Composition of turpentines of Mexican pines

by N. T. MIROV ¹

1 Contribution from the Institute of Forest Genetics a branch of the California Forest and Range Experiment Station, which is maintained at Berkeley, California by the Forest Service, U.S. Dept. of Agriculture in co-operation with the University of California.

The work reported in this paper was aided through a grant from the Rockefeller Foundation.

A large area of Mexico is covered with pine forest (See map). On the lower slopes of the northwestern desert ranges are found nut pines, called piñones, and at higher elevations are excellent stands of Pinus engelmannii, P. cooperi, P. durangesis, P. arizonica, and some lesser species. Southward, pine forests are to be found most extensively along the Sierra Madre Occidental, which extends parallel to the Pacific coast southeasterly as far as the State of Jalisco. Along the Atlantic coast, between the central plateau and the Gulf coastal plains, is the Sierra Madre Oriental, its several mountain chains protruding into the deserts of northeastern Mexico and extending south to the State of Puebla: it is much narrower than Sierra Madre Occidental and its pine forests are not as extensive. Connecting these two ranges, from southeastern Jalisco to Puebla, are numerous short mountain chains and plateaus covered with stands of pines, seriously depleted in some places but in others fully stocked and, as in Michoacan, still occupying large areas. The continuation of the pine-covered mountains southeast of Michoacan is known as Sierra Madre del Sur. At the Istmo de Tehuantepec the mountains disappear, but farther east, in Chiapas, is located a highland covered with pine forests that extends into Guatemala.

The peninsula of Baja California has several desert ranges, such as Sierra de San Pedro Martir. On the higher elevations of this plateau-like range are found Pinus contorta forests and park-like stands of Pinus jeffreyi with an occasional admixture of P. lambertiana; in the lower elevations scattered pinyon pines (piñones) occur.

The largest pine forests are found (in order both of area and timber volume) in Durango, Chihuahua, Michoacan, Mexico, Veracruz, and Coahuila.

Martinez recognizes 66 different pines in Mexico. Of them, 39 are given species rank, and 27 are given varietal rank. Possibly, some of the pines regarded by Martinez as species, such as P. remorata, will be reduced to varietal rank, whereas others, such as P. pseudo-strobus var. oaxacana, will be elevated to species rank. In any event, no other equal area of the earth is host to so many different pines.

The great diversity of pines in the tropical highlands of Mexico suggests that the environment of this region has been highly inducive to mutation among the pines. Among the mutagenic agents that may have contributed to the remarkable diversification of pines in these highlands may be mentioned ultraviolet radiation, which is higher there than at low elevations, and cosmic ray particles which are more abundant there and carry more energy than in more northerly latitudes.

It seems probable that the topography and climate of the region are particularly favorable not only for the survival of mutants, but also for the production and survival of hybrids. Coffee and banana plantations, intermingled with pine groves, flourish within sight of snow-capped peaks whose slopes are covered with pine forests. Thus, pollen of high-elevation P. hartwegii, for example, may reach stands of lower-elevation P. montezumae (and vice versa) within a few minutes. The mild and uniform temperature of early summer, together with adequate precipitation during the long growing season, probably favor natural crossing and the establishment and survival of seedlings.

All these conditions seem to explain the unbelievable variability of pines in the tropical highlands of Mexico. Many States have more than a dozen different pines counting both species and varieties (Table 1).

Table 1. - Distribution of pines in Mexico by states ¹

State	Number of pines
Aguascalientes	2
Baja California	14
Campeche	none
Coahuila	11
Colima	none
Chiapas	11
Chihuahua	12
Durango	16
Guanajuato	3
Guerrero	10
Hidalgo	12
Jalisco	17
México	17
Michoacán	16
Morelos	9
Nayarit	11
Neuvo Leon	12
Oaxaca	18
Puebla	15
Quintana Roo	none
Queretaro	5
San Luis Potosi	5
Sinaloa	9
Sonora	7
Tabasco	none
Tamaulipas	6
Tlaxcala	8
Veracruz	12
Yucatan	none
Zacatecas	12

1 Source: Martinez, Maximino. Los Pinos Mexicanos, pp. 57-51,1948

In Mexico, pines generally grow at elevations between 1,800 and 3,800 meters. Pinus hartwegii is a pine growing at the highest elevations, reaching the snowline. Pines growing in relatively low altitudes are: Pinus lawsonii, P. pringlei, and P. strobus chiapensis. P. strobus chiapensis has been observed by Martinez at 800 meters above sea level often growing among coffee and banana plantations. Possibly, P. caribaea may be growing at sea level along the coast in Quintana Roo.

Turpentine and rosin industry

Production of turpentine and rosin (resinación) is a well-established industry of Mexico. The principal species tapped are: Pinus montezumae, P. michoacana, P. leiophylla, P. pseudostrobus, P. teocote, P. oocarpa and P. hartwegii. The French system of tapping is used in all regions.

The annual production of oleoresin (resina) amounts to 30,000 metric tons. Michoacan is the leading producer, followed by Jalisco, Mexico, Puebla and Oaxaca. Turpentining in the northern States, Durango and Nuevo León, has been discontinued. Data on oleoresin production in Mexico, kindly supplied in March 1954 by Señor Ramón Martín del Campo, Vice-President of the Unión de Resineros, is presented, in Table 2.

As this Table shows, the largest turpentining operations are not necessarily located in the largest forest areas of Mexico, but rather in the warmer parts of the country, where resin yield is higher than in the north. (Pine forests of Chiapas are not yet exploited for turpentining because of their remoteness from industrial centers.) From the 30,000 metric tons of oleoresin, the operators distill about 5.1 million kilos of turpentine, or about 17 percent of the weight of crude oleoresin. Of this amount, 25 percent is consumed in Mexico, while 75 percent is exported to the United States, chiefly to Los Angeles, San Francisco and some cities of Texas.

Pine forests of Mexico

Table 2. - Oleoresin production in Mexico

Locality	Oleoresin in production in metric tons
Uruapan, Michoacan	8,000
Morelia, Michoacan	5,000
Ciudad Hidalgo, Michoacan	8,000
Jalisco (mostly Guadalajara)	4,500
State of México	2,500
Puebla	1,000
Oaxaca	1,000
TOTAL	30,000

Mexican turpentine distilleries are modern, using pretreatment and filtering of oleoresin and employing steam distillation. The turpentine and the rosin are of excellent quality.

Until recently, very little was known about the chemical composition of turpentines of Mexican pines. In 1946, Ing. José Iriarte reported on the composition of turpentines of Pinus montezumae, P. pseudostrobus, and P. leiophylla from Uruapan, Michoacan and of P. hartwegii from Rio Frio, México. Iriarte's findings are incorporated in Table 3, which summarizes information on physical characteristics and chemical composition of the turpentines of Mexican pines.

TABLE 3 - COMPOSITION OF TURPENTINES OF MEXICAN PINES

TABLE 3 - COMPOSITION OF TURPENTINES OF MEXICAN PINES (Continued)

TABLE 3 - COMPOSITION OF TURPENTINES OF MEXICAN PINES (Concluded)

In 1950, the author, with the assistance of the University of California, made his first oleoresin-collecting trip to Mexico. In 1952 and in 1954, grants from the Rockefeller Foundation enabled him to visit Mexico again. Materials collected during these three trips were analyzed in the laboratory of the California Forest and Range Experiment Station. The laboratory work also was supported by the Rockefeller Foundation.

It has been found that longifolene, a sesquiterpene which previously was reported only in two pines of India, is the most common sesquiterpene in Mexican (as well as in western North American) turpentines. Occurrence of a kerosene-like paraffin hydrocarbon, normal undecane (C₁₁H₂₄), in Mexican turpentines is of scientific interest; but another paraffin hydrocarbon, normal heptane (C₇H₁₆), which is found in at least 6 Mexican pines, is a product not only of scientific, but also of considerable practical importance. Heptane is used in testing motor fuels and commands a price (about U.S. $10.00 per liter) much higher than ordinary turpentine. On the other hand, its presence in ordinary turpentine lowers the quality of the product. Chemically pure n-heptane can be obtained from Mexican pines in a very simple manner.

Need for further research

It is seen from Table 3 that turpentine composition of 12 Mexican pines is still unknown. Some of these pines are not very important in the management of Mexican forests; others are. The complex and extremely variable species, Pinus pseudostrobus, its varieties, and the closely related species, such as Pinus douglasiana and Pinus tenuifolia, should be thoroughly studied. The turpentines of these pines should be carefully examined; great variations might be found in their composition. Another species that awaits investigation is Pinus montezumae. It is possible that natural crossing of this species with certain forms of Pinus pseudostrobus, gives rise to hybrids having turpentine unlike the turpentines of the parents. We have found that the turpentine of P. montezumae of Chiapas differs considerably from the turpentine of this pine growing in Michoacan. We are inclined to think that this pine crosses with P. pseudostrobus var. oaxacana.

Some of the compounds listed in Table 3, such as ocimene, methyl chavicol and camphene, occur only in a few pines and in very minute quantities. Others, chiefly terpenes like alpha-pinene (C₁₀H₁₆), are very common. Some Mexican turpentines consist almost entirely of alpha-pinene, which makes them suitable for use in manufacturing synthetic camphor. Beta-pinene is surprisingly rare in Mexican pines. Delta-3-carene, which is found in abundance in western United States, is rather rare in Mexico, while limonene (always in its laevo-form) is relatively frequent, being found in at least nine pines (Table 4) and in some of them, as Pinus lumholtzii, in very large quantities. Turpentine of Pinus contorta of Baja California consists almost entirely of 1-beta-phellandrene, a monocyclic terpene which may prove to be a valuable commercial product.

Table 4. - Chemical compounds of Mexican turpentines

Compounds		Species
A. Aliphatic hydrocarbons
	n-heptane	P. ayacahuite, P. coulteri. P. jeffreyi, P. montezumae (Chiapas). P. pseudostrobus var. oaxacana (Chiapas), P. reflexa.
	n-undecane	P. coulteri, P. pseudostrobus, var. oaxacana (Chiapas), P. reflexa
	ocimene	P. quadrifolia.
	beta-myrcene	P. hartwegii..
B. Monacyclic terpenes
	dipentene	P. engelmannii, P. rudis, P. pinceana.
	1-limonene	P. chihuahuana, P. edulis, P. hartwegii, P. lumholtzii. P. monophylla P. montezumae (Chiapas), P. oocarpa (Chiapas), P. pseudostrobus var. oaxacana (Chiapas).
	1-b (beta)-phellandrene	P. contorta, P. coulteri.
	Terpinolene	P. ayacahuite, P. reflexa.
C. Bicyclic terpenes
	a -(alpha) pinene	Present in all Mexican pines except P. Jeffreyi and perhaps P. contorta.
	b -(beta)³ pinene	P. chihuahuana, P. cooperi, P. durangensis, P. engelmannii, P. lambertiana, P. radiata, P. rudis.
	D -(delta)³-carene	P. hartwegii, P. leiophylla, P. ponderosa, P. reflexa.
	camphene	P. muricata.
D. Sesquiterpenes
	longifolene	P. cembroides, P. chihuahuana P. flexilis, P. hartwegii, P. lumholtzii, P. montezumae, (Chiapas), P. oocarpa (Chiapas), P. oocarpa var. trifoliata, P. pseudostrobus var. oaxacana (Chiapas), P. teocote
	albicaulene	P. flexilis.
	maderene	P. pinceana.
	unidentified monocyclic	P. flexilis.
	unidentified bicyclic	P. ayacahuite, P. lambertiana.
E. Alcohols
	A sesquiterpene alcohol	P. lambertiana.
F. Aldehydes
	Decyl aldehyde	P. jeffreyi
G. Phenolic compounds
	Methyl chavicol	P. lumholtzii.

Among sesquiterpenes (that is, terpenes having the formula C₁₅H₂₄) of some possible commercial importance are the cadinene-like substances (i.e. sesquiterpenes that yield crystalline cadinene hydrochloride, but which are not necessarily identical with cadinene). These are used as fixatives (odor-carriers) in the perfume industry. Pinus quadrifolia is very rich in these sesquiterpenes.

References

(1) BLANCO, CENOBIO E. Pinus cooperi blanco, SO. nova, Anales del Instituto de Biología 20: pp. 185-87. Mexico D. F. 1949.

(2) HAAGEN SMIT, A. J., WANG, TIAO-HSIN, and MIROV N. T., "Composition of Gum Turpentines of Pinus aristata, P. balfouriana, P. flexilis and P. Parviflora". Jour. Amer. Pharm. Assoc. Sci. Ed., 39: pp. 254-259. 1950.

(3) ILOFF, P. M. and MIROV. N. T. Composition of gum turpentines of pines, XVI. A report on Pinus oocarpa and P. pseudostrobus var. oaxacana. from Chiapas and P. cooper from Durango. Jour. Amer. Pharm. Assoc. Sci. Ed., 42: pp. 46-49. 1953.

(4) ILOFF, P. M. and MIROV. N. T. Composition of gum turpentines of pines, XVII. A report on P. montezumae from Chiapas, and P. oocarpa var. trifoliata and P. durangensis from Durango, Mexico. Jour. Amer. Pharm. Assoc. Sci. Ed., 42: pp. 464-467. 1953.

(5) ILOFF, P. M. and MIROV. N. T. Composition of gum turpentines of pines, XIX. A report on P. ponderosa from Arizona, Colorado, South Dakota and Northern Idaho. Jour. Amer. Pharm. Assoc. Sci. Ed. 43: 373-378 pp. 1954.

(6) ILOFF, P. M. and MIROV. N. T. Composition of gum turpentines of pines, XXI. A report on Pinus quadrifolia from Southern California, P. lumholtzii from Durango, Mexico and P. caribaea from Nicaragua. Jour. Amer. Pharm. Assoc. Sci. Ed. 1954. In preparation.

(7) ILOFF, P. M. and MIROV. N. T. Composition of gum turpentines of pines, XXII. A report on Pinus rudis and P. hartwegii from Mexico and P. insularis from Philippines. Jour. Amer. Pharm. Assoc. Sci. Ed. (1954). In preparation.

(8) IRIARTE, JOSE. Estudio de los aguarrases mexicanos. Quimica (Mexico) 4: pp. 117-119. 1946.

(9) MARTINEZ, MAXIMINO. Los pinos mexicanos. Segunda Edición. Mexico, pp. 361. Ediciones Botas. 1948.

(10) MIROV, N. T. Composition of gum turpentine of Coulter pine. Ind. Eng. Chem. 38: pp. 405-8. 1946.

(11) MIROV, N. T. Composition of gum turpentine of Bishop pine. Jour. of Forestry 45: pp. 659-60. 1947.

(12) MIROV, N. T. Composition of gum turpentine of pines XII. A report on Pinus montezumae, P. oocarpa and P. leiophylla. Jour. Amer. Pharm. Assoc. Sci. Ed., - 40: pp. 550-551. 1951.

(13) MIROV, N. T. Composition of gum turpentines of pines, XIV. A report on three Mexican pines: Pinus ayacahuite, P. cembroides and P. pinceana. Jour. Amer. Pharm. Assoc. Sci. Ed., 41: pp. 673-76. 1952.

(14) MIROV, N. T. Composition of gum turpentines of pines, XV. A report on P. resinosa and P. reflexa. Jour. Amer. Pharm. Assoc. Sci. Ed. 41: pp. 677-79. 1952.

(15) MIROV, N. T., and HAAGEN SMIT, A. J. Composition of gum turpentine of Knobcone pine. Jour. of Forestry 47: pp. 721-22. 1949.

(16) MIROV, N. T., HAAGEN SMIT, A. J. and THURLOW, JAMES. composition of gum turpentine of Pinus lambertiana. Jour. Amer. Pharm. Assoc. Sci. Ed. 38: pp. 407-8. 1949.

(17) MIROV, N. T., ILOFF, P.M., JR. and GORDON, L. B. Composition of gum turpentines of pines, XVIII. A report on Pinus pungens, P. glabra and P. teocote. Jour. Amer. Pharm. Assoc. Sci. Ed. 43: pp. 13-15. 1954.

(18) MIROV, N. T. and ILOFF, P. M. JR. Composition of gum turpentines of pines, XX. A report on Pinus chihuahuana from Durango, P. apacheca from Arizona and P. monticola from Idaho. Jour. Amer. Pharm. Assoc. Sci. Ed. 43: pp. 378-381, 1954.

(19) MIROV, N. T., WANG, T. H. and HAAGEN SMIT, A. J. Chemical composition of gum turpentines of pines. A report on Pinus strobus, P. cembra, P. taeda, P. radiata, and P. virginiana. Jour. Amer. Pharm. Assoc. Sci. Ed. 38: 403-07. 1949.

(20) SCHORGER, A. W. An examination of the oleoresins of some western pines. U.S. Dept. of Agric. Forest Service Bull. 119, Washington, 1913.

(21) SCHORGER, A. W. Contribution to the chemistry of American conifers. Transactions of the Wisconsin Academy of Sciences, Arts and Letters 19, part 2, 728-766. 1919.

Near East seminar on forest policy

During the period 13-25 September, the Turkish Government was host at Istanbul to a seminar on Forest Policy for Near Eastern countries.

This Seminar dealt with long-term forest policy in conservation of forests and range management, with particular emphasis on principles, delimitation, sustained yield, legislation, administration, and trends in forest research and education. It also covered such subjects as methods of implementing forest policy; publicity by means of tree festivals and public education; political aspects of the grazing problem; organizing protection against insect pests, diseases and fire; improvement of afforestation and plantations outside the forest; improvements in forest utilization, with particular emphasis on training of forest labor; products utilization through development of wood-using industries; and development of markets.

The Co-Director, J. Moser FAO and Fehim Firat (Turkey), reported a very successful seminar with the participation of twenty-one forest officers from Cyprus, Egypt, Iraq, Iran, Lebanon, Libya, Syria and Turkey. Lecturers included H. Benan (Iran), G. Chapman (Cyprus), H. Etter FAO and Refik Erdem, Savni Hus, and Esat Muhlis Oksal (Turkey).