Caffeic Acid Conjugates Research Articles

Design and synthesis of phyto-Saxagliptin conjugates: Targeting DPP IV, AChE, and β-amyloid in cognitive impairment

Cognitive impairment is a major secondary consequence of Type II diabetes mellitus. The present investigation is designed to enhance the efficacy of an antidiabetic drug (Saxagliptin/SXG) against diabetes-induced cognitive impairment in rats. SXG has limited blood-brain barrier (BBB) permeability due to its hydrophilic nature. Phytochemical-based carboxylic acid conjugates enhance the lipophilicity and anti-oxidant properties of the drugs. Virtually SXG was conjugated with 10 different carboxylic acids and evaluated for drug-likeness, pre-ADMET, Molecular docking, and HUMO-LUMO study. Based on the molecular weight, log P value, docking score, and toxicity profile; three carboxylic acids were selected. Gallic acid (GA), Isonicotinic acid (INA), and Caffeic acid (CA) conjugates of SXG were synthesized and characterized by FTIR, and NMR studies. Diabetes-induced cognitive impairment was induced in the rats by administration of STZ, 45 mg kg-1 i.p. Learning and memory were evaluated by assessing spontaneous alternation behavior (SAB), number of correct responses, and transfer latency using Y-maze, radial arm maze, and elevated plus maze respectively. The antioxidant activity, nitrite levels, acetylcholine esterase level, and Aβ42 content in the rat brain was also evaluated. Histopathology of the hippocampal area was also done. The carboxamides of SXG have improved the efficacy of SXG against diabetes-induced cognitive impairment. This neuroprotective effect of carboxamides of SXG may be attributed to anti-oxidant activity, cholinergic activity, and anti-amyloid β activity.

In vitro and in silico study of eggplant extract on human cancer cell lines.

The aim of this research was to study the metabolite composition, antioxidative potential and cytotoxic activities of Solanum melongena fruit extracts. Phytochemical analyses of extracts were performed using LC-MS. Phenolic compounds were the major constituents present in the fruit extracts. Free radical scavenging activities were recorded and the highest activities were reported in methanolic extracts using DPPH (103.70 ± 2.75 EC50 μg/mL), ABTS (81.74 ± 3.64 EC50 μg/mL), and FRAP (22.39 ± 1.52 μmol TE/g) assays. Quantification has suggested the presence of delphinidin derivatives, and caffeic acid conjugates as major constituents of fruit extracts. The potential binding of these derivatives with human cell surface receptors was analysed using in silico analysis and validated for cytotoxic and apoptotic effects using in vitro studies on human cancer cell lines. The methanolic extract has shown the highest cytotoxic activity.

Molecular mechanisms of resistance to Myzus persicae conferred by the peach Rm2 gene: A multi-omics view.

The transcriptomic and metabolomic responses of peach to Myzus persicae infestation were studied in Rubira, an accession carrying the major resistance gene Rm2 causing antixenosis, and GF305, a susceptible accession. Transcriptome and metabolome showed both a massive reconfiguration in Rubira 48 hours after infestation while GF305 displayed very limited changes. The Rubira immune system was massively stimulated, with simultaneous activation of genes encoding cell surface receptors involved in pattern-triggered immunity and cytoplasmic NLRs (nucleotide-binding domain, leucine-rich repeat containing proteins) involved in effector-triggered immunity. Hypersensitive reaction featured by necrotic lesions surrounding stylet punctures was supported by the induction of cell death stimulating NLRs/helpers couples, as well as the activation of H2O2-generating metabolic pathways: photorespiratory glyoxylate synthesis and activation of the futile P5C/proline cycle. The triggering of systemic acquired resistance was suggested by the activation of pipecolate pathway and accumulation of this defense hormone together with salicylate. Important reduction in carbon, nitrogen and sulphur metabolic pools and the repression of many genes related to cell division and growth, consistent with reduced apices elongation, suggested a decline in the nutritional value of apices. Finally, the accumulation of caffeic acid conjugates pointed toward their contribution as deterrent and/or toxic compounds in the mechanisms of resistance.

1H NMR metabolomic approach reveals chlorogenic acid as a response of sugarcane induced by exposure to Diatraea saccharalis

Sugarcane (Saccharum officinarum) has been considered one of the most efficient energy crops, but its production yield is sensitive to outbreaks of pest insects, especially the sugarcane borer Diatraea saccharalis. Genetic breeding programs and biotechnology projects have been developed to decode the defense mechanisms of sugarcane against herbivorous insect attacks, and the develop plague-resistant plants. We performed metabolic profile analysis of the SP791011 sugarcane variety’s response to Diatraea saccharalis herbivory, using Nuclear Magnetic Resonance (NMR) spectroscopy of organic leaf extracts. The leaf response of SP791011 to D. saccharalis resulted in depletion of choline, alanine, sucrose, glutamate, trigonelline, and isomers (E)-aconitate, (Z)-aconitate, and higher expression of chlorogenic acid and other caffeic acid conjugates in sugarcane leaves. The increase in chlorogenic acid suggests the shikimic acid pathway was induced by D. saccharalis herbivory, increasing the biosynthesis of phenylpropanoids such as chlorogenic acid in the sugarcane leaves. In addition to the herbivory test, we performed an in vivo biological assay by adding chlorogenic acid to an artificial diet to D. saccharalis caterpillars. This assay demonstrated a decrease in the development time of the pupae compared with pupae from caterpillars raised under normal diet. However, deformations in moth wings fed with chlorogenic acid were observed for three concentrations tested (0.05 mg/mL, 0.5 mg/mL and 5 mg/mL) during the in vivo bioassay. Chlorogenic acid may be considered a natural biopesticide and its production could be induced to develop more resistant sugarcane varieties against D. saccharalis.

What happens in the pith stays in the pith: tissue-localized defense responses facilitate chemical niche differentiation between two spatially separated herbivores.

Herbivore attack is known to elicit systemic defense responses that spread throughout the host plant and influence the performance of other herbivores. While these plant-mediated indirect competitive interactions are well described, and the co-existence of herbivores from different feeding guilds is common, the mechanisms of co-existence are poorly understood. In both field and glasshouse experiments with a native tobacco, Nicotiana attenuata, we found no evidence of negative interactions when plants were simultaneously attacked by two spatially separated herbivores: a leaf chewer Manduca sexta and a stem borer Trichobaris mucorea. T.mucorea attack elicited jasmonic acid (JA) and jasmonoyl-l-isoleucine bursts in the pith of attacked stems similar to those that occur in leaves when M. sexta attacks N. attenuata leaves. Pith chlorogenic acid (CGA) levels increased 1000-fold to levels 6-fold higher than leaf levels after T.mucorea attack; these increases in pith CGA levels, which did not occur in M.sexta-attacked leaves, required JA signaling. With plants silenced in CGA biosynthesis (irHQT plants), CGA, as well as other caffeic acid conjugates, was demonstrated in both glasshouse and field experiments to function as a direct defense protecting piths against T.mucorea attack, but not against leaf chewers or sucking insects. T.mucorea attack does not systemically activate JA signaling in leaves, while M.sexta leaf-attack transiently induces detectable but minor pith JA levels that are dwarfed by local responses. We conclude that tissue-localized defense responses allow tissue-specialized herbivores to share the same host and occupy different chemical defense niches in the same hostplant.

Phenolic screening by HPLC–DAD–ESI/MSn and antioxidant capacity of leaves, flowers and berries of Rubus grandifolius Lowe

In Madeira Island (Macaronesia Island), Rubus grandifolius Lowe berries, locally known by amoras, are widely consumed fresh or processed as jam, juice or liquor. Folk medicine describes R. grandifolius Lowe fruits and leaves being used to treat diabetes, as depurative, diuretic and to relieve sore throat.The aim of this study was to investigate phenolic composition and antioxidant capacity of the different edible parts of the plant (berries, leaves and flowers). HPLC–DAD–ESI/MSn was used to establish the phenolic profile. Phenolic monomers such as flavonol O-glycosilated (quercetin and kaempferol), quinic acid and caffeic acid conjugates were characterized using the electrospray source in the negative mode; while positive mode was employed to detect glycosylated anthocyanins (cyanidin, delphinin and petunidin).The berries presented a higher radical scavenger capacity (DPPH and ABTS assays) and reducing properties (FRAP) than the leaves and the flowers. Ethanolic extracts showed highest antioxidant capacity when compared with water based extracts: DPPH values of 147.9±0.7μmol eq Trolox/g DM; ABTS value of 255.8±1.9μmol eq Trolox/g DM and FRAP value 9455±29mmol Fe(II)/mgDM).

Phenolic sulfates as new and highly abundant metabolites in human plasma after ingestion of a mixed berry fruit purée.

Bioavailability studies are vital to assess the potential impact of bioactive compounds on human health. Although conjugated phenolic metabolites derived from colonic metabolism have been identified in the urine, the quantification and appearance of these compounds in plasma is less well studied. In this regard, it is important to further assess their potential biological activity in vivo. To address this gap, a cross-over intervention study with a mixed fruit purée (blueberry, blackberry, raspberry, strawberry tree fruit and Portuguese crowberry) and a standard polyphenol-free meal was conducted in thirteen volunteers (ten females and three males), who received each test meal once, and plasma metabolites were identified by HPLC-MS/MS. Sulfated compounds were chemically synthesised and used as standards to facilitate quantification. Gallic and caffeic acid conjugates were absorbed rapidly, reaching a maximum concentration between 1 and 2h. The concentrations of sulfated metabolites resulting from the colonic degradation of more complex polyphenols increased in plasma from 4h, and pyrogallol sulfate and catechol sulfate reached concentrations ranging from 5 to 20μm at 6h. In conclusion, phenolic sulfates reached high concentrations in plasma, as opposed to their undetected parent compounds. These compounds have potential use as biomarkers of polyphenol intake, and their biological activities need to be considered.

Developmental changes in leaf phenolics composition from three artichoke cvs. (Cynara scolymus) as determined via UHPLC–MS and chemometrics

The metabolomic differences in phenolics from leaves derived from 3 artichoke cultivars (Cynara scolymus): American Green Globe, French Hyrious and Egyptian Baladi, collected at different developmental stages, were assessed using UHPLC–MS coupled to chemometrics. Ontogenic changes were considered as leaves were collected at four different time intervals and positions (top and basal) during artichoke development. Unsupervised principal component analysis (PCA) and supervised orthogonal projection to latent structures-discriminant analysis (O2PLS-DA) were used for comparing and classification of samples harvested from different cultivars at different time points and positions. A clear separation among the three investigated cultivars was revealed, with the American Green Globe samples found most enriched in caffeic acid conjugates and flavonoids vs. other cultivars. Furthermore, these metabolites also showed a marked effect on the discrimination between leaf samples from cultivars harvested at different positions, regardless of the plant age. Metabolite absolute quantifications further confirmed that discrimination was mostly influenced by phenolic compounds, namely caffeoylquinic acids and flavonoids. This study demonstrates an effect of artichoke leaf position, regardless of plant age, on its secondary metabolites composition. To the best of our knowledge, this is the first report for compositional differences among artichoke leaves, based on their positions, via a metabolomic approach and suggesting that top positioned artichoke leaves present a better source of caffeoylquinic acids, compared to basal ones.

Helichrysum arenarium subsp. arenarium: phenolic composition and antibacterial activity against lower respiratory tract pathogens

The aim of this study was to investigate the phenolic content and antibacterial activity of the methanol extract from Helichrysum arenarium (L.) Moench subsp. arenarium inflorescences against lower respiratory tract pathogens (standard strains and clinical isolates). The extract was characterised by a total phenolic content of 160.17 mg/g. Several caffeic acid conjugates (chlorogenic acid and dicaffeoylquinic acids) and flavonoids (apigenin, naringenin, apigenin-7-O-glucoside and naringenin-O-hexosides) were identified as major constituents by HPLC-DAD-ESI-MS. Staphylococcus aureus ATCC 25923 was more susceptible to Helichrysum extract than Streptococcus pneumoniae ATCC 49619 (minimum inhibitory concentration [MIC] = 0.62 and 1.25 mg/mL, respectively). The extract exhibited similar antibacterial effects against methicillin-resistant S. aureus and penicillin-resistant S. pneumoniae clinical isolates (MIC = 2.5 mg/mL) displaying a higher activity against ampicillin-resistant Moraxella catarrhalis isolate (MIC = 0.15 mg/mL). The combination with ciprofloxacin exhibited additivity against both standard strains (fractional inhibitory concentration [FIC] index = 0.75 and 0.73) and S. aureus isolates (FIC index = 0.62) and synergy against S. pneumoniae isolates (FIC index = 0.5).

Evaluation of the hepatoprotective and antioxidant activities of Rubus parvifolius L.

The hepatoprotective and antioxidant activities of the n-butanol extract of Rubus parvifolius L. (RPL), a widely used medicinal plant, were evaluated. Results demonstrated that RPL extract possessed pronounced hepatoprotective effects against carbon tetrachloride (CCl(4))-induced hepatic injury in mice, which was at least partially attributed to its strong antioxidant capacity. Treatment with RPL extract markedly attenuated the increases in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels caused by CCl(4) intoxication. It also significantly prevented the decrease in superoxide dismutase (SOD) activity and the increase in malondialdehyde (MDA) content of liver tissue. Meanwhile, histopathological changes of hepatic damage were also remarkably ameliorated. Phytochemical analysis based on high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) revealed the presence of various phenolic compounds, including caffeic acid conjugates, ellagic acid glycosides, and flavonol glycosides, which might be responsible for the hepatoprotective and antioxidant activities of RPL.

Isolation, structure determination and cannabinoid receptor activating effect of new metabolites of Echinacea purpurea root

Extracts of Echinacea purpurea are extensively used in the therapy of common cold and upper respiratory tract infections as immunomodulators and anti-inflammatory agents. The extracts of the root and herb of E. purpurea have a complex chemical composition, including alkamides, caffeic acid conjugates, and polysaccharides. Alkamides, the main lipophilic compounds, are the modulators of the endocannabinoid system in consequence of their structural similarity to the endogenous ligand anandamide. Recently, receptor binding assays demonstrated the CB2 receptor affinity of Echinacea alkamides, proving by this the CB2-receptor-dependent immunomodulatory effect [1,2]. The aim of the present study was to reinvestigate the chemical composition of the roots of E. purpurea and to gain new information about the affinity of the isolated compounds to the cannabinoid system. The nhexane-soluble extract of the root was subjected to multiple chromatographic separations affording 19 compounds. The structures were analysed by extensive NMR and MS studies resulting the identification of four new natural products (3 alkamides and nitidanin-diisovalerianate). In addition, five compounds were detected for the first time in this species, and ten known E. purpurea metabolites were identified. Cannabinoid receptor activation of thirteen isolated compounds has been studied by [35S]GTPγS binding assays in rat brain membranes. This test measures (i) receptor-mediated G-protein activation induced by agonists and (ii) inhibition by antagonist ligands. A number of E. purpurea compounds turned out to be weak-to-moderate partial agonists, while others displayed inverse-agonist actions. In the presence of a reference CB1 receptor agonist, both sort of compounds exhibited concentration-dependent competitive antagonist effects.

Polyphenol content and antioxidant capacity of eggplant skin

Eggplant (Solanum melongena) represents one of the best dietary sources of biologically active polyphenolic compounds. Polyphenolic‐rich extracts from darkly colored grape and cranberry fruit skins are known to inhibit the oxidative modification of low density lipoprotein (LDL) lipids and proteins. Dark purple skinned Blackbell and Millionaire eggplant varieties were grown under controlled agricultural conditions after which the skin polyphenolic content was extracted. Skin extracts contained phenolic acids (3‐caffeoylquinic acid, 4‐caffeoylquinic acid,5‐caffeoylqunic, dihydroxy cinnamoyl amide, caffeic acid conjugates), flavonols (myricetin‐3‐galactoside, quercitin‐3‐glucoside, quercitin‐3‐rhamanoside), in addition to anthocyanins, and proanthocyanidins whose specific identity were not determined. Polyphenolic extracts from all sources potently delayed the cupric ion‐mediated lag‐time for LDL lipid oxidation (234 nm), the formation of thiobarbituric acid reactive substances, and protected Apo‐B100 proteins against oxidative modification. Future studies of the biological activities of eggplant polyphenolics may improve eggplant cultivar selection for nutritional health benefits.

Bioavailability of Echinacea Constituents: Caco-2 Monolayers and Pharmacokinetics of the Alkylamides and Caffeic Acid Conjugates

Many studies have been done over the years to assess the effectiveness of Echinacea as an immunomodulator. We have assessed the potential bioavailability of alkylamides and caffeic acid conjugates using Caco-2 monolayers and compared it to their actual bioavailability in a Phase I clinical trial. The caffeic acid conjugates permeated poorly through the Caco-2 monolayers. Alkylamides were found to diffuse rapidly through Caco-2 monolayers. Differences in diffusion rates for each alkylamide correlated to structural variations, with saturation and N-terminal methylation contributing to decreases in diffusion rates. Alkylamide diffusion is not affected by the presence of other constituents and the results for a synthetic alkylamide were in line with those for alkylamides found in an ethanolic Echinacea preparation. We examined plasma from healthy volunteers for 12 hours after ingestion of Echinacea tablets manufactured from an ethanolic liquid extract. Caffeic acid conjugates could not be identified in any plasma sample at any time after tablet ingestion. Alkylamides were detected in plasma 20 minutes after tablet ingestion and for each alkylamide, pharmacokinetic profiles were devised. The data are consistent with the dosing regimen of one tablet three times daily and supports their usage as the primary markers for quality Echinacea preparations.

Echinacea alkamide disposition and pharmacokinetics in humans after tablet ingestion

Echinacea is a widely used herbal remedy for the treatment of colds and other infections. However, almost nothing is known about the disposition and pharmacokinetics of any of its components, particularly the alkamides and caffeic acid conjugates which are thought to be the active phytochemicals. In this investigation, we have examined serial plasma samples from 9 healthy volunteers who ingested echinacea tablets manufactured from ethanolic liquid extracts of Echinacea angustifolia and Echinacea purpurea immediately after a standard high fat breakfast. Caffeic acid conjugates could not be identified in any plasma sample at any time after tablet ingestion. Alkamides were rapidly absorbed and were measurable in plasma 20 min after tablet ingestion and remained detectable for up to 12 h. Concentration–time curves for 2,4-diene and 2-ene alkamides were determined. The maximal concentrations for the sum of alkamides in human plasma were reached within 2.3 h post ingestion and averaged 336 ± 131 ng eq/mL plasma. No obvious differences were observed in the pharmacokinetics of individual or total alkamides in 2 additional fasted subjects who took the same dose of the echinacea preparation. This single dose study provides evidence that alkamides are orally available and that their pharmacokinetics are in agreement with the one dose three times daily regimen already recommended for echinacea.

Permeability studies of alkylamides and caffeic acid conjugates from echinacea using a Caco-2 cell monolayer model.

Echinacea is composed of three major groups of compounds that are thought to be responsible for stimulation of the immune system--the caffeic acid conjugates, alkylamides and polysaccharides. This study has focussed on the former two classes, as these are the constituents found in ethanolic liquid extracts. To investigate the absorption of these two groups of compounds using Caco-2 monolayers, which are a model of the intestinal epithelial barrier. The caffeic acid conjugates (caftaric acid, echinacoside and cichoric acid) permeated poorly through the Caco-2 monolayers although one potential metabolite, cinnamic acid, diffused readily with an apparent permeability (Papp) of 1 x 10(-4) cm/s. Alkylamides were found to diffuse through Caco-2 monolayers with Papp ranging from 3 x 10(-6) to 3 x 10(-4) cm/s. This diversity in Papp for the different alkylamides correlates to structural variations, with saturation and N-terminal methylation contributing to decreases in Papp. The transport of the alkylamides is not affected by the presence of other constituents and the results for synthetic alkylamides were in line with those for the alkylamides in the echinacea preparation. Alkylamides but not caffeic acid conjugates are likely to cross the intestinal barrier.

Phenolic Acid Content and Composition of Eggplant Fruit in a Germplasm Core Subset

Eggplant (Solanum melongena L.) is ranked among the top ten vegetables in terms of oxygen radical absorbance capacity due to its fruit's phenolic constituents. Several potential health promoting effects have been ascribed to plant phenolic phytochemicals. We report here a first evaluation of phenolic acid constituents in eggplant fruit from accessions in the USDA eggplant core subset. The core subset includes 101 accessions of the cultivated eggplant, S. melongena, and 14 accessions representing four related eggplant species, S. aethiopicum L., S. anguivi Lam., S. incanum L., and S. macrocarpon L. Significant differences in phenolic acid content and composition were evident among the five eggplant species and among genotypes within species. Fourteen compounds separated by HPLC, that were present in many but not all accessions, were identified or tentatively identified as hydroxycinnamic acid (HCA) derivatives based on HPLC elution times, UV absorbance spectra, ES-—MS mass spectra, and in some cases proton NMR data. These phenolics were grouped into five classes: chlorogenic acid isomers, isochlorogenic acid isomers, hydroxycinnamic acid amide conjugates, unidentified caffeic acid conjugates, and acetylated chlorogenic acid isomers. Among S. melongena accessions, there was a nearly 20-fold range in total HCA content. Total HCA content in S. aethiopicum and S. macrocarpon was low relative to S. melongena. A S. anguivi accession had the highest HCA content among core subset accessions. Chlorogenic acid isomers ranged from 63.4% to 96% of total HCAs in most core accessions. Two atypical accessions, S. anguivi PI 319855 and S. incanum PI500922, exhibited strikingly different HCA conjugate profiles, which differed from those of all other core subset accessions by the presence of several unique phenolic compounds. Our findings on eggplant fruit phenolic content provide opportunities to improve eggplant fruit quality and nutritive value.

Distribution of hydroxycinnamic acid conjugates in fruit of commercial eggplant (Solanum melongena L.) cultivars.

There is gathering evidence that antioxidant phytonutrients in fruits and vegetables have health-promoting effects. Eggplant fruit have a high content of antioxidant phenolic compounds. We evaluated the main class of eggplant phenolics, hydroxycinnamic acid conjugates, in the fruit of seven commercial cultivars. Fourteen conjugates were quantified and identified by high-performance liquid chromatography, ES(-)-MS, and (1)H NMR data. Significant differences in their content and composition were evident among cultivars and in tissue from stem, middle, and blossom end segments. Chlorogenic acid (5-O-caffeoylquinic acid) was the predominant compound, and its 3-O-, 4-O-, and 5-O-cis isomers were also present. The 10 other phenolics fell into four groups, including 3,5- and 4,5-dicaffeoylquinic acid isomers, four amide conjugates, two unknown caffeic acid conjugates, and 3-O-acetyl esters of 5-O- and 4-O-caffeoylquinic acid. Dicaffeoylquinic and 3-O-acetyl chlorogenic acids were most variable among the cultivars. Dicaffeoyquinic acids were most abundant in the blossom end, whereas 3-O-acetyl esters were highest in the midsection.

CYP98A3 from Arabidopsis thaliana Is a 3′-Hydroxylase of Phenolic Esters, a Missing Link in the Phenylpropanoid Pathway

The 4- and 5-hydroxylations of phenolic compounds in plants are catalyzed by cytochrome P450 enzymes. The 3-hydroxylation step leading to the formation of caffeic acid from p-coumaric acid remained elusive, however, alternatively described as a phenol oxidase, a dioxygenase, or a P450 enzyme, with no decisive evidence for the involvement of any in the reaction in planta. In this study, we show that the gene encoding CYP98A3, which was the best possible P450 candidate for a 3-hydroxylase in the Arabidopsis genome, is highly expressed in inflorescence stems and wounded tissues. Recombinant CYP98A3 expressed in yeast did not metabolize free p-coumaric acid or its glucose or CoA esters, p-coumaraldehyde, or p-coumaryl alcohol, but very actively converted the 5-O-shikimate and 5-O-d-quinate esters of trans-p-coumaric acid into the corresponding caffeic acid conjugates. The shikimate ester was converted four times faster than the quinate derivative. Antibodies directed against recombinant CYP98A3 specifically revealed differentiating vascular tissues in stem and root. Taken together, these data show that CYP98A3 catalyzes the synthesis of chlorogenic acid and very likely also the 3-hydroxylation of lignin monomers. This hydroxylation occurs on depsides, the function of which was so far not understood, revealing an additional and unexpected level of networking in lignin biosynthesis.

Flavonoids and verbascoside as chemotaxonomic characters in the genera Oxera and Faradaya (Labiatae)

Most known species belonging to the closely related genera Oxera and Faradaya (Labiatae) were investigated for their caffeic acid conjugates and flavonoids. Verbascoside was detected in all species, varying from very high concentrations in Faradaya and the Oxera pulchella-group, to trace amounts in the O. neriifolia-group and O. sulfurea. Rosmarinic acid was absent. The most common flavonoids in both genera were 7-O-glucuronides of flavones. In addition, more than 50% of the species contained flavones glycosylated in the B-ring. Flavone C-glycosides were restricted to Faradaya, the O. neriifolia-group and O. crassifolia, whereas O. coriacea contained a flavonol glycoside. No 6-hydroxylated flavones were found, which are characteristic flavonoids in the related genus Clerodendrum in which Faradaya was formerly included. On the whole, the range of phenolics was very similar in Oxera and Faradaya, but in Oxera total flavonoid levels were more or less equal to or higher than those of verbascoside-type compounds, whereas in Faradaya the latter were much higher. Ratios of the levels of flavonoids and verbascosides also correlated with informal classification within Oxera mainly based on morphological characters, as did presence of flavone C- and certain di-O-glycosides.

Synthesis and evaluation of lysozyme derivatives exhibiting an enhanced antimicrobial action

In order to generate novel preservatives exhibiting a broad antimicrobial spectrum against Gram-positive as well as Gram-negative bacteria, lysozyme was modified by the covalent attachment of caffeic acid and cinnamic acid, respectively. Linkage of these organic acids to lysozyme was achieved by the constitution of amide bindings between the carboxyl group of ligands and primary amino groups of the enzyme mediated by a carbodiimide. Compared to nonmodified lysozyme, the lytic activity of all resulting conjugates was reduced. In contrast, bacterial growth of Escherichia coli (ATCC 8739) could be strongly inhibited by lysozyme–caffeic acid conjugates and to a lower degree also by lysozyme–cinnamic acid conjugates. The minimal inhibitory concentration against E. coli was 0.05% for the lysozyme derivative of the highest antimicrobial activity. However, the efficacy of lysozyme derivatives against Staphylococcus aureus (ATCC 6538) was slightly reduced. As the antimicrobial spectrum of lysozyme altogether could be substantially widened, these derivatives represent promising candidates as novel preservatives for various pharmaceutical and cosmetic formulations.