Antiproliferative and Pro-Apoptotic Effect of Uvaol in Human Hepatocarcinoma HepG2 Cells by Affecting G0/G1 Cell Cycle Arrest, ROS Production and AKT/PI3K Signaling Pathway.

Natural products have a significant role in the development of new drugs, being relevant the pentacyclic triterpenes extracted from Olea europaea L. Anticancer effect of uvaol, a natural triterpene, has been scarcely studied. The aim of this study was to understand the anticancer mechanism of uvaol in the HepG2 cell line. Cytotoxicity results showed a selectivity effect of uvaol with higher influence in HepG2 than WRL68 cells used as control. Our results show that uvaol has a clear and selective anticancer activity in HepG2 cells supported by a significant anti-migratory capacity and a significant increase in the expression of HSP-60. Furthermore, the administration of this triterpene induces cell arrest in the G0/G1 phase, as well as an increase in the rate of cell apoptosis. These results are supported by a decrease in the expression of the anti-apoptotic protein Bcl2, an increase in the expression of the pro-apoptotic protein Bax, together with a down-regulation of the AKT/PI3K signaling pathway. A reduction in reactive oxygen species (ROS) levels in HepG2 cells was also observed. Altogether, results showed anti-proliferative and pro-apoptotic effect of uvaol on hepatocellular carcinoma, constituting an interesting challenge in the development of new treatments against this type of cancer.

Water Stress, Irrigation and Concentrations of Pentacyclic Triterpenes and Phenols in Olea europaea L. cv. Picual Olive Trees.

Pentacyclic triterpenes and phenols are two types of bioactive molecules found in olive trees that have important activities related to health and disease prevention. Triterpenes, including oleanolic acid, maslinic acid, erythrodiol and uvaol, show antitumoral activities, and phenols such as oleuropein, tyrosol, and hydroxytyrosol are natural antioxidants. The concentration of these metabolites is considered a marker of the quality of olives and olive oil. In recent years, a lack of rain water has caused important economic losses relating to olive trees grown in Jaén, Spain. In this work, we investigated the effect of water stress by drought on the concentration of pentacyclic triterpenes and phenols in the fruits, leaves, stems and roots of cv. Picual olive trees, by comparing the concentration found in water-stressed versus irrigated plants. We used HPLC-UV/Vis and HPLC-MS to identify and determine the concentration of each individual compound. Our results showed that important changes in the concentration of these compounds are produced in response to water stress in different organs. The total content of most of these compounds in the fruits was significantly reduced, affecting their quality and production.

Proteomics Analysis Reveals the Implications of Cytoskeleton and Mitochondria in the Response of the Rat Brain to Starvation.

Long-term starvation provokes a metabolic response in the brain to adapt to the lack of nutrient intake and to maintain the physiology of this organ. Here, we study the changes in the global proteomic profile of the rat brain after a seven-day period of food deprivation, to further our understanding of the biochemical and cellular mechanisms underlying the situations without food. We have used two-dimensional electrophoresis followed by mass spectrometry (2D-MS) in order to identify proteins differentially expressed during prolonged food deprivation. After the comparison of the protein profiles, 22 brain proteins were found with altered expression. Analysis by peptide mass fingerprinting and MS/MS (matrix-assisted laser desorption-ionization-time of flight mass spectrometer, MALDI-TOF/TOF) enabled the identification of 14 proteins differentially expressed that were divided into 3 categories: (1) energy catabolism and mitochondrial proteins; (2) chaperone proteins; and (3) cytoskeleton, exocytosis, and calcium. Changes in the expression of six proteins, identified by the 2D-MS proteomics procedure, were corroborated by a nanoliquid chromatography-mass spectrometry proteomics procedure (nLC-MS). Our results show that long-term starvation compromises essential functions of the brain related with energetic metabolism, synapsis, and the transmission of nervous impulse.

Target molecules in 3T3-L1 adipocytes differentiation are regulated by maslinic acid, a natural triterpene from Olea europaea.

BACKGROUND: Metabolic syndrome is a set of pathologies among which stand out the obesity, which is related to the lipid droplet accumulation and changes to cellular morphology regulated by several molecules and transcription factors. Maslinic acid (MA) is a natural product with demonstrated pharmacological functions including anti-inflammation, anti-tumor and anti-oxidation, among others. PURPOSE: Here we report the effects of MA on the adipogenesis process in 3T3-L1 cells. METHODS: Cell viability, glucose uptake, cytoplasmic triglyceride droplets, triglycerides quantification, gene transcription factors such as peroxisome proliferator-activated receptor γ (PPARγ) and adipocyte fatty acid-binding protein (aP2) and intracellular Ca2+ levels were determined in pre-adipocytes and adipocytes of 3T3-L1 cells. RESULTS: MA increased glucose uptake. MA also decreased lipid droplets and triglyceride levels, which is in concordance with the down-regulation of PPARγ and aP2. Finally, MA increased the intracellular Ca2+ concentration, which could also be involved in the demonstrated antiadipogenic effect of this triterpene. CONCLUSION: MA has been demonstrated as potential antiadipogenic compound in 3T3-L1 cells.

NADPH production, a growth marker, is stimulated by maslinic acid in gilthead sea bream by increased NADP-IDH and ME expression.

NADPH plays a central role in reductive biosynthesis of membrane lipids, maintenance of cell integrity, protein synthesis and redox balance maintenance. Hence, NADPH is involved in the growth and proliferation processes. In addition, it has been shown that changes in nutritional conditions produced changes in NADPH levels and growth rate. Maslinic acid (MA), a pentacyclic triterpene of natural origin, is able to stimulate NADPH production, through regulation of the two oxidative phase dehydrogenases of the pentose phosphate pathway. Our main objective was to study the effects of MA on the kinetic behaviour and on the molecular expression of two NADPH-generating systems, NADP-dependent isocitrate dehydrogenase (NADP-IDH) and malic enzyme (ME), in the liver and white muscle of gilthead sea bream (Sparus aurata). Four groups of 12g of a mean body mass were fed for 210days in a fish farm, with diets containing 0 (control), and 0.1g of MA per kg of diet. Two groups were fed ad libitum (C-AL and MA-AL) and another's two, with restricted diet of 1% of fish weight (C-R and MA-R). Results showed that MA significantly increased the main kinetic parameter of the NADPH-forming enzymes (NADP-IDH and ME). In this sense, specific activity, maximum velocity, catalytic efficiency and activity ratio values were higher in MA conditions than control groups. Moreover, these changes were observed in both feeding regimen, AL and R. Meanwhile, the Michaelis constant changed mainly in groups fed with the MA and restricted diet, these changes are related to the best substrate affinity by enzyme. Moreover, in the Western-blot result, we found that MA increased both protein levels studied, this behaviour being consistent with the regulation of the number of enzyme molecules. All results, indicate that MA, independently of the fed regimen, could potentially be a nutritional additive for fish as it improved the metabolic state of fish, as consequence of increased activity and expression of NADP-IDH and ME enzymes.

Maslinic Acid, a Natural Triterpene, Induces a Death Receptor-Mediated Apoptotic Mechanism in Caco-2 p53-Deficient Colon Adenocarcinoma Cells.

Maslinic acid (MA) is a natural triterpene present in high concentrations in the waxy skin of olives. We have previously reported that MA induces apoptotic cell death via the mitochondrial apoptotic pathway in HT29 colon cancer cells. Here, we show that MA induces apoptosis in Caco-2 colon cancer cells via the extrinsic apoptotic pathway in a dose-dependent manner. MA triggered a series of effects associated with apoptosis, including the cleavage of caspases -8 and -3, and increased the levels of t-Bid within a few hours of its addition to the culture medium. MA had no effect on the expression of the Bax protein, release of cytochrome-c or on the mitochondrial membrane potential. This suggests that MA triggered the extrinsic apoptotic pathway in this cell type, as opposed to the intrinsic pathway found in the HT29 colon-cancer cell line. Our results suggest that the apoptotic mechanism induced in Caco-2 may be different from that found in HT29 colon-cancer cells, and that in Caco-2 cells MA seems to work independently of p53. Natural antitumoral agents capable of activating both the extrinsic and intrinsic apoptotic pathways could be of great use in treating colon-cancer of whatever origin.

Gene expression profiling to investigate tyrosol-induced lifespan extension in Caenorhabditis elegans.

PURPOSE: We have previously reported that tyrosol (TYR) promotes lifespan extension in the nematode Caenorhabditis elegans, also inducing a stronger resistance to thermal and oxidative stress in vivo. In this study, we performed a whole-genome DNA microarray in order to narrow down the search for candidate genes or signaling pathways potentially involved in TYR effects on C. elegans longevity. METHODS: Nematodes were treated with 0 or 250 µM TYR, total RNA was isolated at the adult stage, and derived cDNA probes were hybridized to Affymetrix C. elegans expression arrays. Microarray data analysis was performed, and relative mRNA expression of selected genes was validated using qPCR. RESULTS: Microarray analysis identified 208 differentially expressed genes (206 over-expressed and two under-expressed) when comparing TYR-treated nematodes with vehicle-treated controls. Many of these genes are linked to processes such as regulation of growth, transcription, reproduction, lipid metabolism and body morphogenesis. Moreover, we detected an interesting overlap between the expression pattern elicited by TYR and those induced by other dietary polyphenols known to extend lifespan in C. elegans, such as quercetin and tannic acid. CONCLUSIONS: Our results suggest that important cellular mechanisms directly related to longevity are influenced by TYR treatment in C. elegans, supporting our previous notion that this phenol might act on conserved genetic pathways to increase lifespan in a whole organism.

A New HPLC-MS Method for Measuring Maslinic Acid and Oleanolic Acid in HT29 and HepG2 Human Cancer Cells.

Maslinic acid (MA) and oleanolic acid (OA), the main triterpenic acids present in olive, have important properties for health and disease prevention. MA selectively inhibits cell proliferation of the HT29 human colon-cancer cell line by inducing selective apoptosis. For measuring the MA and OA concentration inside the cell and in the culture medium, a new HPLC-MS procedure has been developed. With this method, a determination of the amount of MA and OA incorporated into HT29 and HepG2 human cancer-cell lines incubated with different concentrations of MA corresponding to 50% growth inhibitory concentration (IC50), IC50/2, IC50/4, and IC50/8 has been made. The results demonstrate that this method is appropriate for determining the MA and OA concentration in different types of cultured cells and reveals the specific dynamics of entry of MA into HT29 and HepG2 cells.

Maslinic Acid, a Triterpene from Olive, Affects the Antioxidant and Mitochondrial Status of B16F10 Melanoma Cells Grown under Stressful Conditions.

Maslinic acid (MA) is a natural compound whose structure corresponds to a pentacyclic triterpene. It is abundant in the cuticular lipid layer of olives. MA has many biological and therapeutic properties related to health, including antitumor, anti-inflammatory, antimicrobial, antiparasitic, antihypertensive, and antioxidant activities. However, no studies have been performed to understand the molecular mechanism induced by this compound in melanoma cancer. The objective of this study was to examine the effect of MA in melanoma (B16F10) cells grown in the presence or absence of fetal bovine serum (FBS). We performed cell proliferation measurements, and the reactive oxygen species (ROS) measurements using dihydrorhodamine 123 (DHR 123) and activities of catalase, glucose 6-phosphate dehydrogenase, glutathione S-transferase, and superoxide dismutase. These changes were corroborated by expression assays. FBS absence reduced cell viability decreasing IC50 values of MA. The DHR 123 data showed an increase in the ROS level in the absence of FBS. Furthermore, MA had an antioxidant effect at lower assayed levels measured as DHR and antioxidant defense. However, at higher dosages MA induced cellular damage by apoptosis as seen in the results obtained.

Proteomic characterization of nitrated cell targets after hypobaric hypoxia and reoxygenation in rat brain.

This study analyzes the nitrated protein profile of the rat-brain cortex in a model of hypoxia/reoxygenation, identifying the nitrated proteins and assessing spot changes. The proteins identified were grouped into categories, according to their function: 1) metabolism: pyruvate kinase (PK), α-enolase, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), phosphoglycerate mutase 1 (PGAM1), and glutamine synthetase (GS); 2) cytoskeletal proteins: α-tubulin, ß-tubulin, γ-actin, and glial fibrillary acidic protein (GFAP); 3) chaperones: heat-shock protein 71kDa (HSP71); and 4) carrier proteins: voltage-dependent anion-selective channel protein 1 (VDAC-1) and Atp6v1a. PK, α-enolase, and GS nitration rates were upregulated, increasing progressively during reoxygenation and peaking at 24h. GAPDH and PGAM1 nitration levels fell after hypoxia/reoxygenation. α-Tubulin, ß-tubulin, γ-actin, and GFAP nitration rates augmented at 24h, but diminished at 5d. HSP71 suffered from nitration immediately after hypoxia, but not during reoxygenation. VDAC-1 tyrosine nitration was identified only in the control group, whereas detectable Atp6v1a nitration levels were observed only immediately after hypoxia. The data have been deposited to the ProteomeXchange with identifier PXD001049. Our findings suggest a hypothetically crucial linkage between nitration-related protein modifications and metabolic and cell-structure alterations. These changes are probably needed for the remodeling and plasticity processes activated by the hypoxic brain response. BIOLOGICAL SIGNIFICANCE: For the first time the spectrum of nitrated proteins in the hypoxic brain as well as its changes during reoxygenation are described. Our findings suggest a hypothetically crucial linkage between nitration-related protein modifications and metabolic and cell-structure alterations. These changes are probably needed for the remodeling and plasticity processes activated by the hypoxic brain response. The biological relevance of these findings is linked to the important role developed by the signaling molecule NO in the hypoxic brain, and could be interpreted in two different but complementary ways: first, as a mechanism of damage due to nitration impacts over some key proteins affecting its structure and function; and second, as a regulation mechanism involved in the hypoxic response. Hence, based on the modified proteins identified and their functions, it would be possible to design new tools and therapies to prevent brain damage in low-oxygen-pressure atmospheres.

Proteomics analysis in Caenorhabditis elegans to elucidate the response induced by tyrosol, an olive phenol that stimulates longevity and stress resistance.

Tyrosol (TYR, 2-(4-hydroxyphenyl)ethanol), one of the main phenols in olive oil and olive fruit, significantly strengthens resistance to thermal and oxidative stress in the nematode Caenorhabditis elegans and extends its lifespan. To elucidate the cellular functions regulated by TYR, we have used a proteomic procedure based on 2DE coupled with MS with the aim to identify the proteins differentially expressed in nematodes grown in a medium containing 250 µM TYR. After the comparison of the protein profiles from 250 µM TYR and from control, 28 protein spots were found to be altered in abundance (≥twofold). Analysis by MALDI-TOF/TOF and PMF allowed the unambiguous identification of 17 spots, corresponding to 13 different proteins. These proteins were as follows: vitellogenin-5, vitellogenin-2, bifunctional glyoxylate cycle protein, acyl CoA dehydrogenase-3, alcohol dehydrogenase 1, adenosylhomocysteinase, elongation factor 2, GTP-binding nuclear protein ran-1, HSP-4, protein ENPL-1 isoform b, vacuolar H ATPase 12, vacuolar H ATPase 13, GST 4. Western-blot analysis of yolk protein 170, ras-related nuclear protein, elongation factor 2, and vacuolar H ATPase H subunit supported the proteome evidence.

Antitumour activity on extrinsic apoptotic targets of the triterpenoid maslinic acid in p53-deficient Caco-2 adenocarcinoma cells.

We report that a novel triterpenoid, (2a,3b)-2,3-dihydroxyolean-12-en-28-oic acid (maslinic acid), isolated from olive pomace from Olea europaea, triggers primarily the extrinsic and later the intrinsic apoptotic pathways in Caco-2 human colon-cancer cells. Apoptosis induced by maslinic acid was confirmed by FACS analysis using annexine-V FICT staining. This induction of apoptosis was correlated with the early activation of caspase-8 and caspase-3, the activation of caspase-8 was also correlated with higher levels of Bid cleavage and decreased Bcl-2, but with no change in Bax expression. Maslinic acid also induced a sustained activation of c-Jun N-terminal kinase (JNK). Incubation with maslinic acid also resulted in the later activation of caspase-9, which, together with the lack of any Bax activation, suggests that the mitochondrial pathway is not required for apoptosis induced by maslinic acid in this cell line. In this study we found that the mechanism of apoptotic activation in p53-deficient Caco-2 cells differs significantly from that found in HT-29 cells. Natural agents able to activate both the extrinsic and intrinsic apoptotic pathways by avoiding the mitochondrial resistance mechanisms may be useful for treatment against colon cancer regardless of its aetiology.

Time course of pentacyclic triterpenoids from fruits and leaves of olive tree (Olea europaea L.) cv. Picual and cv. Cornezuelo during ripening.

Pentacyclic triterpenoids are plant secondary metabolites of great interest for health and disease prevention. HPLC-UV/vis was used to determine the concentration of the pentacyclic triterpenoids present in fruits and leaves of Picual and Cornezuelo olive tree cultivars. Maslinic acid (MA) and oleanolic acid (OA) are the only two compounds present in fruits, MA being the more abundant. In leaves, in addition to MA and OA, uvaol (UO), and erythrodiol (EO) are found, with OA being the most abundant. In this work, the changes in the concentrations of these compounds during ripening as well as the effect of Jaén-style table-olive processing are reported. The amount of MA and OA found in Picual and Cornezuelo olives after processing was 1.26 ± 0.06, 1.30 ± 0.06, 0.31 ± 0.02, and 0.23 ± 0.01 mg per fruit, respectively. These results enable us to calculate the average intake of pentacyclic triterpenoids and reinforce the importance of table olives as a source of healthy compounds.

Maslinic acid, a triterpenic anti-tumoural agent, interferes with cytoskeleton protein expression in HT29 human colon-cancer cells.

Maslinic acid (MA) is an anti-tumoural agent which shows potent anti-proliferative properties against the HT29 colon-cancer cells. To shed light upon the active mechanism of MA we have investigated its effects upon the cytoskeleton. We used a proteomics procedure based on two-dimensional gel electrophoresis, mass analysis and peptide mass fingerprinting. The incubation of HT29 cells with MA led to G1 cell-cycle arrest. After 24hours' exposure to 3.7µM (IC50/8) and 30µM (IC50) MA fourteen differentially expressed cytoskeletal proteins could be discerned. One group of these proteins, made up of keratin 2, keratin 8, keratin type II cytoskeletal 8, keratin type I cytoskeletal 9, keratin type I cytoskeletal 18, cytokeratins 18 and 19, and ß-actin, exert a structural function, whilst another group, made up of lamin B1, gelsolin 1, septin 2, villin 1, actin-related protein 2 and moesin, is related to the nucleation of actin and cytoskeleton formation. Changes in the expression of moesin, villin 1 and ß-actin identified by the proteomics techniques were corroborated by Western blotting. This is the first evidence obtained of the regulatory effects of MA on the cytoskeleton, which may prove to be one of the bases of its anti-proliferative effect against colon-cancer cells. BIOLOGICAL SIGNIFICANCE: In this paper we describe the changes in the expression of different cytoskeleton proteins identified by the proteomics techniques and corroborated by Western blotting. This is the first evidence obtained of the regulatory effects of MA on the cytoskeleton, which may prove to be one of the bases of its anti-proliferative effect against colon-cancer cells.

Hypobaric hypoxia and reoxygenation induce proteomic profile changes in the rat brain cortex.

Brain, due to its high metabolism, is severely affected by hypoxia/reoxygenation. In this study, cerebral cortexes from rats subjected to hypobaric hypoxia followed by several reoxygenation periods (0 h, 24 h, and 5 days) were compared with normobaric normoxic controls to identify protein-expression differences using proteomic approaches. Only 2-fold differences in spot abundance between controls and experimental groups from each reoxygenation period were considered. The proteins identified were grouped into categories, according to their similarity in function or to their involvement in the same metabolic pathway. We distinguished five groups: (1) glycolysis, including γ-enolase (NSE), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH); (2) tricarboxylic acid cycle, such as aconitate hydratase (ACO2); (3) oxidative phosphorylation, like F1-ATPase chains α and ß; (4) cytoskeletal, including Spna2, α-tubulin, ß-tubulin, ß-actin, and microtubule-associated protein RP/EB family member 3 (EB3); and (5) chaperones, like heat-shock protein 72 kDa (HSP72). NSE was upregulated while GAPDH was downregulated, both peaking at 5 days post-hypoxia. ACO2 and F1-ATPase decreased in all the reoxygenation periods. Spna2 and EB3 were expressed neither in control nor at 0 h, but 5 days post-hypoxia new expression took place. The α- and ß-tubulin levels significantly fell at 0 h, but after 24 h strongly increased. Also, ß-actin and HSP72 were downregulated, and the last one reached the lowest level at 24 h of reoxygenation. We conclude that the molecular mechanisms underlying hypoxia/reoxygenation in the rat cortex might consist of a close relationship between energy metabolism, cytoskeleton, and chaperones. These findings may shed light on therapeutic targets against hypoxia-related damage.

Proteomics in the liver of gilthead sea bream (Sparus aurata) to elucidate the cellular response induced by the intake of maslinic acid.

Maslinic acid (MA) is a pentacyclic triterpene used as a feed additive to stimulate growth, protein-turnover rates, and hyperplasia in fish. To further our understanding of cellular mechanisms underlying the action of MA, we have used 2-DE coupled with MS to identify proteins differentially expressed in the livers of juvenile gilthead sea bream (Sparus aurata) grown under fish-farm conditions and fed with a 100 mg/kg MA-enriched diet (MA(100)). After the comparison of the protein profiles from MA(100) fed fish and from control, 49 protein spots were found to be altered in abundance (≥2-fold). Analysis by MALDI-TOF/TOF allowed the unambiguous identification of 29 spots, corresponding to 19 different proteins. These proteins were: phosphoglucomutase, phosphoglucose isomerase, S-adenosyl methionine-dependent methyltransferase class I, aldehyde dehydrogenase, catalase, 6-phosphogluconate dehydrogenase, fumarylacetoacetate hydrolase, 4-hydroxyphenylpyruvic dioxygenase, methylmalonate-semialdehyde dehydrogenase, lysozyme, urate oxidase, elongation factor 2, 60 kDa heat-shock protein, 58 kDa glucose-regulated protein, cytokeratin E7, type-II keratin, intermediate filament proteins, 17-ß-hydroxysteroid dehydrogenase type 4, and kinase suppressor of Ras1. Western blot analysis of kinase suppressor of Ras1, glucose 6-phosphate dehydrogenase, elongation factor 2, 60 kDa heat-shock protein, and catalase supported the proteome evidence. Based on the changes found in the protein-expression levels of these proteins, we proposed a cellular-signalling pathway to explain the hepatic-cell response to the intake of a diet containing MA.

Phenol metabolism in the leaves of the olive tree (Olea europaea L.) cv. Picual, Verdial, Arbequina, and Frantoio during ripening.

The kinetic behavior and protein-expression level of phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO) have been determined in the leaves of the olive tree (Olea europaea L.) of cv. Picual, Verdial, Arbequina, and Frantoio during fruit ripening. Moreover, the concentration of total phenolic compounds, oleuropein, hydroxytyrosol, and tyrosol has been also determined. This study was carried out in 20-year-old olive trees grown in Jaén (Spain). The concentration of total and specific phenols showed a specific pattern in each cultivar. Frantoio showed the highest phenol concentration followed by Arbequina, Picual, and Verdial. A coordinated response between PAL, PPO, and the concentration of total phenols in the four cultivars was found. Also, specific changes were shown over the course of ripening, indicating a regulation of PAL, PPO, and phenol concentration in the olive-tree leaves during fruit ripening.

Dietary protein differentially regulates the kinetic behaviour of serine dehydratase and tyrosine aminotransferase of liver and white muscle of rainbow trout (Oncorhynchus mykiss).

We have determined the kinetic behaviour of serine dehydratase (SerDH) and tyrosine aminotransferase (TyrAT) in the liver and white muscle of juvenile rainbow trout (Oncorhynchus mykiss) fed on a low-protein/high-fat (LP/HF) and control diets. The relationship between the kinetic parameters and tissue-DNA concentration has also been determined. SerDH and TyrAT showed hyperbolic kinetics in all cases. The partial replacement of protein with fat significantly increased hepatic SerDH-specific activity, maximum velocity (V(max)) and Michaelis constant (K(m)) while no significant changes were detected in the values of these parameters in white muscle. Nevertheless, hepatic and white-muscle TyrAT specific activity and V(max) decreased in trout fed on LP/HF diet with respect to control. The K(m) of hepatic TyrAT was also lower in trout fed on LP/HF diet than in control. The TyrAT kinetic parameters expressed per cell unit also changed in the same sense as previously described. These results show that, in trout, SerDH and TyrAT are two enzymes regulated by the partial replacement of dietary protein by fat.

HPLC analysis of oleuropein, hydroxytyrosol, and tyrosol in stems and roots of Olea europaea L. cv. Picual during ripening.

BACKGROUND: Oleuropein (Ole), hydroxytyrosol (Htyr), and tyrosol (Tyr) are three of the main phenolic compounds present in the olive tree (Olea europaea L.) that have important antioxidant properties. To investigate the role of these phenolic compounds in the metabolism of stems and roots of Olea europaea L. cv. Picual during olive ripening, we identify and quantify the concentration of Htyr, Tyr, and Ole by reversed-phase high-performance liquid chromatography (RP-HPLC). Rain-fed olive trees, 30 years old, under traditional cultivation were studied in Jaén (Spain). From August to November, seven representative samples of the ripening process were taken. RESULTS: The concentration of these phenolic compounds proved higher in the stems than in the roots. From the middle of September to October the Htyr and Tyr concentration significantly increased in stems. The Ole concentration increased from the middle of September to the end of November. In the roots, the concentration of Htyr and Ole significantly declined during ripening. CONCLUSION: Ole, Htyr, and Tyr are present in the stems and roots of the olive tree and significantly change in concentration during ripening, demonstrating the involvement of these compounds in the metabolism of both organs during this phase.

Phenylalanine ammonia-lyase, polyphenol oxidase, and phenol concentration in fruits of Olea europaea L. cv. Picual, Verdial, Arbequina, and Frantoio during ripening.

The kinetics and protein-expression level of phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO) in fruits of olive trees (Olea europaea) cv. Picual, Verdial, Arbequina, and Frantoio have been studied in relation to the concentration of total phenolic compounds, oleuropein, hydroxytyrosol, and tyrosol during fruit ripening. Frantoio was the variety that showed the highest total phenol concentration, the highest PAL activity, the lowest PPO activity, and the lowest protein levels. In contrast, Verdial was the variety that showed the lowest total phenol concentration, the least PAL activity, the greatest PPO activity, and the highest protein levels. Arbequina and Picual showed intermediate levels. These results suggest the existence of a coordinated response between PAL, PPO, and the concentration of total phenols over ripening in the four varieties. The concentration of total and specific phenols differed between varieties and specifically changed over ripening.