α-Tocopherol in chloroplasts: Nothing more than an antioxidant?

Vitamin E, total antioxidant capacity and potassium in tomatoes: A triangle of quality traits on the rise

The quality of tomatoes is closely linked to their antioxidant content. However, the contribution of vitamin E to the total antioxidant capacity of these fruits remains unknown, along with its relationship with other components that benefit health. This study examined vitamin E content and composition and their correlation with the total antioxidant capacity in commercial tomato varieties, together with their modulation by abiotic stresses. We also assessed their relationship with other quality parameters such as total soluble sugars, titratable acidity, and sodium and potassium contents. A significant correlation was found between vitamin E content and the total antioxidant capacity, which was greatly influenced by the variety and abiotic stress. Furthermore, a strong association was found between vitamin E and potassium contents. We conclude that vitamin E, the total antioxidant capacity and potassium form a triangle of traits that can be coordinately selected to improve tomato quality.

Phytochemical Characterization and Antioxidant Activity of Cajanus cajan Leaf Extracts for Nutraceutical Applications

Cajanus cajan (guandú) is a widely cultivated leguminous plant in Panama; however, its phytochemical composition remains underexplored. Traditionally used in Asia and Africa for its medicinal properties, the plant's bioactive compounds responsible for these benefits have not been fully identified. The phytochemical profile and antioxidant capacity of C. cajan leaf extracts from Panama were characterized, highlighting their potential applications. Ethanolic extracts obtained via ultrasonication were analyzed through phytochemical screening, confirming the presence of alkaloids, tannins, saponins, and steroids. Spectrophotometric analysis revealed high total phenolic (71 mg g-1) and flavonoid (30 mg g-1) contents. Antioxidant assays demonstrated significant 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS+) inhibition and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. Gas chromatography-mass spectrometry (GC-MS) analysis identified 35 bioactive compounds in C. cajan leaves for the first time, including lupeol (antimicrobial and antitumor), lupenone (antidiabetic), squalene (antitumor and antioxidant), tocopherol (antioxidant), and β-amyrin (antibacterial and anti-Alzheimer's). These findings expand the known phytochemical profile of C. cajan, supporting its pharmaceutical, nutraceutical, and agro-industrial potential. Moreover, this research provides a foundation for further studies on the plant's bioactive compounds and their applications in human health and sustainable agriculture.

Tocopherol and tocotrienol profile in wild St. John's wort populations in Latvia: impact of the plant's aerial parts

St. John's wort, scientifically known as Hypericum perforatum L., is a medicinal plant with a wide range of secondary metabolites with bioactive properties; however, it has poorly studied lipophilic phytochemicals. Two primary tocochromanols - α-tocopherol (α-T) and δ-tocotrienol (δ-T3) were identified in the aerial parts of wild St. John's wort in Latvia. In the stems and leaves, α-T dominated (62-81%), while δ-T3 - in the flower buds, flowers, dead petals, and immature seed pods (36-70%). The flower buds had the highest content of tocotrienols (42.17-69.65 mg/100 g dw), of which δ-T3 accounted for 36% and α-T3 - for 18% of the total identified tocochromanols. The unripe seed pods exhibited the highest concentration of δ-T3 among all samples tested (38.2-52.7 mg/100 dw). St. John's wort can be considered a natural source of δ-T3 in regions with temperate climates based on the findings of this study.

Cultivated St. John's Wort Flower Heads Accumulate Tocotrienols over Tocopherols, Regardless of the Year of the Plant

St. John's wort (Hypericum perforatum L.) has been extensively utilized across various traditional medicinal systems, including ancient Greek medicine, traditional Chinese medicine, and Islamic medicine. H. perforatum is a well-known medicinal plant due to the presence of hypericin and hyperforin, which are natural antidepressants. Recent studies indicate that the inflorescences of wild H. perforatum are a source of rare tocotrienols, primarily δ-T3. Similar studies are lacking for cultivated species. H. perforatum was grown for three years. At full bloom each year, the plant was cut and separated into its parts: stems, leaves, flower buds, and flowers. Tocotrienols (T3s) were present in each part of the H. perforatum. The lowest concentration of tocotrienols was recorded in stems and the highest in flower buds (1.7-4.2 and 88.2-104.7 mg/100 g dry weight, respectively). Flower buds and flowers were the main source of α-T3 and δ-T3 tocotrienols. The plant part has a significant impact on the tocochromanol profile and concentration, while the year of harvest/plant aging does not. The present study demonstrates that cultivated H. perforatum flower heads are the first known flowers with relatively high concentrations of tocotrienols. St. John's wort flower buds accumulate tocotrienols over tocopherols, regardless of the year of the plant.

Molecular characterization of homogentisate phytyltransferase and methylphytylbenzoquinol methyltransferase genes from olive fruit with regard to the tocopherol content and the response to abiotic stresses

Two cDNA sequences, named OepHPT and OepMPBQ MT, encoding homogentisate phytyltransferase (HPT) and methylphytylbenzoquinol methyltransferase (MPBQ MT), respectively, have been cloned from olive (Olea europaea cv. Picual). Sequence analysis displayed the distinguishing characteristics typical of the HPT and MPBQ MT families and along with phylogenetic analysis indicated that they code for homogentisate phytyltransferase and methylphytylbenzoquinol methyltransferase enzymes, respectively. Transcriptional analysis in distinct olive tissues indicated that expression levels of HPT and MPBQ MT genes are spatially and temporally regulated in a cultivar-dependent manner and together with tocopherol analysis pointed out that both genes participate in the biosynthesis of the tocopherols present in olive mesocarp. These data also suggest that in olive mesocarp, HPT but not MPBQ MT could be implicated in the transcriptional regulation of the tocopherol biosynthetic pathway. In addition, HPT and MPBQ MT transcript levels are regulated by water status, temperature, light, and wounding in the olive fruit mesocarp, suggesting that both genes could be implicated in the abiotic stress response. Overall, this research constitutes a significant advance to elucidate the factors that regulate the tocopherol biosynthesis in olive fruit to obtain virgin olive oils with enhanced α-tocopherol content.

Tocotrienols in Different Parts of Wild Hypericum perforatum L. Populations in Poland

St. John's wort (Hypericum perforatum L.) is a well-known medicinal plant widely used in phytotherapy due to its abundant secondary metabolites with bioactive properties. Research on tocochromanols conducted in nine populations of St. John's wort using reverse-phase high performance liquid chromatography with fluorescent light detector (RP-HPLC-FLD) has provided new insights into their diverse composition in different aerial parts of the plant. Flower buds displayed the most diverse tocochromanol profile, while stems contained the lowest levels of these compounds. In most of the examined tissues, δ-T3 was the predominant tocochromanol (34-69%), except in leaves, where α-T dominated. The highest concentration of total tocotrienols was recorded in flower buds (48.5-74.1 mg/100 g dry weight), with δ-T3 (56%) and α-T3 (38%) as the dominant compounds. The highest δ-T3 content was found in unripe seed pods (29.6-45.1 mg/100 g dw). Principal Component Analysis (PCA) revealed distinct differences in tocochromanol composition among the aerial parts of H. perforatum. The findings highlight that H. perforatum has higher potential applications in the food, pharmaceutical, and medical industries than previously assumed, due to its relatively high content of tocotrienols, mainly δ-T3, in different plant organs.

Fertigation with alpha-tocopherol enhances morphological, physiological, and antioxidant responses in radish (Raphanus sativus L.) under drought stress

Water scarcity is a foremost environmental concern and is expected to hasten in the forthcoming years due to severe fluctuations in weather patterns worldwide. The present work was designed to explore the potential role of alpha-tocopherol (α-Toc), a form of vitamin E, on the morphological, physio-biochemical, and cellular antioxidant responses of two radish genotypes grown under drought conditions (38 ± 3% of field capacity). The individual and combined applications of α-Toc (100 ppm) were used as T0- Control, T1- Control + TF (TF-alpha-tocopherol), T2- Drought (D), and T3- D + TF with three replications. In general, drought conditions cause a marked reduction in, growth traits such as root length (RL), shoot dry weight (SDW), and shoot fresh weight (SFW). However, the sole and combined applications of α-Toc significantly enhanced the SDW, SFW, and RL in both radish genotypes. Drought stress causes a significant upsurge in hydrogen peroxide (H2O2) and lipid peroxidation (LPX) in leaves. At the same time, exogenous fertigation of α-Toc protects the membranes by reducing the level of LPX, enhancing antioxidants such as catalase (CAT) and peroxidase (POX) to scavenge the reactive oxygen species (ROS), and enhancing the osmolyte as total soluble proteins to maintain cell internal osmotic potential. Also, the α-Toc enhanced the photosynthetic pigments and significantly increased photosynthetic activity in the Early Milo (G2) as compared to Laal Pari (G1) genotype under drought, enhancing water use efficiency by maintaining transpiration rate and stomatal conductance. The α-Toc also regulates the beneficial inorganic ions (K+, Ca2+, and PO₄³⁻) in the shoots of both genotypes. Our present findings demonstrate the potential role of α-Toc in mitigating drought stress and infer that it can enhance plant growth under drought conditions.

The use of vitamin E in ocular health: Bridging omics approaches with Tocopherol and Tocotrienol in the management of glaucoma

Vitamin E, encompassing tocopherols and tocotrienols is celebrated for its powerful antioxidant properties, which help neutralize free radicals and protect cells from oxidative damage. Over the years, research has shown that both tocopherols and tocotrienols offer significant benefits, including protection against radiation damage, cholesterol regulation, cardiovascular health, and neurological disorders. This wide range of benefits highlights the need for further exploration of vitamin E's role in managing various diseases. One particularly promising area is its potential application in treating ocular diseases like glaucoma. Despite advances in treatment, current options have limitations, making the investigation of alternative approaches crucial. Omics technologies, which allow for a detailed examination of biological systems, could provide valuable insights into how tocopherols and tocotrienols work at a molecular level. Their neuroprotective and antioxidative properties make them promising candidates for glaucoma management. Additionally, the sustainability of vitamin E is noteworthy, as by-products from its production can be repurposed into valuable resources for nutraceuticals and pharmaceuticals. As research continues, integrating omics technologies with the study of vitamin E derivatives could unveil new therapeutic possibilities, further enhancing our understanding of its diverse health benefits and its potential role in preventing and managing diseases.

Metabolomic profiles of stony coral species from the Dry Tortugas National Park display inter- and intraspecies variation

Coral reefs are experiencing unprecedented loss in coral cover due to increased incidence of disease and bleaching events. Thus, understanding mechanisms of disease susceptibility and resilience, which vary by species, is important. In this regard, untargeted metabolomics serves as an important hypothesis-building tool enabling the delineation of molecular factors underlying disease susceptibility or resilience. In this study, we characterize metabolomes of four species of visually healthy stony corals, including Meandrina meandrites, Orbicella faveolata, Colpophyllia natans, and Montastraea cavernosa, collected at least a year before stony coral tissue loss disease reached the Dry Tortugas, Florida, and demonstrate that both symbiont and host-derived biochemical pathways vary by species. Metabolomes of Meandrina meandrites displayed minimal intraspecies variability and the highest biological activity against coral pathogens when compared to other species in this study. The application of advanced metabolite annotation methods enabled the delineation of several pathways underlying interspecies variability. Specifically, endosymbiont-derived vitamin E family compounds, betaine lipids, and host-derived acylcarnitines were among the top predictors of interspecies variability. Since several metabolite features that contributed to inter- and intraspecies variation are synthesized by the endosymbiotic Symbiodiniaceae, which could be a major source of these compounds in corals, our data will guide further investigations into these Symbiodiniaceae-derived pathways.

IMPORTANCE

Previous research profiling gene expression, proteins, and metabolites produced during thermal stress have reported the importance of endosymbiont-derived pathways in coral bleaching resistance. However, our understanding of interspecies variation in these pathways among healthy corals and their role in diseases is limited. We surveyed the metabolomes of four species of healthy corals with differing susceptibilities to the devastating stony coral tissue loss disease and applied advanced annotation approaches in untargeted metabolomics to determine the interspecies variation in host and endosymbiont-derived pathways. Using this approach, we propose the survey of immune markers such as vitamin E family compounds, acylcarnitines, and other metabolites to infer their role in resilience to coral diseases. As time-resolved multi-omics datasets are generated for disease-impacted corals, our approach and findings will be valuable in providing insight into the mechanisms of disease resistance.

Interactive effects of Orobanche latisquama parasitism and drought stress in Salvia rosmarinus plants growing under Mediterranean field conditions

Mediterranean-type ecosystems are recognized as critical hotspots for both biodiversity and climate change. Within these environments, plants often interact with diverse species, including holoparasitic plants, while simultaneously facing increasing episodes of precipitation shortages and rising temperatures. Here, we investigated the impact of Orobanche latisquama Reut. ex Boiss infestation on the Mediterranean shrub Salvia rosmarinus (L.) Spenn (rosemary) across three populations along an altitudinal gradient, focusing on its effects on host tolerance and resilience to severe summer drought in its natural habitat. Results showed no major physiological impact of the parasite on the host during spring but revealed an enhanced photo- and antioxidant-protective response during the summer drought in rosemary plants infested with O. latisquama. Infested plants showed elevated contents of α-tocopherol and a shift in the ascorbate ratio towards its oxidized state during the summer, particularly in upper and sun-exposed leaves. This was accompanied by elevated malondialdehyde content, indicating enhanced lipid peroxidation. However, despite the heightened photo-oxidative stress observed in leaves from infested plants, no damage to photosystem II was observed, indicating a good tolerance of rosemary to the interaction between parasitism and drought. By autumn, all plants displayed similar recovery patterns, and the differences between infested and non-infested plants disappeared, thus indicating a high resilience to the combination of these biotic and abiotic stresses. Overall, these findings underscore the great adaptive mechanisms S. rosmarinus plants have evolved to endure severe summer drought, even when challenged by holoparasitic plant infestation, and provide new insights into plant-parasite interactions in Mediterranean-type ecosystems.

Rapid Analysis for α-Tocopherol and Its Oxidative Products in the Pisum sativum L. Leaf Using Supercritical Fluid Chromatography-Medium Vacuum Chemical Ionization Tandem Mass Spectrometry

A method for the rapid determination of α-tocopherol (α-T) and its oxidative products in plant tissue has been developed using supercritical fluid extraction (SFE) coupled with supercritical fluid chromatography (SFC) and medium vacuum chemical ionization (MVCI) with tandem mass spectrometry. The method is designed to study changes in levels for α-T and its oxidative products in plant cells during photosynthesis, aiming to observe the light response curves. α-T oxidation is a non-enzymatic self-defense mechanism in plant cells. Unlike enzyme-involved reactions, it cannot be stopped, so the oxidation continues in crude extracts even after extraction. Therefore, a real-time in-situ method is essential for tracking the light response curves. To optimize the selective reaction monitoring method, the reaction mixture of α-T and singlet oxygen (1O2), generated by rose Bengal under light illumination, was used as the source of oxidative products. The relative abundance changes in α-tocopherylquinone and 8a-hydroperoxy tocopherone in Pisum sativum L. (Pea) leaves under excessive light illumination have been preliminarily analyzed as part of the light response curve study. The method archives a throughput of 10-15 minutes for analyzing duplicate leaf samples. This process includes cutting off the leaf, sectioning it, placing the sample in a frozen SFE vessel, and conducting SFE/SFC analysis. Consequently, the average throughput is approximately 5-7 minutes per sample.

Antioxidant Activity of Planar Catechin Conjugated with Trolox

Planar catechin (PCat), a natural antioxidant with a fixed 3D catechin structure on a plane, exhibits radical-scavenging activity approximately five times stronger than the conventional catechin. We synthesized a compound, PCat-TrOH, by binding Trolox (TrOH), an α-tocopherol analog, to PCat to enhance its antioxidant effect against oxidative stress, such as lipid peroxidation. TrOH shows radical-scavenging activity about 6.5 times greater than PCat, and PCat-TrOH exhibited a similar level of radical-scavenging activity to TrOH. Additionally, PCat-TrOH demonstrated twice the radical-scavenging activity against reactive oxygen species compared to PCat or TrOH. This compound is also expected to exhibit an excellent antioxidant effect against lipid peroxidation caused by radical chain reactions, through interactions with vitamin C, similar to that in the case of α-tocopherol.

Effects of the Salt Stress Duration and Intensity on Developmental and Physiological Features of the Moss Polytrichum formosum

The two accessions of the polytrichaceous moss species Polytrichum formosum, namely German and Serbian genotypes, were subjected to salt stress, aiming to study the species' developmental and physiological features. Various concentrations of sodium chloride were applied to an axenic in vitro culture of the two moss genotypes, and the growth parameters as well as physiological feature changes were followed. As inferred by the morpho-developmental parameters and survival index, the Serbian genotype showed higher resistance to salt stress as compared to the German one. However, both moss genotypes survived the highest applied concentration (500 mM). As expected, short exposures to salt were rather easily overcome. No clear patterns in sugar content and changes were observed during the stress, but they are surely included in salt stress response and tolerance in P. formosum. Longer stress increased total chlorophyll content in both genotypes. In short-term applied salt stress, the Serbian genotype had a higher total chlorophyll concentration to control unstressed plants, while the German genotype decreased the total amount of chlorophyll. Similarly, carotenoids were shown to be significantly higher in the Serbian genotype, both in unstressed and treated plants, compared to the German one. The contents of tocopherols were higher in the Serbian genotype in controlled unstressed and subsequently short- and long-stressed plantlets compared to the German accession. In general, we can assume that P. formosum is unexpectedly tolerant to salt stress and that there are differences within various accessions of overall European populations, as referred by two randomly selected genotypes, which is most probably a consequence of different genetic structure.

Both external and internal factors induce heterogeneity in senescing leaves of deciduous trees

Autumn senescence is characterised by spatial and temporal heterogeneity. We show that senescing birch (Betula spp.) leaves had lower PSII activity (probed by the F V /F M chlorophyll a fluorescence parameter) in late autumn than in early autumn. We confirmed that PSII repair slows down with decreasing temperature, while rates of photodamage and recovery, measured under laboratory conditions at 20°C, were similar in these leaves. We propose that low temperatures during late autumn hinder repair and lead to accumulation of non-functional PSII units in senescing leaves. Fluorescence imaging of birch revealed that chlorophyll preferentially disappeared from inter-veinal leaf areas. These areas showed no recovery capacity and low non-photochemical quenching while green veinal areas of senescing leaves resembled green leaves. However, green and yellow leaf areas showed similar values of photochemical quenching. Analyses of thylakoids isolated from maple (Acer platanoides ) leaves showed that red, senescing leaves contained high amounts of carotenoids and α-tocopherol, and our calculations suggest that α-tocopherol was synthesised during autumn. Thylakoids isolated from red maple leaves produced little singlet oxygen, probably due to the high antioxidant content. However, the rate of PSII photodamage did not decrease. The data show that the heterogeneity of senescing leaves must be taken into account to fully understand autumn senescence.

Untangling the role of leaf age specific osmoprotectant and antioxidant responses of two poplar clones under increasing ozone concentrations

Plants possess different degrees of tolerance to abiotic stress, which can mitigate the detrimental effect of environmental inputs affecting carbon balance. Less is known about the functions of osmoprotectants in scavenging of reactive oxygen species (ROS), generated at different sites depending on leaf age. This study aimed to clarify the osmotic adjustments adopted by old and young leaves of Oxford and I-214 poplar clones [differing in ozone (O3) sensitivity] to cope with three levels of O3 [ambient (AA), and two elevated O3 levels]. In both clones, the impact of intermediate O3 concentrations (1.5 × AA) on ROS production appeared to be leaf age-specific, given the accumulation of hydrogen peroxide (H2O2) observed only in old leaves of the Oxford plants and in young leaves of the I-214 ones (2- fold higher than AA and +79%, respectively). The induction of an oxidative burst was associated with membrane injury, indicating an inadequate response of the antioxidative systems [decrease of lutein and β-carotene (-37 and -85% in the old leaves of the Oxford plants), accumulation of proline and tocopherols (+60 and +12% in the young leaves of the I-214 ones)]. Intermediate O3 concentrations reacted with unsaturated lipids of the plasma membrane in old and young leaves of the Oxford plants, leading to an increase of malondialdehyde by-products (more than 2- fold higher than AA), while no effect was recorded for I-214. The impact of the highest O3 concentrations (2.0 × AA) on ROS production did not appear clone-specific, which may react with cell wall components by leading to oxidative pressure. Outcomes demonstrated the ability of young leaves of I-214 plants in contain O3 phytotoxic effects.

Hydrogen sulfide priming enhanced salinity tolerance in sunflower by modulating ion hemostasis, cellular redox balance, and gene expression

BACKGROUND

The salinity threat represents an environmental challenge that drastically affects plant growth and yield. Besides salinity stress, the escalating world population will greatly influence the world's food security in the future. Therefore, searching for effective strategies to improve crop salinity resilience and sustain agricultural productivity under high salinity is a must. Seed priming is a reliable, simple, low-risk, and low-cost technique. Therefore, this work aimed to evaluate the impact of seed priming with 0.5 mM NaHS, as a donor of H2S, in mitigating salinity effects on sunflower seedlings. Primed and nonprime seeds were established in nonsaline soil irrigated with tape water for 14 d, and then exposed to 150 mM NaCl for 7 d.

RESULTS

Salinity stress significantly reduced the seedling growth, biomass accumulation, K+, Ca2+, and salinity tolerance index while elevating Na+ uptake and translocation. Salinity-induced adverse effects were significantly alleviated by H2S priming. Upregulation in gene expression (HaSOS2, HaGST) under NaCl stress was further enhanced by H2S priming. Also, H2S reduced lipid peroxidation, electrolyte leakage, and H2O2 content, but elevated the antioxidant defense system. NaCl-induced levels of ascorbate, glutathione, and α tocopherol, as well as the activities of AsA-GSH cycle enzymes: ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and glutathione S-transferase, were further enhanced by H2S priming. Increased level of H2S and total thiol by NaCl was also further stimulated by H2S priming.

CONCLUSION

H2S priming has proved to be an efficient strategy to improve sunflower seedlings' salinity tolerance by retaining ion homeostasis, detoxifying oxidative damage, modulating gene expression involved in ion homeostasis and ROS scavenging, and boosting endogenous H2S. These findings suggested that H2S acts as a regulatory molecule activating the functional processes responsible for sunflower adaptive mechanisms and could be adopted as a crucial crop management strategy to combat saline conditions. However, it would be of great interest to conduct further studies in the natural saline field to broaden our understanding of crop adaptive mechanisms and to support our claims.

Acclimation to a combination of water deficit and nutrient deprivation through simultaneous increases in abscisic acid and bioactive jasmonates in the succulent plant Sempervivum tectorum L

Activation of hormonal responses defines the drought acclimation ability of plants and may condition their survival. However, aside ABA, little is known about the possible contribution of other phytohormones, such as jasmonates and salicylates, in the response of CAM plants to water deficit. Here, we aimed to study the physiological mechanisms underlying the stress tolerance of house leek (Sempervivum tectorum L.), a CAM plant adapted to survive harsh environments, to a combination of water deficit and nutrient deprivation. We exposed plants to the combination of these two abiotic stresses by withholding nutrient solution for 10 weeks and monitored their physiological response every two weeks by measuring various stress makers together with the accumulation of stress-related phytohormones and photoprotective molecules, such as tocopherols (vitamin E). Results showed that ABA content increased by 4.2-fold after four weeks of water deficit to keep later constant up to 10 weeks of stress, variations that occurred concomitantly with reductions in the relative leaf water content, which decreased by up to 20% only. The bioactive jasmonate, jasmonoyl-isoleucine was the other stress-related phytohormone that simultaneously increased under stress together with ABA. While contents of salicylic acid and the jasmonoyl-isoleucine precursors, 12-oxo-phytodienoic acid and jasmonic acid decreased with water deficit, those of jasmonoyl-isoleucine increased 3.6-fold at four weeks of stress. The contents of ABA and jasmonoyl-isoleucine correlated positively between them and with the content of α-tocopherol per unit of chlorophyll, thus suggesting a photoprotective activation role. It is concluded that S. tectorum not only withstands a combination of water deficit and nutrient deprivation for 10 weeks without any symptom of damage but also activates effective defense strategies through the simultaneous accumulation of ABA and the bioactive jasmonate form, jasmonoyl-isoleucine.