Vincenzo Lattanzio

Browning phenomena in stored artichoke (Cynara scolymus L.) heads: enzymic or chemical reactions?.

Abstract Data concerning phenolics and polyphenol oxidase in artichoke heads are presented. Biochemical changes at different physiological stages and after mechanical damage or chilling injuries, together with the characteristics of iron/phenolic complexes and the subcellular localization of polyphenol oxidase, are considered. Results lead to a proposed mechanism of browning phenomena in cold-stored, non-mechanically damaged, artichoke heads.

Verbascoside, Isoverbascoside, and Their Derivatives Recovered from Olive Mill Wastewater as Possible Food Antioxidants

Olive oil processing industries generate substantial quantities of phenolic-rich byproducts, which could be valuable natural sources of antioxidants. This work is focused on the recovery and structural characterization of antioxidant compounds from olive mill wastewater (OMWW), a polluting byproduct of the olive oil production process. Phenolics were extracted from the waste material using a membrane technology coupled to low-pressure gel filtration chromatography on a Sephadex LH-20. The LH-20 fraction was, in turn, characterized for its phenolic composition by HPLC-DAD-MS/MS analyses. Verbascoside, isoverbascoside, β-hydroxyverbascoside, β-hydroxyisoverbascoside, and various oxidized phenolics were identified. Uptake of verbascoside, purified from the LH-20 fraction, by HT-29 cells, an established model system for studying drug transport properties, was also assayed. Finally, the antioxidant activities of the LH-20 fraction and verbascoside were characterized by two different techniques. Individual verbascoside was more active as a scavenger of reactive oxygen species and as a chemopreventive agent protecting low-density lipoproteins from oxidative damage than the LH-20 fraction.

The beneficial effect of citric and ascorbic acid on the phenolic browning reaction in stored artichoke (Cynara scolymus L.) heads

Abstract Independent of the plant growing season artichoke heads stored at low temperature in closed polyethylene bags showed, with time, an increase in phenolics, especially caffeic acid. After 2 or 4 weeks, dependent on the storage temperature, the phenolic content decreased again while the pattern of changes in the phenolic level proved to be dependent on the harvesting period. Parallel with the increase in phenolic content, PAL activity increased but PPO activity remained almost constant or even decreased. Both citric and ascorbic acid were effective in improving the quality, as well as the shelf life, of the stored artichoke heads and by using either of the acids, an important delay of browning reaction could be noticed in the treated plant material. In order to better understand the nature of the important browning reaction in stored artichoke heads, the effects of citric and ascorbic acid on the phenolic metabolism, the PAL and PPO activity as well as on the iron/5- O -caffeoylquinic acid (IUPAC numbering) complexes, have been studied and the results obtained are discussed.

Changes in phenolic compounds during the development and cold storage of artichoke (Cynara scolymus L.) heads

Abstract The phenolic components of both fresh and stored artichoke heads have been studied. In fresh marketable heads only traces of free apigenin and luteolin were identified, while in badly injured heads measurable amounts of the above flavonoids, as well as of free caffeic acid, were found to occur. In addition to the latter phenolics, vanillic-, syringic-, p-coumaric- and ferulic acids proved to be present in the alkali labile bound state although caffeic acid proved to be the main phenolic component. In addition, the latter phenolic acid increased considerably during storage of the healthy heads for 2 weeks at 20°C or for 1 month at 4°C, the increase at 20°C being the most pronounced. In injured heads (internal blackening) stored for 2 weeks at 20°C, a decrease in caffeic acid, as well as in most other phenolics, has been recorded, while in badly injured heads (external symptoms of injury visible), stored for the same period of time, less than half of the total amount of the caffeic acid present in fresh marketable heads was found. However, in injured heads stored for 1 month at 4°C, the decrease in caffeic acid proceeded less rapidly.

Carbon Fluxes between Primary Metabolism and Phenolic Pathway in Plant Tissues under Stress.

Higher plants synthesize an amazing diversity of phenolic secondary metabolites. Phenolics are defined secondary metabolites or natural products because, originally, they were considered not essential for plant growth and development. Plant phenolics, like other natural compounds, provide the plant with specific adaptations to changing environmental conditions and, therefore, they are essential for plant defense mechanisms. Plant defensive traits are costly for plants due to the energy drain from growth toward defensive metabolite production. Being limited with environmental resources, plants have to decide how allocate these resources to various competing functions. This decision brings about trade-offs, i.e., promoting some functions by neglecting others as an inverse relationship. Many studies have been carried out in order to link an evaluation of plant performance (in terms of growth rate) with levels of defense-related metabolites. Available results suggest that environmental stresses and stress-induced phenolics could be linked by a transduction pathway that involves: (i) the proline redox cycle; (ii) the stimulated oxidative pentose phosphate pathway; and, in turn, (iii) the reduced growth of plant tissues.

Biological Activity of High Molecular Weight Phenolics from Olive Mill Wastewater

Olive oil production generates large amounts of recalcitrant compounds, the olive oil mill wastewater (OMWW), which represent one of the most contaminating effluents among those produced by the agrofood industries. Nowadays, this view has changed to one that recognizes the waste as a low-cost starting material rich in bioactive compounds, particularly biophenols, that can be extracted and applied as natural antioxidants for the food and pharmaceutical industries. The data reported in this paper indicate that the OMWW extracts, besides low molecular weight antioxidant phenolics such as tyrosol and hydroxytyrosol, also contain phenolics with a molecular weight in the range of 600-5000 Da, which exhibit efficient scavenging activities against hydroxyl and peroxyl radicals. This group of phenolics includes, besides verbascoside, isoverbascoside, and an oxidized form of verbascoside, a number of higher molecular weight phenolics arising from oxidative polymerization of hydroxytyrosol and caffeic acid. Overall, these higher molecular weight phenolics prove to be, in some in vitro tests, more efficient scavengers of hydrophilic hydroxyl radicals than hydroxytyrosol, which could be used for industrial applications as natural nontoxic antioxidants.

Polyphenol oxidase from artichoke (Cynara scolymus L.)

Abstract Polyphenol oxidase (PPO) was purified from hearts of artichoke. Starting with a crude 20 m m acetate buffer pH 5·7 extract obtained from an acetone powder originating from the plant material, the enzyme was purified 65-fold (overall yield 9%) by means of hydrophobic followed by gel filtration chromatography. The purified artichoke polyphenol oxidase (APPO), which migrated as a single band during gel filtration chromatography and chromatofocusing, showed an isoelectric point of 4·5 and a molecular weight of 116,000 dalton. The best substrates for the enzyme at pH 6·0 were 5-o-caffeoylquinic acid (5-o-CQA, according to IUPAC 1976 nomenclature) (relative activity 100%) and caffeic acid (relative activity 69%). Pyrocatechol, which was also oxidized by APPO (relative activity 42%), proved to be a less suitable substrate, whereas 1,5-dicaffeoylquinic acid and catechin were only very poorly oxidized. With each of the main substrates the optimum pH was widespread between pH 5·0 and 7·0 for 5-o-CQA and pyrocatechol, while for caffeic acid the maximum activity was widely extended between pH 6·5 and 8·0. The kinetic constants of the enzyme determined at pH 7·0 and 30°C with both 5-o-CQA and caffeic acid as substrate proved to be quite similar (Km = 4·2 ± 0·5 m m , Vmax = 135·6 ± 14·7 Umg and Km = 5·3 ± 0·3 m m , Vmax = 115·1 ± 6·1 U/mg, respectively). The activation energy of the enzyme with caffeic acid was 21·7 ± 0·2 kJ/mole at pH6·5. Cu++ and Fe+++ proved to activate APPO-5-o-CQA oxidation. However, APPO activation by these ions does not appear to be important enough to ascribe them a role in the enzymatic browning of stored artichoke heads. Although both ascorbic and citric acids are known to considerably improve the shelf life of artichoke heads, only ascorbic acid proved to be significantly inhibitory towards APPO.

Mono- and oligosaccharides in fifteen Vicia faba L. cultivars

Abstract Fresh and dry mature seeds of fifteen cultivars or lines of faba bean were compared with respect to their mono- and oligosaccharide contents, in an attempt to determine the possibilities for selection in a breeding programme on the basis of some chemical characteristics. The raffinose content of the whole dry seed ranged from 0·12% to 0·29%, the stachyose content between 0·46% and 1·02%, the verbascose content, the principal α-galactoside, from 0·82% to 1·61% on a dry matter basis. These components occurred in seeds with more than 30% of dry matter, while fructose, glucose and sucrose regularly decreased during seed development.