ROSE ANTHOCYANINS AS ACID BASE INDICATORS

A convenient method of extraction of anthocyanin from Rose flowers (Rosa rosa) has been developed using methanolic solution of 3% citric acid which gave better yield of anthocyanins than the methanolic solution of 0.1% hydrochloric acid. It has been shown that by changing the pH of the extract from 2-9, the hue color changes from dark pink to mehdi green. The extract showed wavelength maxima change from 517 nm (dark pink) to 592 nm (green) between the pH range 2 to 9. In the present study we have made use of anthocyanin extracted from Rose flowers as natural indicator for acid - base titration. The intrinsic pH of the extract was 2.88. Significant changes were observed when stannous salt was added to the rose anthocyanin extract. The spectroscopic data of the extracted anthocyanin pigments indicate a shift in wavelength maxima of the colors by addition of stannous salt and the complex with a change in pH of the aqueous medium. Usefulness of rose flowers as natural acid-base indicator has been exemplified.