Virgin olive oil samples with similar oxidative stabilities and fatty acid compositions were stored for 24 months. Changes in the lipid substrate were followed by peroxide value and K(232) measurements. HPLC was used to evaluate changes in the alpha-tocopherol, pigment, and squalene contents. Total polar phenol content was measured colorimetrically. The loss of alpha-tocopherol and carotenoids was comparable with that of polar phenol content, suggesting an active participation in autoxidation. The limited role of squalene in autoxidation was further confirmed using an olive oil model and in the presence of alpha-tocopherol. Pheophytin a degradation was high, although spectrometric estimation of chlorophyll content did not indicate so. Evaluation of pheophytin a activity at three different levels of addition on the oil model indicated a concentration-dependent antioxidant role more pronounced at elevated temperatures, which could be partially due to the activity of certain degradation products.

Olive oil compounds is a dynamic research area because Mediterranean diet has been shown to protect against cardiovascular disease and cancer. Olive leaves, an easily available natural material of low cost, share possibly a similar wealth of health benefiting bioactive phytochemicals. In this work, we investigated the antioxidant potency and antiproliferative activity against cancer and endothelial cells of water and methanol olive leaves extracts and analyzed their content in phytochemicals using LC-MS and LC-UV-SPE-NMR hyphenated techniques. Olive-leaf crude extracts were found to inhibit cell proliferation of human breast adenocarcinoma (MCF-7), human urinary bladder carcinoma (T-24) and bovine brain capillary endothelial (BBCE). The dominant compound of the extracts was oleuropein; phenols and flavonoids were also identified. These phytochemicals demonstrated strong antioxidant potency and inhibited cancer and endothelial cell proliferation at low micromolar concentrations, which is significant considering their high abundance in fruits and vegetables. The antiproliferative activity of crude extracts and phytochemicals against the cell lines used in this study is demonstrated for the first time.

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Virgin olive oil samples with similar oxidative stabilities and fatty acid compositions were exposed to 12100 lx (25 +/- 1 degrees C) in closed bottles until bleached. The observed low changes in the substrate and polar phenols were related to oxygen availability. HPLC monitoring showed that pheophytin agradual degradation (> 90%) was accompanied by a considerable alpha-tocopherol loss (22-35%) due to the reaction of the latter with singlet oxygen. No changes were recorded for carotenoids, which acted as physical quenchers and light filters. Squalene loss was confined (4-12%). Complementary experiments on the activity of pheophytin a, using olive oil models, indicated a concentration dependence, enhanced by oxygen availability. In closed bottles, the degradation rate constant was higher at low amounts of pheophytin a. Squalene was preferentially consumed to protect alpha-tocopherol. An urgent change in the practice of packaging is needed to preserve the precious characteristics of the product during commercialization.

alpha-Tocopherol, the main tocopherol homologue found in olive oil, was determined using normal phase HPLC. Ninety Greek virgin olive oils, selected according to a designed sampling protocol from different cultivars and regions all over Greece for three successive crop years, were analyzed. For a specific olive cultivar, which is widely used for the production of olive oil in Greece, additional measurements were made to study the effect of milling conditions on alpha-tocopherol concentration. Finally, a significant number of commercial olive oil samples (25) obtained from the retail market were analyzed. High concentrations of alpha-tocopherol were observed in most of the samples selected from various regions. Values ranging between 98 and 370 mg/kg were found (>200 mg/kg in 60% of samples). Extraction conditions were not found to influence alpha-tocopherol level. alpha-Tocopherol content of retail market samples was high, ranging from 120 to 250 mg/kg of oil (>180 mg/kg in 60% of samples). Storage of samples under domestic conditions for two years showed that good handling is quite important for retaining high alpha-tocopherol levels and for increasing, thus, the storage life and nutritional value of this exquisite oil.

The oxidative stability of virgin olive oil is related to triacylglycerol composition and the presence of polar phenolic and other components. The present paper presents an HPLC methodology for the simultaneous determination of tocopherols, major carotenoids, and chlorophylls suitable to monitor their fate during virgin olive oil oxidation. The separation of the above classes of components was carried out using an n-hexane/2-propanol gradient within 20 min. Detection was accomplished using a UV detector in series with a diode array system. The method was validated and applied to oil samples subjected to autoxidation or photo-oxidation. The results indicated that the method could be used to highlight the effect of these components on virgin olive oil oxidative stability. Keywords: Virgin olive oil; HPLC; tocopherols; carotenoids; chlorophylls; oxidation