Abstract

FLOWERS AS NATURAL INDICATORS

Kavitha G.*, Aswathi V., Chinju Sara George, Rakhi Raju and Elessy Abraham

ABSTRACT

Natural pigments in plants are highly colored substances and may show color change with variation of pH. Many flowers, fruits and vegetables contain chemical substances called anthocyanins which are pigments that react in a different way to acids and bases that change colour in solutions of different pH values. Pisum sativum from family Fabaceae, Catharanthus roseus from Apocyanaceae and Euphorbia ligularia (Euphorbiaceae) gives sharp and intense colour change as compared to synthetic indicators in acid-base titrations. The qualitative chemical test for Pisum sativum, Catharanthus roseus and Euphorbia ligularia shows presence of flavanoid pigment anthocyanins, which may be the reason for their activity as an indicator. The Pisum sativum, Euphorbia ligularia and Catharanthus roseus indicator was found to be more significant in strong acid-strong base titration. The result obtained showed that the routinely used indicators could be replaced successfully by herbal extract prepared as they are simple, accurate and precise and can be prepared just before experiment. The isolation of pure compounds possessing indicator properties help to know the mechanism by which they show indicator properties and new theories of indicator could be established.

Keywords: Catharanthus roseus (Apocynaceae), Pisum sativum (Fabaceae), Euphorbia ligularia (Euphorbiaceae).