Improvement of olive oil phenolics content by means of enzyme formulations: Effect of different enzyme activities and levels

The present work deals with the development of an enzymatic treatment aiming at producing high-quality olive oil with increased phenolics content and antioxidant activity. Three different enzyme formulations, specifically pectinase, hemicellulase and cellulase (A), pectinase and hemicellulase (B), and only pectinase (C), were used either at three different level of each or in ternary and binary mixtures at a constant level. All of them were added to the olive paste (Italian cultivar Coratina) at the beginning of the malaxation step. Results demonstrated that an increased enzyme level led to higher phenolics content in the oils, and such an effect was found to be enzyme dependent, being greater when using formulation A, followed by formulations B and C. Two significant correlations were obtained between total polyphenols and o-diphenols contents versus antiradical power (R² = 0.8743 and R² = 0.8635, respectively), which pointed out the effectiveness of the proposed enzymatic treatment to produce olive oils characterized by low susceptibility to oxidation. A synergistic effect between the different enzymatic activities contained in the single formulations was observed by combining enzymes A and B. The ternary mixture was selected as the most efficient enzymatic system ensuring the highest phenolics content increase (40 and 37% for total polyphenols and o-diphenols contents, respectively) compared to the other enzymes when used at the same level.     

Wound-induced lignin and suberin deposition in a woody angiosperm (Eucalyptus gunnii Hook.): Histochemistry of early changes in young plants

Summary A simple system was developed to investigate the deposition of lignin and synthesis occurring in response to mechanical wounding in the woody angiospermEucalyptus gunnii Hook. The spatiotemporal deposition of these phenolic polymers was histochemically characterized in stem tissue through a combination of fluorescent microscopy and specific stains. Lignin and suberin deposition was detectable 24 h post wounding in the xylem wound zone and by 3 days post wounding in the bark wound zone where a welldeveloped necrophylactic (wound) periderm could be observed by 7 days post wounding. Close examination suggests that the spatial reinforcement of cell walls with lignin and/or suberin is carefully orchestrated so as to rapidly produce an effective protective barrier. Specific lignin colour reactions indicate that the lignin formed in response to wounding in both the bark and xylem wound zones is relatively poor in syringyl monomers as compared to that of developmental xylem lignin.Abbreviations P-HCl phloroglucinol-HCl - RH relative humidity - NP necrophylactic periderm     

The influence of pH on concentrations of protein and phenolics and resource quality of decomposing floating leaf material of Nymphaea alba L. (Nymphaeaceae) for the detritivore Asellus aquaticus (L.)

Summary Senescent floating leaf material of Nymphaea alba L., collected in an acidified moorland pool, was used in decomposition studies in two aquatic systems that differed greatly in pH, alkalinity and nutrient concentration. Concentrations of extractable protein and phenolics in the decomposing leaf material were measured during the incubation period. Protein levels were not significantly different in the leaf material from the two study sites, whereas the concentrations of phenolics in the degrading leaf blades from the acid site remained higher than in the material from the alkaline site. The resource quality of the decomposing leaf material was estimated by feeding tests using Asellus aquaticus (L.) in the laboratory. The effect of an artificially increased level of tannin on the feeding activity of A. aquaticus was also studied. Material from the acid system was consumed at a lower rate than material from the other system. The phenolic content of the material was found to be the most important feeding cue. The protein level of the leaf blade detritus seems to be of less importance. The structure of the decomposing leaf blades may have influenced the resource quality in the later stages of the experiment.     

Fungal elicitor-mediated responses in pine cell cultures

A tissue culture system has been developed to examine phenylpropanoid metabolism induced in pine tissues by an ectomycorrhizal symbiont. An elicitor preparation from the ectomycorrhizal fungus Thelephora terrestris Fr. induced enhanced phenolic metabolism in suspension cultured cells of Pinus banksiana Lamb., as indicated by tissue lignification and accumulation of specific methanol-extractable compounds in the cells. Induction of lignification was observed as early as 12 h after elicitation. The activity of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), the entry-point enzyme into phenylpropanoid metabolism, also increased within the same time-frame in elicited cells. Significant increases in PAL activity were evident by 6 h after elicitation, and, by 12 h after elicitation, PAL activity in elicited cells was ten times greater than that in the corresponding controls. Lignification of the elicited tissue was also accompanied by an increase in the activity of other enzymes associated with lignin synthesis, including caffeic acid O-methyl transferase (EC 2.1.1.46), hydroxycinnamate:CoA ligase (EC 6.2.1.12), cinnamyl alcohol dehydrogenase (EC 1.1.1.-), coniferin glucosidase (EC 3.2.1.21) and peroxidase (EC 1.11.1.7). The increase in total peroxidase activity was associated with a change in the pattern of soluble peroxidase isoforms. The pine cell culture-ectomycorrhizal elicitor system provides a good model for molecular analysis of the process of lignification in an economically important softwood species.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - 4CL hydroxycinnamate:Coenzyme A ligase (EC 6.2.1.12) - CAD cinnamyl alcohol dehydrogenase (EC 1.1.1.-) - COMT S-adenosyl-l-methionine:caffeate O-methyl transferase (EC 2.1.1.46) - HPLC high-pressure liquid chromatography - PAL phenylalanine ammonia-lyase (EC 4.3.1.5) - TGA thioglycolic acid To whom correspondence should be addressedFinancial assistance for this work was provided by the Natural Sciences and Engineering Research Council of Canada.     

Structural analysis of 1l-chiro-inositol diester from Taraxacumudum

1l-1,5-Di-O-p-hydroxyphenylacetyl-chiro-inositol was isolated from the leaves of Taraxacumudum, along with seven other secondary metabolites. Identification of the inositol derivative, based on extensive spectroscopic analyses (¹H, ¹³C and 2D NMR) in two solvents, allowed the correction of previously published data and conformational studies. This is the second report on the presence of inositol esters with p-hydroxyphenylacetic acid in plants.     

Biochemical side effects of genetic transformation of pineapple

Evaluations were made during 30 days of in vitro-plantlet hardening. Transformed (bar, chitinase, ap24 transgenes) and non-transformed plantlets were compared. Both groups of plantlets were similar in regard with plant height and weight and peroxidase activity. However, statistical significant changes, caused by transformation, were recorded in levels of malondialdehyde, other aldehydes, chlorophyll (a, b, total), phenolics (free and cell wall-linked) and proteins.     

Why some leaves are anthocyanic and why most anthocyanic leaves are red?

The adaptive significance of leaf reddening, as it occurs during specific developmental stages or after stress, has puzzled biologists for more than a century. Theoretically, the accumulation of a non-photosynthetic pigment competing with chlorophylls for photon capture would impose a photosynthetic cost, which should be paid off by the benefits afforded by anthocyanins under some circumstances. Hence, the proposed hypotheses presume protective functions against excess light, UV-B radiation, reactive oxygen species, water stress (osmoregulation) and herbivory. The existing arguments in favor of an anti-oxidant, anti-UV-B and osmoregulatory role are confounded by the co-occurrence in leaves of other compounds having the same properties, not absorbing visible light, attaining much higher concentrations and, in some cases, having a more appropriate location to fulfill the ascribed functions. Moreover, the excess light hypothesis should take into account that anthocyanins mainly absorb green photons, which are used photosynthetically in deeper cell layers needing less photoprotection. The more ecological, anti-herbivore hypotheses, consider red leaf color as a signal denoting high defensive commitment, as a camouflage obscuring the green reflectance indicative of a healthy leaf and/or as a device undermining the folivorous insects camouflage. The anti-herbivore hypotheses have not been thoroughly tested, yet they are compatible with the known optical preferences of insects and their underlying physiology. Overall, although a multiplicity of potential roles can be argued, the primary role may depend on the reference system, i.e. species, developmental stage or specific biotic and abiotic stressors.     

Induction of phenolic compounds in Hypericum perforatum L. cells by Colletotrichum gloeosporioides elicitation

Changes in phenolic metabolism after elicitation with Colletotrichum gloeosporioides (CG) has been studied in Hypericum perforatum L. (HP) cell suspension cultures. Soluble phenolics were analysed by HPLC-DAD and HPLC-DAD-MS/MS. HP cultures elicited with the CG elicitor showed a significant increase in xanthone accumulation. Xanthone accumulation increased twelve fold when the cells were primed with methyl-jasmonate (MeJ) or salicylic acid (SA), before elicitation. HP cultures exposed only to MeJ produced a set of flavonoids, the flavones which represent a substantial part (approx. 40%) of the total flavonoids accumulated in these cells. The possible importance of xanthones as a component of defence mechanism of HP against biotic stress is discussed.