Rafaela Guimarães

Targeting excessive free radicals with peels and juices of citrus fruits: Grapefruit, lemon, lime and orange

A comparative study between the antioxidant properties of peel (flavedo and albedo) and juice of some commercially grown citrus fruit (Rutaceae), grapefruit (Citrus paradisi), lemon (Citrus limon), lime (Citrusxaurantiifolia) and sweet orange (Citrus sinensis) was performed. Different in vitro assays were applied to the volatile and polar fractions of peels and to crude and polar fraction of juices: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, reducing power and inhibition of lipid peroxidation using beta-carotene-linoleate model system in liposomes and thiobarbituric acid reactive substances (TBARS) assay in brain homogenates. Reducing sugars and phenolics were the main antioxidant compounds found in all the extracts. Peels polar fractions revealed the highest contents in phenolics, flavonoids, ascorbic acid, carotenoids and reducing sugars, which certainly contribute to the highest antioxidant potential found in these fractions. Peels volatile fractions were clearly separated using discriminant analysis, which is in agreement with their lowest antioxidant potential.

Characterisation of phenolic compounds in wild fruits from Northeastern Portugal

This study aimed to analyse the phenolic composition of wild fruits of Arbutus unedo (strawberry-tree), Prunus spinosa (blackthorn), Rosa canina and Rosa micrantha (wild roses). Analyses were performed by HPLC-DAD-ESI/MS. P spinosa fruits presented the highest concentration in phenolic acids (29.78 mg/100 g dry weight), being 3-O-caffeoylquinic acid the most abundant one, and flavone/ols (57.48 mg/100 g), among which quercetin3-O-rutinoside (15.63 mg/100 g) was the majority compound. (+)-Catechin was the most abundant compound in A. unedo (13.51 mg/100 g) and R. canina (3.59 mg/100 g) fruits. A. unedo fruits presented the highest concentration in flavan-3-ols (36.30 mg/100 g). Cyanidin 3-O-glucoside was found in all the studied fruits, being the major anthocyanin in most of them, with the exception of P. spinosa samples, in which cyaniding 3-O-rutinoside and peonidin 3-O-rutinoside predominated; P. spinosa fruit presented the more complex anthocyanin profile among the analysed fruits and also the highest anthocyanin concentrations, which was coherent with its greater pigmentation. All in all, P. spinosa presented the highest levels of phenolic acids and flavonoids, including anthocyanins, flavonols and flavones, although no flavan-3-ols could be identified in its fruits. The present study represents a contribution to the chemical characterisation of phenolic compounds from wild fruits with acknowledged antioxidant activity and traditionally used for several folk medicinal applications.

Nutrients, phytochemicals and bioactivity of wild Roman chamomile: a comparison between the herb and its preparations.

Roman chamomile, Chamaemelum nobile L. (Asteraceae), has been used for medicinal applications, mainly through oral dosage forms (decoctions and infusions). Herein, the nutritional characterisation of C. nobile was performed, and herbal material and its decoction and infusion were submitted to an analysis of phytochemicals and bioactivity evaluation. The antioxidant activity was determined by free radicals scavenging activity, reducing power and inhibition of lipid peroxidation, the antitumour potential was tested in human tumour cell lines (breast, lung, colon, cervical and hepatocellular carcinomas), and the hepatotoxicity was evaluated using a porcine liver primary cell culture. C. nobile proved to be an equilibrated valuable herb rich in carbohydrates and proteins, and poor in fat, providing tocopherols, carotenoids and essential fatty acids (C18:2n6 and C18:3n3). Moreover, the herb and its infusion are a source of phenolic compounds (flavonoids such as flavonols and flavones, phenolic acids and derivatives) and organic acids (oxalic, quinic, malic, citric and fumaric acids) that showed antioxidant and antitumour activities, without hepatotoxicity. The most abundant compounds in the plant extract and infusion were 5-O-caffeoylquinic acid and an apigenin derivative. These, as well as other bioactive compounds, are affected in C. nobile decoction, leading to a lower antioxidant potential and absence of antitumour potential. The plant bioactivity could be explored in the medicine, food, and cosmetic industries.

Infusion and decoction of wild German chamomile: Bioactivity and characterization of organic acids and phenolic compounds

Natural products represent a rich source of biologically active compounds and are an example of molecular diversity, with recognised potential in drug discovery. Herein, the methanol extract of Matricaria recutita L. (German chamomile) and its decoction and infusion (the most consumed preparations of this herb) were submitted to an analysis of phytochemicals and bioactivity evaluation. The antioxidant activity was determined by free radicals scavenging activity, reducing power and inhibition of lipid peroxidation; the antitumour potential was tested in human tumour cell lines (breast, lung, colon, cervical and hepatocellular carcinomas), and the hepatotoxicity was evaluated using a porcine liver primary cell culture (non-tumour cells). All the samples revealed antioxidant properties. The decoction exhibited no antitumour activity (GI(50)>400 μg/mL) which could indicate that this bioactivity might be related to compounds (including phenolic compounds) that were not extracted or that were affected by the decoction procedure. Both plant methanol extract and infusion showed inhibitory activity to the growth of HCT-15 (GI(50) 250.24 and 298.23 μg/mL, respectively) and HeLa (GI(50) 259.36 and 277.67 μg/mL, respectively) cell lines, without hepatotoxicity (GI(50)>400 μg/mL). Infusion and decoction gave higher contents of organic acids (24.42 and 23.35 g/100g dw). Otherwise, the plant methanol extract contained the highest amounts of both phenolic acids (3.99 g/100g dw) and flavonoids (2.59 g/100g dw). The major compound found in all the preparations was luteolin O-acylhexoside. Overall, German chamomile contains important phytochemicals with bioactive properties (mainly antitumour potential selective to colon and cervical carcinoma cell lines) to be explored in the pharmaceutical, food and cosmetics industries.

Studies on chemical constituents and bioactivity of Rosa micrantha: an alternative antioxidants source for food, pharmaceutical, or cosmetic applications.

Rose species have long been used for food and medicinal purposes. Rosa micrantha is one of the rose species that grow feral in the northeastern Portuguese region so-called Nordeste Transmontano. For the first time, chemical composition and bioactivity of their petals, fertilized flowers, unripe, ripening, and overripe hips were evaluated in order to valorize them as sources of important phytochemicals. Chemical characterization included determination of proteins, fats, ash, and carbohydrates, particularly sugars, by HPLC-RI, fatty acids by GC-FID, tocopherols by HPLC-fluorescence, and phenolics, flavonoids, carotenoids, and ascorbic acid by spectrophotometric techniques. Bioactivity was evaluated through screening of antioxidant properties: radical scavenging effects, reducing power, and inhibition of lipid peroxidation. Ripening and overripe hips showed high nutritional value including proteins, carbohydrates, omega-3 and omega-6 fatty acids, energy, sugars, particularly the reducing sugars fructose and glucose, and ascorbic acid (>693 mg/100 g). Fertilized flowers and petals revealed the highest antioxidant activity (EC(50) > 152 microg/mL) and phenolics, flavonoids, and tocopherols contents (>35 mg/100 g). Furthermore, petals, ripening, and overripe hips are important sources of carotenoid pigments (>64 mg/100 g). Because of the diversity and abundance of antioxidants found in this species, some food, cosmetic, and pharmaceutical applications could be explored.

Infusions and Decoctions of Mixed Herbs used in Folk Medicine: Synergism in Antioxidant Potential

Infusions (herbal teas) and decoctions are used frequently to administer oral doses of herbs. Although some herbs are used as single ingredients, they are often prepared as mixtures, as reported by numerous ethnobotanical surveys. The present work was carried out to identify the different types of interaction (synergistic, additive and antagonistic effects) which may be found in the antioxidant activity of preparations from mixtures of the popular herbs Aloysia citrodora (lemon verbena), Foeniculum vulgare (fennel) and Mentha spicata (spearmint). Herbs were prepared using traditional methods, and the effects after different periods of storage, up to 120 days, were also evaluated. Antioxidant activity was evaluated using DPPH radical scavenging activity, reducing power and inhibition of lipid peroxidation by the β‐carotene – linoleate system and the TBARS assay. Known antioxidant compounds such as total phenolics, flavonoids, ascorbic acid and reducing sugars were also determined. Spearmint was found to be present in the herb mixtures with the greatest antioxidant activity and these also had the highest flavonoid content. The most potent antioxidant activity was found in combinations of different herbs, suggesting synergistic effects. Copyright

Wild Roman chamomile extracts and phenolic compounds: enzymatic assays and molecular modelling studies with VEGFR-2 tyrosine kinase

Angiogenesis is a process by which new blood vessels are formed from the pre-existing vasculature, and it is a key process that leads to tumour development. Some studies have recognized phenolic compounds as chemopreventive agents; flavonoids, in particular, seem to suppress the growth of tumor cells modifying the cell cycle. Herein, the antiangiogenic activity of Roman chamomile (Chamaemelum nobile L.) extracts (methanolic extract and infusion) and the main phenolic compounds present (apigenin, apigenin-7-O-glucoside, caffeic acid, chlorogenic acid, luteolin, and luteolin-7-O-glucoside) was evaluated through enzymatic assays using the tyrosine kinase intracellular domain of the Vascular Endothelium Growth Factor Receptor-2 (VEGFR-2), which is a transmembrane receptor expressed fundamentally in endothelial cells involved in angiogenesis, and molecular modelling studies. The methanolic extract showed a lower IC50 value (concentration that provided 50% of VEGFR-2 inhibition) than the infusion, 269 and 301 μg mL(-1), respectively. Regarding phenolic compounds, luteolin and apigenin showed the highest capacity to inhibit the phosphorylation of VEGFR-2, leading us to believe that these compounds are involved in the activity revealed by the methanolic extract.