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665 Acid Fraction Evolution in Wood Extractives of Pinus pinaster Ait. Carlos Arrabal* and Manuel Cortijo Universidad Polit6cnica de Madrid, Escuela T6cnica Superior de Ingenieros de Montes, Departamento de Ingenieria Forestal, Ciudad Universitaria, 28040 Madrid, Spain The changes in the acid fraction of wood extracts from Pinus pinaster Air. have been studied. Qualitative and quantitative compositions have been determined in sam- ples that were just extracted and then seven and twelve months after extraction. Samples were prepared according to Technical Association of Pulp and Paper Industry Stan- dards, extracted with petroleum ether (b.p. 40-60~ in a Soxhlet apparatus and saponified with ethanolic 0.4N potassium hydroxide. The acid fraction was methylated with diazomethane, and its qualitative composition was determined by combined gas chromatography/mass spe~ trometry. The quantitative composition was determined by gas chromatography with a DEGS packed column. An increase was observed in the percentage of palmitic, oleic, pimaric and dehydroabietic acids, and there was a decrease in the percentage of linoleic and abietic acids. No varia- tion was observed in extract composition after seven and twelve months. KEY WORDS: Extractives, fatty acids, Pinus pinaster Ait., resin acids, wood. Fatty and resin acids from coniferous wood can be obtained either from the oleoresin by tapping living pine trees, from tall oil as by-product of softwood kraft pulping or by sol- vent extraction of stumps {1). Literature about quantitative extracts from felled trees {2-4) and about thermal isomerization of resin acids (5-8) is available, but little is known about the changes in com- position of the extracts over time Knowledge of acid frac- tion changes after extraction is of interest to improve use This work studies the acid fraction of wood extracts from Pinus pinaster Ait. and their composition seven and twelve months after the extractiorL EXPERIMENTAL PROCEDURES Samples of P. pinaster Ait., Mediterranean subspecies, from mountain "El Alijar" in Las Navas del Marquis (Avila, Spain), were prepared according to Technical Association of Pulp and Paper Industry Standards (9). The bark was removed. Samples were chipped and ground to a size of 40-60 mesh and the moisture was determined. Powdered wood was extracted with petroleum ether (b.p. 40-60~ in a Soxhlet apparatus for 24 h. Extracts were saponified with ethanolic 0.4N potassium hydroxide at 70~ for 4 h. After dilution with water (1:1, vol/vol), the unsaponifiables were extracted with petro- leum ether (b.p. 40-60~ and the water solution was acidified with 0.4N sulfuric acid and extracted with diethyl ether. The acid fraction was methylated with diazo- methane and studied by combined gas chromatog- raphy/mass spectrometry (GC/MS). Qualitative analyses were made with a Hewlett-Packard (Palo Alto, CA) 5995 GC/MS equipped with a 50 m • 0.20 mm capillary column of crosslinked 5% Ph Me Silicone under the following conditions: injection temperature, *To whom correspondence should be addressed. 250~ carrier gas (N2) flow rate, 1 mL/min; column temperature, 120-220~ 20~ electron energy set- ting, 70 eV. Acids were identified by comparing their methyl esters' mass spectra with previously published data (10,11). Quantitative analyses were made with a Hewlett-Pack- ard 5840A GO, equipped with a 2 m • 1/8 inch packed column of 10% DEGS (Supelcr S.A., Gland, Switzerland) and a flame-ionization detector (FID) under these condi- tions: injection temperature, 200~ carrier gas (N2) flow rate, 20 mL/min; column temperature, 180~ FID temperature, 250~ Quantitative analyses were made of the fresh methy- lated sample and then after seven and twelve months of storage. Samples were stored at room temperature after the extraction. RESULTS Figures 1 and 2 show acid fraction chromatograms on a DEGS column of methylated fresh sample and of a sam- ple stored seven months. No variation was observed be- tween samples stored for seven months and those stored for twelve months. Quantitative compositions of the fresh extracts and of those stored for seven months are shown in Table 1. Other minor acids found were 14:0, 10 Me-14:0, 15:0, 2 Me-15:0, 7-16:1, 17:1, 17:0, 5,9-18:2, 9,12-19:2, 10-19:1. DISCUSSION Neoabietic acid was not detected in the initial extracts. Increases were observed in the percentages of palmitic, oleic, pimaric and dehydroabietic acids, and decreases in the percentages of linoleic and abietic acids. Abietic acid was not detected in the extracts stored for seven months. A decrease of abietic acid and an increase of dehydro- abietic has been reported in tall oil destillation (12). Ther- mal isomerization of methyl abietate upon heating at 200 oC to yield methyl esters of palustric, neoabietic and dehydroabietic acids has also been reported (7). TABLE 1 Quantitative Composition over Time of the Acid Fraction of Wood Extracts from Pinus pinaster Ait. Extract seven Initial extract months later Acid (%) (%) Palmitic 1.9 4.2 Oleic 18.7 31.6 Linoleic 12.0 4.5 Pimaric 7.0 10.5 Sandaracopimaric 1.1 1.9 Levopimaric 2.3 3.4 Isopimaric 6.9 7.0 Abietic 24.5 -- Dehydroabietic 20.6 30.1 Neoabietic -- 1.9 Copyright 1994 by AOCS Press JAOCS, Vol. 71, no. 6 (June 1994)

Acid fraction evolution in wood extractives ofPinus pinaster ait

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Page 1: Acid fraction evolution in wood extractives ofPinus pinaster ait

665

Acid Fraction Evolution in Wood Extractives of Pinus pinaster Ait. Carlos Arrabal* and Manuel Cortijo Universidad Polit6cnica de Madrid, Escuela T6cnica Superior de Ingenieros de Montes, Departamento de Ingenieria Forestal, Ciudad Universitaria, 28040 Madrid, Spain

The changes in the acid fraction of wood extracts from Pinus pinaster Air. have been studied. Qualitative and quantitative composit ions have been determined in sam- ples that were just extracted and then seven and twelve months after extraction. Samples were prepared according to Technical Association of Pulp and Paper Industry Stan- dards, extracted with petroleum ether (b.p. 40-60~ in a Soxhlet apparatus and saponified with ethanolic 0.4N potassium hydroxide. The acid fraction was methylated with diazomethane, and its qualitative composit ion was determined by combined gas chromatography/mass spe~ trometry. The quantitative composit ion was determined by gas chromatography with a DEGS packed column. An increase was observed in the percentage of palmitic, oleic, pimaric and dehydroabietic acids, and there was a decrease in the percentage of linoleic and abietic acids. No varia- t ion was observed in extract composit ion after seven and twelve months.

KEY WORDS: Extractives, fatty acids, Pinus pinaster Ait., resin acids, wood.

Fatty and resin acids from coniferous wood can be obtained either from the oleoresin by tapping living pine trees, from tall oil as by-product of softwood kraft pulping or by sol- vent extraction of stumps {1).

Literature about quantitative extracts from felled trees {2-4) and about thermal isomerization of resin acids (5-8) is available, but little is known about the changes in com- position of the extracts over t ime Knowledge of acid frac- tion changes after extraction is of interest to improve use

This work studies the acid fraction of wood extracts from Pinus pinaster Ait. and their composition seven and twelve months after the extractiorL

EXPERIMENTAL PROCEDURES

Samples of P. pinaster Ait., Mediterranean subspecies, from mountain "El Alijar" in Las Navas del Marquis (Avila, Spain), were prepared according to Technical Association of Pulp and Paper Indus t ry Standards (9). The bark was removed. Samples were chipped and ground to a size of 40-60 mesh and the moisture was determined. Powdered wood was extracted with petroleum ether (b.p. 40-60~ in a Soxhlet apparatus for 24 h.

Extracts were saponified with ethanolic 0.4N potassium hydroxide at 70~ for 4 h. After dilution with water (1:1, vol/vol), the unsaponifiables were extracted with petro- leum ether (b.p. 40-60~ and the water solution was acidified with 0.4N sulfuric acid and extracted with diethyl ether. The acid fraction was methylated with diazo- methane and studied by combined gas chromatog- raphy/mass spect rometry (GC/MS).

Qualitative analyses were made with a Hewlett-Packard (Palo Alto, CA) 5995 GC/MS equipped with a 50 m • 0.20 mm capillary column of crosslinked 5% Ph Me Silicone under the following conditions: injection temperature,

*To whom correspondence should be addressed.

250~ carrier gas (N2) flow rate, 1 mL/min; column temperature, 120-220~ 20~ electron energy set- ting, 70 eV. Acids were identified by comparing their methyl esters' mass spectra with previously published da ta (10,11).

Quanti tat ive analyses were made with a Hewlett-Pack- ard 5840A GO, equipped with a 2 m • 1/8 inch packed column of 10% DEGS (Supelcr S.A., Gland, Switzerland) and a flame-ionization detector (FID) under these condi- tions: injection temperature, 200~ carrier gas (N2) flow rate, 20 mL/min; column temperature, 180~ FID temperature, 250~

Quanti tat ive analyses were made of the fresh methy- lated sample and then after seven and twelve months of storage. Samples were stored at room temperature after the extraction.

RESULTS

Figures 1 and 2 show acid fraction chromatograms on a D E G S column of methyla ted fresh sample and of a sam- ple stored seven months. No variation was observed be- tween samples stored for seven months and those stored for twelve months. Quantitative compositions of the fresh extracts and of those stored for seven months are shown in Table 1.

Other minor acids found were 14:0, 10 Me-14:0, 15:0, 2 Me-15:0, 7-16:1, 17:1, 17:0, 5,9-18:2, 9,12-19:2, 10-19:1.

DISCUSSION

Neoabietic acid was not detected in the initial extracts. Increases were observed in the percentages of palmitic, oleic, pimaric and dehydroabietic acids, and decreases in the percentages of linoleic and abietic acids. Abietic acid was not detected in the extracts stored for seven months.

A decrease of abietic acid and an increase of dehydro- abietic has been reported in tall oil destillation (12). Ther- mal isomerization of methyl abietate upon heat ing at 200 o C to yield methyl esters of palustric, neoabietic and dehydroabietic acids has also been reported (7).

TABLE 1

Quantitative Composition over Time of the Acid Fraction of Wood Extracts from Pinus pinaster Ait.

Extract seven Initial extract months later

Acid (%) (%)

Palmitic 1.9 4.2 Oleic 18.7 31.6 Linoleic 12.0 4.5 Pimaric 7.0 10.5 Sandaracopimaric 1.1 1.9 Levopimaric 2.3 3.4 Isopimaric 6.9 7.0 Abietic 24.5 -- Dehydroabietic 20.6 30.1 Neoabietic -- 1.9

Copyright �9 1994 by AOCS Press JAOCS, Vol. 71, no. 6 (June 1994)

Page 2: Acid fraction evolution in wood extractives ofPinus pinaster ait

666

SHORT COMMUNICATION

u ' U / :.3 E .&

, 0

u

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FIG. 1. Gas chromatogram of fresh methylated acid fraction. Conditions: packed column 2 m X 1/8 inch 10% DEGS; carrier gas, N 2 20 mL/min; 180~ flame-ionization detector temperature, 250~

u

E

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N

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FIG. 2. Gas chromatogram of methylated acid fraction seven months after the extraction. Conditions as in Figure 1.

L e v o p i m a r i c i somer i za t i on , r e p o r t e d in t he l i t e r a t u r e {6,8,13} to fo rm abiet ic , d e h y d r o a b i e t i c a n d n e o a b i e t i c acids, was n o t obse rved .

I s o m e r i z a t i o n of ab i e t i c ac id was o b s e r v e d w i t h o u t h e a t i n g t h e ex t r ac t s . The ob jec t ion t h a t t h e s e r e a c t i o n s m a y occur in t h e c o l u m n m u s t be d i s m i s s e d b e c a u s e t h e r e a c t i o n s d id n o t a p p e a r in t h e a n a l y s i s of t h e in i t i a l ex t r ac t s .

REFERENCES 1. Gardner, F.H., Jr., in Naval Stores (production, chemistr3~ utiliza-

tion), edited by D.E Zinkel and J. Russell, Pulp Chemicals Association, New York, 1989, Chapter 5.

2. Fengel, D., and G. Wegener, Wood: Chemistry, Ultrastructur~ Reactions, Walter de Gruyter, Berlin, 1984.

3. Herrick, F.W., and H.L. Hergert, in The Structurg Biosynthesis and Degradation of Wood, edited by EA. Loewns, and V.C. Runeckles, Plenum Press, 1977.

JAOCS, Vol. 71, no. 6 (June 1994)

Page 3: Acid fraction evolution in wood extractives ofPinus pinaster ait

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4. SjOstrom, E., Wood Chemistry. Fundamentals and Applications, Academic Press, New York, 1981.

5. Tekeda, H., W. SchuUer and R.V. Lawrence, J. Org. Chem. 33:1683 (1968).

6. Takeda, H., W.H. Schuller and R.V. Lawrence, Ibid. 33:3718 (1968). 7. Takeda, H., W.H. Schuller and R.V. Lawrence, J. Chem. and Eng.

Data 13:579 (1968). 8. Takeda, H., W.H. Schuller and R.V. Lawrence, J. Org. Chem.

34:1459 {1969). 9. Technical Association Pulp and Paper Industry, Tappi Text

Methods, Method T 11m-59, Sampling and Preparing Wood for Analysis, Atlanta, 1988.

10. The Mass Spectrometry Data Centre in collaboration with Im- perial Chemical Industry, PLC, Eight Peak Index of Mass Spec- tra, The Mass Spectrometry Data Centre in collaboration with Royal Society of Chemistry, Nottingham, 1983.

11. Zinkel, D.F., L.C. Zank and M.F. Wesolowski, Diterpene Resin Acids, U.S. Department of Agricultural, Forest Service, Forest Products Laboratory, Madison, 1971.

12. Holmbom, B., E. Avela and S. Pekkala, J. Am. Oil Chem. Soa 51:397 11974).

13. Foster, D.O., and D.F. Zinkel, J. Chromatogr. 248:89 {1982).

[Received September 17, 1993; accepted March 16, 1994]

JAOCS, Vol. 71, no. 6 (June 1994)