Manejo de mudas de Teca e prospecção fitoquímica para avaliação do potencial indicador de pH

Tectona grandis L.f. has an extensive history of logging exploitation in Brazil but also presents a high potential for non-woody product use, when extracting diverse metabolic compounds from the plant. These compounds can be used as pH indicators when properly handled. The aim of this study was to manage Tectona grandis seedlings at different ages to produce a natural pH indicator. For preparing the pH indicator the following steps were taken: 1) Identification and determination of seedling extracts of Tectona grandis L.f. for application as acid-base indicator; 2) evaluation of plant age and extraction method on the acid-base indicator potential; 3) loss of the extracts acid-base indicator potential; and finally 4) use of the extract as pH indicator. All extracts from the seedlings’ vegetative parts changed color when exposed to acidic and basic solutions. However, leaves proved to be the best part for extraction. When the age and methods of obtaining the compound were evaluated, 120-days-old seedlings extracted with a solution of 96ºGL ethyl alcohol and water at 100ºC were found to be the most efficient. However, alcohol extraction reduced the loss of acid-base indicator potential. The best extract obtained by all factors analyzed in this study can be used as a substitute for the commercial indicator phenolphthalein. The alcoholic extract obtained from leaves of 120-days-old Tectona grandis seedlings can be used as pH indicator mostly for more alkaline substances (pH 9 - 14).