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Shellac

Scientific Name(s): Laccifer lacca
Common Name(s): Gommelaque, Lac, Lacca, Shellac

Clinical Overview

Use

The most common use is as a furniture finish, but it has also been used in the pharmaceutical industry, in dentistry, and in cosmetics.

Dosing

There is no clinical evidence to support specific doses of shellac for therapeutic purposes.

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

None well documented.

Adverse Reactions

Little data are available. Several cases of allergic contact dermatitis of the eyelids due to shellac in mascara and one report of contact cheilitis have been documented.

Toxicology

Shellac NF is food grade and is listed as Generally Recognized as Safe (GRAS) by the FDA.

Source

Shellac is the purified product of lac, the red, hardened secretion of the insect Laccifer (Tachardia) lacca Kerr. This tiny insect sucks the sap of selected trees and bushes, and secretes lac as a protective covering. The name lac is said to derive from lakh, the Sanskrit word for one hundred thousand, a reference to the very large number of insects involved in producing appreciable amounts of the product.1

Lac is cultivated in India, Thailand, and Burma. The whitest lac is produced by insects infesting the kusum tree (Schleichera trijuga). The harvester cuts twigs coated with lac into small pieces called sticklac. The crude material is ground and soaked in water to remove debris and insect bodies. The remaining material is soaked in sodium carbonate, which removes laccaic acid, a complex mixture of at least four structurally related pigments. The resulting granules retain the yellow pigment erythrolaccin and are dried to form seedlac. Further treatment by melting, evaporating, or filtering yields shellac.2

History

Shellac is most often used as a finish for fine furnitures. Further, the material has been used for almost 100 years by the pharmaceutical industry. Examples of shellac's role in this field include: Tablet coating formulations,3, 4, 5, 6 microencapsulation,7, 8, 9, 10, 11 matrix formation,12 enteric coating,13 humidity tolerance,14 and binding ability.15

Shellac is used in dentistry, as a binding agents for dentures, restorations, and mouldings, and for training purposes in dental schools.16, 17, 18, 19, 20, 21, 22

Shellac has also been used as an ingredient in hair spray and in other cosmetics23, 24 However, shellac undergoes an aging effect upon storage and thus has fallen into disfavor as an ingredient in some preparations.2

Chemistry

The National Formulary XV recognizes 4 grades of shellac: Orange, dewaxed orange, regular bleached and refined wax-free bleached. The grades differ in the manner in which the seedlac is treated. Orange shellac is obtained by the evaporation of filtered ethanolic solutions of seedlac. It may be dewaxed by further filtration. Regular bleached shellac is obtained by dissolving the seedlac in aqueous sodium carbonate at a high temperature. After filtration, a bleaching agent (such as sodium hypochlorite) is added. The resin is removed by sulfuric acid precipitation. Refined wax-free bleached shellac adds another filtration step to remove the waxes.25

The exact chemical composition of shellac is unknown. It appears to be composed of a network of hydroxy fatty acid esters and sesquiterpene acid esters with a molecular weight of about 1000. Aleuretic acid, r-butolic acid, shellolic acid, and jalaric acid are the major constituents. The composition is a function of the source and time of harvest of the sticklac. Variability in the product may be a problem for commercial users of shellac. The physical properties of shellac also vary. For example, the reported melting point ranges from 77° to 120°C. Shellac is soluble in ethanol, methanol, glycols, glycol ethers, and alkaline water.1

Uses and Pharmacology

Gangrene

Clinical studies

A 1-year prospective, randomized, controlled trial was conducted to determine the ability of shellac to prevent infection and progression of dry gangrene to wet gangrene in 26 patients with type 2 diabetes. The patients presented with peripheral dry, well-demarcated gangrene in their feet and were awaiting nonsurgical autoamputation because of contraindications to revascularization or surgery, limited life expectancy, and/or refusal of surgical amputation. Compared to conventional treatment with 10% povidone-iodine, the slightly lower rate of surgical amputation in the shellac group (46.2% vs 60%) was not statistically significant. None of the patients in the shellac group developed an allergic reaction.26

Other uses

Animal data

Research reveals no recent animal data regarding the use of shellac in a therapeutic application.

Clinical data

A randomized double-blind, controlled, clinical study evaluated the efficiency of shellac in reducing dentin hypersensitivity, which appeared to be as effective as the control agents tested.27

Dosing

There is no clinical evidence to support specific doses of shellac for therapeutic purposes.

Pregnancy / Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

None well documented.

Adverse Reactions

Allergy and contact dermatitis have been reported.28

Several cases of allergic contact dermatitis or eczema of the eyelids in women using mascara (Great Lash, Diorshow) have been documented with confirmed positive sensitivity to shellac through breakdown analysis of the product ingredients.29, 30

Toxicology

Studies suggest cytotoxicity is low.31 Shellac NF is food grade and is listed as Generally Recognized as Safe (GRAS) by the FDA.32

References

1. Yates P, Field GF. Tetrahedron. 1970;26:3135.
2. Der Marderosian A. Natural Product Medicine. Philadelphia, PA: George F. Stickley Co. 1988;356–57.
3. Pandula E, et al. Acta Pharm Hung 1970 Jan;40:25–28.
4. Alam A, et al. J Pharm Sci 1972 Feb;61:265–68.5059797
5. Tuerck P, et al. J Pharm Sci 1973 Sep;62:1534–37.4743112
6. Sheorey D, et al. Indian J Pharm Sci 1992;54(5):169–73.
7. El Banna H, et al. Pharm Indus 1982;44(6):641–45.
8. Labhasetwar V, et al. J Microencapsul 1989;6(1):115–18.2715911
9. Labhasetwar V, et al. J Microencapsul 1990:7(4):553–54.2266478
10. Sheorey D, et al. Int J Pharm 1991 Feb 1;68:19–23.
11. Sheorey D, et al. J Microencapsul 1991;8(3):375–80.1941444
12. Serajuddin A, et al. J Pharm Sci 1984 Sep;73:1203–8.6491936
13. Chang R, et al. Int J Pharm 1990 Apr 30;60;171–73.
14. Gursoy A, et al. Pharmazie 1986;41(8):575–78.3786379
15. Labhasetwar V, et al. Indian J Pharm Sci 1988 Nov-Dec:50:343–45.
16. Azouka A, et al. J Oral Rehabil 1993;20(4):393–400.8350174
17. Harrison A, et al. J Oral Rehabil 1995;22(7):509–13.7562216
18. Lie T, et al. J Clin Periodontal 1987;14(3):149–55.3549795
19. Escoe R. Int J Prosthodon 1989;2(3):243–44.2699421
20. Hitge M, et al. Ned Tijdschr Tandheelkd 1989;96(8):372–77.2700772
21. Lee C, et al. J Pros Dent 1991;66(5):623–30.1805000
22. Heath J, et al. J Oral Rehabil 1993;20(4):363–72.8350170
23. Tannert U. Seifen, Oele, Fette, Wachse 1992 Oct 30;118:1079–80.
24. Penning M. Seifen, Oele, Fette, Wachse 1990 Apr 5;116:221–24.
25. Pharmaceutical Glazes, Bulletin 70-09-01, William Zinsser and Co.
26. Alzahrani H, Bedir Y, Al-Hayani A. Efficacy of shellac, a natural product, for the prevention of wet gangrene. J Int Med Res. 2013;41(3):795-803.23637276
27. Hoang-Dao BT, Hoang-Tu H, Tran-Thi NN, et al. Clinical efficiency of a natural resin fluoride varnish (Shellac F) in reducing dentin hypersensitivity. J Oral Rehabil. 2009;36(2):124-131.19522897
28. Das S, Jacob SE. Shellac. Dermatitis. 2011;22(4):220-222.21781639
29. Le Coz CJ, Leclere JM, Arnoult E, Raison-Peyron N, Pons-Guiraud A, Vigan M; Members of Revidal-Gerda. Allergic contact dermatitis from shellac in mascara. Contact Dermatitis. 2002.46(3):149-152.12000323
30. Gallo R, Marro I, Pavesi A. Allergic contact dermatitis from shellac in mascara. Contact Dermatitis. 2005;53(4):238-239.16191026
31. Lu J, Wang H, Huang J, et al. Sesquiterpene acids from Shellac and their bioactivities evaluation. Fitoterapia. 2014;97:64-70.24879899
32. CFR - Code of Federal Regulations Title 21. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=175.300. Accessed September 2016.

Disclaimer

This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.

This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.

Further information

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