Leaf Age-Dependent Photosystem II Photochemistry and Oxidative Stress Responses to Drought Stress in Arabidopsis thaliana Are Modulated by Flavonoid Accumulation

We investigated flavonoid accumulation and lipid peroxidation in young leaves (YL) and mature leaves (ML) of Arabidopsis thaliana plants, whose watering stopped 24 h before sampling, characterized as onset of drought stress (OnDS), six days before sampling, characterized as mild drought stress (MiDS), and ten days before sampling, characterized as moderate drought stress (MoDS). The response to drought stress (DS) of photosystem II (PSII) photochemistry, in both leaf types, was evaluated by estimating the allocation of absorbed light to photochemistry (Φ_PSII), to heat dissipation by regulated non-photochemical energy loss (Φ_NPQ) and to non-regulated energy dissipated in PSII (Φ_NO). Young leaves were better protected at MoDS than ML leaves, by having higher concentration of flavonoids that promote acclimation of YL PSII photochemistry to MoDS, showing lower lipid peroxidation and excitation pressure (1 − q_p). Young leaves at MoDS possessed lower 1 − q_p values and lower excess excitation energy (EXC), not only compared to MoDS ML, but even to MiDS YL. They also possessed a higher capacity to maintain low Φ_NO, suggesting a lower singlet oxygen (¹O₂) generation. Our results highlight that leaves of different developmental stage may display different responses to DS, due to differential accumulation of metabolites, and imply that PSII photochemistry in Arabidopsis thaliana may not show a dose dependent DS response.     

Drought Stress Effects on Growth,ROS Markers,Compatible Solutes,Phenolics, Flavonoids,and Antioxidant Activity in <Emphasis Type="Italic">Amaranthus tricolor</Emphasis>

Four selected Amaranthus tricolor cultivars were grown under four irrigation regimes (25, 50, 80, and 100% field capacity) to evaluate the mechanisms of growth and physiological and biochemical responses against drought stress in randomized complete block design with three replications. Drought stress led to decrease in total biomass, specific leaf area, relative water content (RWC), photosynthetic pigments (chlorophyll a, chlorophyll b, chlorophyll ab), and soluble protein and increase in MDA, H₂O₂, EL, proline, total carotenoid, ascorbic acid, polyphenols, flavonoids, and antioxidant activity. However, responses of these parameters were differential in respect to cultivars and the degree of drought stresses. No significant difference was observed in control and LDS for most of the traits. The cultivars VA14 and VA16 were identified as more tolerant to drought and could be used for further evaluations in future breeding programs and new cultivar release programs. Positively significant correlations among MDA, H₂O₂, compatible solutes, and non-enzymatic antioxidant (proline, TPC, TFC, and TAC) suggested that compatible solutes and non-enzymatic antioxidant played vital role in detoxifying of ROS in A. tricolor cultivar. The increased content of ascorbic acid indicated the crucial role of the ASC–GSH cycle for scavenging ROS in A. tricolor.     

Characterization,Large-Scale HSCCC Separation and Neuroprotective Effects of Polyphenols from Moringa oleifera Leaves

Moringa oleifera leaves have been widely used for the treatment of inflammation, diabetes, high blood pressure, and other diseases, due to being rich in polyphenols. The main objective of this work was to largely separate the main polyphenols from Moringa oleifera leaves using the technique of high-speed counter-current chromatography (HSCCC). The phenolic composition in Moringa oleifera leaves was first analyzed qualitatively and quantitatively by UPLC-Q-Exactive Orbitrap/MS and UPLC-QqQ/MS, respectively, indicating that quercetin and kaempferol derivatives, phenolic acid and apigenin are the main polyphenols in Moringa oleifera leaves, with quercetin and kaempferol derivatives predominating. Furthermore, the conditions of HSCCC for large-scale separation of polyphenols from Moringa oleifera leaves were optimized, which included the selection of the solvent system, flow rate and the sample load. Only by one-step HSCCC separation (within 120 min) under the optimized conditions, six quercetin and kaempferol derivatives, a phenolic acid and an apigenin could be individually isolated at a large scale (yield from 10% to 98%), each of which possessed high purity. Finally, the isolated polyphenols and phenolic extract from Moringa oleifera leaves (MLPE) were verified to have strong neuroprotective activities against H₂O₂-induced oxidative stress in PC-12 cells, suggesting that these compounds would contribute to the main beneficial effects of Moringa oleifera leaves.     

Activity Guided Isolation of Phenolic Compositions from Anneslea fragrans Wall. and Their Cytoprotective Effect against Hydrogen Peroxide Induced Oxidative Stress in HepG2 Cells

Anneslea fragrans Wall., commonly known as “Pangpo Tea”, is traditionally used as a folk medicine and healthy tea for the treatment of liver and intestine diseases. The aim of this study was to purify the antioxidative and cytoprotective polyphenols from A. fragrans leaves. After fractionation with polar and nonpolar organic solvents, the fractions of aqueous ethanol extract were evaluated for their total phenolic (TPC) and flavonoid contents (TFC) and antioxidant activities (DPPH, ABTS, and FRAP assays). The n-butanol fraction (BF) showed the highest TPC and TFC with the strongest antioxidant activity. The bio-guided chromatography of BF led to the purification of six flavonoids (1–6) and one benzoquinolethanoid (7). The structures of these compounds were determined by NMR and MS techniques. Compound 6 had the strongest antioxidant capacity, which was followed by 5 and 2. The protective effect of the isolated compounds on hydrogen peroxide (H₂O₂)-induced oxidative stress in HepG2 cells revealed that the compounds 5 and 6 exhibited better protective effects by inhibiting ROS productions, having no significant difference with vitamin C (p > 0.05), whereas 6 showed the best anti-apoptosis activity. The results suggest that A. fragrans could serve as a valuable antioxidant phytochemical source for developing functional food and health nutraceutical products.     

Response Surface Methodology for Optimization of Process Parameters and Antioxidant Properties of Mulberry (Morus alba L.) Leaves by Extrusion

Mulberry (Morus alba L.) leaves (MLs), originally used to feed silkworms, have recently been recognized as a food ingredient containing health-beneficial, bioactive compounds. In this study, the extrusion process was applied for the enhancement of the amount of extractable flavonoids from MLs. Extrusion conditions were optimized by water solubility index, total phenolic content, and total flavonoid content (TF) using response surface methodology, and antioxidative stress activities were evaluated in macrophage cells. According to the significance of regression coefficients of TF, the optimal extrusion parameters were set as barrel temperature of 114 °C, moisture feed content of 20%, and screw speed of 232 rpm. Under these conditions, the TF of extruded ML reached to 0.91% and improved by 63% compared with raw ML. Fifteen flavonoids were analyzed using ultra-high-performance liquid chromatograph coupled with photodiode array detection and quadrupole time-of-flight mass spectrometry (UPLC-PDA-QTOF/MS), and the extrusion resulted in increases in quercetin-3-gentiobioside, quercetin-3,7-di-O-glucoside, kaempferol-3,7-di-O-glucoside, rutin, isoquercitrin, and moragrol C. Besides, regarding antioxidative activity, extruded ML water extract inhibited the production of H₂O₂-induced reactive oxygen species and attenuated nuclear morphology alterations in macrophage cells. The findings of this study should be useful in food processing design to improve the extractable functional compounds in MLs.     

Short‐term UV‐B Dose Stimulates Production of Protective Metabolites in Matricaria chamomilla Leaves

Physiological response of two cultivars of Matricaria chamomilla plants on UV irradiation was studied. The impact of used short‐time UV dose was evaluated in three time points; 2, 24 and 48 h after irradiation. Used UV irradiation immediately resulted in changes in plant oxidative status monitored as increased concentration of H₂O₂. Decrease in chlorophyll a and b indicated the impact on photosynthetic apparatus. For phenolic secondary metabolites, an increase in total soluble phenols and AlCl₃‐reactive flavonols was observed. The activity of main phenolic enzyme, phenylalanine ammonia‐lyase, increased with time after irradiation. Significant changes, mainly decreasing trends, in the content of free coumarins and their glycosidic precursors were observed. Enhanced accumulation in chlorogenic and 1,5‐dicaffeoylquinic acid and in (Z)‐isoform of dicycloethers was detected. From these results, the redirecting precursors of coumarin biosynthesis to biosynthesis of substances with higher antioxidative potential can be assumed. Different reactions in diploid and tetraploid plants were recorded, too.     

Endophytic Fungi Produce Gibberellins and Indoleacetic Acid and Promotes Host-Plant Growth during Stress

We isolated and examined two endophytic fungi for their potential to secrete phytohormones viz. gibberellins (GAs) and indoleacetic acid (IAA) and mitigate abiotic stresses like salinity and drought. The endophytic fungi Phoma glomerata LWL2 and Penicillium sp. LWL3 significantly promoted the shoot and allied growth attributes of GAs-deficient dwarf mutant Waito-C and Dongjin-beyo rice. Analysis of the pure cultures of these endophytic fungi showed biologically active GAs (GA₁, GA₃, GA₄ and GA₇) in various quantities. The cultures of P. glomerata and Penicillium sp. also contained IAA. The culture application and endophytic-association with host-cucumber plants significantly increased the plant biomass and related growth parameters under sodium chloride and polyethylene glycol induced salinity and drought stress as compared to control plants. The endophytic symbiosis resulted in significantly higher assimilation of essential nutrients like potassium, calcium and magnesium as compared to control plants during salinity stress. Endophytic-association reduced the sodium toxicity and promoted the host-benefit ratio in cucumber plants as compared to non-inoculated control plants. The symbiotic-association mitigated stress by compromising the activities of reduced glutathione, catalase, peroxidase and polyphenol oxidase. Under stress conditions, the endophyte-infection significantly modulated stress through down-regulated abscisic acid, altered jasmonic acid, and elevated salicylic acid contents as compared to control. In conclusion, the two endophytes significantly reprogrammed the growth of host plants during stress conditions.     

Chemical constituents,antioxidant and hepatoprotective properties of ethanol extract from Artemisia japonica Thumb. Leaves

The tender leaves of Artemisia japonica Thumb. are often used as vegetables and tea in China. They also used as a traditional Chinese medicine for the treatment of liver disease. However, the identity of components responsible for health benefits remains unclear. The present study aimed to investigate the antioxidant and hepatic protective effects of a 60 % ethanol extract of Artemisia japonica Thumb. leaves (AJLEE). Total phenol content of AJLEE was determined using Folin Ciocalteau Method and it was calculated to be 123.142 ± 8.441 mg GAE/g. AJLEE shows remarkable antioxidant activity in vitro; pretreatment at 150 µg/mL can almost completely eliminate H₂O₂-induced ALM12 cell death. Moreover, AJLEE at a dosage of 400 mg/kg exhibits a strong hepatic protective effect against α-naphthylisothiocyanate (ANIT)-induced liver injury though the upregulation of genes for the antioxidant enzymes Sod1, Cat, Gpx4 and Ho-1, while decreasing the level of MDA. These properties of AJLEE may be attributed to the existence of abundant phenolic acids, flavonoids and coumarins, identified by UPLC/QTOF-MS as chlorogenic acid, isochlorogenic acid A, 7-methoxycoumarin and quercetin, apigenin and luteolin glycoside derivatives. Our data support the use of Artemisia japonica leaves as functional tea and food additives to improve human health.     

Impact of Peels Extracts from an Italian Ancient Tomato Variety Grown under Drought Stress Conditions on Vascular Related Dysfunction

Background: Tomato by-products contain a great variety of biologically active substances and represent a significant source of natural antioxidant supplements of the human diet. The aim of the work was to compare the antioxidant properties of a by-product from an ancient Tuscan tomato variety, Rosso di Pitigliano (RED), obtained by growing plants in normal conditions (-Ctr) or in drought stress conditions (-Ds) for their beneficial effects on vascular related dysfunction. Methods: The antioxidant activity and total polyphenol content (TPC) were measured. The identification of bioactive compounds of tomato peel was performed by HPLC. HUVEC were pre-treated with different TPC of RED-Ctr or RED-Ds, then stressed with H₂O₂. Cell viability, ROS production and CAT, SOD and GPx activities were evaluated. Permeation of antioxidant molecules contained in RED across excised rat intestine was also studied. Results: RED-Ds tomato peel extract possessed higher TPC than compared to RED-Ctr (361.32 ± 7.204 mg vs. 152.46 ± 1.568 mg GAE/100 g fresh weight). All extracts were non-cytotoxic. Two hour pre-treatment with 5 µg GAE/mL from RED-Ctr or RED-Ds showed protection from H₂O₂-induced oxidative stress and significantly reduced ROS production raising SOD and CAT activity (* p < 0.05 and ** p < 0.005 vs. H₂O₂, respectively). The permeation of antioxidant molecules contained in RED-Ctr or RED-Ds across excised rat intestine was high with non-significant difference between the two RED types (41.9 ± 9.6% vs. 26.6 ± 7.8%). Conclusions: RED-Ds tomato peel extract represents a good source of bioactive molecules, which protects HUVECs from oxidative stress at low concentration.     

Chemical Composition,Antioxidant and Cytoprotective Potentials of Carica papaya Leaf Extracts: A Comparison of Supercritical Fluid and Conventional Extraction Methods

The leaves of Carica papaya (CP) are rich in natural antioxidants. Carica papaya has traditionally been used to treat various ailments, including skin diseases. This study aims to decipher the antioxidant effects and phytochemical content of different CP leaf extracts (CPEs) obtained using supercritical carbon dioxide (scCO₂) and conventional extraction methods. The antioxidant activities of CPEs were evaluated by cell-free (1,1-diphenyl-2-picryl-hydrazyl (DPPH) and ferric-reduced antioxidative power (FRAP)) and cell-based (H₂O₂) assay. Both C. papaya leaf scCO₂ extract with 5% ethanol (CPSCE) and C. papaya leaf scCO₂ extract (CPSC) exhibited stronger DPPH radical scavenging activity than conventional extracts. In the FRAP assay, two hydrophilic extracts (C. papaya leaf ethanol extract (CPEE) and C. papaya freeze-dried leaf juice (CPFD)) showed relatively stronger reducing power compared to lipophilic extracts. Cell-based assays showed that CPFD significantly protected skin fibroblasts from H₂O₂-induced oxidative stress in both pre-and post-treatment. CPEE protected skin fibroblasts from oxidative stress in a dose-dependent manner while CPSCE significantly triggered the fibroblast recovery after treatment with H₂O₂. GC-MS analysis indicated that CPSCE had the highest α-tocopherol and squalene contents. By contrast, both CP hydrophilic extracts (CPEE and CPFD) had a higher total phenolic content (TPC) and rutin content than the lipophilic extracts. Overall, CPEs extracted using green and conventional extraction methods showed antioxidative potential in both cell-based and cell-free assays due to their lipophilic and hydrophilic antioxidants, respectively.     

An organosilyl derivative of trivacant tungstophosphate. Synthesis, characterization and crystal structure determination of α-A-[NBu4]3[PW9O34(C2H5SiO)3(C2H5Si)]

In the presence of NBu₄ⁿBr acting as phase-transfer reagent, organosilicon trichloride C₂H₅SiCl₃ reacts in acetonitrile with the trivacant tungstophosphate sodium salt β-A-Na₈H[PW₉O₃₄]·24H₂O to give hybrid organosilyl polyoxotungstate derivative α-A-[NBu₄ⁿ]₃[PW₉O₃₄(C₂H₅SiO)₃(C₂H₅Si)]. X-ray single crystal structural analysis indicates that the title compound is monoclinic, space group Cc, with lattice constants a=26.828(5), b=22.459(5), c=17.517(4) Å, β=103.19(3)°, V=10,276(4) Å³, Z=4, R=0.0462. According to the result of X-ray single crystal diffraction and chemical analysis, the hybrid polyanion consists of one α-A-[PW₉O₃₄]⁹⁻ framework on which are grafted simultaneously three RSiO groups through six Si-O-W bridge bonds, each of which is attached to the fourth RSi group through three Si-O-Si bridge bonds. The hybrid polyanion becomes a partial saturated, closed cage structure and also has an assembly of virtual C_3V symmetry.     

Syntheses,structures and properties of four organic–inorganic hybrid nicotinate-bridging rare-earth-containing phosphotungstates

Four novel organic–inorganic hybrid nicotinate-bridging dimeric rare-earth (RE)-containing phosphotungstates [H₂N(CH₃)₂]₈[RE(H₂O)(NA)(α-HPW₁₁O₃₉)]₂·24H₂O (RE = Ho^III for 1, Er^III for 2, Tb^III for 3, Dy^III for 4; HNA = nicotinic acid) have been synthesized from the reaction of trivacant Keggin precursor Na₉[α-PW₉O₃₄]∙16H₂O, RE(NO₃)₃·6H₂O, HNA by employing dimethylamine hydrochloride as organic solubilizing agent in the conventional aqueous solution system, which have been further characterized by elemental analyses, IR spectra, thermogravimetric analyses and single-crystal X-ray diffraction. Structural analysis indicates that the hybrid dimeric {[RE(H₂O)(NA)(α-HPW₁₁O₃₉)]₂}⁸⁻ polyoxoanion in 1–4 can be considered as two head-to-head mono-RE-containing Keggin [RE(H₂O)(NA)(α-HPW₁₁O₃₉)]⁴⁻ subunits bridged by two (η²,μ-1,1)-nicotinate linkers, which stands for the first organic–inorganic hybrid RE-containing phosphotungstates functionalized by nicotinate ligands. What's more, the solid-state photoluminescence properties and lifetime decay behaviors of 1–4 have been measured at room temperature and their photoluminescence spectra display the characteristic emission bands of corresponding trivalent RE cations.