 Hz, H-α′),
2.91 (2H, t, J = 7.2 Hz, H-β′), 2.79 (2H, t, J = 7.8 Hz, H-α), 2.55 (2H,
t, J = 7.8 Hz, H-β); HRESIMS [M − H]− m/z 285.1120 (Calcd for
C17H17O4, 285.1127).
Caffeic Acid Phenylacetamide (16). The title compound was
prepared according to method C as light yellow powder (81 mg, 28.6%
yield). mp 153−155 °C; IR (KBr) νmax 3488, 3346, 1649, 1602, 1551,
1326, 1287, 1189 cm−1; 1H NMR (400 MHz, CDCl3) δ 7.34 (1H, d, J
= 16.0 Hz, H-β), 7.13−7.24 (5H, m, H-2′, 3′, 4′, 5′, 6′), 6.93 (1H, d, J
= 1.6 Hz, H-2), 6.82 (1H, dd, J = 1.6, 8.4 Hz, H-6), 6.71 (1H, d, J = 8.4
Hz, H-5), 6.16 (1H, d, J = 16.0 Hz, H-α), 3.48 (2H, t, J = 7.2 Hz, H-
α′), 2.78 (2H, t, J = 7.2 Hz, H-β′); HRESIMS [M − H]− m/z
282.1125 (Calcd for C17H16NO3, 282.1130).
Caffeic Acid 4-Hydroxyphenylacetamide (17). The title com-
pound was prepared according to method C as light yellow powder
(35 mg, 11.7% yield). mp 211−212 °C; IR (KBr) νmax 3369, 1646,
1604, 1516, 1241 cm−1; 1H NMR (400 MHz, CD3OD) δ 7.37 (1H, d,
J = 15.6 Hz, H-β), 7.05 (2H, d, J = 8.4 Hz, H-2′, 6′), 6.99 (1H, d, J =
2.0 Hz, H-2), 6.89 (1H, dd, J = 2.0, 8.4 Hz, H-6), 6.75 (1H, d, J = 8.4
Hz, H-5), 6.70 (2H, d, J = 8.4 Hz, H-3′, 5′), 6.33 (1H, d, J = 15.6 Hz,
Cytotoxicities of CAPE and Its Derivatives 1-21 in PC12 Cells.
Differentiated PC12 cells were maintained in DMEM medium
supplemented with 1% L-glutamine and 10% fetal bovine serum at
37 °C under a humidified 5% CO2 atmosphere. Each test compound
with appropriate concentration was dissolved in DMSO and diluted
with serum-free media. Before treatment, cells were seeded on a 96
well plate at the density of 5 × 103 cells/well and cultured for 24 h.
Then the medium was changed and cells were treated with CAPE and
its derivatives at 4 and 40 nM for 24 h, respectively. Then, 20 μL of
MTT solution (final concentration, 0.5 mg/mL) were added to each
well, and cells were incubated for 4 h. The resultant formazan product
was dissolved by the addition of 150 μL of DMSO. The absorbance
was measured at the wavelength of 570 nm using a Thermo Scientific
5048
dx.doi.org/10.1021/jf500464k | J. Agric. Food Chem. 2014, 62, 5046−5053