Microwave-Assisted Extraction Coupled to HPLC-UV Combined with Chemometrics for the Determination of Bioactive Compounds in Pistachio Nuts and the Guarantee of Quality and Authenticity

Two novel microwave-assisted extraction (MAE) methods were developed for the isolation of phenols and tocopherols from pistachio nuts. The extracts were analyzed by reversed-phase high-pressure liquid chromatography coupled with a UV detector (RP-HPLC-UV). In total, eighteen pistachio samples, originating from Greece and Turkey, were analyzed and thirteen phenolic compounds, as well as alpha-tocopherol, (beta + gamma)-tocopherol, and delta-tocopherol, were identified. The analytical methods were validated and presented good linearity (r(2) > 0.990) and a high recovery rate over the range of 82.4 to 95.3% for phenols, and 93.1 to 96.4% for tocopherols. Repeatablility was calculated over the range 1.8-5.8%RSD for intra-day experiments, and reproducibility over the range 3.2-9.4%RSD for inter-day experiments, respectively. Principal component analysis (PCA) was employed to analyze the differences between the concentrations of the bioactive compounds with respect to geographical origin, while agglomerative hierarchical clustering (AHC) was used to cluster the samples based on their similarity and according to the geographical origin.

Automated summary

Two novel microwave-assisted extraction methods were developed for isolating phenols and tocopherols from pistachio nuts. The extracts were analyzed using RP-HPLC-UV, and thirteen phenolic compounds as well as alpha, beta + gamma, and delta tocopherols were identified. The analytical methods showed good linearity and high recovery rates. Principal component analysis and agglomerative hierarchical clustering were used to analyze differences in the compounds' concentrations and to cluster the samples based on their geographical origin.