title: Aqueous extracts of Mozambican plants as alternative and environmentally safe acid-base indicators.
abstract: Indicators are substances that change color as the pH of the medium. Many of these substances are dyes of synthetic origin. The mulala plant (Euclea natalensis), which roots are commonly used by rural communities for their oral hygiene, and roseira (Hibiscus rosa-sinensis), an ornamental plant, are abundant in Mozambique. Currently, synthetic acid-base indicators are most commonly used but have environmental implications and, on the other hand, are expensive products, so the demand for natural indicators started. This study investigated the applicability of aqueous extracts of H. rosa-sinensis and E. natalensis as acid-base indicators. Ground on this work, the extracts can be used as acid-base indicators. On the basis of the absorption spectroscopy in both the UV-Vis region and previous studies, it was possible to preliminarily pinpoint anthocyanins and naphthoquinones as responsible for the shifting of colors depending on the pH range of aqueous extracts of H. rosa-sinensis and E. natalensis. These natural indicators are easily accessible, inexpensive, easy to extract, environmentally safe, and locally available.
authors.affiliation: Department of Chemistry, Universidade Pedagógica-Branch of Niassa, Lichinga, Mozambique. lusitaneom24@gmail.com.
authors.forename: Domingos Lusitaneo Pier
authors.initials: DL
authors.lastname: Macuvele
authors.affiliation: Department of Chemistry, Pedagogical University, Branch of Beira, Beira, Mozambique.
authors.forename: Gerre Zebedias Samo
authors.initials: GZ
authors.lastname: Sithole
authors.affiliation: Department of Chemical Engineering, Universidade Federal de Santa Catarina, Florianópolis, Brazil.
authors.forename: Karina
authors.initials: K
authors.lastname: Cesca
authors.affiliation: Department of Biology, Faculty of Science, Universidade Eduardo Mondlane, Maputo, Mozambique.
authors.forename: Suzana Lília Pinare
authors.initials: SL
authors.lastname: Macuvele
authors.affiliation: Department of Chemical Engineering, Universidade Eduardo Mondlane, Maputo, Mozambique.
authors.forename: Jonas Valente
authors.initials: JV
authors.lastname: Matsinhe
mesh_terms: D000872:Anthocyanins / Q000032:analysis / Q000737:chemistry; D031262:Ebenaceae / Q000737:chemistry*; D031584:Hibiscus / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000737:chemistry*; D009073:Mozambique; D009285:Naphthoquinones / Q000032:analysis / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry*
chemical_list: D000872:Anthocyanins; D007202:Indicators and Reagents; D009285:Naphthoquinones; D010936:Plant Extracts
keywords: Acid-base indicators; Environmental safety; Mozambican plant extracts