Analisis Aktivitas Antosianin dari Buah Senggani (Melastoma candidum L.), Kulit Kopi (Coffea arabica L.), dan Ubi Jalar Ungu (Ipomea batatas L.) Sebagai Indikator Asam Basa

This study aims to analyze the activity of anthocyanin compounds from the extract of senggani fruit (Melastoma candidum L.), coffee skin (Coffee arabica L.), and purple sweet potato (Ipomea batatas L.) as an indicator of acid-base. The extract of the three samples was obtained by maceration. Testing of sample extracts to analyze the activity of anthocyanin compounds was carried out using Buffer pH 1-12. Testing of the sample extract as an indicator of acid-base was carried out by means of titration. In testing the activity of anthocyanin compounds, the results showed that senggani fruit extract at pH 4-5 was colorless, coffee skin extract at pH 1-5 was red, while at pH 6-12 was blue, even colorless, and purple sweet potato extract at pH 1-9 it turns red and at pH 10-12 turns green. In testing the sample extract as a natural indicator, the results showed that in the titration of a weak acid-strong base using 0.1 M CH3COOH and 50 mL 0.1 M NaOH, each extract experienced a different titration end point, namely 14 mL, 25 mL, and 27 mL for extracts of senggani fruit, coffee skin, and purple sweet potato; whereas in the strong acid-base titration using 0.1 M HCl and 50 mL 0.1 M NaOH, each extract experienced a different end point of the titration, namely 19 mL, 23 mL, and 22 mL for senggani fruit extract, coffee skin, and purple sweet potato, so it can be concluded that the extracts of senggani fruit (Melastoma candidum L.), coffee skin (Coffee arabica L.), and purple sweet potato (Ipomea batatas L.) contain anthocyanins which can be used as natural indicators on acid-base titrations which are environmentally friendly, inexpensive, and non-toxic.