Characterisation of alkylphenols in pistachio (Pistacia vera L.) kernels

Pistachio kernels were extracted with n-hexane and the oil obtained was saponified with methanolic KOH. The extracted unsaponifiable matter was fractionated on Thin Layer Chromatography (TLC) plates. The band with Rf = 0.47, analysed by Gas Chromatography–Mass Spectrometry (GC–MS), showed the presence of long-chain alkylphenols: this is the first time that alkylphenols are reported in pistachio kernels. To elucidate the structures, Nuclear Magnetic Resonance (NMR) and GC–MS analyses (on the trimethylsilyl derivatives) were used. Sixteen different 3-alkylphenols (cardanols) with a saturated, monounsaturated and diunsaturated chain were detected. A reaction with dimethyl disulphide was successfully used to determine the double bond position in the monounsaturated compounds. Three phenols were new natural compounds. The most abundant cardanols were 3-(8-pentadecenyl)-phenol, 3-(10-pentadecenyl)-phenol, 3-pentadecyl-phenol and 3-(10-eptadecenyl)-phenol. Total amount of cardanols in the oils (mean of five samples) was roughly evaluated as 440 ± 95 mg kg−1.