Phenolics are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants. Plant polyphenols have drawn increasing attention due to their potent antioxidant properties and their marked effects in the prevention of various oxidative stress associated diseases such as cancer. In the last few years, the identification and development of phenolic compounds or extracts from different plants has become a major area of health- and medical-related research. This review provides an updated and comprehensive overview on phenolic extraction, purification, analysis and quantification as well as their antioxidant properties. Furthermore, the anticancer effects of phenolics in-vitro and in-vivo animal models are viewed, including recent human intervention studies. Finally, possible mechanisms of action involving antioxidant and pro-oxidant activity as well as interference with cellular functions are discussed.

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Plant phenolics: extraction, analysis and their antioxidant and anticancer properties.

Degradation of plant cell wall polysaccharides is of major importance in the food and feed, beverage, textile, and paper and pulp industries, as well as in several other industrial production processes. Enzymatic degradation of these polymers has received attention for many years and is becoming a more and more attractive alternative to chemical and mechanical processes. Over the past 15 years, much progress has been made in elucidating the structural characteristics of these polysaccharides and in characterizing the enzymes involved in their degradation and the genes of biotechnologically relevant microorganisms encoding these enzymes. The members of the fungal genus Aspergillus are commonly used for the production of polysaccharide-degrading enzymes. This genus produces a wide spectrum of cell wall-degrading enzymes, allowing not only complete degradation of the polysaccharides but also tailored modifications by using specific enzymes purified from these fungi. This review summarizes our current knowledge of the cell wall polysaccharide-degrading enzymes from aspergilli and the genes by which they are encoded.

Aspergillus Enzymes Involved in Degradation of Plant Cell Wall Polysaccharides

Wine is a highly complex mixture of compounds which largely define its appearance, aroma, flavour and mouth-feel properties. The compounds responsible for those attributes have been derived in turn from three major sources, viz. grapes, microbes and, when used, wood (most commonly, oak). The grape-derived compounds provide varietal distinction in addition to giving wine its basic structure. Thus, the floral monoterpenes largely define Muscat-related wines and the fruity volatile thiols define Sauvignon-related wines; the grape acids and tannins, together with alcohol, contribute the palate and mouth-feel properties. Yeast fermentation of sugars not only produces ethanol and carbon dioxide but a range of minor but sensorially important volatile metabolites which gives wine its vinous character. These volatile metabolites, which comprise esters, higher alcohols, carbonyls, volatile fatty acids and sulfur compounds, are derived from sugar and amino acid metabolism. The malolactic fermentation, when needed, not only provides deacidification, but can enhance the flavour profile.

The aroma and flavour profile of wine is the result of an almost infinite number of variations in production, whether in the vineyard or the winery. In addition to the obvious, such as the grapes selected, the winemaker employs a variety of techniques and tools to produce wines with specific flavour profiles. One of these tools is the choice of microorganism to conduct fermentation. During alcoholic fermentation, the wine yeast Saccharomyces cerevisiae brings forth the major changes between grape must and wine: modifying aroma, flavour, mouth-feel, colour and chemical complexity. The wine bacterium Oenococcus oeni adds its contribution to wines that undergo malolactic fermentation. Thus flavour-active yeasts and bacterial strains can produce desirable sensory results by helping to extract compounds from the solids in grape must, by modifying grape-derived molecules and by producing flavour-active metabolites. This article reviews some of the most important flavour compounds found in wine, and their microbiological origin.

Yeast and bacterial modulation of wine aroma and flavour

Plants have the capacity to synthesize, accumulate and emit volatiles that may act as aroma and flavor molecules due to interactions with human receptors. These low-molecular-weight substances derived from the fatty acid, amino acid and carbohydrate pools constitute a heterogenous group of molecules with saturated and unsaturated, straight-chain, branched-chain and cyclic structures bearing various functional groups (e.g. alcohols, aldehydes, ketones, esters and ethers) and also nitrogen and sulfur. They are commercially important for the food, pharmaceutical, agricultural and chemical industries as flavorants, drugs, pesticides and industrial feedstocks. Due to the low abundance of the volatiles in their plant sources, many of the natural products had been replaced by their synthetic analogues by the end of the last century. However, the foreseeable shortage of the crude oil that is the source for many of the artificial flavors and fragrances has prompted recent interest in understanding the formation of these compounds and engineering their biosynthesis. Although many of the volatile constituents of flavors and aromas have been identified, many of the enzymes and genes involved in their biosynthesis are still not known. However, modification of flavor by genetic engineering is dependent on the knowledge and availability of genes that encode enzymes of key reactions that influence or divert the biosynthetic pathways of plant-derived volatiles. Major progress has resulted from the use of molecular and biochemical techniques, and a large number of genes encoding enzymes of volatile biosynthesis have recently been reported.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.2008.03446.x

Biosynthesis of plant-derived flavor compounds.

Carotenoid Metabolism in Plants

Plant and microbial glycoside hydrolases: Volatile release from glycosidic aroma precursors

High-performance liquid chromatography with diode array (LC-DAD) and electrospray ionization mass spectrometric detection (ESI-MS) was used to analyze phenolic compounds of two blackberry species ( Rubus glaucus Benth. and Rubus adenotrichus Schlech.) growing in South America. UV-visible spectrophotometry was a valuable tool for identifying the class of phenolic compound, whereas MS and MS ( n ) fragmentation data were useful for their structural characterization. Ellagitannins were the major compounds, with sanguiin H-6 and lambertianin C being the predominant ones. The anthocyanin composition as well as the presence or absence of kaempferol glycosides can be used to distinguish the Rubus species studied. Flavonol hexoside-malonates were identified in both berries. Hydroxycinnamic acids were minor compounds and found as ferulic, caffeic, and p-coumaric acid esters. Similar contents were obtained by analysis of soluble ellagitannins and ellagic acid glycosides as ellagic acid equivalents and by analysis of ellagic acid equivalents released after acid hydrolysis.

Analysis of phenolic compounds in two blackberry species (Rubus glaucus and Rubus adenotrichus) by high-performance liquid chromatography with diode array detection and electrospray ion trap mass spectrometry.

A potential Carotenoid Cleavage Dioxygenase (CCD) gene was identified among a Vitis vinifera L. EST collection and a full-length cDNA (VvCCD1) was isolated. Recombinant expression of VvCCD1 confirmed that the gene encoded a functional CCD. Experimental evidence was obtained that VvCCD1 cleaves zeaxanthin symmetrically yielding 3-hydroxy-beta-ionone, a C(13)-norisoprenoidic compound, and a C(14)-dialdehyde. Expression of the gene was studied by real-time PCR at different developmental stages of grape berries from Muscat of Alexandria and Shiraz cultivars. A significant induction of the gene expression approaching veraison was observed in both cultivars. In parallel, the C(13)-norisoprenoid level increased from veraison to maturity in both cultivars.

A Carotenoid Cleavage Dioxygenase from Vitis vinifera L.: functional characterization and expression during grape berry development in relation to C13-norisoprenoid accumulation

Ziya Günata

Papers

Plant and microbial glycoside hydrolases: Volatile release from glycosidic aroma precursors

Analysis of phenolic compounds in two blackberry species (Rubus glaucus and Rubus adenotrichus) by high-performance liquid chromatography with diode array detection and electrospray ion trap mass spectrometry.

A Carotenoid Cleavage Dioxygenase from Vitis vinifera L.: functional characterization and expression during grape berry development in relation to C13-norisoprenoid accumulation

Interactions between aroma compounds and whole mannoprotein isolated from Saccharomyces cerevisiae strains

Glycosidase activities of three enological yeast strains during winemaking