Ethyl hexanoate

Octan-2-ol (97%), 1-hexanol (99%), cis-3-hexenol (98%), trans-3-hexenol (97%), vanillin (99%), 2,6-dimethoxyphenol (99%), linalool (97%), terpinen-4-ol (≥95%), α-terpineol (90%), nerol (≥97%), geraniol (98%), linalool oxide (≥97%), β-citronellol (95%), p-cymene (99%), terpinolene (≥85%), γ-terpinene (≥97%), limonene (97%), 1,8-cineole (99%), 1,4-cineole(≥98.5%), β-damascenone (≥98%), isoamyl alcohol (98%), benzyl alcohol (≥99%), 2-phenylethanol (≥99%), ethyl acetate (99%), ethyl butanoate (99%), ethyl 3-methyl butanoate (≥98%), isoamyl acetate (≥95%), ethyl hexanoate (≥95%), phenylethyl acetate (99%), n-hexyl acetate (≥98%), ethyl lactate (≥98%), ethyl octanoate (≥98%), ethyl decanoate (≥98%), hexanoic acid (≥99%), octanoic acid (≥98%), α-phellandrene (95%), p-menthane-1,8-diol (97%), 3-methylbutanoic acid (99%), α-ionone (90%), 1-pentanol (99%), 1-butanol (≥99%), 2-butanol (≥99%), ethyl guaiacol (≥99%), vinyl guaiacol (≥98%), methyl-vanillate (99%), ethyl vanillate (99%), were supplied by Sigma Aldrich (Milan, Italy). Dichloromethane (≥99.8%) and methanol (≥99.8%), were provided by Honeywell (Seelze, Germany). Sodium chloride (≥99.5%) was supplied by Sigma Aldrich (Milan, Italy).

The standards of volatile compounds were purchased from Sigma-Aldrich (St. Louis, MO, USA), including isobutanol, 3-methyl-1-butanol, cis-3-hexen-1-ol, 1-hexanol, heptanol, octanol, phenethyl alcohol, 2,6-nonadien-1-ol, dodecanol, ethyl acetate, isoamyl acetate, ethyl lactate, ethyl hexanoate, ethyl octanoate, diethyl succinate, phenethyl acetate, ethyl decanoate, butanoic acid, hexanoic acid, octanoic acid, dodecanoic acid, octanal, (2e,6z)-2,6-nonadienal, benzaldehyde, furfural, citronellol, linalool, rose oxide, geraniol, nerol, β-damascenone, β-ionone, nerolidol, hexanal, guaiacol, 4-Ethylphenol, and 2-octanol which were used as the internal standard.
Folin–Ciocalteu reagent and sodium chloride were purchased from Beijing Chemical Works (Beijing, China). Potassium hydrogen tartrate were purchased at Kemiou Chemical Reagent Co. (Tianjin, China). Bovine serum albumin was obtained from Asahi Kasei Corporation (Tokyo, Japan). Deionized water (<18 MW resistance) was purified by using a Milli-Q purification system (Molecular, Chongqing, China). Bentonite, soybean protein and potassium metabisulfite were purchased from Lallemand Company (Lallemand, Toulouse, France).

All reagents utilized in this assay were of analytical quality. Sodium chloride (NaCl, 99.5%), and calcium chloride (CaCl₂, >99.0%) were obtained from Panreac (Spain, Barcelona). Ultrapure water was supplied from a Milli-Q^® system (Millipore); the 3-octanol used as internal standard and other VOCs for identification, namely, 1-butanol, 1-heptanol, 1-octanol, 1-propanol, (E)-2-hexenal, 2-methyl-butanal, 2-ethyl-1-hexanol, 2-methyl-1-propanol, 2-phenylethanol, acetaldehyde, benzaldehyde, ethanol, ethyl acetate, ethyl butanoate, ethyl decanoate, ethyl hexanoate, ethyl octanoate, ethyl propanoate, ethyl 3-hydroxybutanoate, hexyl acetate, and pentanal with purity up to 98% were acquired from Sigma Aldrich (Madrid, Spain). Helium gas purity of 5.0 (Air Liquide, Portugal) was utilized as the GC carrier gas. Solid-phase microextraction holder and divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber were supplied from Supelco (Bellefonte, PA, USA). The Kovats index (KI) was calculated by the injection of a series of C₈ to C₂₀ straight-chain n-alkanes (at 40 mg L⁻¹ in n-hexane) produced by Fluka (Buchs, Switzerland).

VUAA1 (2-(4-Ethyl-5-(pyridin-3-yl)-4H-1,2,4-triazol-3-ylthio)-N-(4-ethylphenyl) acetamide) was synthesized by the group “Mass Spectrometry/Proteomics” of the Max Planck Institute for Chemical Ecology (Jena, Germany). W7 (N-(6-Aminohexyl)-5-chlor-1-naphthalinsulfonamid-HCl) was purchased from Tocris bioscience (Wiesbaden-Nordenstadt, Germany). Ethyl hexanoate (99% purity) from Sigma Aldrich (Steinheim, Germany). Vinegar (Aceto balsamico di modena 1.G.P (500 ml)) and pure grape juice (Merlot) were purchased. Chemicals used for Ca²⁺ imaging experiments were dissolved in dimethyl sulfoxide (DMSO) to obtain required stock solutions, except for vinegar and grape juice, which were directly dissolved in Drosophila Ringer solution.

Ethanol (>99.8%), 1-propanol (≥99.8%), isobutanol (≥99.5%), isoamyl alcohol (≥99.8%), acetic acid (≥99.8%), l-lactic acid (≥90.0%), n-butyric acid (>99.5%), n-hexanoic acid (≥99.5%), ethyl acetate (≥99.7%), ethyl lactate (≥99.0%), ethyl butyrate (≥99.5%), ethyl hexanoate (>99.0%), and sodium heparin (Grade I-A, ≥180 USP units/mg) were all purchased from Sigma-Aldrich (St. Louis, MO, USA).