Photosynthetic activity, pigment composition and antioxidative response of two mustard (Brassica juncea) cultivars differing in photosynthetic capacity subjected to cadmium stress

Photosynthetic performance, contents of chlorophyll and associated pigments, cellular damage and activities of antioxidative enzymes were investigated in two mustard (Brassica juncea L.) cultivars differing in photosynthetic capacity subjected to cadmium (Cd) stress. Exposure to Cd severely restricted the net photosynthetic rate (P(N)) of RH-30 compared to Varuna. This corresponded to the reductions in the activities of carbonic anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase (Rubisco) in both the cultivars. Decline in chlorophyll (Chl) (a+b) and Chl a content was observed but decrease in Chl b was more conspicuous in Varuna under Cd treatments, which was responsible for higher Chl a:b ratio. Additionally, the relative amount of anthocyanin remained higher in Varuna compared to RH-30 even in the presence of high Cd concentration, while percent pheophytin content increased in RH-30 at low Cd concentration. A higher concentration of Cd (100 mg Cd kg(-1) soil) resulted in elevated hydrogen peroxide (H(2)O(2)) content in both the cultivars. However, Varuna exhibited lower content of H(2)O(2) in comparison to RH-30. This was reflected in the increased cellular damage in RH-30, expressed by greater thiobarbituric acid reactive substances (TBARS) content and electrolyte leakage. The enhanced activities of antioxidative enzymes, ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) and also lower activity of superoxide dismutase (SOD) in Varuna alleviated Cd stress and protected the photosynthetic activity.     

Phenolic compounds in berries and flowers of a natural hybrid between bilberry and lingonberry (Vaccinium × intermedium Ruthe)

Hybridization between species plays an important role in the evolution of secondary metabolites and in the formation of combinations of existing secondary metabolites in plants. We have investigated the content of phenolic compounds in berries and flowers of Vaccinium × intermedium Ruthe, which is a rare natural hybrid between bilberry (Vaccinium myrtillus L.) and lingonberry (Vaccinium vitis-idaea L.). The berries and flowers of the hybrid showed characteristics inherited from both parent species in the distribution and contents of phenolic compounds. Bilberry is known as one of the richest sources of anthocyanins and to have a profile of 15 major forms combining cyanidin, delphinidin, petunidin, peonidin and malvidin with galactose, glucose and arabinose. Lingonberry contains only cyanidin glycosides. Hybrid berries contained all bilberry anthocyanins with pronounced cyanidin content. With regard to proanthocyanidins and flavonol glycosides, the hybrid inherited diverse profiles combining those of both parental species. The distribution of hydroxycinnamic acids was quite uniform in all studied berries. Of the identified compounds, 30 were detected in lingonberry, 46 in bilberry, 53 in hybrid berries and 38 in hybrid flowers. Hence, compared with the parent species, hybrid berries possess a more diverse profile of phenolic compounds and, therefore, can offer interesting material for breeding purposes.     

Anthocyanins from red onion,Allium cepa,with novel aglycone

Four anthocyanins with the same novel 4-substituted aglycone, carboxypyranocyanidin, have been isolated from acidified, methanolic extracts of the edible scales as well as from the dry outer scales of red onion, Allium cepa L. The structures of 1 and 2 were identified as the 3-O-beta-glucopyranoside and 3-O-(6"-O-malonyl-beta-glucopyranoside) of 5-carboxypyranocyanidin, respectively. This aglycone, 5-carboxy-2-(3,4-dihydroxyphenyl)-3,8-dihydroxy-pyrano[4,3,2-de]-1-benzopyrylium, is with exception of the substitution pattern on the phenyl ring similar to carboxypyranomalvidin (vitisidin A) recently isolated from red wines. In addition to 1 and 2, two analogues of 2 methylated at the terminal carboxyl group of the acyl moiety (3) or at the aglycone carboxyl (4), respectively, were also identified. These latter compounds are most probably formed by esterification of 2 with the solvent (acidified methanol) during the isolation process. The structures were elucidated by 2D NMR spectroscopy and LC-MS.     

Anthocyanins from flowers of the orchids Dracula chimaera and D. cordobae

The main anthocyanins from flowers of the orchids Dracula chimaera and D. cordobae were isolated from a purified methanolic extract by preparative HPLC. Their structures were determined to be cyanidin 3-O-(6"-O-malonyl-beta-glucopyranoside), cyanidin 3-O-(6"-O-alpha-rhamnopyranosyl-beta-glucopyranoside), cyanidin 3-O-beta-glucopyranoside, peonidin 3-O-(6"-O-alpha-rhamnopyranosyl-beta-glucopyranoside) and peonidin 3-O-(6"-O-malonyl-beta-glucopyranoside). The structure determinations were mainly based on extensive use of 2D and 1D NMR spectroscopy, UV-vis spectroscopy and MS. The anthocyanin contents of species belonging to the subtribe Pleurothallidinae including genus Dracula Luer (Orchidaceae) have previously not been determined. The high content of anthocyanin rutinosides found in D. chimaera and D. cordobae (78 and 28% of the total anthocyanin content, respectively) differs from previously analysed orchid species, in which glucose is found as the only anthocyanin sugar moiety.     

Engineering of flower color in forsythia by expression of two independently-transformed dihydroflavonol 4-reductase and anthocyanidin synthase genes of flavonoid pathway

Flower color was modified in forsythia (Forsythia x intermedia cv Spring Glory) by inducing anthocyanin synthesis in petals through sequential Agrobacterium-mediated transformation with dihydroflavonol 4-reductase from Antirrhinum majus (AmDFR) and anthocyanidin synthase from Matthiola incana (MiANS) genes. This is the second report of flower color modification of an ornamental shrub after rose, and the first time an ANS gene is used for this purpose. Double transformants (AmDFR+MiANS) displayed a novel bronze-orange petal color, caused by the de novo accumulation of cyanidin-derived anthocyanins over the carotenoid yellow background of wild type (wt), and intense pigmentation of vegetative organs. Transformation with single genes (either AmDFR or MiANS) produced no change in flower color, showing a multistep control of late anthocyanin pathway in petals of forsythia. Analysis of relevant late flavonoid pathway genes – an endogenous flavonoid glycosyltransferase (FiFGT) and transformed DFR and ANS genes – showed appropriate expression in flower organs. Functional characterization of FiFGT expressed in E. coli revealed its ability to metabolize both flavonols and anthocyanidin substrates, a prerequisite for effective anthocyanin accumulation in petals of plants transformed with constructs leading to anthocyanidin synthesis. Biochemical analyses of flavonoid compounds in petals and leaves showed that, besides anthocyanin induction in petals of double transformants, the accumulation pattern of flavan-3-ols was quantitatively and qualitatively modified in petals and leaves of transformants, in agreement with the most recent model proposed for flavan-3-ol synthesis. On the other hand, phenylpropanoid, flavone and flavonol pools were not quantitatively affected, indicating a tight regulation of early flavonoid pathway.     

Anthocyanins from red wine--their stability under simulated gastrointestinal digestion

The stability of anthocyanins from red wine was assessed using an in vitro digestion system that simulated the physiochemical changes that occur in the upper gastrointestinal tract. Anthocyanins in red wine were stable to gastric conditions whereas there was a small loss in total phenol content. After pancreatic digestion, the total anthocyanins were very poorly recovered compared to the bulk phenols in the IN sample, which was previously described as the "serum-available" fraction, and the majority of the anthocyanins and phenols were recovered in the OUT fraction, previously described as the "colon-available" fraction. Removing alcohol from the wine samples prior to the procedure did not markedly affect this pattern. The composition of anthocyanins in the post gastric, IN and OUT samples was analysed using liquid chromatography mass-spectrometry. The red wine used contained over 20 identifiable anthocyanins of which the main components were 3-O-glucosides of malvidin, peonidin, petundin, delphidin and cyanidin. Coumaroylated-glucoside derivatives of malvidin, petundin, peonidin, and delphinidin were observed and acetylated glucosides of peonidin, petundin and malvidin were also identified. Anthocyanins with modified aglycones similar to vitisin A derivatives of delphinidin, peonidin, petunidin and malvidin were also identified. After the in vitro digestion procedure, only five anthocyanins could be detected in the IN (serum-available) and the OUT (colon-available) fractions, which were confirmed as malvidin-3-O-glucoside and the vitisin A adducts of malvidin-3-O-glucoside, malvidin-3-O-acetylglucoside, malvidin-3-O-coumaroylglucoside and peonidin-3-O-glucoside. Malvidin-3-O-glucoside was recovered at 0.2% in the IN fraction and 0.9% in the OUT fraction. However, the vitisin derivatives were much more stable to pancreatic digestion. Assuming that the vitisin A derivatives display similar biological properties to their parent anthocyanins, their enhanced gastrointestinal stability could lead to enhanced bioavailability and bio-effectiveness in vivo.     

Color genes in the orchid Oncidium Gower Ramsey: identification, expression, and potential genetic instability in an interspecific cross

Orchids are one of the most unique and evolved of flowering plants, with many being valuable floricultural crops. Spatial localization of pigments within the flower of the commercially important bi-color Oncidium Gower Ramsey demonstrated a mixture of carotenoids and anthocyanins concentrated in the adaxial epidermis. Chromatography identified the predominant yellow pigment to be an equal mixture of all-trans and 9-cis isomers of violaxanthin, with esterification specific to the 9-cis isomer. Red ornamentation was comprised of the anthocyanins cyanidin and its methylated derivate, peonidin. Five key pigment biosynthesis genes encoding dihydroflavonol 4-reductase (DFR), phytoene synthase (PSY), phytoene desaturase, carotenoid isomerase, and the downstream 9-cis epoxycarotenoid dioxygenase were isolated and their expression profiles determined. Northern analyses showed both phytoene desaturase and carotenoid isomerase expression to be up-regulated in floral tissue relative to leaves whereas PSY was not. Three closely related DFR genes were isolated, including one with an insertion in the 3′ coding region. DFR expression occurred throughout flower development in Oncidium, unlike in Dendrobium and Bromheadia orchids. A number of the isolated anthocyanin and carotenoid genes showed variations due to insertion events. These findings raise questions about the genetic stability in interspecific crosses in orchids, such as the tri-specific Oncidium Gower Ramsey.     

Cyclooxygenase inhibitory and antioxidant cyanidin glycosides in cherries and berries

Anthocyanins from tart cherries, Prunus cerasus L. (Rosaceae) cv. Balaton and Montmorency; sweet cherries, Prunus avium L. (Rosaceae); bilberries, Vaccinum myrtillus L. (Ericaceae); blackberries, Rubus sp. (Rosaceae); blueberries var. Jersey, Vaccinium corymbosum L. (Ericaceae); cranberries var. Early Black, Vaccinium macrocarpon Ait. (Ericaceae); elderberries, Sambucus canadensis (Caprifoliaceae); raspberries, Rubus idaeus (Rosaceae); and strawberries var. Honeoye, Fragaria x ananassa Duch. (Rosaceae), were investigated for cyclooxygenase inhibitory and antioxidant activities. The presence and levels of cyanidin-3-glucosylrutinoside 1 and cyanidin-3-rutinoside 2 were determined in the fruits using HPLC. The antioxidant activity of anthocyanins from cherries was comparable to the commercial antioxidants, tert-butylhydroquinone, butylated hydroxytoluene and butylated hydroxyanisole, and superior to vitamin E, at a test concentration of 125 microg/ml. Anthocyanins from raspberries and sweet cherries demonstrated 45% and 47% cyclooxygenase-I and cyclooxygenase-II inhibitory activities, respectively, when assayed at 125 microg/ml. The cyclooxygenase inhibitory activities of anthocyanins from these fruits were comparable to those of ibuprofen and naproxen at 10 microM concentrations. Anthocyanins 1 and 2 are present in both cherries and raspberry. The yields of pure anthocyanins 1 and 2 in 100 g Balaton and Montmorency tart cherries, sweet cherries and raspberries were 21, 16.5; 11, 5; 4.95, 21; and 4.65, 13.5 mg, respectively. Fresh blackberries and strawberries contained only anthocyanin 2 in yields of 24 and 22.5 mg/100 g, respectively. Anthocyanins 1 and 2 were not found in bilberries, blueberries, cranberries or elderberries.     

The importance of red pigments to plant life: experiments with anthocyanins

Some simple methods for the extraction of anthocyanins from plant tissues are described, as well as methods of measuring and assaying their potential use as UV radiation protectants. Anthocyanin-less mutant Fast Plants (Brassica rapa) are more severely affected by doses of UV than wild-type controls, and thus show the value of such pigments in protection from UV radiation. Some possible roles for anthocyanins in plants are reviewed. A bioassay using bacteria is suggested, as well as a range of possible investigations suitable for post-16 students.     

Flavonoid chemistry ofWeigela (Caprifoliaceae) in Korea

Fifteen flavonoids were isolated from flowers and leaves of four species ofWeigela [W. florida (Bunge) A. DC.,W. praecox (Lemoine) Bailey,W. hortensis (Sieb. et Zucc.) K. Koch, andW. subsessilis (Nakai) Bailey] of Korea and one species (W. coraeensis Thunb.) of Japan. The flavonoid data indicated the presence of two distinct chemical groups: the “yellow flower” type producing flavonols and the “red flower” type producing flavonols and flavones. Two cyanidin 3-O-glycosides (glucoside and glucose-xylose) also occurred in all examined taxa. In the floral color-changing species,W. subsessilis, only quercetin glycosides predominated in floral tissue at first, decreasing in number and quantity with time. Instead, cyanidin 3-O-glycosides became present predominantly in flower color changing tissue from yellow to mauve.Weigela florida produced apigenin and luteolin glycosides, along with cyanidin 3-O-glycosides, which were also found inW. subsessilis. Within a relatively limited number of individuals (five),W. hortensis was unique in its production of all flavonols, flavones, and anthocyanins, although two individuals lacked flavone compounds but possessed all flavonols and anthocyanins. In effect, the putative hybrid,W. hortensis of Korea showed additive profiles of the parental marker compounds ofW. subsessilis andW. florida. Pollinator (andrenid bees) non-discrimination betweenWeigela flower-color morphs leading to non-assortive mating was a common, which indicated no breeding barrier among species. This flavonoid study indicated that species of both sections,Weigela andCalysphyrum appeared in each chemical grouping and it was obvious that the arrangement based on flavonoids cut across the sectional treatment of Hara. Floral tissues may be directly involved in the evolutionary strategy of pollination mechanisms and hence, their inherent flavonoids may no longer support taxonomic relationships. The presence of flavone glycosides inWeigela would support that tribe Dievilleae have a closer affinity to tribe Lonicereae within the Family Caprifoliaceae.