Marcelo D. Catarino

Antioxidant Capacities of Flavones and Benefits in Oxidative-Stress Related Diseases

Flavonoids, a group of secondary metabolites widely distributed in the plant kingdom, have been acknowledged for their interesting medicinal properties. Among them, natural flavones, as well as some of their synthetic derivatives, have been shown to exhibit several biological activities, including antioxidant, anti-inflammatory, antitumor, anti-allergic, neuroprotective, cardioprotective and antimicrobial. The antioxidant properties of flavones allow them to demonstrate potential application as preventive and attenuating agents in oxidative stress, i.e., a biological condition that is closely associated to aging processes and to several diseases. Some flavones interfere in distinct oxidative-stress related events by directly reducing the levels of intracellular free radicals (hydroxyl, superoxide and nitric oxide) and/or of reactive species (e.g. hydrogen peroxide, peroxynitrite and hypochlorous acid) thus preventing their amplification and the consequent damage of other biomolecules such as lipids, proteins and DNA. Flavones can also hinder the activity of central free radical-producing enzymes, such as xanthine oxidase and nicotinamide adenine dinucleotide phosphate oxidase (NADPH-oxidase) or inducible nitric oxide synthase (iNOS) and can even modulate the intracellular levels of oxidant and/or antioxidant enzymes. The evaluation of flavones antioxidant ability has been extensively determined in chemical or biological in vitro models, but in vivo therapy with individual flavones or with flavones-enriched extracts has also been reported. The present manuscript revises relevant studies focusing the preventive effects of flavones on stress-related diseases, namely the neurological and cardiovascular diseases and diabetes and its associated complications.

Fucaceae: A Source of Bioactive Phlorotannins

Fucaceae is the most dominant algae family along the intertidal areas of the Northern Hemisphere shorelines, being part of human customs for centuries with applications as a food source either for humans or animals, in agriculture and as remedies in folk medicine. These macroalgae are endowed with several phytochemicals of great industrial interest from which phlorotannins, a class of marine-exclusive polyphenols, have gathered much attention during the last few years due to their numerous possible therapeutic properties. These compounds are very abundant in brown seaweeds such as Fucaceae and have been demonstrated to possess numerous health-promoting properties, including antioxidant effects through scavenging of reactive oxygen species (ROS) or enhancement of intracellular antioxidant defenses, antidiabetic properties through their acarbose-like activity, stimulation of adipocytes glucose uptake and protection of β-pancreatic cells against high-glucose oxidative stress; anti-inflammatory effects through inhibition of several pro-inflammatory mediators; antitumor properties by activation of apoptosis on cancerous cells and metastasis inhibition, among others. These multiple health properties render phlorotannins great potential for application in numerous therapeutical approaches. This review addresses the major contribution of phlototannins for the biological effects that have been described for seaweeds from Fucaceae. In addition, the bioavailability of this group of phenolic compounds is discussed.

The Antiinflammatory Potential of Flavonoids: Mechanistic Aspects

Abstract Flavonoids are a subclass of phenolic compounds that occur ubiquitously in food plants and vegetables. This class of compounds shares a common 15-carbon structure represented by a benzene ring (A) condensed with a heterocyclic six-membered pyran or pyranone ring (C) that carries a phenyl ring (B) in the 2-, 3-, or 4-position. These compounds are known to modulate important cellular signaling processes including those associated with inflammatory diseases, hence rendering them a clinical potential in this area. In general, the antiinflammatory properties of flavonoids involve the inhibition of the activity of several proinflammatory biochemical mediators (cytokines, adhesion molecules, NO ) and enzymes (COX-2, LOX, iNOS). In addition, these compounds may also interact with important transcription factors and signaling pathways, including nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) thus regulating the proinflammatory genes’ expression. Importantly, the capacity of flavonoids to interact with these cellular markers is dependent on specific structural features. In general, the hydroxyl substitutions at the 3′-, 4′-, 5-, and 7-positions, the unsaturated C2 C3 function and the 4-keto group of the C-ring are the main structural requirements to provide efficient inhibition of signaling molecules. This manuscript revises relevant studies focusing the structure–affinity relationship between flavonoids and key inflammatory markers, underlying the specific structural features involved in these interactions, as well as an approach to some synthetic strategies aiming the enhancement of flavonoids antiinflammatory properties.Flavonoids are a subclass of phenolic compounds that occur ubiquitously in food plants and vegetables. This class of compounds shares a common 15-carbon structure represented by a benzene ring (A) condensed with a heterocyclic six-membered pyran or pyranone ring (C) that carries a phenyl ring (B) in the 2-, 3-, or 4-position. These compounds are known to modulate important cellular signaling processes including those associated with inflammatory diseases, hence rendering them a clinical potential in this area. In general, the antiinflammatory properties of flavonoids involve the inhibition of the activity of several proinflammatory biochemical mediators (cytokines, adhesion molecules, NO) and enzymes (COX-2, LOX, iNOS). In addition, these compounds may also interact with important transcription factors and signaling pathways, including nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) thus regulating the proinflammatory genes’ expression. Importantly, the capacity of flavonoids to interact with these cellular markers is dependent on specific structural features. In general, the hydroxyl substitutions at the 3′-, 4′-, 5-, and 7-positions, the unsaturated C2C3 function and the 4-keto group of the C-ring are the main structural requirements to provide efficient inhibition of signaling molecules. This manuscript revises relevant studies focusing the structure–affinity relationship between flavonoids and key inflammatory markers, underlying the specific structural features involved in these interactions, as well as an approach to some synthetic strategies aiming the enhancement of flavonoids antiinflammatory properties.

Plant Growth Modulates Metabolites and Biological Activities in Retama raetam (Forssk.) Webb

This work focuses on the variability of Retama raetam (Forssk.) Webb bioactive compounds as a function of the plant cycle. The main results showed that it exhibited the highest percentage of polyunsaturated fatty acids, along with superior levels of vitamin C and total phenolic compounds (66.49%, 645.6 mg·100 g−1 FW and 23.9 mg GAE·g−1, respectively) at the vegetative stage. Instead, at the flowering and mature fruiting stages, R. raetam (Forssk.) Webb exhibited notable contents of proline (25.4 μmol·g−1 DW) and carotenoids (27.2 μg·g−1 FW), respectively. The gathered data concerning the antioxidant activity highlighted the effectiveness of the vegetative stage in comparison to the other periods. Actually, IC50 and EC50 values of the hydromethanolic extract obtained from the plant shoots at the vegetative stage were of 23, 380, 410, 1160 and 960 μg·mL−1 (DPPH• and ABTS•+ radicals scavenging activity, reducing power, chelating power and β-carotene bleaching activity, respectively). Furthermore, the four studied stages showed appreciable antibacterial capacities against human pathogens with a higher efficiency of the vegetative stage extract. Finally, the LC-DAD-ESI/MSn analysis revealed the predominance of isoflavonoids as main class of phenolic compounds and demonstrates that individual phenolic biosynthesis was clearly different as a function of plant growth. These findings highlight that reaching the optimum efficiency of R. raetam (Forssk.) Webb is closely linked to the physiological stage.

Phycochemical Constituents and Biological Activities of Fucus spp.

Seaweeds are known to be a good supply of key nutrients including carbohydrates, protein, minerals, polyunsaturated lipids, as well as several other health-promoting compounds capable of acting on a wide spectrum of disorders and/or diseases. While these marine macroalgae are deeply rooted in the East Asian culture and dietary habits, their major application in Western countries has been in the phycocolloid industry. This scenario has however been gradually changing, since seaweed consumption is becoming more common worldwide. Among the numerous edible seaweeds, members of the genus Fucus have a high nutritional value and are considered good sources of dietary fibers and minerals, especially iodine. Additionally, their wealth of bioactive compounds such as fucoidan, phlorotannins, fucoxanthin and others make them strong candidates for multiple therapeutic applications (e.g., antioxidant, anti-inflammatory, anti-tumor, anti-obesity, anti-coagulant, anti-diabetes and others). This review presents an overview of the nutritional and phytochemical composition of Fucus spp., and their claimed biological activities, as well as the beneficial effects associated to their consumption. Furthermore, the use of Fucus seaweeds and/or their components as functional ingredients for formulation of novel and enhanced foods is also discussed.

Minerals from Macroalgae Origin: Health Benefits and Risks for Consumers

Seaweeds are well-known for their exceptional capacity to accumulate essential minerals and trace elements needed for human nutrition, although their levels are commonly very variable depending on their morphological features, environmental conditions, and geographic location. Despite this variability, accumulation of Mg, and especially Fe, seems to be prevalent in Chlorophyta, while Rhodophyta and Phaeophyta accumulate higher concentrations of Mn and I, respectively. Both red and brown seaweeds also tend to accumulate higher concentrations of Na, K, and Zn than green seaweeds. Their valuable mineral content grants them great potential for application in the food industry as new ingredients for the development of numerous functional food products. Indeed, many studies have already shown that seaweeds can be used as NaCl replacers in common foods while increasing their content in elements that are oftentimes deficient in European population. In turn, high concentrations of some elements, such as I, need to be carefully addressed when evaluating seaweed consumption, since excessive intake of this element was proven to have negative impacts on health. In this regard, studies point out that although very bioaccessible, I bioavailability seems to be low, contrarily to other elements, such as Na, K, and Fe. Another weakness of seaweed consumption is their capacity to accumulate several toxic metals, which can pose some health risks. Therefore, considering the current great expansion of seaweed consumption by the Western population, specific regulations on this subject should be laid down. This review presents an overview of the mineral content of prevalent edible European macroalgae, highlighting the main factors interfering in their accumulation. Furthermore, the impact of using these marine vegetables as functional ingredients or NaCl replacers in foods will be discussed. Finally, the relationship between macroalgae’s toxic metals content and the lack of European legislation to regulate them will be addressed.

Chromatography as a tool for identification of bioactive compounds in honeybee products of botanical origin

The authors gratefully acknowledge the financial support provided by the Foundation for Science and Technology (FCT) to CERNAS (Project PEstOE/ AGR/UI0681/2011) and of FCT the European Union, QREN, FEDER, COMPETE, for funding the Organic Chemistry Research Unit (QOPNA) (project PEst-C/QUI/UI0062/2013; FCOMP-01-0124-FEDER- 037296).