Decreasing δ13C and δ15N values in four coastal species at different trophic levels indicate a fundamental food-web shift in the southern North and Baltic Seas between 1988 and 2016.

Marine ecosystems are exposed to increasing human pressures and climatic change worldwide. It has therefore become essential to describe ecosystem statuses with respect to multinational protection schemes, often necessitating long-term monitoring programmes. Changes in the food-web structure, which can be monitored via stable isotope measurements, represent an important descriptor of the status of marine ecosystems. We investigated long-term changes (29 years) in isotopic values (δ13C and δ15N) in four indicative organisms at different trophic levels in the southern North and Baltic Seas: bladderwrack (Fucus vesiculosus), blue mussel (Mytilus ssp.), eelpout (Zoarces viviparus), and herring gull (Larus argentatus). Time series analyses using generalised additive models revealed largely consistent declines in δ13C and δ15N throughout all trophic levels of the coastal food web at all study sites, indicating a clear change in these coastal regions from 1988 to 2016. There were no clear long-term patterns in egg biometrics for herring gulls, except for a consistent increase in eggshell thickness. The declines in stable isotope values were in line with the results of previous long-term studies of single higher-trophic-level species, which suggested that the noted changes were mainly caused by altered foraging patterns of the studied species. The current results demonstrate that declines in δ13C and δ15N have occurred throughout the whole food web, not just in particular species. We discuss the possible reasons for the decrease in stable isotope values, including decreasing eutrophication and an increase in terrestrial carbon sources.

Limited stability in cell culture medium and hydrogen peroxide formation affect the growth inhibitory properties of delphinidin and its degradation product gallic acid.

In the present study we investigated the stability of anthocyanidins under cell culture conditions and addressed the question whether degradation products might contribute to the cellular effects assigned to the parent compounds. Substantial degradation was found already after 30 min, measured by HPLC/DAD. However, the decrease of detectable anthocyanidins exceeded by far the formation of the respective phenolic acids. From the formed phenolic acids only gallic acid (GA) exhibited growth inhibitory properties. However, also GA was found to be degraded rapidly. Furthermore, the incubation with delphinidin (DEL) or GA resulted in a substantial formation of hydrogen peroxide. The suppression of hydrogen peroxide accumulation by catalase modified significantly the growth inhibitory effects of DEL and GA, indicating that hydrogen peroxide formation might generate experimental artefacts. In summary, the results show that the phenolic acids formed by the degradation of cyanidin (CY), pelargonidin (PG), peonidin (PN) and malvidin (MV) do not contribute to the growth inhibitory effect of the parent compound. The degradation of DEL generates a phenolic acid with substantial growth inhibitory properties (GA). However, taken into account the small proportion of generated GA and its lacking stability, the contribution of GA to the growth inhibitory properties of DEL might be limited.

Natural flavonoids are potent inhibitors of glycogen phosphorylase.

There is little known about effects to be expected from high intake of flavonoids with respect to regulation of glucose/glycogen homeostasis. Glucose/glycogen homeostasis is mainly regulated by glycogen synthase (GS) and glycogen phosphorylase (GP). We investigated effects of naturally occurring flavonoids with varying substitution pattern on the activity of isolated muscle GP. Almost all flavonoids tested inhibited phosphorylated, active GPa, as well as unphosphorylated, adenosine monophosphate-activated GPb. However, inhibition of GPa was two-to-fourfold stronger than that of GPb. The flavonol quercetin and the anthocyanidins cyanidin and delphinidin turned out to be the most potent inhibitors of GPa, with concentration values where enzymatic activity is 50% of the respective control in the low micromolar range (<5 microM). Furthermore, by comparing GPa inhibitory activity of typical representatives from all known flavonoid classes, structural elements of flavonoids required for effective GP inhibition could be identified.