<![CDATA[Anthocyanin-containing plants have potential as environmentally friendly natural acid–base indicators. However, information regarding the suitability of Ruellia tuberosa L. flower extract as a titration indicator remains limited. The aim of this study was to explore the potential of purple trumpet flower extract (Ruellia tuberosa L.) as an alternative acid-base titration indicator. The method used for flower extraction was stepwise maceration with n-hexane, ethyl acetate, and 70% ethanol. The extract was tested for anthocyanin content, color response in buffer solutions at pH 1–14, and performance in strong acid–strong base, weak acid–strong base, and weak base–strong acid titrations. The extract exhibited red at pH 1–3, pink at pH 4–5, colorless at pH 6–8, green at pH 9–12, and yellow at pH 13–14. Endpoint detection was comparable to phenolphthalein and methyl orange, with only slight differences in endpoint pH values. Purple trumpet flower extract shows potential as a natural acid-base indicator and may serve as an alternative for educational and laboratory applications, although further research on stability and quantitative anthocyanin content is still needed.]]>
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