Grafted and non-grafted tomato plants were grown at 25 and 35 ◦C for 30 days. In tomato leaves we analysed total phenols, o-diphenols, enzymatic activities (PAL, PPO and GPX) and dry weight. Our results indicate that heat stress in both grafted and non-grafted tomato plants occurred at 35 ◦C and resulted in (1) increased PAL activity, (2) increased total phenols and o-diphenols, (3) decreased P...

Red clover (Trifolium pratense) leaves accumulate several mumol g(-1) fresh weight of phaselic acid [2-O-(caffeoyl)-l-malate]. Postharvest oxidation of such o-diphenols to o-quinones by endogenous polyphenol oxidases prevents breakdown of forage protein during storage. Forage crops like alfalfa (Medicago sativa) lack both polyphenol oxidase and o-diphenols, and breakdown of their protein upon h...

Claus T. Fuchs and G erhard Spiteller Institut für Organische Chemie I, Universität Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany Z. Naturforsch. 52c, 761-765 (1997); received July 30/August 19, 1997 Polyphenoloxidase, o-Diphenols, 4-Pentadecylpyridine, Competitive Inhibitor, Taphrina pruni 4-Pentadecylpyridine was isolated from plums infected by Taphrina pruni. This fungal me­ tabolit...

The Strecker-type degradation of phenylalanine in the presence of 2-pentanal and phenolic compounds was studied to investigate possible interactions that either promote or inhibit the formation of Strecker aldehydes in food products. Phenylacetaldehyde formation was promoted by 2-pentenal and also by o- and p-diphenols, but not by m-diphenols. This is consequence of the ability of phenolic comp...

An amperometric biosensor based on the enzyme polyphenoloxidase (PPO), which makes the bioelectrocatalysis of phenolic compounds, was developed and optimized using cathecol as substrate. Polyethersulphone membranes were used for enzyme immobilization. Polyphenoloxidase oxidizes monophenols (cresolase activity) and diphenols (catecholase activity) into the corresponding o-quinones; the o-quinone...

Photosynthetic oxygen reduction by isolated chloroplast lamellar systems has been studied with the aid of superoxide dismutase. Two mechanisms of oxygen reduction by illuminated chloroplast lamellar systems can be differentiated: 1. In the presence of low potential electron acceptors like AQ or MV the superoxide free radical ion is the product of autooxidation of the reduced acceptor. Addition ...

The dry olive residue (DOR) obtained from the olive oil extraction process has toxic components against plants and microorganism growth, particularly monomeric phenols. In this investigation nine saprobic fungi were found to be capable of completely removing these phenols from the solid after 20 weeks of growth, although the rate depended on the type of fungi and phenol. Results showed that mos...

Polyphenol oxidase (PPO) (monophenol, o-diphenol: oxygen oxidoreductase; EC 1.14.18.1) is a binuclear copper-cluster-containing monooxygenase ubiquitously present in biological systems (1, 2). PPO may be distinguished from the related oxidase laccase [p-diphenol:oxygen oxidoreductase; EC 1.10.3.2] by its substrate specificity and the type and number of catalytic coppers. PPO catalyzes the oxida...

Tyrosinases (monophenol, o-diphenol:oxygen oxidoreductase, EC (1.14.18.1) are copper-containg enzymes which catalyze the o-hydroxylation of monophenols and subsequent oxidation of o-diphenols to quinones. The enzymes are involved in the pigmentation and are important factors in wound healing and primary immune response. Tyrosinases are found in prokaryotic and eukaryotic microorganisms, in mamm...