Plant sources, techniques of production and uses of tar: A review.

Throughout history, Humans have always used tar for different purposes such as gluing materials, waterproofing, and conserving wood, but today, it is also used in medicines and cosmetics. Many countries around the world, Norway and Morocco to name a few, obtain tar from endemic trees. In a process of dry distillation, the organic material, endemic trees in this case, is exposed to a high temperature with a restricted amount of oxygen. Eventually, it cracks the large molecules in the matter and turns it into tar. This review article sheds light on tar production and the species that have been used in the process. Equal emphasis is placed on its uses, chemical composition, and toxicity. Meta-analysis (PRISMA) guidelines have been used to review this article. The review is put together from various articles, theses, documents in "Science Direct", "Hal (Archive ouvert)", "Web of knowledge" without limitation date. It turns out that tar can be produced by 18 tree taxonomic families, notably Cupressaceae, Pinaceae, and Betulaceae. As for the production techniques, two methods are considered: Per ascensum and Per descensum, which can take different forms. The chemical composition of tar consists of acids, phenols, and aromatic hydrocarbons. The uses of tar have changed over time, while its toxicity is strongly related to its chemical composition. The different species used in tar production have been highlighted in this research review. Equal importance has been given to its methods of extraction, uses and its chemical components. We hope that future studies will focus more on these species used to produce tar in other biological activities.

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Published by Elsevier B.V.