Oil content,phenolic profiling and antioxidant potential of Tunisian olive drupes

BACKGROUND: The aim of this work was to investigate the effect of the maturation process of the olive fruit on oil content, phenolic profile and antioxidant activity of four Tunisian cultivars (Zelmati, Chemchali, Chemlali and Chétoui). RESULTS: The average oil content of the studied varieties ranged between 17.50% and 20.25% at the first stage of maturation and from 30.20% to 35% in the last harvest. Qualitative and quantitative analysis of phenolic compounds were carried out using HPLC and LC‐MS/MS. Twenty‐six biophenolic compounds were identified. In all samples, hydroxytyrosol and oleuropein were the major compounds identified while rutin and luteolin 7‐O‐glucoside were the two main flavonoids. The total phenolic content varied from 3.46 to 4.30 g kg^?1 at the first stage of maturation and from 8.71 to 11.52 g kg^?1 of fruit fresh weight at the last maturation phase. Total flavonoid content reached 432.80 mg kg^?1. The antioxidant activity of the extract was evaluated by DPPH and ABTS assays. The IC₅₀ values of the olive extracts ranged from 2.69 to 10.96 µg L^?1 and from 2.15 to 3.03 mmol L^?1 trolox equivalent at the last stage of maturation. CONCLUSION: A relationship between the changes in phenolic content and the physicochemical changes in Tunisian olive fruit during maturation was established. These findings could be used for controlling the production processes and correlating the oil sensorial characteristics to the polyphenolic pattern. Copyright © 2010 Society of Chemical Industry     

Polyphenol oxidase activity of two olive (Olea europaea L.) cultivars as an early criterion of Mn toxicity

BACKGROUND: The time course of polyphenol oxidase (PPO) activity in the leaves of two olive cultivars (Picual and FS‐17) irrigated with nutrient solutions differing in Mn concentration (0, 2 and 1280 µmol L^?1) was studied under hydroponic conditions to determine whether PPO activity could be used as an early criterion of Mn status of olive plants, and to elucidate whether genotypic differences exist between the two olive cultivars studied, concerning the effect of Mn concentration on PPO activity. RESULTS: In all the Mn treatments, PPO activity was greater in Picual than in FS‐17. Under excess Mn (1280 µmol L^?1), PPO activity gradually increased with time, starting from day 30 of the experiment in both cultivars, and this increase preceded the appearance of Mn toxicity symptoms. In contrast, in the other two Mn treatments (0 and 2 µmol L^?1) PPO activity increased and afterwards decreased during the experiment, but the trend was not clear. In the 1280 µmol L^?1 treatment, PPO activity linearly increased (R = 0.8836 for Picual and 0.943 for FS‐17) with the increase of Mn concentration in the leaves of both cultivars. In the 1280 µmol L^?1 Mn treatment, PPO activity was negatively related with Fe and Zn concentrations in the leaves, and positively in the 0 and 2 µmol L^?1 Mn treatments with the Ca, Mg and K concentrations. CONCLUSION: From the differential time course of PPO activity in the three Mn treatments (0, 2 and 1280 µmol L^?1), it is concluded that periodic measurements of PPO activity in the leaves of the olive cultivars Picual and FS‐17 can be used for the early detection of Mn toxicity (before the appearance of symptoms). Copyright © 2010 Society of Chemical Industry     

L‐Phenylalanine ammonia‐lyase activity and concentration of phenolics in developing olive (Olea europaea L cv Arbequina) fruit grown under different irrigation regimes

Changes in L ‐phenylalanine ammonia‐lyase (PAL, EC 4.3.1.5) activity and total phenolic, ortho‐diphenolic and fat contents of olive flesh in response to different irrigation treatments applied to olive tree cv Arbequina were studied during fruit ripening. Results indicate that the fat content of olive flesh at harvest was not affected by irrigation, although olives from the most heavily irrigated treatment reached their final fat content (dry weight) earlier than those from other irrigation treatments. PAL activity and phenolic content, expressed on a dry weight basis, decreased during fruit development and were affected by irrigation, being lowered as the water supplied increased. Good correlations were established between PAL enzymatic activity and the polyphenol and ortho‐diphenol contents of olive flesh, indicating that PAL is involved in the phenolic metabolism of olive fruit. The phenolic content of the oil depends on the PAL activity in the fruit, which varies with changes in water status. © 2002 Society of Chemical Industry     

Non-destructive and objective methods for the evaluation of the maturation level of olive fruit

The maturation level of two olive varieties (Olea europaea, cvs. Arbequina and Picual) was objectively evaluated using two non-destructive methods: checking the fruit firmness using a hand densimeter, and the skin colour with a portable colourimeter. These methods were compared with the Ripening Index (RI), habitually used by olive oil industry, and based on the subjective determination of skin and flesh colour. The values of skin colour [L*(b*–a*)/100] only monitor the olive maturation in both varieties, when the olive is losing its initial green colour, while fruit firmness is decreasing throughout the maturation process. Fruit firmness is directly related to RI and could be useful in objectively estimating the maturation level of the olives.     

The response of phenylalanine ammonia‐lyase,polyphenol oxidase and phenols to cold stress in the olive tree (Olea europaea L. cv. Picual)

BACKGROUND: In this study the activities of phenylalanine ammonia‐lyase (PAL) and polyphenol oxidase (PPO) and the concentrations of hydroxytyrosol, tyrosol and oleuropein in olive tree (Olea europaea L. cv. Picual) leaves were investigated before and after cold stress by freezing. The air temperature fell to below ?7 °C and, according to the specific field conditions, four categories of orchard were selected: not cold stressed (NS), lightly cold stressed (LS), moderately cold stressed (MS) and heavily cold stressed (HS). RESULTS: In LS and MS samples the PAL specific activity at saturated substrate concentration rose 4.8‐ and 1.9‐fold respectively compared with NS samples. In HS samples the PAL activity declined by 47% compared with NS samples. A low level of PAL protein was detected in all samples affected by cold stress. In LS, MS and HS samples the PPO specific activity at saturated substrate concentration was 1.9‐, 4.4‐ and 9.8‐fold higher respectively than in NS samples. K_m values also increased after cold stress. In MS and HS samples the concentration of oleuropein was 69 and 82% higher respectively than in NS samples, while the concentrations of hydroxytyrosol and tyrosol decreased. CONCLUSION: The response of PAL activity may be part of a recovery process of the olive leaf against cold stress, while the response of PPO and oleuropein may be part of an antioxidant protection mechanism. Copyright © 2009 Society of Chemical Industry     

Pre‐ or post‐harvest applications of putrescine and low temperature storage affect fruit ripening and quality of ‘Angelino’ plum

BACKGROUND: Plum has a very short storage life. The role of pre‐ or post‐harvest applications of putrescine (PUT) and low temperature storage on fruit ripening and quality was investigated in plum fruit (Prunus salicina Lindl. cv. Angelino). RESULTS: Pre‐ or post‐harvest PUT treatments [(0.1, 1.0 or 2.0 mmol L^?1) + 0.01% Tween‐20 as a surfactant] delayed and suppressed the climacteric ethylene production and respiration rate irrespective of the method used to apply PUT. PUT‐treated fruit following low temperature storage (0 ± 1 °C; 90 ± 5% RH), at the ripe stage exhibited higher fruit firmness and titratable acidity (TA), while soluble solids content (SSC), levels of ascorbic acid, total carotenoids and total antioxidants were lower than in untreated fruit. Fruit both sprayed with PUT and stored in low temperature for 6 weeks, at the ripe stage showed reduced respiration rate, delayed changes in the SSC:TA ratio and levels of total carotenoids compared to post‐harvest PUT application. CONCLUSION: Pre‐harvest application of 2.0 mmol L^?1 PUT 1 week before the anticipated commercial harvest was more effective in delaying plum fruit ripening and can be used to extend the storage (0 ± 1 °C) life of plums for up to 6 weeks with minimum losses in fruit quality. Copyright © 2008 Society of Chemical Industry     

Enhancing disease resistance in harvested mango (Mangifera indica L. cv. ‘Matisu’) fruit by salicylic acid

To learn how salicylic acid (SA) may affect disease resistance in mango, mango fruit (Mangifera indica L. cv. ‘Matisu’) were treated with 1 mmol L^?1 SA solution under vacuum infiltration for 2 min at a low pressure (?80 kPa) and for an additional 10 min at air pressure. The fruit were inoculated with anthracnose (Colletotichum gloeosporioides Penz.) spore suspension (1 × 10⁴ CFU mL^?1) and incubated at 13 °C, 85–95% RH. Disease incidence and lesion diameter in/on the SA‐treated fruit were 37.5% and 20.9% lower than that in/on control fruit on the 4th day of incubation. The study further showed that activities of defensive enzymes in the fruit were significantly enhanced by SA treatment. The activity of phenylalanine ammonia‐lyase (PAL) and β‐1,3‐glucanase in the SA‐treated fruit was over 6‐ or 0.9‐fold higher than that in control fruit on the 4th day after the fruit being treated with SA, respectively. Level of hydrogen peroxide (H₂O₂) or superoxide radicals (O₂^?) generation rate in SA‐treated fruit was 22.3% or 79.4% higher than that in controls on the 8th day after the fruit being treated with SA, respectively. These results suggested that PAL and β‐1,3‐glucanase, as well as H₂O₂ or O₂^?, may be involved in the enhancement of disease resistance in mango fruit. Copyright © 2006 Society of Chemical Industry     

Time of methyl jasmonate application influences the development of ‘Cripps Pink’ apple fruit colour

BACKGROUND: The effects of time and numbers of pre‐harvest sprays of methyl jasmonate (MJ) on the development of red blush, export‐grade fruit, accumulation of flavonoids in fruit skin and quality of ‘Cripps Pink’ apple were investigated in 2005 and 2006. In the first experiment during 2005, whole trees were sprayed once with 10 mmol L^?1 MJ at weekly intervals from 155 to 183 days after full bloom (DAFB). In second experiment during 2006, different numbers of sprays (0, 1, 2, 3, 4, 5 or 6) of 5 mmol L^?1 MJ were applied from 151 to 179 DAFB. RESULTS: A single spray of MJ (10 mmol L^?1) at 169 DAFB resulted in the highest increase in the red blush, export‐grade fruit, accumulation of anthocyanins, cyanidin 3‐galactosides, chlorogenic acid, phloridzin, flavanols and flavonols in fruit skin as compared to all other treatments without affecting fruit quality. A single spray of 5 mmol L^?1 MJ at 186 DAFB was more effective in improving red blush, export‐grade fruit and accumulation of anthocyanins in fruit skin as compared to its multiple applications. The exposed sides of fruit developed better colour than the shaded sides, regardless of time and numbers of MJ sprays. Time of a single spray of MJ is more effective than its multiple applications. CONCLUSIONS: A single pre‐harvest spray of MJ (10 mmol L^?1) at 169 DAFB or MJ (5 mmol L^?1) at 186 DAFB was effective in improving the red blush and export grade fruit through accumulation of flavonoids in fruit skin without adversely affecting quality at harvest. © 2012 Society of Chemical Industry     

The effects of 1-methylcyclopropene on peach fruit (Prunus persica L. cv. Jiubao) ripening and disease resistance

In order to learn how 1‐methylcyclopropene (1‐MCP) affects ripening and disease‐resistance of peach fruit (Prunus persica L. cv. Jiubao) after harvest, they were treated with 1‐MCP and some were inoculated with Penicillium expansum. Treating peach fruit with 0.2 μL L^?1 of 1‐MCP at 22 °C for 24 h effectively slowed the decline in fruit firmness. The minimal concentration of 1‐MCP able to inhibit fruit softening was 0.6 μL L^?1. Changes in other parameters related to peach ripening, such as content of soluble solids, total soluble sugar, titratable acidity, soluble pectin and ethylene production were also significantly reduced or delayed by 1‐MCP. Repeated treatment of peach with 1‐MCP resulted in more effective inhibition of ripening. Post‐harvest decay of peach fruit was reduced by treatment with 1‐MCP and disease progress in fruit inoculated with P. expansum was reduced. The activities of phenylalanine ammonialyase, polyphenoloxidase and peroxidase in the inoculated fruit were also enhanced by 1‐MCP.     

Effect of cultivar and ripening on minor components in Spanish olive fruits and their corresponding virgin olive oils

Phenolics and volatiles are the compounds mainly responsible for the desirable flavour of extra virgin olive oils and therefore to a large extent determine the degree of consumer preference for this highly regarded product. The effect of both (i) the nature of the cultivar and (ii) the degree of ripening of the olive fruit on the biophenolic and volatile profiles of six different Spanish varieties (Arbequina, Cornicabra, Morisca, Picolimón, Picudo and Picual) and their corresponding virgin olive oils was determined in this study. A clear and statistically significant difference was observed for the oleuropein content, the main phenolic component found in the olive varieties studied. Demethyloleuropein was only found in the Arbequina variety and its content doubled during the ripening process. Verbascoside steadily increased throughout fruit maturation and cyanidin 3-O-rutinoside was the most abundant anthocyanin in all the varieties studied. Within the same cultivar a relationship between the oleosides content in the fruit and the presence of secoiridoids in the virgin olive oils was observed; however, the ratio between biophenols content in the olive fruit and in the virgin olive oil varied significantly for each of the cultivars studied (ranging from 2.3 for Picudo and 28 for Picolimon). The major volatile component was the C6 aldehyde fraction whose content varied greatly between the different varieties studied: E-2-hexenal content ranged from 20.5 mg of internal standard (4-methyl-2-pentanol) per kg of oil in the Arbequina variety to 3.1 mg/kg for Cornicabra; the amount of hexanal ranged from 1.75 mg/kg in Morisca to 0.70 mg/kg for Picual samples.     

The influence of ripening stage and cultivation system on the total antioxidant activity and total phenolic compounds of yellow passion fruit pulp

BACKGROUND: This work aimed to investigate the influence of both ripening stage and cultivation system on the total phenolic compounds (TPC) and total antioxidant activity (TAA) of passion fruit pulp. TPC extraction was optimized using a 2³ central composed design. The variables were fruit pulp volume, methanol volume and extraction solution volume. TPC was determined using the Folin–Ciocalteu reaction, and TAA using the ABTS radical reaction. RESULTS: The conditions to extract TPC were 2 mL passion fruit pulp and 9 mL extraction solution containing 40% methanol:water (v/v). TPC values increased in the passion fruit pulp during ripening for both cultivation systems, ranging from 281.8 to 361.9 mg gallic acid L^?1 (P?0.05) for the organic pulp and from 291.0 to 338.6 mg gallic acid L^?1 (P?0.05) for the conventional pulp. CONCLUSION: TPC values increased during ripening for both organic and conventional passion fruit. The same was true for TAA values for conventional passion fruit. For organic passion fruit, however, TAA values were highest at the initial ripening stages. These results suggest that antioxidant compounds exert strong influence on the initial ripening stages for organic passion fruit, when TPC still did not reach its maximum level. Copyright © 2012 Society of Chemical Industry     

New genotypes of table olives: profile of bioactive compounds

New table olive genotypes (48) coming from a cross‐breeding programme were evaluated. Most of the fruit traits covered a wide range of variability on the set of genotypes, fruit weight (1.1–9.7 g), pulp‐to‐pit ratio (1.7–10.0), fruit shape (1.0–1.6) and oil content (1.3–15.2%). This is the first time that healthy compounds such as triterpenic acids and phenolic compounds have also been evaluated in olive progenies. Genotypes were stored for 2 months in sterilised brine (5% NaCl and 0.5% acetic acid). A high amount of maslinic (685.0–1394.2 mg kg^?1 olive flesh) and oleanolic acids (275.3–817.9 mg kg^?1 olive flesh) was found in the flesh of olives stored. The main oleosidic and phenolic compounds evaluated in brines were hydroxytyrosol (1.9–8.4 mmol L^?1), hydroxytyrosol glucosides (0.4–19.8 mmol L^?1), oleuropein (0.0–4.7 mmol L^?1) and the antimicrobial compounds, dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol (0.0–3.4 mmol L^?1) and decarboxymethyl elenolic acid (0.0–1.7 mmol L^?1), the latter two being observed in only ten genotypes. The wide range of variation observed for most compounds indicates that the contents of these healthy compounds may be used as selection criteria in table olive breeding programmes.     

How to prevent ripening blockage in 1-MCP-treated 'Conference' pears

BACKGROUND: Some European pear varieties treated with 1‐methylcyclopropene (1‐MCP) often remain ‘evergreen’, meaning that their ripening process is blocked and does not resume after removal from cold storage. In this work this was confirmed also to be the case in ‘Conference’ pears. To reverse the blockage of ripening 1‐MCP treatments combined with external exogenous ethylene were tested. RESULTS: 1‐MCP treatment of ‘Conference’ pears is very effective in delaying ripening and, more specifically, softening. The same 1‐MCP concentration in different experimental years caused a different response. The higher dose of 1‐MCP (600 nL L^?1) always resulted in irreversible blockage of ripening, whereas the behaviour of fruit receiving a lower dose (300 nL L^?1) depended on the year, and this did not depend on maturity at harvest or on storage conditions. Simultaneous exposure to 1‐MCP and exogenous ethylene significantly affected fruit ripening, allowing significant softening to occur but at a lower rate compared with control fruit. CONCLUSION: The application of exogenous ethylene and 1‐MCP simultaneously after harvest permitted restoration of the ripening process after storage in ‘Conference’ pears, extending the possibility of marketing and consumption. Copyright © 2011 Society of Chemical Industry     

Physiological changes, phenolic content and antioxidant activity of Salvia officinalis L. grown under saline conditions

BACKGROUND: Hydroponic culture was used to investigate the effect of NaCl concentrations on the growth, nutrient uptake, phenolic content and antioxidant activity of Salvia officinalis L. leaves. The antioxidant capacity of the methanolic extract of S. officinalis was evaluated by using 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging test and β‐carotene‐linoleic acid bleaching assay. Physiological and biochemical parameters of S. officinalis were assessed after 4 weeks of salt treatment with 0, 25, 50, 75 and 100 mmol L^?1 NaCl. RESULTS: Plant growth exhibited a reduction of 61% at 100 mmol L^?1 NaCl. Assessment of Na⁺, K⁺ and Ca²⁺ and water contents of shoots and roots showed that S. officinalis is able to regulate Na⁺ concentration by active compartmentation in vacuoles. Salvia officinalis phenolics were increased in response to salinity at the threshold of 75 mmol L^?1 NaCl. This herb was also found to be able to achieve important DPPH^? quenching activity and to inhibit the β‐carotene‐linoleic acid bleaching notably enhanced by salt treatment. It is interesting to highlight the correlation between the phenolic and antioxidant activity, suggesting the involvement of these compounds in this activity. CONCLUSION: Salvia officinalis treated with 75 mmol L^?1 NaCl constitutes a potential source for production of secondary metabolites useful in several applications. Copyright © 2011 Society of Chemical Industry     

Physical changes and physiological characteristics of red and green peel during nectarine (cv. Hu018) maturation

BACKGROUND: The aim of this study was to determine physical changes in nectarine and distinctive physiological characteristics related to red and green peel under stresses occurring during fruit maturation, information on which is currently not available. RESULTS: Fruit firmness increased from 4 to 6 weeks after blooming (WAB) then decreased from 6 WAB until ripening. Anthocyanins in red and green peel during nectarine maturation were identified by high‐performance liquid chromatography as cyanidin 3‐glucoside together and, at a much lower level, cyanidin 3‐rutinoside. Cyanidins in red and green peel decreased from 4 to 8 WAB then increased from 8 to 12 WAB. Anthocyanin contents were positively correlated with PAL, POD, A*, MDA and O$_{2}^{\bullet-}$ values and inversely correlated with L* and B* values. Red and green peel during maturation could be separated by hierarchical cluster analysis of the tested data. CONCLUSION: This study has provided an overview of red and green peel characteristics during nectarine (cv. Hu018) maturation. Values of A*, anthocyanins, O$_{2}^{\bullet-}$ , MDA, PAL, PPO and POD in red peel were higher than those in green peel, while values of L*, B* and chroma in red peel were lower than those in green peel throughout fruit maturation. Copyright © 2011 Society of Chemical Industry     

Enhanced preservation effects of sugar apple fruits by salicylic acid treatment during post‐harvest storage

BACKGROUND: Salicylic acid (SA) is recognised as an endogenous signal, mediating in plant defense and against pathogens. It has been reported that SA treatment can reduce decay and extend storage life of various fruit, such as bananas, peaches and apples. RESULTS: Physiological and biochemical responses in harvested sugar apple fruit (Annona squamosa L.) to SA at 0.4, 0.8 and 1.2 mmol L^?1 were investigated during post‐harvest storage. Results indicated that SA treatments lowered respiration, increased activities of antioxidant enzymes of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), decreased lipoxygenase (LOX) activity and correspondingly lowered Malondialdehyde (MDA) contents in treated fruits was observed as compared to the control. Moreover, production of superoxide free radical (O₂^{?, ?}) and ethylene was significantly decreased in the treated fruits. Total soluble solids, total soluble sugar, softness and decay rate were significantly lowered in treated fruits, and in turn a delay in the fruits ripening process was achieved after 10 days of storage. CONCLUSION: SA has positive effects in maintaining membrane integrity and in delaying fruit ripening process, which results in improved storability of sugar apple. Copyright © 2008 Society of Chemical Industry     

Screening of phenylalanine ammonia lyase in plant tissues,and retention of activity during dehydration

BACKGROUND: Oral therapy with phenylalanine ammonia lyase (PAL), naturally encapsulated in plant cells, may provide a potential alternative treatment for hyperphenylalaninemic patients, including those with phenylketonuria. Therefore different sources of plant tissue were investigated for PAL activity. RESULTS: Enzyme activity was highest in grain seedlings, with maximal enzyme activity in 7‐day‐old red spring wheat (Triticum aestivum L.) seedlings. The PAL activities of leaves and roots/endosperm of wheat seedlings were 11.90 ± 2.64 and 6.48 ± 1.59 µmol h^?1 g^?1 dry weight respectively. Three PAL‐related polypeptides with molecular weights of 74, 83 and 103 kDa were identified in wheat seedling leaf tissues, while only the 74 kDa polypeptide was detected in root/endosperm tissues. Dehydration was investigated as a method of concentrating PAL in wheat seedlings. Freeze‐drying was found to retain the most PAL activity (>90% recovery on a dry weight basis) compared with air drying and vacuum microwave drying for both leaf and root/endosperm samples. CONCLUSION: This study has led to a better understanding of PAL activity and stability in plant tissues and provides the basis for developing a natural plant preparation as a dietary supplement for the treatment of hyperphenylalaninemia. Copyright © 2007 Society of Chemical Industry     

Role of polyphenol oxidase and peroxidase in shaping the phenolic profile of virgin olive oil

The main objective of this study was to assess the ability of polyphenol oxidase (PPO) and peroxidase (POX) enzymatic activities present in olive fruit tissues to oxidize main phenolic compounds related to the process to obtain virgin olive oil (VOO) in order to ascertain their involvement in shaping the phenolic profile of this product. In the two olive cultivars under study, Arbequina and Picual, olive PPO activity was found to be largely present in the fruit mesocarp whereas most olive POX activity is in the seed. Moreover, both enzymatic activities display relatively constant values after the onset of fruit ripening when the fruit is harvested for VOO production. Results showed that both PPO and POX activities present in olive fruit at ripening stages are able to oxidize main phenolic glycosides present in the fruit as well as those phenolic compounds arising during the industrial process to obtain the oil, especially secoiridoid compounds derived from oleuropein that mainly determine VOO nutritional and sensorial properties. Experimental data suggest a key role for endogenous olive PPO and POX enzymatic activities in determining the phenolic profile of VOO.     

Effect of nitrogen fertilization on quality markers of strawberry (Fragaria × ananassa Duch. cv. Aromas)

BACKGROUND: Nitrogen is an indispensable element for fruit metabolism and low or excessive N levels can affect the accumulation of the most important components that contribute to the flavour and aroma of the fruit. Among them, sugars, acids and volatile compounds can be considered quality markers. The objective of this study was to evaluate the effect of N fertilization on these quality markers of the fruit at two harvest dates. RESULTS: Strawberry plants were grown in a hydroponic system and N was applied as Ca(NO₃)₂ at concentrations of 0.3, 3 and 6 mmol L^?1 in the nutrient solution. Total soluble solids, soluble carbohydrates, amino acids and organic acids and volatile compounds of the fruit were analyzed. The fruits produced at 3 and 6 mmol L^?1 N had higher contents of esters, soluble carbohydrates and amino acids. The hexanal content increased with the 6 mmol L^?1 dose. The effect of fertilization was more marked at the second harvest date. CONCLUSION: The availability of N in strawberry plants affected the accumulation of quality markers. The fruits expected to have the best flavour and aroma, with both high levels of soluble carbohydrate and esters and low levels of hexanal, were obtained with 3 mmol L^?1 nitrate in the solution. Copyright © 2009 Society of Chemical Industry     

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. Copyright © 2010 Society of Chemical Industry