Herbal indicators as a substituent to synthetic indicators

Vishwas C. Bhagat, Radheshyam D. Patil, P.R. Channekar, S.C. Shetty, Atul S. Akarte


In acid - base titrations, indicators are used to show sharp color change at intervals of pH. Natural pigments in plants are highly colored substances and may show color changes with variation of pH. An attempt has been made to investigate the indicator activity of methanolic extract of fl ower pigments and to replace synthetic indicators as they have certain disadvantages like chemical pollution, availability problems and high cost.
Methanolic extract of Rosa indica (L) from family Rosaceae and Hibiscus rosa-sinensis (L) from family Malvaceae gives sharp and
intense color change as compared to phenolphthalein and methyl orange. Herbal indicators are evaluated by using strong acid - strong base, strong acid - weak base, weak acid - strong base, and weak acid - weak base. In all these titrations the extract was found to be very useful and accurate for indicating the equivalence point (neutralization point).
From photochemical investigation and qualitative chemical tests for Rosa indica and Hibiscus rosa-sinensis shows presence of
anthocyanins; which are the pigmented fl avonoids; which may be the reason for its activity as an indicator. Apart from the above advantages the isolation of pure compounds possessing indicator’s properties help to know the mechanism by which they shows indicator’s properties and new theories of indicators could be established.
Key words: End point, herbal indicator, methanolic extracts, titrations

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DOI: http://dx.doi.org/10.22377/ijgp.v2i3.24


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