The human cytochrome P450 enzymes (P450s) catalyze oxidative reactions of a broad spectrum of substrates and play a critical role in the metabolism of xenobiotics, such as drugs and dietary compounds. CYP3A4 is known to be the main enzyme involved in the metabolism of drugs and most other xenobiotics. Dietary compounds, of which polyphenolics are the most studied, have been shown to interact with CYP3A4 and alter its expression and activity. Traditionally, the liver was considered the prime site of CYP3A-mediated first-pass metabolic extraction, but in vitro and in vivo studies now suggest that the small intestine can be of equal or even greater importance for the metabolism of polyphenolics and drugs. Recent studies have pointed to the role of gut microbiota in the metabolic fate of polyphenolics in human, suggesting their involvement in the complex interactions between dietary polyphenols and CYP3A4. Last but not least, all the above suggests that coadministration of drugs and foods that are rich in polyphenols is expected to stimulate undesirable clinical consequences. This review focuses on interactions between dietary polyphenols and CYP3A4 as they relate to structural considerations, food-drug interactions, and potential negative consequences of interactions between CYP3A4 and polyphenols.

BACKGROUND: Macronutrients play fundamental roles in processes affecting olive oil productivity and are expected to influence oil composition. A necessary step in optimal nutrient application management for olives is an understanding of the relationship between olive tree nutritional status and oil quality parameters. We studied the independent effects of N, P and K concentrations in irrigation solution on the oil quality of 'Barnea' olives by applying a wide range of macronutrient concentrations under highly controlled conditions.

BACKGROUND: Olive trees are generally grown under rain-fed conditions. Since yield response to application of water in the growing season may be considerable, irrigation is increasingly introduced to existing, mature orchards. An additional feature of modernization of olive cultivation is mechanical harvesting. To investigate the effect of irrigation level on the quality of virgin olive oil (VOO) produced from cv. Souri, six regimes, ranging from deficit to excess, were applied to trees in a mature, traditional orchard as it was converted to irrigation. Furthermore, in order to investigate the effect of damage incurred during harvest, oil quality of hand-picked fruit was compared to that of mechanically harvested olives.

Studying the composition of olive oil requires cold-press olive oil extraction. One of the most common laboratorial mills is the Abencor system. However, its operation protocol was formulated decades ago for Spanish olive varieties from traditionally rain-fed orchards. We modified this protocol for use with ''Barnea'' and ''Picual'' olives from irrigated orchards that are characterized by high water content. Independent effects of malaxation time, temperature, water addition and talc addition on extraction efficiency, and major quality indices of virgin olive oil were studied. Overall, addition of talc to the fruit paste was the most significant treatment in terms of yield and quality of the oil although its effect was cultivar dependent. Improved oil yield was particularly significant for ''Picual.'' Extended malaxation time was also effective in improving oil extractability. Addition of talc generally improved oil-quality parameters, while water addition had the opposite effect. Yet, quality parameters remained within the extra virgin level. Temperature increments reduced oil quality. The need to adapt a modified protocol for use with fruits from irrigated orchards that will facilitate critical comparison of results obtained from different agronomic theses and different laboratories is highlighted. It is recommended that each laboratory develops an appropriate protocol for the operation of the Abencor system in accordance to the characteristics of the olive fruit they are working with.Practical applications: Abencor system serves as the major laboratorial mill world-wide. Those mills allow the researchers to characterize olive oil in accordance to the treatments received by the trees. This cannot be done in commercial mills. The system operation protocol was established decades ago for fruits from rain-fed orchards. In the past decade there was a rapid increase in the use of irrigation in olive orchards and therefore it is crucial to optimize the operation protocol for fruit with relatively high water content. In the current work we have evaluated the influence of a series of technological parameters (i.e., talc and water addition, malaxation time, and temperature) on the extraction efficiency and quality indices of olive oil. This allowed us to present a modified protocol for the Abencor system operation suitable for olive fruit of irrigated orchards that will facilitate a reliable representation of the influence of different treatments on the yield and characteristics of the olive oil.

The influence of macronutrient status on olive oil properties was studied for three years. Data were analyzed by a multivariate model considering N, P, K, and fruiting year as explanatory factors. Oil quality parameters were primarily associated with N concentration in leaves and fruits which increased with N in irrigation solution. The effect of P on oil quality was mainly indirect since increased P availability increased N accumulation. The potassium level had negligible effects. The oil phenolic content decreased linearly as a function of increased leaf N, indicating protein-phenol competition in leaves. The overall saturation level of the fatty acids decreased with fruit N, resulting in increased polyunsaturated fatty acids. Free fatty acids increased with increased levels of fruit N. High fruit load tended to reduce fruit N and subsequently improve oil quality. The effect of N on oil properties depended solely on its concentration in leaves or fruits, regardless of the cause.

Five rates of water application were applied in a 4 year study on olive (Olea europaea) varieties 'Barnea' and 'Souri'. Increased irrigation lead to increased tree-scale oil yields, lower polyphenol content, and, frequently, higher oil acidity. These effects were predominant in "off" years. The fatty acid profile was influenced primarily by bearing level and variety and secondarily by irrigation rate. The saturated to unsaturated fatty acid ratio was higher in "off" than in "on" years, and the monounsaturated fatty acid to polyunsaturated fatty acid ratio was higher in "on" years as a result of the fact that oleic and stearic acids were higher in "on" years, while palmitic, palmitoleic, and linoleic acids were greater in "off" years. Squalene was higher in 'Souri' than in 'Barnea' oils, was not affected by bearing cycle, and was consistently lower in oil from trees receiving the lowest irrigation level.

CYP3A4 is recognized as the main enzyme involved in the metabolism of drugs and xenobiotics in the human body and its inhibition may lead to undesirable consequences. Stilbenes, including resveratrol, belong to a group of dietary health-promoting compounds that also act as inhibitors of CYP3A4. The aim of this study was to examine the use of computer modeling of enzyme-ligand interactions to analyze and predict the inhibition of structurally related compounds. To this end, an aldehyde group was attached to resveratrol and the interactions of CYP3A4 with resveratrol, its aldehyde analogue (RA) and a known synthetic inhibitor were studied and compared in two biological models. Specifically, the metabolism of testosterone was examined in a human intestine cell line (Caco-2/TC7) and in rat liver microsomes (RLM). The results demonstrated a weak inhibitory effect of RA on CYP3A4, as compared to resveratrol itself, in both biological models. Human CYP3A4 was more susceptible to inhibition than the commonly used model isozyme from rat. Modeling of the binding site of CYP3A4 revealed a combination of three types of interactions: hydrophobic interactions, electrostatic interactions and hydrogen bonds. A docking simulation revealed that the RA lacked an important binding feature, as compared to resveratrol, and that that difference may be responsible for its lower level of affinity for CYP3A4. Software analysis of binding affinity may serve as a predictive tool for designing new therapeutic compounds in terms of inhibition of CYP3A4 and help to reveal the biochemical nature of the interactions of dietary compounds, herbal compounds and drugs whose metabolism is mediated by this enzyme.

Many dietary compounds, including resveratrol, are potent inhibitors of CYP3A4. Here we examined the potential to predict inhibition capacity of dietary polyphenolics using an in silico and in vitro approaches and synthetic model compounds. Mono, di, and tri-acetoxy resveratrol were synthesized, a cell line of human intestine origin and microsomes from rat liver served to determine their in vitro inhibition of CYP3A4, and compared to that of resveratrol. Docking simulation served to predict the affinity of the synthetic model compounds to the enzyme. Modelling of the enzyme’s binding site revealed three types of interaction: hydrophobic, electrostatic and H-bonding. The simulation revealed that each of the examined acetylations of resveratrol led to the loss of important interactions of all types. Tri-acetoxy resveratrol was the weakest inhibitor in vitro despite being the more lipophilic and having the highest affinity for the binding site. The simulation demonstrated exclusion of all interactions between tri-acetoxy resveratrol and the heme due to distal binding, highlighting the complexity of the CYP3A4 binding site, which may allow simultaneous accommodation of two molecules. Finally, the use of computational modelling may serve as a quick predictive tool to identify potential harmful interactions between dietary compounds and prescribed drugs.