Determination of bioactive compounds in extra virgin olive oils from 19 Moroccan areas using liquid chromatography coupled to mass spectrometry: a study over two successive years

Olive oil quality has received much attention during the last 2 decades. However, in some countries e.g. Morocco data reported so far are still deficient and incomplete since only a few researchers have so far addressed the impact of pedoclimatic factors on its quality. For this purpose, thirty-eight Moroccan extra virgin olive oils from the “Picholine Marocaine” variety were collected over two successive crop years (2018 and 2019) and nineteen soil samples were sampled during the first agricultural campaign considering the appropriate sampling equipment recommended. Twenty-three polar phenolic compounds and five Vitamin E isomers (α, β, γ, δ tocopherol and α-tocotrienol) were detected, using HPLC–PDA-ESI–MS and NP-HPLC-FLD, respectively. The most abundant phenolic class was represented by secoiridoids and derivates with an average amount of 1112.3 mg kg−1, whereas among Vitamin E homologs, α-tocopherol was the most abundant, accounting for 91% of total vitamin E. The correlation test and the Principal Components Analysis revealed the significant influence of the pedoclimatic factors on some classes of phenolic compounds (phenolic acids, flavonoids, and secoiridoids); nevertheless, no correlation was detected between phenolic alcohols and other variables under study. Furthermore, the dendrogram cluster allowed to classify the studied areas into five zones, indicating the discrimination of olive oil quality in terms of geographical origin. Besides, phenolic compounds and tocopherols showed significant dependence on the crop year of production. Further, the harvest time turned out to be another factor that can influence the antioxidant fraction quantitatively.