Comparative Evaluation of Hydroethanolic Extracts of Clitoria Ternatea Flowers, Malus Domestica Peel, and Their Combined Extract as Potential Eco-Friendly Acid–Base Indicators

Natural plant pigments have attracted considerable attention as environmentally friendly alternatives to synthetic acid–base indicators due to their biodegradability, low toxicity, and easy availability. The present study investigated the visual responses of hydroethanolic extracts of Clitoria ternatea (Butterfly Pea) flowers, Malus domestica (Apple) peels, and their combined extract in selected chemical solutions. Fresh flower petals and apple peels were washed with distilled water, ground using a mortar and pestle, and extracted using a hydroethanolic solvent system consisting of 70% ethanol and 30% distilled water. Three extracts—flower, fruit peel, and mixed extract—were prepared and individually introduced into sodium hydroxide (NaOH), ammonia solution (NH3), ammonium chloride (NH4Cl), and calcium hydroxide [Ca(OH)2] solutions. Visible colour changes were observed in all reaction mixtures. The flower extract produced light green, sky blue, sky blue, and light pale-yellow colours in NaOH, NH3, NH4Cl, and Ca(OH)2, respectively. The fruit peel extract exhibited similar colour changes with slight variations in colour intensity, while the mixed extract showed responses comparable to the flower extract. The pH of the resulting solutions was verified using universal pH paper, which produced consistent colour responses for each chemical irrespective of the extract used, indicating that the extracts did not significantly alter the measured pH of the solutions under the experimental conditions. The findings demonstrate that hydroethanolic extracts of Clitoria ternatea flowers and Malus domestica peels exhibit distinct visual responses when exposed to different chemical environments. These observations suggest that the plant extracts possess potential for use in educational demonstrations and preliminary investigations of naturally derived colour-responsive materials. Further studies employing standardized buffer solutions, quantitative colour analysis, and spectroscopic techniques are recommended to comprehensively evaluate their suitability as natural acid–base indicators.

Clitoria ternatea, Malus domestica, natural indicator, hydroethanolic extraction

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