Journal of Agricultural and Food Chemistry
Article
3-Methylbutyl 2-methylbutanoate (3MB-2MB): GC-MS, m/z (%).
157 (0.3, M+−CH3), 144 (1.1), 129 (2.9), 115 (2.2), 103 (20.8), 85
(42.9), 70 (100.0), 57 (62.9), 55 (31.1).
3-Methyl-2-butenyl 2-methylbutanoate (IP-2MB): GC-MS, m/z
(%): 170 (2.1, M+), 103 (1.4), 85 (25.0), 74 (18.0), 69 (100.0), 68
(76.7), 67 (75.1), 57 (71.7), 53 (42.1).
Butyl 2-methylbutanoate (C4-2MB): GC-MS, m/z (%); 143 (0.2,
M+−CH3), 130 (5.5), 115 (1.9), 103 (78.7), 85 (61.9), 74 (20.8), 57
(100.0), 56 (41.0).
The entire completely experiment was repeated four times. The order
of the ester compounds was randomly determined. The tested plates
were stored under a 14:10 h (light−dark) regime at 25 1 °C and
60% relative humidity. Nematode mortality was recorded after 48 h of
treatment as follows: 10 μL of the test suspension was transferred to
100 μL of fresh water with a micropipette. Ten minutes after transfer,
nematode mortality was observed under a microscope. Nematodes
were classified as dead if their bodies were motionless and
straightened. The mortality of termites was transformed to the arcsine
square root values for analysis of variance (ANOVA). Mean values for
Pentyl 2-methylbutanoate (C5-2MB): GC-MS, m/z (%); 172 (0.1,
M+), 144 (3.5), 115 (5.1), 103 (100.0), 85 (60.6), 74 (20.1), 71
(10.4), 70 (45.0), 57 (77.6), 56 (10.0), 55 (22.5).
treatment data were compared and separated by Scheffe’
́
s test.20 Five
chemicals (i.e., isobutyl 2-methylbutanoate, 3-methylbutyl 2-methyl-
butanoate, 3-methyl-2-butenyl 2-methylbutanoate, 3-methylbutyl
tiglate, and pentyl 2-methylbutanoate) that showed strong nematicidal
activity at a concentration of 1 mg/mL against the pine wood
nematode were chosen for testing at a lower concentration. These
chemicals were serially diluted with ethanol to obtain four different
concentrations; the final concentrations were 0.250, 0.125, 0.0625, and
0.03125 mg/mL for pentyl 2-methylbutanoate; 0.125, 0.0625, 0.03125,
and 0.015625 mg/mL for isobutyl 2-methylbutanoate, 3-methylbutyl
2-methylbutanoate, and 3-methyl-2-butenyl 2-methylbutanoate; and
0.0625, 0.03125, 0.015625, and 0.0078125 mg/mL for 3-methylbutyl
tiglate. The LC50 was estimated by probit analysis.20
Isobutyl isovalerate (IB-IV): GC-MS, m/z (%) 158 (0.08, M+), 143
(0.1), 128 (1.5), 115 (3.6), 103 (22.0), 85 (100.0), 73 (2.1), 60 (13.7),
57 (74.3).
2-Methylbutyl isovalerate (2MB-IV): GC-MS, m/z (%) 172 (0.4,
M+), 142 (0.8), 115 (4.1), 103 (8.3), 85 (100.0), 71 (23.6), 70 (66.2),
57 (44.0), 55 (16.7).
3-Methylbutyl isovalerate (3MB-IV): GC-MS, m/z (%) 157 (0.2,
M+-CH3), 142 (0.1), 115 (3.2), 103 (14.9), 85 (56.8), 71 (29.7), 70
(100.0), 57 (34.1), 55 (28.2).
3-Methyl-2-butenyl isovalerate (IP-IV): GC-MS, m/z (%) 170 (1.6,
M+), 128 (1.0), 110 (0.5), 103 (1.8), 85 (69.6), 69 (82.5), 68 (100.0),
67 (92.1), 60 (38.0), 57 (65.1), 53 (45.6).
Butyl isovalerate (C4-IV): GC-MS, m/z (%) 158 (0.1, M+), 143
(0.2), 116 (5.0), 103 (69.1), 87 (20.9), 85 (100.0), 73 (1.5), 60 (24.1),
57 (74.3), 56 (68.0)
RESULTS AND DISCUSSION
■
The nematicidal activity of the ester compounds is shown in
Table 2. Among the ester compounds tested, isobutyl 2-
methylbutanoate, 3-methylbutyl 2-methylbutanoate, and 3-
methylbutyl tiglate showed 100% nematicidal activity against
the pine wood nematode at a concentration of 1 mg/mL. The
nematicidal activities of 3-methyl-2-butenyl 2-methylbutanoate
and pentyl 2-methylbutanoate were 98.73% and 97.63% against
the pine wood nematode at a concentration of 1 mg/mL,
respectively. The nematicidal activities of the other ester
compounds were <11%. The nematicidal activities of isobutyl
2-methylbutanoate, 3-methylbutyl 2-methylbutanoate, 3-meth-
ylbutyl tiglate, 3-methyl-2-butenyl 2-methylbutanoate, and
pentyl 2-methylbutanoate, which showed strong nematicidal
activities at a 1 mg/mL concentration, were also tested at a
lower concentration (Table 3). The LC50 values of 3-
methylbutyl tiglate, isobutyl 2-methylbutanoate, 3-methylbutyl
2-methylbutanoate, 3-methyl-2-butenyl 2-methylbutanoate, and
pentyl 2-methylbutanoate were 0.0218, 0.0284, 0.0326, 0.0402,
and 0.0480 mg/mL, respectively. Nematicidal activities of many
phytochemicals from essential oils have been reported.9−17
Choi et al.9 reported that LC50 values of thymol, carvacrol,
citral, citronellol, and citronellal were 0.119, 0.125, 0.187, 0.245,
and 0.321 mg/mL, respectively. Some natural ester compounds
tested in this study have been reported as the main compounds
of certain plant essential oils.21,22 Isobutyl angelate was the
most abundant compound identified in Chamaemelum nobile
plant essential oil, followed by 2-methylbutyl angelate, isobutyl
isobutyrate, methyl 2-methylbuyrate, prenyl acetate, 2-methyl-
butyl 2-methylbutyrate, and 2-methylbutyl acetate.21 Mieren-
dorff et al.22 reported that the main compounds of Eriocephalus
punctulatus were 2-methylbutyl isobutanoate (21.2%), 2-
methylbutyl 2-methylbutanoate (5.6%), isobutyl isobutanoate
(5.3%), and linalyl acetate (4.4%). Bail et al.21 reported the
antimicrobial activities of some ester compounds identified in
Chamaemelum nobile plant essential oils. Seo et al.23 reported
the fumigant toxicities of some ester compounds derived from
E. punctulatus and C. mobile plant essential oils against Japanese
termites (Reticulitermes speratus); however, there have been no
reports on the nematicidal activities of the natural ester
Pentyl isovalerate (C5-IV): GC-MS, m/z (%) 170 (0.1, M+), 157
(0.2), 130 (3.4), 115 (6.6), 103 (89.1), 85 (100.0), 71 (16.9), 70
(85.7), 61(14.7), 60 (18.3), 57 (55.9), 55 (26.3).
Isobutyl 3-methyl-2-butenoate (IB-IP): GC-MS, m/z (%) 156 (1.7,
M+), 156 (1.7), 141 (0.2), 126 (0.1), 113 (0.5), 101 (16.8), 100
(36.8), 99 (0.3), 83 (100.0), 73 (0.4), 67 (0.8), 57 (10.6), 55 (19.7).
2-Methylbutyl 3-methyl-2-butenoate (2MB-IP): GC-MS, m/z (%)
170 (0.7, M+), 155 (0.1), 113 (0.5), 101 (16.4), 100 (34.7), 83
(100.0), 70 (17.2), 67 (1.0), 55 (25.6).
3-Methylbutyl 3-methyl-2-butenoate (3MB-IP): GC-MS, m/z (%)
170 (3.0, M+), 155 (0.3), 113 (0.4), 101 (23.9), 100 (42.2), 83
(100.0), 82 (10.3), 71 (19.6), 70 (23.2), 67 (2.2), 55 (40.7).
3-Methyl-2-butenyl 3-methyl-2-butenoate (IP-IP): GC-MS, m/z
(%) 168 (0.7, M+), 153 (0.7), 109 (6.9), 100 (42.2), 95 (0.8), 83
(43.3), 77 (1.4), 69 (24.6), 68 (69.6), 67 (100.0), 55 (10.4), 53 (60.9).
Butyl 3-methyl-2-butenoate (C4-IP): GC-MS, m/z (%) 156 (7.5,
M+), 141 (0.9), 113 (0.6), 101 (19.3), 100 (57.2), 85 (11.1), 83
(100.0), 82 (19.6), 55 (25.6).
Pentyl 3-methyl-2-butenoate (C5-IP): GC-MS, m/z (%) 170 (5.4,
M+), 155 (0.4), 101 (32.1), 100 (68.9), 83 (100.0), 82 (17.3), 71
(3.2), 70 (5.6), 55 (33.8).
2-Methylbutyl angelate (2MB-A): GC-MS, m/z (%) 170 (1.6, M+),
100 (100.0), 83 (90.0), 71 (23.4), 70 (21.9), 55 (85.4). IR (neat,
cm−1), 3005 (w), 2980 (s), 1710 (s), 1670 (m), 1220 (s), 1160 (s),
850 (s).
3-Methylbutyl tiglate (3MB-T): 1H NMR (ppm), δ 0.936 (6H, d, J
= 6.5), 1.567 (2H, dt, J = 7, 6.5), 1.722 (1H, nonet, J = 6.5), 1.785
(3H, dq, J = 7, 1.5), 1.829 (3H, quin., J = 1.5), 4.159 (2H, t, J = 7),
6.840 (1H, qq, J = 7, 1.5); 13C NMR (ppm), δ 12.03 (CH3), 14.13
(CH3), 22.52 (CH3 × 2), 25.22 (CH), 37.47 (CH2), 63.07 (CH2),
128.83 (C), 136.79 (CH), 168.22 (OC). IR (neat, cm−1),
2980 (s), 2105 (m), 1710 (s), 1670 (m), 1280 (s), 1110 (s), 730 (s).
Nematicidal Activity. To test the nematicidal activity of ester
compounds, test compounds were suspended in ethanol (100 mg/
mL). Test solutions (1 μL) were placed in the wells of a 96-well plate
(Falcon, USA) containing 50−150 nematodes (mixture of juvenile and
adult nematodes, male−female−juvenile ≈1:1:2) in 99 μL of water.
Thus, the total volume of the solution in each well was 100 μL, and the
concentration of the test ester compounds was 1 mg/mL. As a control,
four wells were treated with ethanol (1 μL) in the same volume as the
test samples. In four adjacent wells (i.e., in a column) on the plate,
nematodes were treated with the ester compounds, and a set of
treatment samples was placed in the wells of every second column.
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dx.doi.org/10.1021/jf503631e | J. Agric. Food Chem. 2014, 62, 9103−9108