Micro- and nanoplastic toxicity on aquatic life: Determining factors.

Plastic pollution has become a major environmental concern due to its omnipresence and degradation to smaller particles. The potential toxicological effects of micro- and nanoplastic on biota have been investigated in a growing number of exposure studies. We have performed a comprehensive review of the main determining factors for plastic particle toxicity in the relevant exposure systems, from publications until including the year 2018. For a focused scope, effects of additives or other pollutants accumulated by the plastic particles are not included. In summary, current literature suggests that plastic particle toxicity depends on concentration, particle size, exposure time, particle condition, shape and polymer type. Furthermore, contaminant background, food availability, species, developmental stage and sex have major influence on the outcome of plastic particles exposures. Frequently reported effects were on body and population growth, energy metabolism, feeding, movement activity, physiological stress, oxidative stress, inflammation, the immune system, hormonal regulation, aberrant development, cell death, general toxicity and altered lipid metabolism. Several times reported were increased growth and food consumption, neuro-, liver- or kidney pathology and intestinal damage. Photosynthesis disruption was reported in studies investigating effects on phytoplankton. For the currently unquantified plastic particles below 10 µm, more toxic effects were reported in all aquatic life, as compared to plastic particles of larger size.

Structural properties of anthocyanins: rearrangement of C-glycosyl-3-deoxyanthocyanidins in acidic aqueous solutions.

Seven C-glycosyl-3-deoxyanthocyanidins were made from their corresponding C-glycosylflavones. The structures of their rearrangement products, which were formed in acidic aqueous solutions, were elucidated. Rotameric conformers were detected for all of the 8-C-glycosyldeoxyanthocyanidins but were absent for their isomeric 6-C-analogues in acidified methanolic NMR solvent. A correlation method based on HPLC-DAD and NMR integration of similar samples made it possible for the first time to determine accurately the proportions of two isomeric 6-C- and 8-C-glycosylflavonoids occurring in mixtures. Each of the C-glycosyldeoxyanthocyanidins established fixed equilibrium proportions with their corresponding A-ring isomer in aqueous solutions, even under relatively strong acidic conditions (pH approximately 1), whether one started with pure 6-C- or 8-C-glycosyl-3-deoxyanthocyanidin. The nature of the aglycone, C-glycosyl moiety, and temperature were found to affect the equilibrium proportions. Increased water content (to a certain level) and temperatures were shown to increase the isomerization rates. The flavylium cations were the only equilibrium forms present at detectable quantities. The significance of rotation of the A-ring during isomerization was confirmed by lack of rearrangement of both 6-C- and 8-C-glycosyl-3-deoxy-5-carboxypyranoanthocyanidins. The intermediary C-ring open forms of the C-glycosyldeoxyanthocyanidins experience fast ring closure to their cyclic forms, which may reduce irreversible degradation reported for open chalcone forms of the common anthocyanins. The stable C-glycosyl-3-deoxyanthocyanidins may thus attract interest as possible colorants in the food industry, etc.

C-glycosylanthocyanidins synthesized from C-glycosylflavones.

Nine C-glycosyldeoxyanthocyanidins, 6-C-beta-glucopyranosyl-7-O-methylapigeninidin, 6-C-beta-glucopyranosyl-7-O-methylluteolinidin, 6-C-beta-(2''-O-beta-glucopyranosylglucopyranosyl)-7-O-methylapigeninidin, 6-C-beta-(2''-O-beta-glucopyranosylglucopyranosyl)-7,4'-di-O-methylapigeninidin, 8-C-beta-glucopyranosylapigeninidin, 8-C-beta-(2''-O-alpha-rhamnopyranosylglucopyranosyl)apigeninidin, 8-C-beta-(2''-O-alpha-(4'''-O-acetylrhamnopyranosyl)glucopyranosyl)apigeninidin, 6,8-di-C-beta-glucopyranosylapigeninidin (8), 6,8-di-C-beta-glucopyranosyl-4'-O-methylluteolinidin (9), have been synthesized from their respective C-glycosylflavones (yields between 14% and 32%) by the Clemmensen reduction reaction using zinc-amalgam. The various precursors (C-glycosylflavones) of the C-glycosylanthocyanidins were isolated from either flowers of Iris sibirica L., leaves of Hawthorn 'Crataegi Folium Cum Flore', or lemons and oranges. This is the first time C-glycosylanthocyanidins have been synthesized. The structures of all flavonoids including the flavone rotamers were elucidated by 2D NMR techniques and high-resolution electrospray MS. The distribution of the various structural forms of 8 and 9 are different at pH 1.1, 4.5, and 7.0, however, the two pigments undergoes similar structural transformations at the various pH values. Pigments 8 and 9 with C-C linkages between the sugar moieties and the aglycone, were found to be far more stable towards acid hydrolysis than pelargonidin 3-O-glucoside, which has the typical anthocyanidin C-O linkage between the sugar and aglycone. This stability may extend the present use of anthocyanins as nutraceuticals, pharmaceuticals or colorants.

Anthocyanin 3-galactosides from Cornus alba 'Sibirica' with glucosidation of the B-ring.

The three anthocyanins, delphinidin 3-O-beta-galactopyranoside-3',5'-di-O-beta-glucopyranoside (1), delphinidin 3-O-beta-galactopyranoside-3'-O-beta-glucopyranoside (2) and cyanidin 3-O-beta-galactopyranoside-3'-O-beta-glucopyranoside (3), and the 3-O-beta-galactopyranosides of delphinidin (4) and cyanidin (5) were isolated from the bluish white berries and compound umbel of Siberian dogwood, Cornus alba 'Sibirica'. The ornamental autumn leaves and the characteristic purplish red bark of this variety were found to contain only pigment 5.