J Chem Ecol (2013) 39:28–36 DOI 10.1007/s10886-012-0225-4
Propionates and Acetates of Chiral Secondary Alcohols: Novel Sex Pheromone Components Produced by a Lichen Moth Barsine expressa (Arctiidae: Lithosiinae) Toru Fujii & Rei Yamakawa & Yoshie Terashima & Shinya Imura & Keiichi Ishigaki & Masakatsu Kinjo & Tetsu Ando
Received: 22 August 2012 / Revised: 22 October 2012 / Accepted: 1 December 2012 / Published online: 19 December 2012 # Springer Science+Business Media New York 2012
Abstract Females of a lichen moth, Barsine expressa (Arctiidae, Lithosiinae), which inhabit Iriomote Island in Japan, were captured by a black-light trap, and the pheromone gland extract was analyzed by gas chromatography (GC) with an electroantennographic (EAG) detector, and by GC coupled with mass spectrometry. The females produced several EAG-active esters, and the mass spectrum of a major component indicated the mixture consists of propionates derived from C17-saturated secondary alcohols, which were inseparable on the capillary GC column. In addition to these main components, the pheromone glands included two acetate derivatives of C17 alcohols, and other propionates of C16 and C15 alcohols. The crude extract was treated with K2CO3, and a 1:1 mixture of C17 alcohols with a C6- or C7-chain moiety was obtained. The two alcohols were uniformly converted into monodeuterated n-heptadecane by mesylation and succeeding LiAlD4 reduction. This result revealed a straight-chain structure of the C17 alcohols with the acyl groups located at the 7or 8-position. Field tests on Iriomote Island showed that the synthetic esters were behaviorally active. A 1:1 mixture of racemic 7-propioxyheptadecane and 8-propioxyheptadecane, which were prepared from the secondary alcohols synthesized by a Grignard coupling reaction, attracted male moths. Furthermore, propionates of the alcohols synthesized enantioselectively by using a hydrolytic kinetic resolution with T. Fujii : R. Yamakawa : T. Ando (*) Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan e-mail:
[email protected] Y. Terashima : S. Imura : K. Ishigaki : M. Kinjo Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, Uehara, Taketomi-cho, Okinawa 907-1541, Japan
Jacobsen’s catalyst were evaluated. Only the traps baited with a mixture of the two esters with the same S-configuration significantly attracted B. expressa males. In the Tokyo area, the propionate mixture attracted a closely related species, Barsine aberrans aberrans. Keywords Female sex pheromone . Lepidoptera . Arctiidae . Lithosiinae . (S)-7-propioxyheptadecane . (S)-8-propioxyheptadecane . 8-acetoxyheptadecane
Introduction Currently, lepidopteran sex pheromones have been identified from females of about 630 species (Ando, 2012; ElSayed, 2012). Since these synthetic pheromones are useful monitoring tools, these identifications have been conducted primarily for agricultural pests. The larvae of Lithosiinae species, which feed mainly on forest lichens, cause no agricultural damage, but are an integral part of the forest ecosystem. Lithosiinae is a large arctiid subfamily (78 species inhabit Japan), but their ecology is poorly known. Because lichen moth sex pheromones might be utilized for ecological studies, we started chemical determination of their pheromones, and recently successfully identified novel compounds from Lyclene dharma dharma Moore (6-methyl, 14-methyl, and 6,14-dimethyloctadecan-2-one) (Yamamoto et al., 2007; Adachi et al., 2010) and Miltochrista calamine Butler (5-methylheptadecan-7-ol) (Yamakawa et al., 2011). In addition to the well-known lepidopteran pheromones with a straight chain, some methyl-branched hydrocarbons have been identified from female moths in the Lyonetiidae, Geometridae, and Arctiidae, but methyl-branched ketones and alcohols had
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not been identified from female moths (Ando et al., 2004). These previous investigations suggested that Lithosiinae species established a unique mating communication system, which was mediated by a new type of pheromone compounds having a branched carbon skeleton. In order to clarify the characteristic structure of Lithosiinae pheromones, we examined the pheromone of another Lithosiinae species, Barsine (0 Miltochrista) expressa Inoue that is found only in Iriomote Island and other Yaeyama Islands (Inoue, 1988). These islands are located near Taiwan in a subtropical zone of the East China Sea. While the female moths produced no pheromone components with a branched skeleton, we discovered a novel sex pheromone composed of propionates and acetates of straight-chain secondary alcohols, indicating unexpected diversity of these lepidopteran pheromones. Furthermore, a synthetic pheromone attracted another Barsine species in a Tokyo forest, suggesting Barsine spp. have similar sex pheromones.
Methods and Materials Analytical Instruments Gas chromatography with an electroantennographic detector (GC-EAD) was used to identify physiologically active compounds in a female gland extract. An HP-5890 Series II gas chromatograph (Hewlett Packard, Wilmington, DE, USA) was equipped with a DB-23 column (0.25 mm ID, 30 m length, 0.25 μm film thickness, J & W Scientific, Folsom, CA, USA). The oven temperature was maintained at 50 °C for 2 min, and programmed at 10 °C/ min to 160 °C and 4 °C/min to 220 °C. The effluent from the column was split between a flame ionization detector (FID) and an EAD in a 1:1 ratio (Inomata et al., 2005). GC-mass spectrometry (GC-MS) in electron impact (EI) ionization mode (70 eV) was achieved by using an HP-5975 mass spectrometer system (quadrupole type, Hewlett Packard) equipped with the same DB-23 column operated at the same temperatures as the GC-EAD. 1H- and 13C-NMR spectra were recorded with a JNM-ECA 500 FT-NMR spectrometer (JEOL, Tokyo, Japan) at 500.16 and 125.77 MHz, respectively, for CDCl3 solutions containing TMS as an internal standard. HPLC employed a system composed of a pump (PU-980, Jasco), a refractive index (RI) detector (RI98SCOPE, Labo System, Tokyo, Japan), and an integrator (807-IT, Jasco). Resolution of the enantiomers was accomplished with a chiral column (Chiralpak AS-H, 4.6 mm ID× 25 cm; Daicel Chemical Industry, Osaka, Japan), which was eluted with 0.1 % 2-propanol in hexane at a flow rate of 0.5 ml/min. Insects and Pheromone Extraction Adults of B. expressa were collected with a black light at a mixed forest area that
29
included many broad-leaved evergreen trees on Iriomote Island (24.23ºN, 123.48ºE). The collection was carried out from 17:00 to 23:00 on several days in 2008 and 2009. Captured moths were placed individually into small glass vials and sent to the TUAT laboratory in Tokyo. Each abdominal tip of five females was excised 1 hr after the beginning of scotophase and soaked in hexane (0.1 ml) for 15 min to extract the pheromone. Microchemical Reactions of the Natural Pheromone After removal of the solvent, a crude extract (2.0 FE) was treated with K2CO3 (2 mg) in methanol (0.5 ml). The mixture was stirred for 1 hr at room temperature, and then water (1.0 ml) was added. Crude products were extracted with hexane and analyzed by GC-MS. Next, the saponified products that dissolved in CH2Cl2 (0.5 ml) were mixed with triethylamine (5 mg), N,N-dimethyl-4-aminopyridine (DMAP, 1 mg) and methanesulfonyl chloride (10 mg), stirred at 0 °C for 2 hr, and held at room temperature for 1 d. After routine extraction and neutralization, the produced mesylates were dissolved in dry THF (0.3 ml), and treated with LiAlD4 (2 mg) under an argon atmosphere. The reaction mixture was acidified with 1 M HCl (2.0 ml) after 3 hr of stirring, and then extracted with hexane. After neutralization, the extract was analyzed by GC-MS. Synthesis of Racemic Pheromone Candidates A Grignard coupling reaction between heptanal and n-decylmagnesium bromide, which was prepared from 1-bromodecane and magnesium turnings, produced heptadecan-7-ol; ν max (cm−1): 3367 (s, O-H), 2925 (s), 2854 (s), 1466 (m), 1379 (m); δH: 0.88 (6H, t, CH3CH2, J06.6 Hz), 1.26 (24H, broad s), 1.43 (4H, broad s), 3.58 (1H, m, CHOH); δC: 14.11, 14.14, 22.65, 22.72, 25.65, 25.69, 29.37, 29.41, 29.65 (×2), 29.67, 29.75, 31.88, 31.94, 37.51 (×2), 72.05; GC-MS: RT 14.17 min, m/z 238 (M-18, 3 %), 171 (18 %), 115 (27 %), 97 (100 %), 83 (30 %), 69 (28 %). A Grignard coupling reaction between octanal and n-nonylmagnesium bromide, which was prepared from 1-bromononane and magnesium turnings, produced heptadecan-8-ol; νmax (cm−1): 3367 (s, O-H), 2925 (s), 2854 (s), 1466 (m), 1379 (m); δH: 0.88 (6H, t, CH3CH2, J06.6 Hz), 1.27 (24H, broad s), 1.43 (4H, broad s), 3.57 (1H, m, CHOH); δC: 14.13 (×2), 22.68, 22.70, 25.68 (×2), 29.33, 29.35, 29.60, 29.66, 29.70, 29.74, 31.86, 31.92, 37.50 (×2), 72.06; GC-MS: RT 14.17 min, m/z 238 (M-18, 4 %), 157 (26 %), 129 (31 %), 111 (36 %), 97 (35 %), 83 (73 %), 69 (100 %). Each alcohol was treated with a mixture of propionic acid, DCC, and DMAP in CH2Cl2 to yield a propionate: 7-propioxyheptadecane (17:7-OPr), νmax (cm−1): 2925 (s), 2856 (s), 1736 (s, C0O), 1464 (m), 1190 (s); δH: 0.88 (6H, t, CH3CH2, J 06.5 Hz), 1.14 (3H, t, CH3CH2C 0O, J0 7.5 Hz), 1.25 (24H, broad s), 1.50 (4H, m, CH2CH), 2.31
30
J Chem Ecol (2013) 39:28–36
(2H, q, CH3CH2C0O, J07.5 Hz), 4.87 (1H, tt, CHOC0O, J06.2, 6.2 Hz); δC: 9.36, 14.09, 14.14, 22.61, 22.72, 25.30, 25.34, 27.96, 29.24, 29.36, 29.57 (×2), 29.60, 29.63, 31.78, 31.94, 34.18 (×2), 74.19, 174.37; 8-propioxyheptadecane (17:8-OPr), νmax (cm−1): 2925 (s), 2856 (s), 1736 (s, C0O), 1464 (m), 1189 (s); δH: 0.88 (6H, t, CH3CH2, J06.5 Hz), 1.14 (3H, t, CH3CH2C0O, J07.6 Hz), 1.25 (24H, broad s), 1.50 (4H, m, CH2CH), 2.31 (2H, q, CH3CH2C0O, J07.6 Hz), 4.87 (1H, tt, CHOC0O, J06.2, 6.2 Hz); δC: 9.36, 14.10, 14.13, 22.66, 22.70, 25.33 (×2), 27.96, 29.22, 29.33, 29.52, 29.55 (×3), 31.80, 31.91, 34.16 (×2), 74.20, 174.38. Each alcohol was also treated with acetic anhydride in pyridine to yield an acetate: 7-acetoxyheptadecane (17:7-OAc); νmax (cm−1): 2925 (s), 2856 (s), 1739 (s, C0O), 1466 (m), 1375 (m), 1242 (s), 1022 (m); δH: 0.88 (6H, t, CH3CH2, J06.6 Hz), 1.26 (24H, broad s), 1.50 (4H, m), 2.04 (3H, s, CH3C0 O), 4.86 (1H, tt, CHOC0O, J06.2, 6.2 Hz); δC: 14.10, 14.14, 21.32, 22.62, 22.69, 25.31, 25.35, 29.24, 29.37, 29.57 (×2), 29.61, 29.64, 31.78, 31.95, 34.15 (×2), 74.48, 171.00; 8acetoxyheptadecane (17:8-OAc); νmax (cm−1): 2925 (s), 2856 (s), 1739 (s, C0O), 1465 (m), 1375 (m), 1242 (s), 1022 (m); 0.88 (6H, t, CH3CH2, J06.6 Hz), 1.26 (24H, broad s), 1.50 (4H, m), 2.04 (3H, s, CH3C0O), 4.86 (1H, tt, CHOC0O, J0 6.2, 6.2 Hz); δC: 14.11, 14.14, 21.32, 22.68, 22.71, 25.35 (×2), 29.25, 29.34, 29.54, 29.57 (×3), 31.83, 31.93, 34.14 (×2), 74.48, 170.99. Enantioselective Synthesis of Secondary Alcohol Esters Propionates and acetates of chiral secondary alcohols were enantioselectively synthesized from 1-dodecene (1a) and 1-undecene (1b) as shown in Fig. 1. Oxidation of 1a with m-chloroperoxybenzoic acid (MCPBA) produced a racemic mixture of 1,2-epoxydodecane [(SR)-2a], which then was subjected to a hydrolytic kinetic resolution with Jacobsen’s catalysts (Schaus et al., 2002). Selective hydrolysis of (S)-2a catalyzed with (R,R)-(salen)Co(III)OAc was monitored by GC, and the optical purity of the unhydrolyzed epoxide (R)2a (>98 % ee) was analyzed by chiral HPLC equipped with a Fig. 1 Synthesis of (S)-7propioxyheptadecane [(S)-17:7-OPr], (S)-8propioxyheptadecane [(S)-17:8OPr], and the acetate derivatives [(S)-17:7-OAc and (S)-17:8-OAc]. Reagents (yield): (i) MCPBA, CH2Cl2 (72 %);(ii) (R,R)-(salen)Co (III)OAc, H2O, dimethoxymethane (42 %); (iii) n-C5H11MgBr, THF (58 %); (iv) n-C6H13MgBr, THF (83 %); (v) CH3CH2CO2H, DCC, DMAP, CH2Cl2 (88 %); (vi) Ac2O, pyridine (94 %)
Chiralpak AS-H column (Yamakawa et al., 2011). Grignard coupling between (R)-2a and n-pentylmagnesium bromide, which was prepared from 1-bromopentane and magnesium turnings, produced (S)-heptadecan-7-ol [(S)-3a]. In the same procedure, oxidation of 1b and a coupling reaction between (R)-2b (>98 % ee) and n-hexylmagnesium bromide produced (S)-heptadecan-8-ol [(S)-3b]. In contrast, hydrolysis of the racemic epoxides with (S,S)-(salen)Co(III)OAc yielded (S)2a and (S)-2b (>98 % ee), which were used for the synthesis of (R)-3a and (R)-3b, respectively. Since enantiopurities of chiral secondary alcohols were not determined by chiral GC or HPLC analyses, the esters of (S)- and (R)-3a with (S)-acetoxypropionic acid were analyzed by 13C-NMR. While the spectra of two diastereomers were quite similar, some methylene carbons in the alcohol chain resonated at different chemical shifts, indicating high enantiopurity. The results were 22.62 and 22.74 ppm (C-2 and C-16) and 25.15 and 25.21 ppm (C-5 and C-9) for the ester of (S)-3a; 22.60 and 22.71 ppm (C-2 and C-16) and 25.18 and 25.19 ppm (C-5 and C-9) for the ester of (R)-3a. Each chiral alcohol was converted into the propionate and acetate in the same manner used for the racemic alcohols. Field Tests The attraction of B. expressa males by synthetic lures was examined on Iriomote Island in 2012. Three tests were carried out: Test A with racemic mixtures, and Tests B and C with compounds synthesized enantioselectively. Rubber septa (white rubber, OD 8 mm; Sigma-Aldrich) were used as dispensers, and synthetic components dissolved in hexane (100 μl) were applied to them. Each lure was placed at the center of a sticky board trap (SE-trap®, 30×27 cm bottom plate with a roof; Sankei Chemical Co., Tokyo, Japan), which was set apart from the other traps by at least 10 m at about 1.5 m above the ground in a mixed forest area. Two or three traps were used for each synthetic lure. Septa treated only with hexane (100 μl) were used as a control. The number of captured males was counted at least every 2 wk. Some lures baited with chiral propionates also O
i
O
ii
n
n
n
1a (n = 7)
(SR)-2a (n = 7)
(R)-2a (n = 7)
1b (n = 6)
(SR)-2b (n = 6)
(R)-2b (n = 6)
OH
OR v or vi
iii or iv m
n
m
n
(S)-3a (m = 3, n = 7)
(S)-17:7-OPr (R = OPr, m = 3, n = 7)
(S)-3b (m = 4, n = 6)
(S)-17:8-OPr (R = OPr, m = 4, n = 6) (S)-17:7-OAc (R = OAc, m = 3, n = 7) (S)-17:8-OAc (R = OAc, m = 4, n = 6)
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31
were tested in a mixed forest at Tama Forest Science Park in Hachioji in western Tokyo (35.38°N, 139.16°E) in 2012.
alcohol. The spectrum, which did not indicate a specified position for the acetoxy group, suggested a mixture of multiple components inseparable by GC. In contrast, the spectrum at the main peak IV (RT 14.23 min) showed a strong base peak at m/z 57 ([C2H5C0O]+) and characteristic ions at m/z 75 and 238 (M-74) (Fig. 3a). Except for these differences, the two spectra showed high similarity, indicating that a propionate mixture of the same C17 secondary alcohols was detected at IV. The spectrum recorded at the minor peak II (RT 13.17 min) was similar to that of IV, except for the ion at m/z 220 (M-74), indicating the corresponding propionate mixture of C16-saturated secondary alcohols. While a clear spectrum was not recorded at peak I (RT 12.35 min), the monitoring of an ion at m/z 57 suggested trace occurrence of propionate(s) of the C15 alcohol(s) in the crude extract.
Results Structure Elucidation of Pheromone Components The GCEAD analysis of a crude pheromone extract of B. expressa females (0.5 female equivalent, FE) showed four EAGactive peaks, I–IV (Fig. 2a). While FID recorded no peaks corresponding to I, compounds corresponding to II–IV were detected in a ratio of about 1:10:100. The same ratio was also indicated by GC-MS analysis of the extract (1.0 FE) as shown in a total ion chromatogram (TIC) (Fig. 2b). The mass spectrum detected at peak III (RT 13.57 min) showed a strong base peak at m/z 43 ([CH3C0O]+) and characteristic fragment ions at m/z 61 and 238 (M-60) (Fig. 2c), indicating an acetate of a C17-saturated secondary Fig. 2 Analyses of the sex pheromone of Barsine expressa females by GC-EAD and GC-MS. a Chromatograms of the pheromone extract (0.5 FE) recorded by EAD and FID; b TIC of the pheromone extract (1.0 FE); and c A mass spectrum detected at a peak III (a mixture of 7-acetoxyheptadecane and 8-acetoxyheptadecane)
Structure Determination by Microchemical Reactions In order to determine the position of the acyl groups, the crude
a
I
II
III
IV
0.1 mV
EAD
FID 14.0
13.0
15.0
16.0
RT
(min)
IV
b GC-MS (TIC) III II I
12.0
10.0
c (%)
14.0
43 111 83 55
125 139 50
(min)
69
20
0
RT
Natural (peak III) 17:7-OAc (MW 298) 17:8-OAc
97
40
16.0
100
[M-60]+ 238
153
150
171 200
250
300
m/z
32 Fig. 3 Mass spectra of natural and synthetic propionates and alcohols derived from the natural Barsine expressa esters. a Natural components detected as a main peak IV (a mixture of 7propioxyheptadecane and 8propioxyheptadecane); b Synthetic 7-propioxyheptadecane; c Synthetic 8-propioxyheptadecane; and d Alcohols produced by saponification of the natural pheromone (a mixture of heptadecan7-ol and heptadecan-8-ol)
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a
57
(%)
Natural (peak IV) 17:7-OPr (MW 312) 17:8-OPr
97 20 69
111
83
[M-74]+ 238
10 125 139
155 171
0 50
b
150
100
300
250
200
m/z
57
(%)
Synthetic 17:7-OPr
97
20
97 69 83
OPr
n-C 6H13
10
153 n-C10H21
[M-74]+ 238
111 171
125
153
0 50
c
200
150
100
300
250
m/z
57
(%)
Synthetic 17:8-OPr
20
111 69
83
111 OPr 97 n-C7H15
10 139
139 n-C9H 19
[M-74]+ 238
155
0 50
d
(%)
150
100
200
m/z
97
69
115
83
80
300
250
55
129 OH
n-C 6H13
111
40
115
OH n-C10H21
n-C 7H15
171 129
157
n-C9H19
157 [M-18]+ 238
171
0 50
extract was treated with K2CO3, and the resulting products were analyzed by GC-MS. Figure 3d shows the mass spectrum of a mixture of two C17-saturated secondary alcohols with [M-18]+ at m/z 238 (RT 14.17 min), which were the main saponified products estimated to be derived from acyl components occurring predominantly in the pheromone gland. The fragment ions at m/z 115 and 171 indicated C6and C10-chain moieties attached to a carbinol carbon, and those at m/z 129 and 157 indicated C7- and C9-chain moieties. Intensities of these ions suggested a mixing ratio of the two alcohols at about 1:1. Additionally, these alcohols were converted into mesylates, which were treated with LiAlD4 and analyzed by GC-MS to understand the carbon skeletons. The main product was monodeuterated heptadecane with M+ (7 %) at m/z 241 (RT 8.04 min), indicating a straightchain structure of the C17 alcohols and the acyl groups
100
150
200
250
300
m/z
located at 7- and 8-positions. These experiments revealed that the pheromone extract included 7-propioxyheptadecane (17:7-OPr) and 8-propioxyheptadecane (17:8-OPr) as main components, and 7-acetoxyheptadecane (17:7-OAc) and 8acetoxyheptadecane (17:8-OAc) as minor components. Identification with Authentic Compounds Each racemic mixture of heptadecan-7-ol and heptadecan-8-ol was synthesized by a Grignard coupling reaction and converted into propionates and acetates. Two positional isomers showed almost the same chromatographic behaviors on a capillary GC column (DB-23), and the mixture was inseparable. Their RT values were 17:7-OPr (RT 14.24 min), 17:8-OPr (RT 14.23 min), 17:7-OAc (RT 13.57 min), and 17:8-OAc (RT 13.56 min). These values coincided well with those of the natural components. The mass spectrum of synthetic
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33
17:7-OPr included characteristic fragment ions at m/z 97 and 153, indicating a propioxy group at the 7-position (Fig. 3b). Ions at m/z 111 and 139 of synthetic 17:8-OPr indicated the group at the 8-position (Fig. 3c). These spectra confirmed Fig. 3a, which showed the spectrum measured with 17:7OPr and 17:8-OPr mixed approximately at a 1:1 ratio. The mass spectrum in Fig. 2c also was similar to that measured with a 1:1 mixture of synthetic 17:7-OAc and 17:8-OAc. Field Evaluation of the Synthetic Pheromone on Iriomote Island Attraction of B. expressa males was first attempted in the field using four racemic esters of C17 alcohols: 17:7-OPr, 17:8-OPr, 17:7-OAc, and 17:8-OAc (Test A). One 4component lure, four kinds of 3-component lures, and six kinds of 2-component lures were examined. The 4component lure included the four esters in a ratio of 10:10:1:1 (0.5 mg each of the two propionates and 0.05 mg each of the two acetates). The other lures were prepared in all possible combinations of three or two esters selected among the four esters. Except for the lure baited with the two acetates only, all lures attracted some males. The lures that included two propionates had a greater attraction for males than the lure with one propionate (Fig. 4). This result revealed that traps baited with at least two propionates could effectively capture B. expressa males. Activities of the propionates synthesized enantioselectively were evaluated next (Test B; Table 1). Among four mixtures, including each stereoisomer of 17:7OPr and 17:8-OPr in a ratio of 1:1, the combination of two (S)isomers significantly attracted males. The mixture of two (R)isomers attracted no males. The number of males captured by the traps baited with the racemic propionates was much fewer than the number captured by (S)-isomers. Furthermore, the effect of acetate components on the propionates was examined
Total captured males
20 15
10
5 0
17:7-OPr 17:8-OPr 17:7-OAc 17:8-OAc
0.5 0.5 0.05 0.05
0 0.5 0.05 0.05
0.5 0 0.05 0.05
0.5 0.5 0 0.05
0.5 0.5 0.05 0
0 0 0.05 0.05
0.5 0 0 0.05
0.5 0.5 0 0
0 0.5 0.05 0
0.5 0 0.05 0
0 0.5 0 0.05
0 0 0 0
Fig. 4 Attraction of Barsine expressa males to lures loaded with racemic synthetic pheromone components. Each lure was tested with two traps on Iriomote Island from 7 March to 16 April 2012. Components: 7-propioxyheptadecane (17:7-OPr, 0.5 mg/septum), 8propioxyheptadecane (17:8-OPr, 0.5 mg/septum), 7-acetoxyheptadecane (17:7-OAc, 0.05 mg/septum), and 8-acetoxyheptadecane (17:8-OAc, 0.05 mg/septum)
Table 1 Field attraction of Barsine expressa males by lures baited with a mixture of chiral 7- and 8-propioxyheptadecane (17:7-OPr and 17:8-OPr) Lure component (mg/rubber septum)
Captured malesa
17:7-OPr (0.5) (S)-Isomer (S)-Isomer (R)-Isomer (R)-Isomer Racemic None (control)
/trapb 15.7±5.4 a 0.7±0.3 c 2.3±1.0 bc 0 2.3±0.7 b 0
17:8-OPr (0.5) (S)-Isomer (R)-Isomer (S)-Isomer (R)-Isomer Racemic
Total 47 2 7 0 7 0
a
Tested with three traps of each lure on Iriomote Island from May 2 to June 13, 2012
b
Mean ± SE. Values within each test followed by a different letter are significantly different at P
