Federico Ferreres

Phenolic compounds from Brazilian propolis with pharmacological activities.

Four compounds were isolated from Brazilian propolis. They are identified as: (1) 3-prenyl-4-hydroxycinnamic acid (PHCA), (2) 2,2-dimethyl-6-carboxyethenyl-2H-1-benzopyrane (DCBEN), (3) 3,5-diprenyl-4-hydroxycinnamic acid (DHCA), and (4) 2,2-dimethyl-6-carboxyethenyl-8-prenyl-2H-1-benzopyran (DPB). The structures of the compounds were determined by MS and NMR techniques. All compounds were assayed against Trypanosoma cruzi and the bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus faecalis. Compounds (1) to (4) were active against T. cruzi. Except (1), all compounds presented activity against the bacteria tested. When compounds (1)-(3) were tested in the guinea pig isolated trachea, all induced a relaxant effect similar to propolis extract.

Characterisation of polyphenols and antioxidant properties of five lettuce varieties and escarole.

Salad vegetables could be relevant as dietary sources of natural antioxidants. A better knowledge of their composition can be useful for understanding their potential bioavailability and biological activities. The antioxidant compounds, polyphenols and vitamin C, have been determined in five varieties of lettuce (iceberg, romaine, continental, red oak leaf, lollo rosso) and one variety of escarole (frissé). The polyphenol study by HPLC-DAD-MS/MS ESI allowed the identification of two compounds previously not reported in lettuce; quercetin and luteolin rhamnosyl-hexosides. Qualitative and quantitative differences were observed between the polyphenol profiles. Caffeic acid derivatives were the main phenolics in green varieties, while flavonols were detected in higher quantities in red varieties and escarole, and anthocyanins were only present in red-leafed varieties. The highest total phenolic content was observed in red-leafed varieties while the highest level of vitamin C was detected in the continental variety. The red varieties showed the highest antioxidant activity by all the methods assayed.

Flavonoids, phenolic acids and abscisic acid in Australian and New Zealand Leptospermum honeys

Flavonoids, phenolic acids and abscisic acid of Australian and New Zealand Leptospermum honeys were analyzed by HPLC. Fifteen flavonoids were isolated in Australian jelly bush honey (Leptospermum polygalifolium), with an average content of 2.22 mg/100 g honey. Myricetin (3,5,7,3′,4′,5′-hexahydroxyflavone), luteolin (5,7,3′,4′-tetrahydroxyflavone) and tricetin (5,7,3′,4′,5′-pentahydroxyflavone) were the main flavonoids identified. The mean content of total phenolic acids in jelly bush honey was 5.14 mg/100 g honey, with gallic and coumaric acids as the potential phenolic acids. Abscisic acid was quantified as twice the amount (11.6 mg/100 g honey) of the phenolic acids in this honey. The flavonoid profile mainly consisted of quercetin (3,5,7,3′,4′-pentahydroxyflavone), isorhamnetin (3,5,7,4′-tetrahydroxyflavone 3′-methyl ethyl), chrysin (5,7-dihydroxyflavone), luteolin and an unknown flavanone in New Zealand manuka (Leptospermum scoparium) honey with an average content of total flavonoids of 3.06 mg/100 g honey. The content of total phenolic acids was up to 14.0 mg/100 g honey, with gallic acid as the main component. A substantial quantity (32.8 mg/100 g honey) of abscisic acid was present in manuka honey. These results showed that flavonoids and phenolic acids could be used for authenticating honey floral origins, and abscisic acid may aid in this authentication.

Phytochemical evidence for the botanical origin of tropical propolis from Venezuela

Abstract The phenolic compounds present in 38 propolis samples produced in tropical Venezuela by imported Apis mellifera and five indigenous species of stingless bees, and seven propolis samples from different temperate regions were analysed by HPLC. The different tropical propolis generally showed a single phenolic profile characterized by the occurrence of polyprenylated benzophenones as major components. Flavonoids were present in only a few samples, and in each case they were found to be lipophilic methylated 6-oxygenated flavones (eupatorin, hispidulin, 5-hydroxy-6,7,3′,4′-tetramethoxyflavone, etc.). Generally, no correlations between the composition of tropical propolis and the place of collection or the bee species were found. However, propolis from temperate areas contained flavonoids (with an unsubstituted ring B) as the main phenolic components (pinobanksin, pinobanksin 3-acetate, pinocembrin, chrysin, galangin and tectochrysin). These analyses confirmed that the source of the phenolics found in propolis produced in temperate regions was different Populus species of section Aigeiros (Salicaceae). The resins exuded by the flowers of Clusia minor and C. major (Guttiferae) contained the polyprenylated benzophenones found in the majority of the propolis studied, suggesting that this is the main source for propolis in tropical Venezuela.

Analysis of Honey Phenolic Acids by HPLC, Its Application to Honey Botanical Characterization

In this work we described an analytical technique that allowed the identification of 12 phenolic acids in honey samples, with emphasis on those phenolics acids which are markers of the botanical origin. After optimization of the HPLC conditions, this was applied to the phenolic acids analysis of 20 Erica sp. (heather) and 20 Lavandula stoechas (lavander) portuguese honeys. A close correlation between the phenolic acids patterns and the botanical origin of honey has been found. Erica sp. honeys are characterized by ellagic, p-hydroxybenzoic, syringic and o-coumaric acids, and Lavandula stoechas honeys by gallic acid.

Identification of phenolic compounds in isolated vacuoles of the medicinal plant Catharanthus roseus and their interaction with vacuolar class III peroxidase: an H2O2 affair?

Class III peroxidases (Prxs) are plant enzymes capable of using H(2)O(2) to oxidize a range of plant secondary metabolites, notably phenolic compounds. These enzymes are localized in the cell wall or in the vacuole, which is a target for secondary metabolite accumulation, but very little is known about the function of vacuolar Prxs. Here, the physiological role of the main leaf vacuolar Prx of the medicinal plant Catharanthus roseus, CrPrx1, was further investigated namely by studying its capacity to oxidize co-localized phenolic substrates at the expense of H(2)O(2). LC-PAD-MS analysis of the phenols from isolated leaf vacuoles detected the presence of three caffeoylquinic acids and four flavonoids in this organelle. These phenols or similar compounds were shown to be good CrPrx1 substrates, and the CrPrx1-mediated oxidation of 5-O-caffeoylquinic acid was shown to form a co-operative regenerating cycle with ascorbic acid. Interestingly, more than 90% of total leaf Prx activity was localized in the vacuoles, associated to discrete spots of the tonoplast. Prx activity inside the vacuoles was estimated to be 1809 nkat ml(-1), which, together with the determined concentrations for the putative vacuolar phenolic substrates, indicate a very high H(2)O(2) scavenging capacity, up to 9 mM s(-1). Accordingly, high light conditions, known to increase H(2)O(2) production, induced both phenols and Prx levels. Therefore, it is proposed that the vacuolar couple Prx/secondary metabolites represent an important sink/buffer of H(2)O(2) in green plant cells.

Determination of phenolic compounds in honeys with different floral origin by capillary zone electrophoresis

Abstract Twenty-six phenolic compounds from honey samples with different floral origin were analysed by capillary zone electrophoresis. All the phenolics were separated on a fused-silica column (50 cm × 50 μm) using 100 mM sodium borate buffer (pH 9.5)−20% methanol. This technique was applied to the separation of phenolic compounds from heather, lavender, acacia, rape, sunflower, rosemary, citrus, rhododendron, thyme, chestnut-tree and calluna honey samples, to establish correlations between the phenolics profiles and the botanical origin of the honey. Some individual honey samples showed potential floral markers. Thus, thyme honey was characterised by the presence of rosmarinic acid, heather honey by ellagic acid, citrus honey by hesperetin and lavender honey by naringenin.

Differential responses of five cherry tomato varieties to water stress: changes on phenolic metabolites and related enzymes.

Different tomato cultivars (Solanum lycopersicum L.) with differences in tolerance to drought were subjected to moderate water stress to test the effects on flavonoids and caffeoyl derivatives and related enzymes. Our results indicate that water stress resulted in decreased shikimate pathway (DAHP synthase, shikimate dehydrogenase, phenylalanine ammonium lyase, cinnamate 4-hydroxylase, 4-coumarate CoA ligase) and phenolic compounds (caffeoylquinic acid derivatives, quercetin and kaempferol) in the cultivars more sensitive to water stress. However, cv. Zarina is more tolerant, and registered a rise in querc-3-rut-pent, kaempferol-3-api-rut, and kaempferol-3-rut under the treatment of water stress. Moreover, this cultivar show increased activities of flavonoid and phenylpropanoid synthesis and decreased in degradation-related enzymes. These results show that moderate water stress can induce shikimate pathway in tolerant cultivar.

Phenolic fingerprint of peppermint leaves

A reversed-phase high-performance liquid chromatography procedure is proposed for the determination of 10 phenolic compounds (eriodictyol 7-O-rutinoside, eriodictyol 7-O-glucoside, luteolin 7-O-rutinoside, luteolin 7-O-glucoside, hesperetin 7-O-rutinoside, apigenin 7-O-rutinoside, rosmarinic acid, 5,6-dihydroxy-7,8,3′,4′-tetramethoxyflavone, pebrellin and gardenin B) in peppermint. The chromatographic separation was achieved using a reversed-phase Spherisorb ODS 2 (5 μm particle size; 25.0×0.46 cm) column. Of the several extractive solvents tried, ethanol was the best for qualitative and quantitative analysis. Best resolution was obtained using a gradient of water-phosphoric acid (999:1) and acetonitrile. Fourteen samples were subjected to quantification and showed a common composition pattern.

Floral nectar phenolics as biochemical markers for the botanical origin of heather honey

In order to find out biochemical markers for the botanical origin of heather (Erica) honey, the phenolic metabolites present in heather floral nectar, collected from the honey-stomach of bees gathering nectar from these flowers, were analysed. The flavonoid fraction of nectar contained four main flavonoids. Two of them were quercetin and kaempferol 3-rhamnosides, and the other two were tentatively identified as myricetin 3′-methyl ether and isorhamnetin 3-rhamnosides. Since the natural glycosides are hydrolysed by bee enzymes to render the corresponding aglycones, which are the metabolites detected in honey, acid hydrolysis of the nectar glycosides was achieved. The aglycones quercetin, myricetin 3′-methyl ether, kaempferol and isorhamnetin were identified, as well as the gallic acid derivative ellagic acid. The analysis of Portuguese heather honey samples showed that ellagic acid was present in all the samples in significant amounts ranging between 100 μg and 600 μg per 100 g honey. The other nectar-derived flavonoids were also present, although some of them in very variable amounts. Ellagic acid and myricetin 3′-methyl ether, which have not been detected in any of the monofloral honey samples investigated so far, with the only exception being a French honey sample of the botanically relatedCalluna (Ericaceae) which also contained ellagic acid, seem to be the most useful potential markers for the floral origin of heather honey. However, more detailed and extensive investigations are needed to prove the utility of these markers.