Levels Of Tyrosol Research Articles

Improving the Biostability of Extra Virgin Olive Oil with Olive Fruit Extract During Prolonged Deep Frying

This study explores approaches to enhancing the biostability of extra virgin olive oil (EVOO) supplemented with olive fruit extract (OFE) enriched with hydroxytyrosol (HTyr). The investigation focuses on prolonged deep frying (DF) conditions at 170 °C and 210 °C, over durations ranging from 3 to 48 h, with the aim of improving sensorial attributes, polyphenolic content, and thermal oxidative stability. Parameters, such as acidity, peroxide value (PV), K232, K270, ΔK, phenolic compounds, and sensory attributes, were monitored. The PV did not exceed the standard limit in HTyr-EVOO at 210 °C/24 h; however, in non-supplemented EVOOs, it remained within the limits only up to 210 °C/18 h. Acidity stayed within the acceptable limit (≤0.8) at 170 °C/24 h in both enriched and non-enriched EVOOs. K232 values were ≤2.5 in HTyr-EVOO fried at 170 °C/18 h. K270 and ΔK did not exceed the limits in HTyr-EVOO at 170 °C/3 h, whereas they surpassed them in non-supplemented oils. Additionally, HTyr and tyrosol levels were significantly higher (p < 0.05) in HTyr-EVOOs. Phenolic compounds, including verbascoside, pinoresinol, 1-acetoxypinoresinol, and phenolic acids, such as chlorogenic, vanillic, homovanillic, 4-dihydroxybenzoic, and caffeic acids, were detected in HTyr-EVOOs. Oxidized secoiridoid derivatives increased significantly as DF progressed. Moreover, sensory analysis revealed that positive attributes in EVOOs—such as fruity, bitter, and pungent notes—decreased significantly with increasing temperature and frying duration (p < 0.05). Beyond 210 °C/6 h, these attributes were rated at zero. However, HTyr-EVOOs exhibited lower rancidity compared to non-enriched oils under identical conditions, attributed to the protective effect of HTyr. In conclusion, HTyr-EVOOs demonstrated thermal stability up to 210 °C/6 h, retaining desirable sensory qualities, higher phenolic content, and reduced degradation. These findings indicate that natural OFEs have strong potential as food additive in deep fried EVOOs, enhancing sensory properties, health benefits, and overall oil stability. This innovation provides a practical solution for the food industry by improving the biostability and versatility of EVOO. Further research is recommended to investigate various EVOO categories and oils from diverse origins.

New monoterpenes and benzylbutanoic acid from snowbell (Styrax japonica) honey and their quantitative analysis by LC-ESI-Q-TOF-MS/MS

• Twelve compounds were isolated from the snowbell ( Styrax japonica ) honey (SH) • Among them, three compounds were new compounds. • Two known compounds were identified for the first time in SH and other honeys. • The content of 3 compounds were lower in SH on storage for 5 years than in fresh SH. • The 3 compounds may be useful as markers for predicting the storage period of SH. Honey varies depending on plant origin and environmental conditions. Chemical constituents can be used to determine the origins, characteristics, and storage period of a specific honey. Styrax japonica (snowbell) honey has excellent flavor, but very few studies have been carried out on its chemical constituents. Therefore, the present study was aimed to identify chemical constituents containing in snowbell honey and to screen candidate marker compounds for predicting the storage period of snowbell honey using the identified compounds. Twelve compounds including three new compounds were purified and isolated from the snowbell honey. Three new compounds were elucidated as 1 α ,3 β ,5 β -bornetriol, 7-hydroxy-2,2,6-trimethyl-1-oxaspiro[2.5]oct-5-en-4-one, and 2-benzyl-2,3-dihydroxybutanoic acid, based on ESI-MS and NMR experiments. 6,7-Dihydroxylinalool and 6,7-dihydroxygeraniol isolated as known compounds in this study were identified for the first time in snowbell honey as well as in other honeys. The isolated compounds were qualified and quantified by LC-ESI-Q-TOF-MS/MS analysis. All compounds were detected in snowbell honeys of different production years. The levels of tyrosol, 7-hydroxy-2,2,6-trimethyl-1-oxaspiro[2.5]oct-5-en-4-one, and (–)-dihydroxyphaseic acid were lower in snowbell honey with long storage period than in short storage period, which is suggested to be used as candidate marker compounds for predicting the storage period of snowbell honey.

Evolution of physicochemical constitution and cultivar-differential maturity configuration in olive (Olea europaea L.) fruit

Analytical characterization of the ripening process is prerequisite to establishing cultivar-specific harvest maturity windows and safeguarding the quality of olive products. In this context, we profiled the ripening of select Cypriot olive (Olea europaea L.) cultivars ‘Ladoelia’, ‘Kato Drys’ and ‘Korakou’ juxtaposed against introduced ‘Koroneiki’. Fruit skin and flesh color-based maturity index (MI) evolved linearly over time but differentially among local cultivars. Anthocyanin content exhibited better correspondence to MI with progressive maturity. Cultivars varied widely in their sugar content (60.2–180.9 mg g−1 dw) and their fructose/glucose ratio, which impacted their relative sweetness. Putative connection of declining mannitol levels with oleogenesis during ripening was not supported by ‘Korakou’, wherein mannitol declined without concomitant oil accumulation. However, fruit firmness correlated negatively with oil content prompting harvest of table olives before oil peak. Succinic and oxalic acid levels may constitute valuable cultivar signature traits. Decline pattern in total phenolic content (TPC) during ripening was cultivar-specific, with oleuropein, rutin and hydroxytyrosol constituting the major constituents in diminishing abundance. No cultivar differences were observed in rutin content, while hydroxytyrosol and tyrosol levels were independent of maturity. At MI3, ‘Ladoelia’ had higher total phenolic content (TPC) than ‘Korakou’ and ‘Kato Drys’ but inferior to ‘Koroneiki’ (12.3, 9.9, 2.5 and 20.4 g kg-1 dw, respectively). Oleuropein relative content in ‘Ladoelia’ (85.6 %TPC) was higher than ‘Kato Drys’ (63.6 %TPC) and ‘Korakou’ (59.2 %TPC). ‘Ladoelia’ exhibited superior but maturity-dependent phenolic acids content. Our results corroborate a cultivar-specific application of MI supported by additional physicochemical parameters of maturity. The current findings may facilitate cultivar and product-specific integrative harvest maturity indices, which are especially critical for dual purpose large-fruited cultivars.

Effect of the Refining Process on Total Hydroxytyrosol, Tyrosol, and Tocopherol Contents of Olive Oil.

The impact of the olive oil refining process on major antioxidant compound levels was evaluated by means of UHPLC analysis of lampante olive oils collected at different stages of the refining procedure (degumming, chemical and physical flash neutralization, bleaching, and deodorization). For this purpose, the evolution of the tocopherol fraction was investigated by means of the UHPLC-FL method, while the influence of the refining process on the total hydrolyzed phenolic content was assessed by measuring hydroxytyrosol and tyrosol levels after acid hydrolysis of the phenolic extracts. Refining was found to have a marked effect on total hydroxytyrosol and tyrosol contents, as they are completely removed in the early steps of the refining procedure. In contrast, the variation trends of tocopherols are not always clear-cut, and significant decreases in content from 7% to 16% were only revealed during refining in four out of nine samples. In addition, five of the nine refined oils showed final tocopherol concentrations higher than 200 mg/kg, the limit imposed by international standards regarding the content of such compounds in commercial olive oils. This study supports the need for a revision of the International Olive Oil Council (IOC) standard relative to the limit established for tocopherol addition to refined oils to avoid possible legal and economic trade issues.

Generation of the Antioxidant Hydroxytyrosol from Tyrosol Present in Beer in a Randomized Clinical Trial (P06-003-19)

ObjectivesHydroxytyrosol (HT) has been associated to health beneficial effects of extra virgin olive oil. Red wine is an indirect source of HT as it contains its precursor tyrosol (TYR), which is endogenously converted into HT. Beer is another source of TYR, which is originated during the fermentation as a secondary a metabolite of the amino acid tyrosine. The present work shows the first clinical study aimed at assessing the endogenous formation of HT following beer consumption. MethodsCross-over randomized clinical trial in healthy volunteers administered 250 mL of a dark beer (3.5 mg of TYR and 17.0 g alcohol), 250 mL of a lager beer (2.3 mg of TYR and 9.0 g alcohol), 250 mL of a non-alcoholic beer (1.4 mg of TYR and 0 g alcohol), and finally 150 mL of red wine (3.7 mg of TYR and 16.8 g alcohol). Urinary recovery of TYR and HT metabolites was quantified by LC/MS-MS. ResultsResults confirm that TYR present in beer is absorbed and endogenously converted into HT after its consumption (Figure 1). Nevertheless, the highest recovery was observed after red wine. Dark beer administration, which TYR and alcohol doses were equal to red wine, presented lower levels of TYR absorbed and hence, lower levels of HT generated. Lager and non-alcoholic beer presented dose-response absorption of TYR, but not an HT generation. ConclusionsThe present study is the first demonstrating that TYR present in beer is absorbed and endogenously biotransformed into HT in humans. HT generation is not TYR and alcohol dose-dependent and, is globally lower than following red wine, suggesting that other factors such as gas or other phenols could interfere in TYR bioavailability. Interestingly, HT recoveries after non-alcoholic beer are similar to those observed after alcoholic ones, limiting alcohol intake and the health and social problems associated to alcohol abuse. These findings could be relevant to understand the health effects associated to beer consumption. Funding SourcesAB is recipient of a fellowship from ISCIII (PFIS), NS is recipient of a fellowship from Centro de Información Cerveza y Salud (Beca Manuel Oya) and CIBEROBN. Supporting Tables, Images and/or Graphs▪

Production of salidroside and tyrosol in cell suspension cultures of Rhodiola crenulata

Salidroside and its aglycone tyrosol are important compounds found in Rhodiola plants. In this study, callus derived from Rhodiola crenulata was induced and grown when explants were incubated on a Murashige and Skoog (MS) medium containing various concentrations of 6-benzyaldenine (BA), naphthalene acetic acid (NAA) and thidiazuron (TDZ). Callus was easily initiated from juvenile leaves in half strength MS medium supplemented with 0.5 mg/L BA and 3.0 mg/L NAA, while full strength MS containing 0.5 mg/L TDZ and 0.5 mg/L NAA was the best for callus subculture and subsequent cell suspension culture. The activities of l-phenylalanine ammonia lyase (PAL) and β-d-glucosidase, two key enzymes in salidroside synthesis, increased at first and subsequently decreased in cell suspension cultures. The salidroside and tyrosol levels in the cell suspension cultures were determined using high-performance liquid chromatography. High levels of salidroside and tyrosol were detected in cell suspension cultures of R. crenulata extracted with 75 % methanol, demonstrating that the biotechnological production of these compounds using plant cell suspension cultures derived from R. crenulata may be an attractive alternative to harvest-based production.

A tyrosine decarboxylase catalyzes the initial reaction of the salidroside biosynthesis pathway in Rhodiola sachalinensis

Salidroside, the 8-O-β-D-glucoside of tyrosol, is the main bioactive component of Rhodiola species and is found mainly in the plant roots. It is well known that glucosylation of tyrosol is the final step in the biosynthesis of salidroside; however, the biosynthetic pathway of tyrosol and its regulation are less well understood. A summary of the results of related studies revealed that the precursor of tyrosol might be tyramine, which is synthesized from tyrosine. In this study, a cDNA clone encoding tyrosine decarboxylase (TyrDC) was isolated from Rhodiola sachalinensis A. Bor using rapid amplification of cDNA ends. The resulting cDNA was designated RsTyrDC. RNA gel-blot analysis revealed that the predominant sites of expression in plants are the roots and high levels of transcripts are also found in callus tissue culture. Functional analysis revealed that tyrosine was best substrate of recombinant RsTyrDC. The over-expression of the sense-RsTyrDC resulted in a marked increase of tyrosol and salidroside content, but the levels of tyrosol and salidroside were 274 and 412%, respectively, lower in the antisense-RsTyrDC transformed lines than those in the controls. The data presented here provide in vitro and in vivo evidence that the RsTyrDC can regulate the tyrosol and salidroside biosynthesis, and the RsTyrDC is most likely to have an important function in the initial reaction of the salidroside biosynthesis pathway in R. sachalinensis.

Effects of overexpression of endogenous phenylalanine ammonia‐lyase (PALrs1) on accumulation of salidroside in Rhodiola sachalinensis

Salidroside, a novel effective adaptogenic drug extracted from the medicinal plant Rhodiola sachalinensis A. Bor, can be derived from phenylalanine or tyrosine. Due to the scarcity of R. sachalinensis and its low yield of salidroside, there is great interest in enhancing production of salidroside by the plant. In this study, a cDNA clone encoding phenylalanine ammonia-lyase (PAL) was isolated from R. sachalinensis using rapid amplification of cDNA ends. The resulting cDNA was designated PALrs1. It is 2407-bp long and encodes 710 deduced amino acid residues. Southern blot analysis of genomic DNA indicated that the PAL gene family is composed of three to five genes in the R. sachalinensis genome. Northern blot analysis revealed that transcripts of PALrs1 were present in calli, leaves and stems, but expression in roots was very low. The PALrs1 under the 35S promoter with double-enhancer sequences from CaMV-Omega and TMV-Omega fragments was transferred into R. sachalinensis via Agrobacterium tumefaciens. PCR and PCR-Southern blot confirmed that the PALrs1 gene had been integrated into the genome of transgenic plants. Northern blot analysis revealed that the PALrs1 gene had been expressed at the transcriptional level. High-performance liquid chromatography indicated that overexpression of the PALrs1 gene resulted in a 3.3-fold increase in p-coumaric acid content, as expected. In contrast, levels of tyrosol and salidroside were 4.7-fold and 7.7-fold, respectively, lower in PALrs1 transgenic plants than in controls. Furthermore, overexpression of the PALrs1 gene resulted in a 2.6-fold decrease in tyrosine content. These data suggest that overexpression of the PALrs1 gene and accumulation of p-coumaric acid did not facilitate tyrosol biosynthesis; tyrosol, as a phenylethanoid derivative, is not derived from phenylalanine; and reduced availability of tyrosine most likely resulted in a large reduction in tyrosol biosynthesis and accumulation of salidroside.

Modulation of the biosynthesis of some phenolic compounds in Olea europaea L. fruits: their influence on olive oil quality.

The phenolic composition of olive fruits (Olea europaea L.) (cv. Picual, Villalonga, Alfafarenca, and Cornicabra) grown in different areas of Spain was studied by high performance liquid chromatography-mass spectrometry. Different levels of tyrosol, catechin, p-coumaric acid, rutin, luteolin, and oleuropein were observed in the different varieties analyzed. Treating the fruit with 0.3% Brotomax 50 days after anthesis had a beneficial effect on fruit size, oil content, levels of polyphenolic compounds, and Trolox-equivalent antioxidant activity (TEAC) in all the varieties analyzed.