First-Time Identification of the PPAT Protein as a Novel Antibacterial Target: Antimicrobial and Antioxidant Insights from E. purpurea.

Echinacea purpurea (Asteraceae) is a perennial medicinal herb with immune-stimulating and anti-inflammatory properties. In this study, the antioxidant and antibacterial properties of the organs of the E. purpurea plant were investigated, and significant amounts of total phenolic and total flavonoid contents were detected in flower extracts. It was determined that the DPPH% values of the water extract were higher than the values of methanol extracts. It was observed that Fe³⁺ reduction capacity increased as the concentration increased in all plant extracts. The highest antimicrobial activity was determined to be against Pseudomonas aeruginosa (35 mm) and Klebsiella pneumonia (20 mm) at the petal (EpP)-methanol extract. In HPLC analysis of component-based phenolic substances, protocatechuic acid, caffeic acid, coumaric acid, chlorogenic acid, and ferulic acid were determined in the extracts. The lowest protein-ligand binding energy (kcal/mol) was found to be -9.6 kcal/mol in chlorogenic acid. Chlorogenic acid can bind with PPAT's T10-(B)-OG1, W12-(b), I127-(B)-O, and S129-(B)-OG and P88-(B)-HN2, T10-(B)-N, F11-(b)-N, D12-(B)-N, S129-(B)-N, and K12-(B)-NZ amino acid residues via hydrogen bonds. The evidence collected indicates that chlorogenic acid inhibits phosphopantetheine adenylyltransferase (PPAT), validating PPAT as a potential target for antibacterial therapy for the first time. The development of selective inhibitors such as chlorogenic acid of bacterial PPAT is promising for the discovery of new antibiotics.