Preliminary Studies on Plant-derived Natural Indicators for Pharmaceutical Applications

Indicators used in titration are generally chemical dyes of synthetic origin that provide distinct color transitions of pH. Nature has abundant source of plants that need to be identified for their indicator property there by promoting SDG 12 (Responsible Consumption and Production) and SDG 15 (Life on Land) goal. The present study focuses on the applicability of vegetables’ and fruits’ extracts as natural indicators. A comparative study of red cabbage (Brassica oleracea), dragon fruit (Selenicereus undatus), pomegranate (Punica granatum), beetroot (Beta vulgaris) and turmeric (Curcuma longa) extracts with synthetic indicator viz. phenolphthalein was carried out to evaluate their potential as acid-base indicator. The findings revealed that all plant extracts tested were effective as acid–base indicators in strong acid–strong base titrations. Additionally, red cabbage (Brassica oleracea) and dragon fruit (Selenicereus undatus) demonstrated indicator activity even in strong acid–weak base titrations. The study detected the presence of anthocyanins in all plant extracts which were analysed by determining their λ_max by UV spectrophotometry and Rf by Thin Layer Chromatography. The choice of such natural indicators can be explained by their wide occurrence, non-toxicity, simple methods of extraction, and low cost, which makes these indicators a sustainable alternative to synthetic ones in the context of pharmaceutical use.