Mechanistic Study on the Formation of Compounds from Thioureas

Formation of 2-(N-arylamino)benzothiazole takes place, when N,N′-diphenylthioureas are treated with polymer-supported tribromide or with iodine-alumina as catalyst under solvent free conditions. However, when N-substituted-N′-benzoylthioureas are treated with polymer-supported tribromide or with iodine-alumina as catalyst either under various conditions or under solvent free conditions, decomposition takes place to give the respective benzamides and thiobenzamides. Mechanistic study of the formation of these compounds is studied using DFT calculations. It is found that electron donating group at the para-position of the aryl group of benzoylthiourea favors the formation of benzamide whereas the presence of electron withdrawing group at para-position of the aryl group of benzoylthiourea, formation of thiobenzamide takes place. When the catalyst is changed to diacetoxyiodobenzene (DIB) under similar reaction conditions, benzoxazole amides are formed; expected benzothiazoles or the decomposition products are not obtained. Mechanistic study of the reaction using DFT calculation again shows that the reaction followed through carbodiimide intermediate undergoes the formation of C-O bond in benzoxazole moiety, instead of the expected C-S bond formation of benzothiazole moiety via a sequential acylation and deacylation process

Phytochemistry, chemotaxonomy, ethnopharmacology, and nutraceutics of lamiaceae

Lamiaceae (or Labiatae) is a family of plants included in the Angiosperms group comprising 12 subfamilies, 16 tribes, 9 subtribes, 236 genera, and more than 7000 species. It represents what is probably one of the best-known and most-studied families from the phytochemical and ethnopharmacological standpoints, because it contains several compounds with great relevance and many important biological properties. In the context of phytochemistry, Lamiaceae can be unofficially divided into two major groups. The first one comprises all those species that mainly produce volatile terpenoids, found in the essential oils, while the second one comprises species that mainly biosynthesize components of the polar fraction. Typical examples of the first class are Salvia L., Mentha L., and Rosmarinus L. species, while typical examples of the second class are Ajuga L., Teucrium L., Melittis L., and Stachys L. species. Several phytochemicals have been isolated from Lamiaceae species, such as α- and β-pinene, menthol, and limonene among the essential oil constituents, and di- and triterpenes, flavonoids, and iridoids among the polar fraction constituents. Some of these compounds are even considered to be chemotaxonomic markers at the family, genus, and species levels. From the ethnopharmacological point of view, the Lamiaceae family is very important. In fact, the essential oil of these species is well known to exert strong antibacterial and antioxidant properties, while the polar fraction constituents are known to exhibit good antiviral, anticancer, and antiinflammatory activities. This may explain (and maybe justify) the ancient and modern use of several Lamiaceae species in traditional medicine. Moreover, some Lamiaceae species are consumed on a daily basis as food, spices, or herbal teas, given that their high nutritional and pharmacological properties are able to produce several beneficial nutraceutical effects. In this chapter, these topics will be explored. For every species, all the known phytochemicals will be described, and an overview of their chemotaxonomic relevance will also be provided. In addition, the pharmacological and nutraceutical activities of every species, as reported in the literature, will be detailed and compared with available phytochemical data in order to verify a possible connection of theirs. One further aspect also will be taken into consideration namely, the recent opinions of the scientific community about the species belonging to the Ajuga and Teucrium genera. These plants have been widely employed in the past in traditional medicine, but the use has now stopped due to the presence of toxic secondary metabolites known as neo-clerodane diterpenoids which have clearly been shown to cause hepatotoxicity