Phytochemistry Reviews (v.14, #6)

Preface by C. García-Viguera; A. Gil-Izquierdo; D. A. Moreno; N. Baenas (871-871).

Carotenoids in cereals: an ancient resource with present and future applications by Elena Mellado-Ortega; Dámaso Hornero-Méndez (873-890).
Cereals are considered to be a major source of carbohydrates and proteins as well as minor micronutrients such as minerals, vitamins and antioxidants, including carotenoids. Carotenoids are natural lipophilic pigments biosynthesized mainly by plants, and certain bacteria and fungi. Cereals, although having a low carotenoid content when compared with the majority of fruits and vegetables, may have an important impact in the nutritional status of consumers. The daily consumption of cereals, and products derived from them, by a large part of the population, especially in under-developed and developing countries, makes cereals a contributor of carotenoids which should not be overlooked and must be taken into consideration in biofortification strategies. In the present manuscript, we revise the existing information about the composition and distribution of carotenoids in cereals, highlighting factors which alter their profile, such as domestication of wild varieties, genotype, storage, milling and processing techniques. Strategies for stimulating the carotenoid content in cereals, either by means of traditional breeding methods or by genetic manipulation, are also discussed.
Keywords: Xanthophylls; Carotenes; Lutein; Wheat; Staple food

Exploring feasible sources for lutein production: food by-products and supercritical fluid extraction, a reasonable combination by María Victoria Álvarez; Sara Hincapié; Nataly Saavedra; Luz María Alzate; Ana María Muñoz; Claudio Jiménez Cartagena; Julián Londoño-Londoño (891-897).
Actually by-products from lettuce and cabbage have not been properly used despite the fact that they are rich in bioactive compounds as lutein. It is known that lutein plays an important role in the prevention of degenerative diseases. Lutein, is recommended as a health supplement for the prevention of cancer and diseases related to retinal degeneration or to ameliorate the effects of degenerative diseases such as age-related macular degeneration. The aim of this work was to extract lutein from a mix of dried cabbage and lettuce using supercritical fluid extraction with CO2 as solvent (SFE-CO2), under different combinations of pressure and temperature in order to determining the lutein yield, total yield and antioxidant capacity. Also the extraction kinetic of lutein from cabbage and lettuce is shown in this work. The best lutein yield was obtained at 350 bar and 65 °C, while the highest antioxidant capacity was at 400 bar and 85 °C.
Keywords: Antioxidant; Cabbage; Carotenoids; Lettuce; Supercritical fluids

Multiple-approach studies to assess anthocyanin bioavailability by Iva Fernandes; Ana Faria; Victor de Freitas; Conceição Calhau; Nuno Mateus (899-919).
Anthocyanins that are commonly ingested from the diet are largely conjugated, metabolized by colon microbiota and excreted in the urine and feces, yielding in a rather low bioavailability. Nevertheless, there are several health-promoting properties attributed to the ingestion of dietary anthocyanins including cardiovascular and neuroprotective effects, and the prevention of some types of cancer. There are many doubts on which compounds are really involved and which are the molecular mechanisms underlying all those biological events. Some evidences have come forth supporting the idea that the dietary phenolics bioactive forms in vivo are not necessarily those which occur in nature, but rather conjugates or metabolites arising from them in the human body. So far, it has been quite difficult to clearly assess both native and metabolized forms in vivo and to distinguish their different biological roles. Also, although some anthocyanins bioavailability has been reported to be low, their tissue distribution and accumulation has to be considered. This may lead to an increase of their levels in some key targets. This feature would be likely to contribute to possible different biological properties of dietary anthocyanins depending on their biological target. The several approaches that have been undertaken to assess anthocyanin bioavailability have been reviewed herein.
Keywords: Anthocyanins; Metabolites; Bioavailability; Bioactivity; Gastric absorption

Grape stems as a source of bioactive compounds: application towards added-value commodities and significance for human health by Ana Barros; Amadeo Gironés-Vilaplana; Ana Texeira; Nieves Baenas; Raúl Domínguez-Perles (921-931).
Phenolic compounds occur in high concentration in grapes (Vitis vinifera L.) and grape’s by-products as secondary metabolites responsible for distinct functions linked to plants protection against biotic and abiotic environmental stress. Once integrated as an ingredient in added-value products, these compounds are responsible for the protective effect described regarding plant material extracts, which has become an increasingly important area of applied research. Grape stems constitute the less valorised residue from grapes derived from the winery industry. Moreover to their value as a source of bioactive (poly)phenols, this material could display an additional advantage due to their content in complex carbohydrates, which provide benefits through improving the digestive process as insoluble fibres that reduce the absorption of unhealthy fats and promote detoxification processes. However, the application of this material as a functional ingredient might entail the modification of the (poly)phenolic profile resulting from processing procedures. These microbiological derived compounds require a further evaluation concerning their biological activity and technological applications. The inclusion of intact (poly)phenolic extracts of grape-stems in cosmetic and pharmaceutical formulations may allow to evaluate directly the biological effect of these compounds in vivo. This is an overview of the compounds present in grape stems and their potential to exert valuable biological and technological applications through their integration in distinct added-value products as well as the impact of available processing alternatives.
Keywords: Winery industry; Waste management; Bioactive compounds; Biological activity; Technological applications

Protection of pancreatic β-cell function by dietary polyphenols by Margherita Dall’Asta; Morgane Bayle; Jérémie Neasta; Francesca Scazzina; Renato Bruni; Gérard Cros; Daniele Del Rio; Catherine Oiry (933-959).
Diabetes mellitus is a complex metabolic disorder and is considered a fast-growing global health problem. Type 2 diabetes (T2D) represents the majority of total diabetes prevalence and β-cell dysfunction has been described as a crucial point for this disease development and progression. To date, all of the common anti-hyperglycaemic drugs used for diabetes management cause undesirable side effects or problems with long-term efficacy or safety and the development of alternative approaches for the prevention as well as for the treatment of T2D might be a valuable solution to meet this rising demand. In this regards, numerous epidemiological studies indicate that exposure to certain polyphenol compounds is associated with the prevention of chronic diseases, including diabetes. Here, we review growing evidence suggesting that polyphenols can modulate the activity of various molecular targets, which are known to control β-cell function, involved in the development and the progression of this diabetes. The protective effects of polyphenols on β-cell function is reported with a particular focus on the mechanism of action behind polyphenol putative bioactivity. Animal and in vitro studies selected in this review, reporting about both flavonoid and non-flavonoid compounds, highlight the direct action of polyphenols on pancreatic β-cells, stimulating insulin secretion through the activation of specific cellular targets and protecting these cells from damages mediated by oxidative stress and inflammation, both typically elevated in diabetes. Some of the reviewed studies describe polyphenol effects comparable to those exerted by many drugs commonly used in diabetes treatment, and, in some occasions, synergistic polyphenol-drug interactions. Finally, future studies need to be addressed to the effects of specific polyphenol human and microbial metabolites, which are still poorly studied, in order to better define the preventive and therapeutic approach to contrast β-cell failure and diabetes progression.
Keywords: β-cell protection; Diabetes; Flavonoids; Insulin secretion

Plant derived inhibitors of bacterial efflux pumps: an update by Sandra Prasch; Franz Bucar (961-974).
Ever increasing numbers of antibiotic resistances are putting more and more pressure on research and global health systems. Multidrug-resistant bacteria even escape from second-line antibiotics and only a few promising candidates are presently in the pipeline. Intrinsic resistance of bacteria mediated by efflux pumps play a crucial role in the development and implementation of resistances. Efflux pump inhibitors represent one possible way to overcome this decreasing sensitivity of bacteria to antibiotics. The co-administration of such efflux pump inhibitors together with an antibiotic reduces the amount needed of the antibiotic for the same therapeutic effect by cutting side effects. These inhibitors have also the possibility to reactivate ineffective antibiotics again for therapy. Plants are facing constant bacterial exposure and are therefore a promising source for new efflux pump inhibitors due to the enormous compound diversity, low toxicity and high tolerability. Reviewing the literature, we herein present an update of newly discovered efflux pump inhibitors with plant-based origin against bacterial strains of concern. Various compounds from 23 different plants have been reported and evaluated for their potential as efflux pump inhibitors based on efflux and accumulation data. This review also discusses the hurdles of clinical implementation.
Keywords: Antibiotic; Bacteria; Efflux pump inhibitor; Plant natural products; Resistance

In a world of increasing resistance to current antibiotics, search of novel therapeutic options is urgently needed. The aim of this work was to screen plant crude extracts for direct or indirect (inhibition of resistance) antimicrobial activity. Four crude extracts from 12 plants traditionally used in Africa for the treatment of infections were obtained by successive extraction with hexane, dichloromethane, ethyl acetate, and methanol. All extracts were tested against Staphylococcus aureus MRSA ATCC33591 [resistant to β-lactams by production of β-lactamases and of a modified PBP target (PBP2a)]. Direct antimicrobial activity was tested by determination of Minimal Inhibitory Concentrations (MIC), and indirect activity, by determining interactions between antibiotics and extracts using checkerboard titration and calculation of Fractional Inhibitory Concentration Index (FICI; synergy: FICI ≤ 0.5; additivity: FICI ≤ 1). Combined antibiotics were ampicillin (sensitive to resistance mediated by β-lactamases and PBP2a) and oxacillin (sensitive to resistance mediated by PBP2a only). The dichloromethane extract of Vitellaria paradoxa leaves, the methanol extracts of Vitellaria paradoxa, Cola gigantea leaves and twigs, and of Tapinanthus bangwensis aerial parts showed direct antimicrobial activity (MIC 250–500 mg/L). The methanol extracts of Vitellaria paradoxa and Cola gigantea leaves and twigs showed additive or synergistic effects with oxacillin and ampicillin on MRSA ATCC33591 (FICI 0.28–1), suggesting a possible inhibition of PBP2a. The methanol extract of Tapinanthus bangwensis aerial parts and Anchomanes difformis roots improved the activity of ampicillin only (FICI 0.38–1), suggesting β-lactamase inhibition. Polyphenols and particularly tannins were shown to be responsible for these last effects, at least partially for Vitellaria paradoxa. These data need further research aiming at identifying the active compounds in these extracts.
Keywords: Plant extracts; Resistance modifying agent; MRSA; β-Lactams; Tannins

Artichoke: botanical, agronomical, phytochemical, and pharmacological overview by Bruna de Falco; Guido Incerti; Mariana Amato; Virginia Lanzotti (993-1018).
Artichoke, Cynara cardunculus, is a dietary and medicinal plant species with a long tradition of use dating back to the ancient Egyptians, Greeks, and Romans. It comprises the globe artichoke, C. cardunculus subsp. scolymus, the cultivated cardoon, C. cardunculus subsp. altilis, and the wild cardoon, C. cardunculus subsp. sylvestris. The edible part of the plant is limited to the fleshy leaves (bracts) and receptacle of a large immature inflorescence, named capitulum or head, that has been shown to be a rich source of bioactive compounds. On the other hand, leaves, external bracts and stems discarded by the artichoke processing industry corresponding to about 80–85 % of the total biomass of the plant, represent a suitable potential source of food additives and nutraceuticals. Nutritional and pharmacological properties of artichoke heads and leaves are attributed mainly to polyphenolic compounds and inulin present at high concentration. Other classes of chemical compounds, including flavonoids, anthocyanins, sesquiterpenes, and triterpenes have been also found in the plant at lower amounts. This review, after a general historical, phytogeographical, and ethnobotanical overview, summarizes the current knowledge on the phytochemistry and pharmacological properties of this plant, with special emphasis on the agronomical and nutritional importance of the plant and to the methods of analysis, including the recently developed metabolomic studies.
Keywords: Caffeoylquinic acids; Cynara cardunculus ; Flavonoids; Inulin; Terpenes

Brassicaceae: a rich source of health improving phytochemicals by P. Avato; M. P. Argentieri (1019-1033).
Brassicaceae Burnett (syn. Cruciferae A.L. de Jussieu) include many important economic plants used as edible or ornamental which are commonly known as the “mustard” plant family due to the sharp, potent flavour of their sulfur metabolites, the glucosinolates. Brassicas also produce phenolics, tocopherols and peculiar seed oils. Current scientific knowledge attributes to species belonging to this botanical family several health benefits such as reduced risk of cancer. This review summarizes information on the phytochemical profile of Brassicaceae plants, with a special regard to glucosinolates and their derived degradation products, the isothiocyanates. In addition, their role as antioxidant and cancer protective metabolites is discussed.
Keywords: Brassicaceae; Glucosinolates; Isothiocyanates; Flavonoids; Lipids; Antioxidant; Chemoprevention

Metabolism and antiproliferative effects of sulforaphane and broccoli sprouts in human intestinal (Caco-2) and hepatic (HepG2) cells by Nieves Baenas; Jose Manuel Silván; Sonia Medina; Sonia de Pascual-Teresa; Cristina García-Viguera; Diego A. Moreno (1035-1044).
The purpose of this work was to study the absorption and metabolism of sulforaphane (SFN) from broccoli sprouts, their major glucosinolate glucoraphanin and its hydrolysis product SFN. This was done by monitoring SFN’s main metabolites, i.e. SFN, SFN-glutathione and SFN-cysteine, in two different cell models of absorption and metabolism (Caco-2 colorectal carcinoma cells and HepG2 hepatocellular carcinoma cells), during 3, 6, and 24 h of treatment, using a selective UHPLC-QqQ-MS/MS procedure. Concentrations ranging 0.5–90 nmol/l were found within the cells and released in the medium, depending on the type of analyte under study. Cells were capable of conjugative metabolism, since the SFN mercapturic derivatives could be identified in the cell medium. The antiproliferative activity of broccoli sprouts, glucoraphanin and sulforaphane was compared in Caco-2 and HT-29 human colorectal carcinoma cells, and HepG2 hepatocellular carcinoma cells, establishing the minimal concentration of a given compound to achieve half inhibition of the maximal cell growth (IC50) for broccoli sprouts extract and sulforaphane. However, glucoraphanin did not show an antiproliferative effect in the cells under study.
Keywords: Brassica oleraceae ; Metabolism; Cytotoxicity; UHPLC-QqQ-MS/MS

Myrosinase in Brassicaceae: the most important issue for glucosinolate turnover and food quality by Maria del Carmen Martinez-Ballesta; Micaela Carvajal (1045-1051).
Glucosinolates and their degradation products, isothiocyanates, have been widely identified by their benefits to human nutrition. Plant myrosinase, is an enzyme found in Brassicaceae family with an essential role on the glucosinolates conversion to isothiocyanates. In this review, we highlight recent progress in myrosinase, with particular emphasis on the involvement on in vivo glucosinolates turnover and the regulation during plant development and in response to environmental changes. Also, the myrosinase as influenced by some intrinsic and extrinsic factors, during postharvest and food processing such as pH, temperature, and pressure is examined as a challenge for increasing isothiocyanates bioactivity.
Keywords: Brassicaceae ; Glucosinolates; Myrosinase; Environmental stress

Brassinosteroids: synthesis and biological activities by Jana Oklestkova; Lucie Rárová; Miroslav Kvasnica; Miroslav Strnad (1053-1072).
Brassinosteroids (BRs) are a relatively recently discovered group of phytohormones that are essential for normal plant growth and development. They participate in regulation of numerous vital physiological processes in plants, such as elongation, germination, photomorphogenesis, immunity and reproductive organ development. Structurally they are very similar to animal steroid hormones and include about 70 polyhydroxylated sterol derivatives. They are found at low levels in practically all plant organs. Recent studies have indicated that BRs have antiproliferative, anticancer, antiangiogenic, antiviral and antibacterial properties in animal cell systems, and thus have potential medical applications. Among others, BRs can inhibit replication of viruses in confluent human cell cultures, sometimes with high selectivity indexes, inducing cytotoxic effects in various types of cancer cells but not normal human cells. Thus, they include promising leads for developing potent new anticancer drugs. The aims of this article are to overview chemical characteristics, biological activities and the potential medical applications of natural BRs.
Keywords: Brassinosteroids; Chemical synthesis; Plant biological activity; Antiproliferative activity; Antiviral activity