Effects of drought stress on phenolic accumulation in greenhouse-grown olive trees (Olea europaea)

The present study evaluates the effects of severe drought stress on the content of phenolic compounds in olive leaves, namely hydroxytyrosol, tyrosol, p-hydroxybenzoic acid, catechin, luteolin 7-O-rutinoside, luteolin 7-O-glucoside, apigenin 7-O-glucoside, quercetin, apigenin, pinoresinol, oleuropein and verbascoside in greenhouse-grown plantlets. The results showed that oleuropein, verbascoside, luteolin 7-O-glucoside and apigenin 7-O-glucoside were the most important phenolic compound of stressed olive plants and can represent up to 84% of the total amount of the identified phenolic compounds. Application of drought stress caused a significant increase in the level of oleuropein (87%), verbascoside (78%), luteolin 7-O-glucoside (72%) and apigenin 7-O-glucoside (85%), when compared to the control. The elevated values of these phenolic compounds can help controlling the water status of olive plants and avoiding serious oxidative damage induced by water deficit stress. To our knowledge, this is the first report to show the boost in the concentrations of verbascoside, luteolin 7-O-glucoside and apigenin 7-O-glucoside in the leaves of olive trees after water deficit stress.     

Flavonoids of Helichrysum chasmolycicum and its antioxidant and antimicrobial activities

From the aerial parts of Helichrysum chasmolycicum P.H Davis, which is an endemic species in Turkey, the flavonoids apigenin, luteolin, kaempferol, 3,5-dihydroxy-6,7,8-trimethoxyflavone, 3,5-dihydroxy-6,7,8,4′-tetramethoxyflavone, apigenin 7-O-glucoside, apigenin 4′-O-glucoside, luteolin 4′-O-glucoside, luteolin 4′,7-O-diglucoside, kaempferol 3-O-glucoside, kaempferol 7-O-glucoside and quercetin 3-O-glucoside were isolated. The methanol extract of the aerial parts of H. chasmolycicum showed antioxidant activity by DPPH method (IC₅₀ 0.92 mg/mL). Antimicrobial activity test was performed on the B, D, E extracts and also 3,5-dihydroxy-6,7,8-trimethoxyflavone and kaempferol 3-O-glucoside which were the major flavonoid compounds obtained from aerial parts of H. chasmolycicum by microbroth dilutions technique. The E (ethanol-ethyl acetate) extract showed moderate antimicrobial activity against Pseudomonas aeruginosa, B (petroleum ether-60% ethanol-chloroform) extract and 3,5-dihydroxy-6,7,8-trimethoxyflavone showed moderate antifungal activity against Candida albicans.     

The identification of flavonoids and the expression of genes of anthocyanin biosynthesis in the chrysanthemum flowers

In order to provide additional information on the coloration of chrysanthemum flowers, the flavonoid composition and the expression of six structural genes involved in anthocyanin pathway in the ray florets of a pink flowering (cv. H5) and two white flowering (cvs. Keikai and Jinba) Chrysanthemum grandiflorum cultivars were examined. HPLCDAD/ESI-MSⁿ analysis showed that cyanidin 3-O-(6″-O-malonylglucoside) and cyanidin 3-O-(3″,6″-O-dimalonylglucoside) were the two major flavonoids presented in H5, while white flowering cultivars contained flavones instead of anthocyanins. Nine flavone derivatives were detected in the three cultivars, the amount of each flavone varied upon cultivars, and seven of these were identified as luteolin 7-O-arabinosylglucuronide, apigenin 7-O-glucoside, luteolin 7-O-malonylglucoside, apigenin 7-O-malonylglucoside, chrysoeriol 7-O-malonylglucoside, acacetin 7-O-rutinoside and acacetin 7-O-malonylglucoside. The two white flowering cultivars showed similar total flavonoid content, which was about two fold higher than that in H5. A high expression of the genes encoding dihydroflavonol 4-reductase and 3-O-glucosyltransferase was detected only in H5 but not in Keikai or Jinba. Chalcone synthase, chalcone isomerase, flavanone 3-hydroxylase, and flavonoid 3′-hydroxylase were expressed in all flowers, suggesting that the lack of anthocyanin in white flowering cultivars cannot be due to any blockage of their expression.     

Evidence of biosynthetic simplicity in the flavonoid chemistry of the ricciaceae

The major flavonoids in Riccia crystallina are naringenin and its 7-O-glucoside, apigenin 7-O-glucoside and apigenin 7-O-glucuronide and derivatives. Ricciocarpus natans is a rich source of luteolin 7,3′-di-O-glucuronide and also contains the 7-O-glucuronides of apigenin and luteolin and the 3′-O-glucuronide of luteolin. A parallel between the production of biosynthetically simple flavonoids and reduced morphology is evident among these liverworts.     

Analysis of flavonoids and characterization of theOsFNS gene involved in flavone biosynthesis in Rice

The major flavonoids in rice leaves were analyzed via LC-MS/MS after their total flavonoid extracts were hydrolyzed. The most abundant flavones were apigenin, luteolin, and tricetin. Of these, tricetin was methylated at its 3′ and 5′-hydroxyl group to form tricin, which was probablyO-glycosylated. Both 3′-O-methylated luteolin and luteolin were found in theC-glycosylated form while apigenin wasC-glycosylated. We also cloned and characterizedOsFNS, which catalyzes the reaction from flavanone (naringenin) to flavone (apigenin). Analysis of the reaction product with recombinant OsFNS showed that it indeed converts naringenin to apigenin.     

Biosynthesis of a water solubility-enhanced succinyl glucoside derivative of luteolin and its neuroprotective effect

The natural flavonoids luteolin and luteoloside have anti-bacterial, anti-inflammatory, anti-oxidant, anti-tumour, hypolipidemic, cholesterol lowering and neuroprotective effects, but their poor water solubility limits their application in industrial production and the pharmaceutical industry. In this study, luteolin-7-O-β-(6″-O-succinyl)-d -glucoside, a new compound that was prepared by succinyl glycosylation of luteolin by the organic solvent tolerant bacterium Bacillus amyloliquefaciens FJ18 in an 8.0% DMSO (v/v) system, was obtained and identified. Its greater water solubility (2293 times that of luteolin and 12 232 times that of luteoloside) provides the solution to the application problems of luteolin and luteoloside. The conversion rate of luteolin (1.0 g l⁻¹) was almost 100% at 24 h, while the yield of luteolin-7-O-β-(6″-O-succinyl)-d -glucoside reached 76.2%. In experiments involving the oxygen glucose deprivation/reoxygenation injury model of mouse hippocampal neuron cells, the cell viability was significantly improved with luteolin-7-O-β-(6″-O-succinyl)-d -glucoside dosing, and the expressions of the anti-oxidant enzyme HO-1 in the nucleus increased, providing a neuroprotective effect for ischemic cerebral cells. The availability of biosynthetic luteolin-7-O-β-(6″-O-succinyl)-d -glucoside, which is expected to replace luteolin and luteoloside, would effectively expand the clinical application value of luteolin derivatives.     

Flavonoid C- and O-glycosides from the Mongolian medicinal plant Dianthus versicolor Fisch

Eighteen flavonoids were identified from an aqueous extract of the aerial parts of Dianthus versicolor, a plant used in traditional Mongolian medicine against liver diseases. The flavonoid C- and O-glycosides isoorientin-7-O-rutinoside, isoorientin-7-O-rhamnosyl-galactoside, isovitexin-7-O-rutinoside, isovitexin-7-O-rhamnosyl-galactoside, isoscoparin-7-O-rutinoside, isoscoparin-7-O-rhamnosyl-galactoside, isoscoparin-7-O-galactoside, and isoorientin-7-O-galactoside were isolated and structurally elucidated. Their structures were established on the basis of extensive spectroscopic techniques including LC–UV–DAD, LC–MSⁿ, LC–HRMS, 1D and 2D NMR spectroscopy, and by GC–MS analysis after hydrolysis. Flavonoids with such a high glycosylation pattern are rare within the genus Dianthus. Furthermore, isovitexin-7-O-glucoside (saponarin), isovitexin-2″-O-rhamnoside, apigenin-6-glucoside (isovitexin), luteolin-7-O-glucoside, apigenin-7-O-glucoside, as well as the aglycons luteolin, apigenin, chrysoeriol, diosmetin, and acacetin were identified by TLC and LC–DAD–MSⁿ in comparison to reference substances or literature data. The NMR data of seven structures have not been reported in the literature to date.     

Phenolic Glycosides with antiproteasomal activity from Centaurea urvillei DC. subsp. urvillei

A new flavanone glycoside, naringenin-7-O-β-d-glucuronopyranoside, and a new flavonol glycoside, 6-hydroxykaempferol-7-O-β-d-glucuronopyranoside were isolated together with 12 known compounds, 5 flavone glycoside; hispidulin-7-O-β-d-glucuronopyranoside, apigenin-7-O-β-d-methylglucuronopyranoside, hispidulin-7-O-β-d-methylglucuronopyranoside, hispidulin-7-O-β-d-glucopyranoside, apigenin-7-O-β-d-glucopyranoside, a flavonol; kaempferol, two flavone; apigenin, and luteolin, a flavanone glycoside; eriodictyol-7-O-β-d-glucuronopyranoside, and three phenol glycoside; arbutin, salidroside, and 3,5-dihydroxyphenethyl alcohol-3-O-β-d-glucopyranoside from Centaurea urvillei subsp. urvillei. The structure elucidation of the new compounds was achieved by a combination of one- (¹H and ¹³C) and two-dimensional NMR techniques (G-COSY, G-HMQC, and G-HMBC) and LC-ESI-MS. The isolated compounds were tested for their antiproteasomal activity. The results indicated that kaempferol, a well known and widely distributed flavonoid in the plant kingdom, was the most active antiproteasomal agent, followed by apigenin, eriodictyol-7-O-β-d-glucuronopyranoside, 3,5-dihydroxyphenethyl alcohol-3-O-β-d-glucopyranoside, and salidroside, respectively.     

Flavonoids from the leaves and flowers of the Himalayan Cathcartia villosa (Papaveraceae)

Five flavonols, four flavones and one C-glycosylflavone were isolated from the leaves of Cathcartia villosa which is growing in the Himalayan Mountains. They were characterized as quercetin 3-O-vicianoside (1), quercetin 7,4′-di-O-glucoside (3), quercetin 3-O-rutinoside (4), quercetin 3-O-glucoside (5), quercetin 3-O-arabinosylarabinosylglucoside (6) (flavonols), luteolin (7), luteolin 7-O-glucoside (8), apigenin (9), chrysoeriol (10) (flavones), and vicenin-2 (11) (C-glycosylflavone) by UV, LC-MS, acid hydrolysis, NMR and/or HPLC and TLC comparisons with authentic samples. On the other hand, two flavonols 1 and kaempferol 3-O-vicianoside (2) were isolated and identified from the flowers of the species. Flavonoids were reported from the genus Cathcartia in this survey for the first time. Their chemical characters were chemotaxonomically compared with those of related Papaveraceous genera, Meconopsis and Papaver.     

Isoscutellarein and hypolaetin 8-glucuronides from the liverwort Marchantia berteroana

The major flavonoid of Marchantia berteroana is hypolaetin 8-O-β-d-glucuronide. This is accompanied by apigenin and luteolin, isoscutellarein (8-hydroxyapigenin) 8-O-β-d-glucuronide, the 7-O-β-d-glucuronide and -galacturonide of apigenin and luteolin, luteolin 3′-O-β-d-glucuronide and -galacturonide, luteolin 7,3′-di-O-β-d-glucuronide and -galacturonide, luteolin 3′,4′-di-O-β-d-glucuronide and -galacturonide, luteolin 7,4′-di-O-β-d-glucuronide, and hypolaetin 8,4′-di-O-β-d-glucuronide. The isoscutellarein and hypolaetin glucuronides, and the galacturonide flavones are all new natural products.     

Flavonoid variation in the liverwort Conocephalum conicum: Evidence for geographic races

The flavonoids of 2 samples of Conocephalum conicum gametophyte tissue have been studied, one from U.S.A. and the other from Germany. Common to both samples were vicenin-2, lucenin-2, the 7-O-glucuronides of apigenin, chrysoeriol and luteolin and the previously unknown 7-O-glucuronide 4′-O-rhamnosides of apigenin, chrysoeriol and luteolin. Additionally the German sample contained the 7,4′-di-O-glucuronides of apigenin and luteolin and a new compound, apigenin 7-O-diglucuronide 4′-O-glucuronide. The North American sample contained, additionally, luteolin 7,3′-di-O-glucuronide, luteolin 7-O-glucuronide 3′,4′-di-O-rhamnoside (a new triglycoside) and 2 further derivatives of luteolin 7-O-glucuronide. Evidence is presented for the existence of geographic faces of C. conicum and for the qualitative invariability of the flavonoid patterns with changing season or environment.     

Constituents of the leaves of Pseuderanthemum carruthersii (Seem.) Guill. var. atropurpureum (Bull.) Fosb.

A new iridoid, 5β,6β-dihydroxyantirrhide (1) was isolated from the dried leaves of Pseuderanthemum carruthersii (Seem.) Guill. var. atropurpureum (Bull.) Fosb. (Acanthaceae), together with 13 known compounds, including two iridoids, linarioside and antirrhinoside; five phenylethanoids, echipuroside A, verbascoside, isoverbascoside, isomartynoside and osmanthuside B; and six flavonoids, luteolin 7-O-β-d-glucopyranoside, luteolin 7-O-rutinoside, apigenin 7-O-rutinoside, apigenin 6-C-α-l-arabinopyranosyl–8-C-β-l-arabinopyranoside, apigenin 6,8-di-C-α-l-arabinopyranoside and apigenin 6-C-β-d-xylopyranosyl–8-C-α-l-arabinopyranoside. Their chemical structures were elucidated by 1D and 2D NMR as well as HR-ESI-MS spectroscopic analysis. Some purified compounds were evaluated the acetylcholinesterase inhibition and cytotoxic activities against the HeLa cervical cancer cell line and the MCF-7 breast cancer cell line at the concentration of 100 μg/mL. Luteolin 7-O-β-d-glucopyranoside exhibited cytotoxic activities against both the HeLa cervical cancer cell line and the MCF-7 breast cancer cell line. Verbascoside and isoverbascoside showed strong cytotoxic activity against the MCF-7 breast cancer cell line. The tested compounds showed the AChE inhibitory activity fairly weak.     

Chemotaxonomic consideration of flavonoids from the leaves of Chrysanthemum arcticum subsp. arcticum and yezoense,and related species

We examined the foliar flavonoids of Chrysanthemum arcticum subsp. arcticum and yezoense, and related Chrysanthemum species. Five flavonoid glycosides (luteolin 7-O-glucoside and 7-O-glucuronides of luteolin, apigenin, eriodictyol and naringenin) were isolated from these taxa. Luteolin 7-O-xylosylglucoside, luteolin, apigenin and quercetin 3-methyl ether were found in subsp. yezoense as very minor compounds that were not recognised by high-performance liquid chromatography/photodiode array (HPLC/PDA). The related species C. yezoense contained acacetin 7-O-rutinoside and some methoxylated flavone aglycones as major compounds. Thus, C. arcticum was distinguished from C. yezoense according to their flavonoid profiles.     

Sesquiterpene lactones,flavonoids and anthraquinones from Asphodeline globifera and Asphodeline Damascena

The known compounds chrysoeriol, apigenin, luteolin, acacetin, scutellarein, 6-methoxyluteolin, apigenin 7-glucoside, luteolin 7-glucoside, esculetin, chrysophanol, asphodeline, mircocarpin, sitosterol, 1-β-acetoxyeudesman-4(15),7(11)dien-2α,12-olide and 1-β-acetoxy-8β-hydroxyeudesman-4(15),7(11)-dien-8α,12-olide were isolated from Asphodeline globifera and A. damascena. A new sesquiterpene lactone 1-β-acetoxy-8β-ethoxyeudesman-4(15),7(11)dien-8α, 12-olide was also characterized. These are the first reports of sesquiterpene lactones in Asphodeline and in the Liliaceae.     

Flavonoid variation and evolution inAsplenium normale and related species (Aspleniaceae)

Flavonoid profiles of 132 populations (472 individuals) ofAsplenium normale, and related species,A. boreale, A. shimurae, andA. oligophlebium var.oligophlebium and var.iezimaense in Japan were surveyed by HPLC and 2D-PC. Of the five taxa, each ofAsplenium boreale, A. shimurae andA. oligophlebium including var.iezimaense had consistent flavonoid composition: apigenin 7, 4′-di-O-rhamnoside (9) inAsplenium boreale, 7-O-glucosyirhamnosides of apigenin and luteolin (6 and 7) inA. shimurae and genkwanin 4′-O-glucosyl-rhamnoside (5) in twoA. oligophlebium varieties. On the other hand,Asplenium normale was divided into seven chemotypes A-G: A-type has 7-O-dirhamnosides of apigenin and luteolin (1 and 2) and genkwanin 4′-O-glucosylrhamnoside (5); B-type, 5 alone; C-type, apigenin 7-O-rhamnoside-4′-O-glucosylrhamnoside (8); D-type, 1 and 2; E-type, 1,2 and 8; F-type, 1, 2, 5 and 8; and G-type, 5 and 8. Among them, the most frequent types were A, B and C, and A-type was mainly distributed in inland of Honshu, Shikoku and Kyushu, while B- and C-types extended their distribution areas southwards in general and occur along the Pacific coast with several exception. Chemical and evolutionary relationships amongAsplenium boreale, A. shimurae, A. oligophlebium, and the chemotypes ofA. normale were discussed on the basis of general biosynthetic pathway.     

Flavonoids of the liverwort Marchantia polymorpha

The major flavonoids of Marchantia polymorpha var. polymorpha and aquatica are the 7-O-β-d-glucuronides of apigenin and luteolin, luteolin 3′-O-β-d-glucuronide, luteolin 7,3′-di-O-β-d-glucuronide, and the 7,4′-di-O-β-d-glucuronides of apigenin and luteolin. These are accompanied by minor amounts of apigenin, luteolin, luteolin 3′,4′-di-O-β-d-glucuronide and luteolin 7,3′,4′-tri-O-β-d-glucuronide. All the luteolin di- and triglucuronides except the 3′,4′-di- substituted compound are new natural products.     

Flavonoids in the leaves of Hillebrandia and Begonia species (Begoniaceae)

The fresh leaves of Hillebrandia sandwicensis and 126 Begonia taxa were chemotaxonomically surveyed for flavonoids. Of their taxa, H. sandwicensis and 119 species, one variety and three hybrids were analyzed for flavonoids for the first time. Ten flavonols and eleven C-glycosylflavones were isolated and characterized as quercetin 3-O-rutinoside (1), kaempferol 3-O-rutinoside (2), isorhamnetin 3-O-rutinoside (3), quercetin 3-O-glucoside (4), quercetin 3-methyl ether 7-O-rhamnosylglucoside (5), quercetin 3,3'-dimethyl ether 7-O-rhamnosylglucoside (6), quercetin glycoside (13), quercetin glycoside (acylated) (14), kaempferol glycoside (17) and quercetin 3-O-rhamnoside (18) as flavonols, and isovitexin (7), vitexin (8), isoorientin (9), orientin (10), luteolin 6-C-pentoside (11), luteolin 8-C-pentoside (12), schaftoside (15), isoschaftoside (16), chrysoeriol 6,8-di-C-pentoside (19), apigenin 6,8-di-C-arabinoside (20) and isovitexin 2''-O-glucoside (21) as C-glycosylflavones. Quercetin 3-O-rutinoside (1) alone was isolated from H. sandwicensis endemic to Hawaii. Major flavonoids of almost Begonia species was also 1. Begonia species were divided into two chemotypes, i.e. flavonol containing type and C-glycosylflavone containing type. Of 14 section of the Begonia, almost species of many section, i.e. sect. Augustia, Coelocentrum, Doratometra, Leprosae, Loasibegonia, Monopteron and Ruizoperonia, were flavonol types. On the other hand, C-glycosyflavone type was comparatively most in sect. Platycentrum.     

The taxonomic position of Sphaerocarpos and Riella as indicated by their flavonoid chemistry

The major flavonoid glycosides of Sphaerocarpos texanus are luteolin 7-O-glucuronide and 7,4′-di-O-glucuronide. Riella americana and R. affinis both contain apigenin, chrysoeriol and luteolin 7-O-glucuronides but R. americana additionally contains luteolin 3′-O-glucuronide. This finding supports the inclusion of Sphaerocarpaceae and Riellaceae in the order Marchantiales rather than their separation into another order.     

A chemotaxonomic study of flavonoids in the leaves of six Trichosanthes species

The 7-, 3′- and 4′-glucosides of luteolin, the 7-glucoside and 6,8-di-C-glucoside of apigenin were isolated from Trichosanthes kirilowii var. japonica. Kaempferol 3,7-di-rhamnoside and 3-glucoside-7-rhamnoside were identified from T. cucumeroides, kaempferol 3-galactoside and 3-sophoroside were also identified from T. anguina. Quercetin-3-rutinoside was detected from T. multiloba and T. rostrata. T. bracteata afforded luteolin 3′-glucoside and kaempferol 3-rutinoside, and T. kirilowii afforded luteolin 7-, 3′- and 4′-glucosides and apigenin 7-glucoside.     

Species Specific Flavone Glucuronides in Elodea Species

The flavonoid patterns of plants of Elodea canadensis, E. ernstae and E. nuttallii apigenin were investigated. The main flavonoids of E. canadensis are apeginin, luteolin and chrysoeriol 7-O-diglucuronides, of E. nuttalli apigenin and luteolin 7-O- diglucuronides, and of E. ernstae apigenin and luteonin 7-O-monoglucoronides. The qualitative stability of these flavonoid patterns is checked by chromatographic comparison of various populations from a wide area of the three species, it is shown that the flavonoid patterns are valuable criteria for the separation of these species.