Dehydroabietic acid

Fig. 1. Abietic-type acids include abietic acid [514-10-3] (1), levopimaiic acid [79-54-9] (2), neoabietic acid [471-77-2] (3), palustiic acid [1945-53-5] (4), and dehydroabietic acid [1740-19-8] (5). Pimaric-type acids are pimaric acid [127-27-5] (6) and isopimaric acid [5835-26-7] (7).

Salt formation. The resin acids have a low acid strength. The pa s (ionization constants) values of resin acids are difficult to obtain, and values of 6.4 and 5.7 have been reported [23] for abietic and dehydroabietic acids, respectively. Resin acids form salts with sodium and aluminium. These salts can be used in detergents because of micelle formation at low concentrations. Other metal salts (resinates) of magnesium, barium, calcium, lead, zinc and cobalt are used in inks and adhesive formulations. These resinates are prepared by precipitation (addition of the heavy metal salt to a solution of sodium resinate) or fusion (rosin is fused with the heavy metal compound). 

The exchange of aromatic protons can be effected in the absence of any -OH or —NH2 activating group during the course of a Clemmensen reduction in deuteriochloric and deuterioacetic acid mixture (see section Ill-D). This reaction has been carried out with various tricyclic diterpenes and is best illustrated by the conversion of dehydroabietic acid into its 12,14-d2-labeled analog (40 -+ 41).Amalgamated zinc is reportedly necessary for the exchange reaction since the results are less satisfactory when a zinc chloride-mercuric chloride mixture is used. 

FIGURE 2.1 Biotransformation of dehydroabietic acid by Mortierella isabellina. 

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. 

Tall oil fatty acids consist of resin acids (25% to 30%) and of a mixture of linolic acid, conjugated Cig fatty acids (45% to 65%), oleic acid (25% to 45%), 5,9,12-octadecatrienic acid (5% to 12%), and saturated fatty acids (1% to 3%). Resin acids are abietinic acid, dehydroabietic acid, and others. Properties of fatty acids are shown in Table 6-1. 

However, in many archaeological samples pimarane diterpenoids are often absent, and of the abietane compounds only dehydroabietic acid remains. In fact, dehydroabietic acid is present as a minor component in the fresh resins, but its abundance increases on ageing at the expense of the abietadienic acids since the latter undergo oxidative dehydrogenation to the more stable aromatic triene, dehydroabietic acid [2,18]. If oxygen is available, dehydroabietic acid can be oxidized to 7-oxodehydroabietic acid and 15-hydroxy-7-oxodehydroabietic acid. Since these diterpenoid compounds are often the dominant components in archaeological samples [95,97], they are considered characteristic for the presence of Pinaceae resins. 

The techniques based on the direct introduction of the sample in the mass spectrometer can also be used with CL This allows just a small amount of fragmentation. Due to the fact that less energy is used than in the El mode, Cl produces relatively stable molecular ions and ion fragments, and does not give as extensive fragmentation as readily as El does. Figure 3.8 compares the mass spectra of 7-oxo-dehydroabietic acid obtained by DE-MS using El at 70 eV and Cl with isobutane. In both these... 

Figure 3.8 Mass spectra of 7 oxo dehydroabietic acid obtained by DE MS using (a) electron ionisation at 70 eVand (b) chemical ionisation with isobutane...

In both the mass spectra, the simultaneous presence of ion fragments related to 7-oxo-dehydroabietic acid and highly oxidised tricyclic diterpenes demonstrates the higher degree of oxidation of the aged colophony with respect to the fresh pine resin [17 19]. In the mass spectra, the peaks attributed to abietadienic and pimaradienic acids are not evident, indicating their depletion in the course of the resin ageing. 

Figure 3.17 shows the mass profile of the resinous material collected from the Roman amphora. It shows the presence of abietane skeleton diterpenoids due to the occurrence of the peaks at m/z 315, 299, 285, 253 and 239. Furthermore, a high degree of oxidation of the resin was ascertained by the abundance of peaks at m/z 315 and 253, deriving from 7-oxo-dehydroabietic acid, and those at m/z 331 and 329, from highly oxidised tricyclic diterpenoid molecules. Finally, the presence of retene was evidenced by the peaks at m/z 234 and 219. The results showed that a pitch from Pinaceae had been in the amphora. 

Figure 8.4 Total ion current chromatograms of the (a) acidic and (b)neutral fractions of a sample collected from an amphora recovered in Fayum. DDA, didehydroabietic acid DA, dehydroabietic acid 70DA, 7 oxo dehydroabietic acid 70A, 7 oxo abietic acid 15Hy70DA, 15 hydroxy 7 oxo dehydroabietic acid 5HyDA, 15 hydroxy dehydroabietic acid R, retene MDA, methyl dehydroabietate. Slf internal standard, hexadecane IS2, internal standard, tridecanoic acid...

Figure 8.14 Mass spectra of 15 hydroxy 7 oxo dehydroabietic acid after (a) methylation, (b) methylation followed by trimcthylsilylation and (c) trimcthylsilylation. Reproduced from K. J. van den Berg, J. J. Boon, I. Pastorova, L. F. M. Spetter, J. Mass Spectrom., 35, 512 533. Copyright 2000, with permission from John Wiley Sons, Ltd...

Figure 12.12 THM GC/MS curves of a Winsor Newton lemon alkyd paint (a) and of an alkyd sample taken from Fontana s work Concetto spaziale (1961) (b). Peak assignments 1, 1,3 dimethoxy 2 propanol 2, 1,2,3 trimethoxy propane 3, 3 methoxy 1,2 propandiol 4, 4 chloro benzenamine 5, 3 methoxy 2,2 bis(methoxymethyl) 1 propanol 6, 3 chloro N methyl benzenamine 7, 3 methoxy 2 methoxymethyl 1 propanol 8, 4 chloro N methyl benzenamine 9, phthalic anhydride 10, 3 chloro 4 methoxy benzenamine 11, suberic acid dimethyl ester 12, dimethyl phthalate 13, azelaic acid dimethyl ester 14, sebacic acid dimethyl ester 15, palmitic acid methyl ester 16, oleic acid methyl ester 17, stearic acid methyl ester 18, 12 hydroxy stearic acid methyl ester 19, 12 methoxy stearic acid methyl ester 20, styrene 21, 2 (2 methoxyethoxy) ethanol 22, 1,1 oxybis(2 methoxy ethane) 23, benzoic acid methyl ester 24, adipic acid dimethyl ester 25, hexadecenoic acid methyl ester 26, dihydroisopimaric acid methyl ester 27, dehydroabietic acid methyl ester 28, 4 epidehydroabietol...

The measurement of the ethoxyresorufin-O-deethylase (EROD) activity is another sensitive parameter to detect the effects of paper mill industrial effluents on living organisms in the receiving waters. The EROD activity is a measure of the activity of the cytochrome P-450 enzyme system, which plays a central role in the transformation and elimination of xenobiotics. Increased EROD activity has been shown as far as 40 km from pulp mills, and EROD induction in fish caused by pulp mill effluents remains after biological treatment [60]. It is specified that EROD activity and erythrocytic nuclear abnormalities are induced by abietic and dehydroabietic acid [60]. 

Terpenoids are susceptible to a number of alterations mediated by oxidation and reduction reactions. For example, the most abundant molecule in aged Pinus samples is dehydroabietic acid [Structure 7.10], a monoaromatic diterpenoid based on the abietane skeleton which occurs in fresh (bleed) resins only as a minor component. This molecule forms during the oxidative dehydrogenation of abietic acid, which predominates in rosins. Further atmospheric oxidation (autoxidation) leads to 7-oxodehydroabietic acid [Structure 7.11]. This molecule has been identified in many aged coniferous resins such as those used to line transport vessels in the Roman period (Heron and Pollard, 1988 Beck et al., 1989), in thinly spread resins used in paint media (Mills and White, 1994 172-174) and as a component of resin recovered from Egyptian mummy wrappings (Proefke and Rinehart, 1992). 

Structure 7.10 Dehydroabietic acid Structure 7.11 7-Oxodehydroabietic acid... 

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