Dehydroabietic acid degradation

The first step in the aerobic degradation of dehydroabietic acid by Pseudomonas abietaniphila strain BMKE-9 is hydroxylation at C-7 (Smith et al. 2004). 

FIGURE 7.44 Pathways for aerobic degradation of dehydroabietic acid. 

Dehydroabietic acid (XIII) is the most abundant of the resin acids that occur naturally in wood and tree bark. These compounds are toxic and persistent in the environment. The effect of DOM on the photolysis of XIII was investigated at 254 nm and at X > 300 nm [74], In pure water, XI (3 mgL x) was degraded both by 254 nm radiation and simulated solar light. The degradation of XIII at 254 nm was slower in the humic surface water (Lake Sarojarvi, Finland) than in pure water. The opposite effect was observed at X > 300 nm. 

Parallel analyses by IR, thin-layer chromatography (TLC), and gas chromatography-mass spectrometry (GC-MS) of organic remains adhering to shards of ancient amphoras excavated in the harbor of Carthage (Tunisia) identified these remains as pine pitches. Capillary GC of methylated acid fractions showed abietic acid, dehydroabietic acid, and 7-ketodehydroabietic acid as the principal components. Two-dimensional TLC of untreated ether extracts revealed abietic acid in 12 of 31 samples and dehydroabietic acid in 26 of 31 samples. IR spectra of solid, raw samples indicated the presence of isopropyl groups, characteristic of the abietane skeleton, in 80% of the samples. Rapid and convenient analysis by TLC and IR was, in most cases, sufficient to identify pine resin products even after extensive pyrolytic and oxidative degradation. 

Resin acids such as abietic and dehydroabietic acid oxidise easily under common conditions, e.g. oxygen, daylight, room temperature, to give (auto) oxidative degradation products, which are more or less strong... 

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