Geranyl acetone

The synthetic standards including (1R)-(+)-α-pinene, (-)-β-pinene, β-myrcene, (S)-(-)-limonene, linalool, octanal, nonanal, decanal, benzaldehyde, butylated hydroxytoluene, methyl benzoate, (-)-bornyl acetate, 6-methyl-5-hepten-2-one, geranyl acetone, decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, myristoleic acid, palmitoleic acid, linoleic acid, oleic acid, (+)-longifolene, caryophyllene oxide, (E)–β-caryophyllene, undecane, dodecane, pentadecane, hexadecane and quercetin were obtained from Sigma-Aldrich (>98% purity).

Five-year-old tea plants of Camellia sinensis cv. “Shu Cha Zao” grown at the experimental farm of Anhui Agricultural University in Hefei, China, were used in this study. Standards of geranyl diphosphate (GDP), farnesyl diphosphate (FDP), β-myrcene, β-ocimene, linalool, geraniol, α-citral, β-citral, methyl geranate, nerol, D-limonene, trans-linalool oxide (furanoid), neryl acetate, L-terpineol, α-terpinen, geranyl acetone, thymol, (Z)-nerolidol, α-farnesene, β-farnesene, (E)-nerolidol, humulene, α-ionone, β-ionone, (E)-γ-bisabolene, cadinol and caryophyllene were purchased from Sigma-Aldrich (St. Louis, MO, USA).

The synthetic chemicals geranylacetone, δ-octalactone, guaiacol, pentanoic acid, and 1-octen-3-ol were purchased from Sigma-Aldrich at the highest available purity. geranylacetone, δ-octalactone, guaiacol, and 1-octen-3-ol were diluted in absolute ethanol (99.8%) (Conde, 2014 (link); Karlsson and Friedman, 2017 (link)) and pentanoic acid in distilled water.

The following synthetic standards were purchased from Sigma-Aldrich and tested in the concentration 5×10^-3 µg µL^-1: methyl (E)-hex-3-enoate, methyl (E)-hex-2-enoate, 6-methylhept-5-en-2-one, ethyl hexanoate, ethyl (E)-hex-3-enoate, methyl (E)-oct-2-enoate, geranyl acetone, (E,E)-α-farnesene, methyl (2E,6E)-farnesoate, linalool, (E)-non-2-enal, (Z)-non-3-enol, and (Z)-non-2-enol. (Z)-Non-3-enal and (Z)-non-2-enal were prepared in our laboratory from the corresponding alcohols (Hazzard 1973 ). The purchased and synthesised chemicals were of analytical grade purity.

Acetonitrile, formic acid, and methanol were purchased from Fisher Company (Fairlawn, NJ, USA). D-(+)-dextronic acid δ-lactone was purchased from Sigma-Aldrich (St. Louis, MO, USA). The Cleanert^® PEP-SPE resin (150 mg/6 mL) was obtained from Bonna-Agela (Wilmington, DE, USA).
The standards (purities > 95%) used for identification and quantification of the volatile compounds 1-hexanol, (E)-2-hexen-1-ol, (Z)-2-hexen-1-ol, (E)-3-hexen-1-ol, (Z)-3-hexen-1-ol, hexanal, (E)-2-hexenal, 1-nonanol, furfural, hexanoic acid, limonene, D-limonene, myrcene, linalol, α-terpineol, 4-terpineol, β-citronellol, citral, geranylacetone, geraniol, nerol, cis-furan oxidin, spirulina, (Z)-orange sterol, (E)-β-damascenone, (E)-β-ionone, and 4-methyl-2-pentanol were all supplied by Sigma-Aldrich (St. Louis, MO, USA). The deionized water (<18 WΩ resistance) was obtained through a Milli-Q Element water purification system (Millipore, Bedford, MA, USA). All the other chemicals or reactives without especial mention were purchased from Beijing Chemical Works (Beijing, China).