Phenolic Monoterpenes Conversion of Conobea scoparioides Essential Oil by Hydrotalcite Synthesized from Blast-Furnace Slag
2024
Monaliza M. Rebelo | Eloisa Helena A. Andrade | José Augusto M. Corrêa | José Guilherme S. Maia
Conobea scoparioides (Plantaginaceae) is an herbaceous plant known as &ldquo:pataqueira&rdquo: that grows wild in seasonally wet areas of the Amazon region. It is used for aromatic baths and anti-protozoan remedies by the Brazilian Amazon native people. The main volatile compounds identified in the essential oil of &ldquo:Pataqueira&rdquo: were the phenolic monoterpenes thymol and thymol methyl ether and their precursors, the monoterpene hydrocarbons &alpha:-phellandrene and p-cymene. A hydrotalcite synthesized from blast-furnace slag exhibited a 3:2 (Mg/Al) molar ratio, and this layered double hydroxide (LDH) was evaluated as a catalyst in converting the main monoterpenes of the &ldquo:Pataqueira&rdquo: oil. This action significantly increased the thymol content, from 41% to 95%, associated with the percentual reduction in other main components, such as thymol methyl ether, &alpha:-phellandrene, and p-cymene. The LDH reaction showed a strong tendency towards producing hydroxylated derivatives, and its behavior was similar to the hypothetical plant biosynthetic pathway, which leads to the production of the monoterpenes of &ldquo:Pataqueira&rdquo: oil. Thymol and its derivatives are potent antiseptics applied in pharmaceutical and hygienic products as antibacterial, antifungal, and antioxidant properties, among others. The present work reports a natural source with a high thymol content in aromatic plants from the Amazon, with evident economic value.
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