Many bacteria utilize sophisticated regulatory systems to ensure that some functions are only expressed when a particular population density has been reached. The term 'quorumsensing' has been coined to describe this form of density-dependent gene regulation which relies on the production and perception of small signal molecules by bacterial cells. As in many pathogenic bacteria the production of virulence factors is quorum-sensing regulated, it has been suggested that this form of gene regulation allows the bacteria to remain invisible to the defence systems of the host until the population is sufficiently large to successfully establish the infection. Here we present first evidence that polyphenolic compounds can interfere with bacterial quorum-sensing. Since polyphenols are widely distributed in the plant kingdom, they may be important for promoting plant fitness.

No abstract

Strawberries and blueberries are two of the most commonly consumed berries. Berries, in general, are characterized by their highly nutritive compounds, including minerals, vitamins, fatty acids, and dietary fiber, as well as their high content and wide diversity of bioactive compounds, such as phenolic compounds and organic acids. These bioactive compounds have been associated with protective effects against chronic diseases, such as cardiovascular disease, cancer, Alzheimer’s and other disorders. In this paper 16 human intervention studies investigating the beneficial health effects of dietary strawberry or blueberry consumption on inflammation, cardiovascular disease or cognitive function and mental health are reviewed.

The contents of 15 different phenolic compounds in apple leaves and fruit skin from various orchards were determined by HPLC. High concentrations of flavan‐3‐ols were found in those orchards which were not infected by Venturia inaequalis. This observation corroborates earlier findings on different cultivars. The hypothesis that these compounds could be involved in the resistance of apple to scab was tested by inhibiting the key enzyme of the phenol biosynthesis, the phenylalanine‐ammonia‐lyase, in young shoots of the resistant genotype ‘Sir Prize'. After inoculation of the inhibitor‐treated leaves, severe symptoms of the disease occurred. The fungal infection was confirmed by histological studies. No flavonal‐accumulation could be observed at the infection site which was the case in the non‐inhibited but inoculated controls.

Light microscopy was used to examine the nuclei of five tree species with respect to the presence of flavanols. Flavanols develop a blue colouration in the presence of a special p-dimethylaminocinnamaldehyde (DMACA) reagent that enables those nuclei loaded with flavanols to be recognized. Staining of the nuclei was most pronounced in both Tsuga canadensis and Taxus baccata, variable in Metasequoia glyptostroboides, faint in Coffea arabica and minimal in Prunus avium. HPLC analysis showed that the five species contained substantial amounts of different flavanols such as catechin, epicatechin and proanthocyanidins. Quantitatively, total flavanols were quite different among the species. The nuclei themselves, as studied in Tsuga seed wings, were found to contain mainly catechin, much lower amounts of epicatechin and traces of proanthocyanidins. Blue-coloured nuclei located centrally in small cells were often found to maximally occupy up to 90% of a cell's radius, and the surrounding small rim of cytoplasm was visibly free of flavanols. A survey of 34 gymnosperm and angiosperm species indicated that the first group has much higher nuclear binding capacities for flavanols than the second group.