Effect of acid hydrolysis on alizarin content, antioxidant and antimicrobial activities of Rubia tinctorum extracts

Purpose The paper aims to analyse the effect of acid hydrolysis on the chemical composition and the biological activities of Rubia tinctorum collected from the south of Tunisia. It proposes to clarify the relationship between alizarin content and the antioxidant and antimicrobial activities of Rubia extract. Design/methodology/approach The paper opted for analytical tools (HPLC) and the in-vitro study of biological activities, namely, the antioxidant activity which is evaluated using the radical scavenging assay (ABTS) and ferric reducing power assay (FRAP); the antimicrobial activity is tested using the wells agar diffusion method. Findings The paper provides information about the positive effect of acid hydrolysis, namely, the enhancement of alizarin content in the extract which has increased its antioxidant and antimicrobial activities. Originality/value This paper fulfils an identified need to study the relationship between the chemical composition, biological activities and colour enhancement.