Utility of Stable Isotopes of Hydrogen and Carbon as Tracers of POPs and Related Polyhalogenated Compounds in the Environment

Fate of free and bound phytol and tocopherols during fruit ripening of two Capsicum cultivars

Phytol and tocopherols and their fatty acid esters (PFAE and TFAE) are isoprenoid lipid components which can be found for instance in vegetables. Their behavior during maturation of fruits and vegetables could reveal valuable information on their biosynthetic formation and biological function. As pods of the genus Capsicum contain considerable amounts of both PFAE and TFAE, two cultivars (i.e. Capsicum annuum var. Forajido and Capsicum chinense var. Habanero) were grown in a greenhouse project. The date of flowering and fruit formation of each blossom was noted and fruits were harvested in four specific periods which corresponded with different stages of ripening, i.e. unripe, semi-ripe, ripe and overripe. Quantification by means of gas chromatography mass spectrometry and creation of development profiles strongly supported the suggestion that PFAE and TFAE were formed as storage molecules during fruit ripening and parallel degradation of chlorophyll. Additionally, compound-specific carbon isotope ratios (δ¹³C values (‰)) of originally in PFAE and chlorophyll bound phytol ultimately proved that PFAE, besides tocopherols, serve as sink for the cytotoxic phytol moiety released from chlorophyll degradation during fruit ripening. Furthermore, color measurements were successfully implemented to simplify the usually cumbersome separation of chili fruits into different ripening degrees.

Occurrence and fate studies (sunlight exposure and stable carbon isotope analysis) of the halogenated natural product MHC-1 and its producer Plocamium cartilagineum

MHC-1 is a halogenated natural product (HNP) produced by the red seaweed Plocamium cartilagineum. MHC-1 concentrations of 550-2700 μg/g dry weight were found in Plocamium collected by divers at Heligoland (Germany). Compared to that MHC-1 concentrations were much lower in samples collected on beaches in Ireland and Portugal. Exposure of leaves of Plocamium to sunlight showed that MHC-1 was readily transformed by hydrodebromination. At Heligoland in March, MHC-1 (δ¹³C value -45.2‰) was lighter in carbon by ~15‰ compared to the bulk δ¹³C value (‰) of Plocamium (-30.7‰). Collected at the same time and location at Heligoland, samples of Halichondria and Mastocarpus sp. were richer in carbon (by ~10‰) as Plocamium. However, the δ¹³C value of MHC-1 in Halichondria (-44.6‰) and Mastocarpus sp. (-42.1‰) was as negative as in Plocamium. This was indirect proof that MHC-1 was produced by Plocamium and then released into the water phase from where it then was bioconcentrated by Halichondria and Mastocarpus sp. In agreement with that, concentrations of MHC-1 in Halichondria and Mastocarpus sp. were much lower than in Plocamium. In addition, a potential isomer of MHC-1 (compound X) was detected in all samples from Heligoland at ~2% of the MHC-1 level.

Stable carbon isotope analysis (δ13C values) of polybrominated diphenyl ethers and their UV-transformation products

Polybrominated diphenyl ethers (PBDEs) are frequently detected in food and environmental samples. We used compound specific isotope analysis to determine the δ(13)C values of individual PBDEs in two technical mixtures. Within the same technical product (DE-71 or DE-79), BDE congeners were the more depleted in (13)C the higher brominated they were. In contrast, the products of light-induced hydrodebromination of BDE 47 and technical DE-79 were more enriched in (13)C because of more stable bonds between (13)C and bromine. As a result, the δ(13)C values of the irradiated solution progressed diametrically compared to those of the technical synthesis. The ratio of the δ(13)C values of BDE 47 to BDE 99 and of BDE 99 to BDE 153 are thus suggested as indicators to distinguish native technical products from transformation products. Ratios <1 are typical for native congeners (e.g. in DE-71) while the reversed ratio (>1) is typical of transformation products.