What is the connection between TANNINS and HYDROCHLORIC acid?

Question

A toothpick dipped in guava leaf extract turned pink upon exposure to hydrochloric acid.

What's the explanation behind this reaction?

:)

or links?

Answer 1

Many naturally occurring plant extracts such as guava leaf extract have colourants that are pH sensitive. They have different colours depending on whether thay are in acidic or basic solutions. Your guava leaf extract appears to be one of these. When you added the acid, you lowered the pH and so the colour changed.