Phytochemistry Reviews (v.11, #2-3)

Phenolic compounds: from plants to foods by Véronique Cheynier (153-177).
Phenolic compounds are a large class of plant secondary metabolites, showing a diversity of structures, from rather simple structures, e.g. phenolic acids, through polyphenols such as flavonoids, that comprise several groups, to polymeric compounds based on these different classes. Phenolic compounds are important for the quality of plant based foods: they are responsible for the colour of red fruits, juices and wines and substrates for enzymatic browning, and are also involved in flavour properties. In particular, astringency is ascribed to precipitation of salivary proteins by polyphenols, a mechanism possibly involved in defence against their anti-nutritional effects. Finally, phenolic compounds are considered to contribute to the health benefits associated to dietary consumption of fruits and vegetables. During food processing and storage, plant phenolics are converted to a variety of derived compounds. While methods to analyse lower molecular weight phenolic compounds are well developed, analysis of polymeric compounds remains a challenge. Indeed, strong interactions of polymeric phenolics with plant cell wall material limit their extraction. Besides, their polydispersity results in poor resolution and detection, especially of derived structures such as oxidation products. However, recent advances of the analytical techniques have allowed some progress in their structural characterisation. This review summarizes the current knowledge on methods to analyse polyphenols. It presents their reactions in foods and beverages and the resulting structures, and highlights some aspects related to their impact on colour, flavour and health properties, with examples taken mostly from wine research.
Keywords: Anthocyanins; Colour properties; Polyphenols; Reactions in food processing; Tannin-protein interactions

Bioactive natural compounds from garlic and onions have been the focus of researches for decades, firstly due to their pharmacological effects, and secondly due to their defence properties against plant diseases. In fact, garlic and onion, belonging to Allium genus, are among the oldest food plants known since ancient times and used as ingredient of many recipes and for therapeutic properties. These plants are well known to produce bioactive apolar sulphur compounds but less is known about their polar natural compounds, such as phenols, sapogenins and saponins, that are more stable to cooking, So, we continued our work on the discovery of polar bioactive metabolites from Allium with the isolation of a number of sapogenins and saponins from the wild onion species Allium elburzense, Allium hirtifolium, Allium atroviolaceum, and Allium minutiflorum, and, more recently, from the cultivated white onion, Allium cepa, and garlic, Allium sativum. In particular, the sapogenins and saponins isolated from A. elburzense and A. hirtifolium, named elburzensosides and hirtifoliosides respectively, exhibited significant antispasmodic properties. In addition, the saponins named minutosides isolated from A. minutiflorum showed promising antimicrobial activity. More recently the phytochemical analysis of A. cepa and A. sativum has been undertaken and afforded the characterization of saponins, phenols and N-cynnamic amides which showed significant antifungal activity.
Keywords: Food plants; Allium ; Garlic; Onion; Saponins; Sapogenins; Phenols; Cymmanic N-amides; Biological activity

Production of nutritionally desirable fatty acids in seed oil of Indian mustard (Brassica juncea L.) by metabolic engineering by Surajit Bhattacharya; Saheli Sinha; Prabuddha Dey; Natasha Das; Mrinal K. Maiti (197-209).
Development of a designer oilseed crop with improved yield attributes and enhanced nutritional quality for the benefits of mankind and animal husbandry is now achievable with the combination of genetic engineering and plant breeding. In spite of their immense importance, the fatty acid profiles of most oilseed crops are imbalanced that necessitate the use of metabolic engineering strategies to overcome the various shortfalls in order to improve the nutritional quality of these edible oils. Indian mustard (Brassica juncea L.), being one of the important oilseed crops in Indian subcontinent naturally contains ~50 % nutritionally undesirable very long chain unsaturated fatty acids (VLCUFAs), e.g. erucic acid (C22:1). For the purpose of nutritional improvement of B. juncea seed oil, several metabolic engineering strategies have been employed to divert the carbon flux from the production of VLCUFAs to other important fatty acids. Stearic acid, being a saturated but nutritionally neutral fatty acid, is naturally inadequate in most of the conventional oil seeds. Due to its neutral effect on consumer’s health and as an important industrial ingredient, increased in planta production of stearic acid in the seed oil not only helps in reduction of production cost but also lessens the trans fatty acid production during commercial hydrogenation process. In this review metabolic engineering strategies to minimize the VLCUFAs along with increased production of stearic acid in the seed oil of B. juncea are discussed, so that further breeding attempts can be made to improve the nutritionally desirable fatty acid profile in the suitable cultivars of this important oilseed crop.
Keywords: Edible oil; Fatty acyl-ACP thioesterase; Indian mustard (Brassica juncea); Metabolic engineering; Stearoyl-ACP desaturase

Hazel and other sources of paclitaxel and related compounds by Mariangela Miele; Anna Maria Mumot; Achille Zappa; Paolo Romano; Laura Ottaggio (211-225).
Taxanes form a large family of compounds, the most famous of which is paclitaxel, an effective antitumor drug currently used against various cancers. First approved for the treatment of ovarian and breast cancer, it was subsequently endorsed for the treatment of many other cancer pathologies. Originally extracted from the bark of Taxus brevifolia, it has also been found in other Taxus species. Most of the drug for clinical use is currently produced by semi-synthesis, starting from a natural precursor, 10-deacetylbaccatin III recovered from the needles of Taxus baccata. The yield of paclitaxel and its precursors from yew is very low, and is not sufficient to satisfy the commercial requirements. Many attempts have been made to explore new paclitaxel-producing species including microorganisms. However, the availability of paclitaxel and related compounds is still low. The discovery of taxanes in differentiated and undifferentiated tissue of Corylus avellana suggested that the production of these compounds is not a peculiarity of the genus Taxus, giving hope for the future availability of these compounds. Here we review works aimed at exploring new paclitaxel-producing organisms with different ecology to Taxus plants. Particular focus has been placed on highlighting the discovery of taxanes in angiosperm plants. Thus, it is conceivable that, by developing appropriate methodologies, new plant species could be employed for the commercial production of paclitaxel and other antineoplastic compounds.
Keywords: Angiosperms; Anticancer drugs; Antimitotic compounds; Corylus avellana ; Taxanes

Bioactive compounds in legumes: pronutritive and antinutritive actions. Implications for nutrition and health by Mercedes Muzquiz; Alejandro Varela; Carmen Burbano; Carmen Cuadrado; Eva Guillamón; Mercedes M. Pedrosa (227-244).
Legume seeds are employed as a protein source for animal and human nutrition not only for their nutritional value (high in protein, lipids and dietary fibre), but also their adaptability to marginal soils and climates. Human consumption of legumes has been increased in recent years, being regarded as beneficial food ingredients. Legume seeds contain a great number of compounds which qualify as bioactive compounds with significant potentials benefits to human health. These compounds vary considerably in their biochemistry and they can be proteins, glycosides, tannins, saponins, alkaloids, etc. Hence, methods for their extraction, determination and quantification are specific of each compound. They do not appear equally distributed in all legumes, and their physiological effects are diverse. Some of these compounds are important in plant defence mechanisms against predators or environmental conditions. Others are reserve compounds, accumulated in seeds as energy stores in readiness for germination. Processing generally improves the nutrient profile of legume seed by increasing in vitro digestibility of proteins and carbohydrates and at the same time there are reductions in some antinutritional compounds. Most antinutritional factors are heat-labile, such as protease inhibitors and lectins, so thermal treatment would remove any potential negative effects from consumption. On the other hand tannins, saponins and phytic acid are heat stable but can be reduced by dehulling, soaking, germination and/or fermentation. New directions in bioactive compounds research in the last decade have led to major developments in our understanding of their role in nutrition. The scientific interest in these compounds is now also turning to studies of their possible useful and beneficial applications as gut, metabolic and hormonal regulators and as probiotic/prebiotic agents.
Keywords: Antinutrients; Phytochemicals; Processing; Pulses

The volatile fraction of herbal teas by Christine Tschiggerl; Franz Bucar (245-254).
The use of herbal teas, infusions or tisanes in folk medicine, medicinal phytotherapy as well as for food purposes is still very popular. In classical phytotherapy the active principles of herbal teas are often attributed to their volatile constituents. On the other hand, safety concerns could arise from volatiles as ingredients of infusions. In any case, information on the aromatic composition and volatile fraction of herbal teas is limited. There is a lack of qualitative and quantitative data on the volatile compounds in infusions as well as on the changes of volatile composition during the tea preparation process. For isolation of the volatile compounds from infusions several methods like liquid–liquid extraction, hydrodistillation or solid phase micro extraction have been used. Primarily, the composition has been determined by GC-FID or GC–MS analysis, in exceptional cases by HPLC-PDA or HPLC–MS analysis. The profile of the volatile fraction of herbal teas classified by chemical functionalities of the compounds (hydrocarbons, oxides, alcohols/ethers, aldehydes/ketones, acids/esters) differs from the profile of the corresponding genuine essential oil. Remarkable are losses of hydrocarbons in infusions. This review will cover the phytochemical research that has been carried out on the volatiles of herbal teas and will focus on results of the volatile fraction especially from rosemary (Rosmarinus officinalis), fennel (Foeniculum vulgare subsp. vulgare), lavender (Lavandula angustifolia), thyme (Thymus vulgaris) and chamomile (Matricaria recutita) infusions.
Keywords: Volatiles; infusions; GC; GC/MS; HPLC-PDA/-MS; Extraction

Durum wheat by-products as natural sources of valuable nutrients by Miriana Durante; Marcello S. Lenucci; Leonardo Rescio; Giovanni Mita; Sofia Caretto (255-262).
This review reports the use of wheat milling by-products for the extraction of high quality oil and vitamin E including our results on the exploitation of durum wheat bran as a valuable source of important healthful compounds. Wheat oil can be used as an ingredient in food, pharmaceutical or cosmetic preparations because it contains important bioactive compounds such as vitamin E, carotenoids and unsaturated fatty acids. Different methods are used for oil recovery from plant materials, such as solvent extraction, mechanical pressing or the eco-friendly supercritical carbon dioxide (SC-CO2) extraction technology. By using SC-CO2, we obtained an oil from durum wheat (Triticum durum Desf.) bran and optimized the extraction conditions to increase oil and vitamin E yields. Wheat bran, which is composed of pericarp, aleurone layer and germ, is discarded during the early stages of durum wheat milling processes to obtain a final product (semolina) that is stable over time. Maximum oil and vitamin E yields were obtained when a durum wheat bran matrix with particle size of ~30 mesh and a moisture content of 2.6 % was used. The optimal conditions for oil extraction were: 300–350 bar, 60–70 °C, and 4 l min−1 gaseous CO2 flow rate for 1 h. The chemical composition (vitamin E forms, carotenoids, quinones, lipids and fatty acids) of the SC-CO2 extracted oil was analyzed and compared to that of the oil extracted by Soxhlet using hexane as solvent. The findings here reported highlight the importance of durum wheat bran as a rich source of valuable natural nutrients.
Keywords: Soxhlet extraction; Supercritical carbon dioxide extraction; Vitamin E; Wheat bran; Wheat germ oil

Fruit cuticular waxes as a source of biologically active triterpenoids by Anna Szakiel; Cezary Pączkowski; Flora Pensec; Christophe Bertsch (263-284).
The health benefits associated with a diet rich in fruit and vegetables include reduction of the risk of chronic diseases such as cardiovascular disease, diabetes and cancer, that are becoming prevalent in the aging human population. Triterpenoids, polycyclic compounds derived from the linear hydrocarbon squalene, are widely distributed in edible and medicinal plants and are an integral part of the human diet. As an important group of phytochemicals that exert numerous biological effects and display various pharmacological activities, triterpenoids are being evaluated for use in new functional foods, drugs, cosmetics and healthcare products. Screening plant material in the search for triterpenoid-rich plant tissues has identified fruit peel and especially fruit cuticular waxes as promising and highly available sources. The chemical composition, abundance and biological activities of triterpenoids occurring in cuticular waxes of some economically important fruits, like apple, grape berry, olive, tomato and others, are described in this review. The need for environmentally valuable and potentially profitable technologies for the recovery, recycling and upgrading of residues from fruit processing is also discussed.
Keywords: Cuticular waxes; Fruit peel; Health benefits; Triterpenoids

Dietary phytochemicals offer protection from oxidative damages and lower the risks of chronic diseases, by complementary and overlapping action mechanisms. These include antioxidant activity, regulation of gene expression and cell cycle, stimulation of the immune and hormonal systems and modulation of cell–cell communication. Gap-junction intercellular communication (GJIC) plays an important role in maintaining tissue homeostasis by allowing the intercellular exchange of ions and regulatory molecules associated with cell proliferation, differentiation and apoptosis, and by contributing to intracellular signaling. This mechanism is strictly regulated and abnormal GJIC can result in several pathological conditions. GJIC is deregulated in cancer cells and reversible GJIC inhibition is strongly related to the promotion phase of carcinogenesis, likely mediated by reactive oxygen species. Whereas, the reversible inhibition of GJIC is related to the promotion phase of carcinogenicity, enhancers of GJIC are expected to prevent cancer. Several dietary plant compounds demonstrated the ability to control GJIC at the epigenetic levels and to prevent GJIC down-regulation by tumor promoting compounds, thus preventing cancers. In this Commentary, a number of reported studies on several phytochemicals in dietary and medicinal plants, which were able to affect GJIC and their structural proteins, i.e., connexins, in different in vivo and in vitro systems, were examined. The growing evidence, on the involvement of plant-derived molecules in the modulation of GJIC and in understanding of the specific action mechanisms, might offer a new perspective of the protective and/or preventive effects of dietary phytochemicals, in addition to possible chemotherapeutic use.
Keywords: Dietary phytochemicals; Gap junction intercellular communication (GJIC); Cancer; Antioxidants; Epigenetic mechanisms

Role of ROS and COX-2/iNOS inhibition in cancer chemoprevention: a review by Manish Kumar; Subodh Kumar; Satwinderjeet Kaur (309-337).
Since the times immemorial, our ancestors have been using medicinal plants or their parts for curing various ailments. The experiences of time have led to the strong system of medicine such as ayurveda. We have now moved to an age/era, where these therapies are now being tested scientifically. The knowledge about the medicinal plants in these ayurvedic scriptures can help us to unfold the mysteries related to the chronic diseases such as cancer. Several therapies are available for cancer prevention including radiation, chemotherapy, immunosuppression and surgery etc. but all these strategies have one or the other disadvantages. Natural plant products are the potential candidates for the cancer chemoprevention due to their antioxidant, anti-inflammatory and antitumor activities. From the time immemorial, plants have been the basis of traditional medicines and keep on to provide new remedies. Antioxidants are necessary for controlling degenerative reactions produced by reactive oxygen and nitrogen species in vivo. Increased intake of antioxidants in the form of fruits and vegetables may reduce the risk of cancer. It has been proposed that modulation of inflammatory mechanisms can be used for the cancer chemoprevention. The primary targets for modulation are cyclooxygenase (COX)-2 and nitric oxide synthase (iNOS). Thus, antioxidant, COX-2, iNOS represents a prime target for potential chemoprevention by phytochemicals. This review highlights various plants and their constituents explored for their antioxidant, COX-2 and iNOS inhibitory potential in various in vitro/in vivo assays and this knowledge can be exploited for the discovery of novel anticancer agents.
Keywords: Anticancer; Antioxidants; COX-2; iNOS; Phytochemicals