Challenging Structure Elucidation of Lumnitzeralactone, an Ellagic Acid Derivative from the Mangrove Lumnitzera racemosa.

The previously undescribed natural product lumnitzeralactone (1), which represents a derivative of ellagic acid, was isolated from the anti-bacterial extract of the Indonesian mangrove species Lumnitzera racemosa Willd. The structure of lumnitzeralactone (1), a proton-deficient and highly challenging condensed aromatic ring system, was unambiguously elucidated by extensive spectroscopic analyses involving high-resolution mass spectrometry (HRMS), 1D 1H and 13C nuclear magnetic resonance spectroscopy (NMR), and 2D NMR (including 1,1-ADEQUATE and 1,n-ADEQUATE). Determination of the structure was supported by computer-assisted structure elucidation (CASE system applying ACD-SE), density functional theory (DFT) calculations, and a two-step chemical synthesis. Possible biosynthetic pathways involving mangrove-associated fungi have been suggested.

Influence of ß-Carotene and Lycopene on Oxidation of Ethyl Linoleate in One- and Disperse-Phased Model Systems.

The induction period (IP) of ethyl linoleate stressed at 60 °C was monitored via the formation of hydroperoxides. The addition of lycopene (1% w/w) increased the IP from 7.0 to 10.0 h to prove the strong antioxidative potential in contrast to ß-carotene with pro-oxidative effects (IP: 6.0 h), both showing strong scavenging activity under fast degradation. When peroxidation was induced by singlet oxygen, both carotenoids effectively inhibited the formation of hydroperoxides, with quenching activity only observed at low singlet oxygen concentrations, while scavenging still dominated. Thus, carotenoids did not interact with the introduced singlet oxygen but rather with the radical intermediates of fat oxidation. These experiments were then transferred to lecithin-based micelles more related to biological systems, where singlet oxygen was generated in the outer aqueous phase. Lycopene and ß-carotene delayed or inhibited lipid peroxidation depending on concentration. In this setup, ß-carotene showed exclusively quenching activity, while lycopene was additionally degraded to about 70%.