Comparative evaluation of the antioxidant, phenolic and antimicrobial activities of Plantago lanceolata L. leaf extracts from two regions of Türkiye: Giresun and Sakarya
TL;DR
It is indicated that Plantago lanceolata is a promising natural source of antioxidant and phenolic compounds with notable antimicrobial activity, and that ultrasound-assisted extraction is an effective approach for recovering its bioactive constituents.
Abstract
Plantago lanceolata is a medicinal plant widely used in phytotherapeutic applications in Türkiye. This study evaluated the antioxidant, total phenolic, and antimicrobial activities of Plantago lanceolata leaf extracts collected from the Tirebolu (Giresun) and Adapazarı (Sakarya) districts. Ethanol, methanol, and aqueous extracts were prepared by ultrasound-assisted extraction. Antioxidant activity was determined using the CUPRAC and ABTS assays, total phenolic content by the Folin–Ciocalteu method, and antimicrobial activity by agar well diffusion and broth microdilution assays. Minimum bactericidal and fungicidal concentrations were also determined. The CUPRAC and ABTS antioxidant capacities (mmol TE/g dw) were 0.136–0.234 and 0.389–0.641, respectively, for the Giresun samples and 0.139–0.207 and 0.406–0.584, respectively, for the Sakarya samples. The total phenolic content (mg GAE/g dw) was 244.61–324.78 for the Giresun samples and 239.87–310.99 for the Sakarya samples. Among the extraction solvents, methanol extracts consistently showed the highest antioxidant capacity and phenolic content. The ethanol extracts formed inhibition zones against Pseudomonas aeruginosa (9.24 and 7.15 mm) and Acinetobacter baumannii (7.25 and 8.19 mm) for the Giresun and Sakarya samples, respectively. All extracts inhibited the tested microorganisms, with minimum inhibitory concentration values of 0.196–1.563 mg/mL. The ethanol extracts also showed bactericidal activity against all tested bacteria, with minimum bactericidal concentration values of 0.396–6.25 mg/mL and 0.781–1.563 mg/mL for the Giresun and Sakarya samples, respectively. These findings indicate that Plantago lanceolata is a promising natural source of antioxidant and phenolic compounds with notable antimicrobial activity, and that ultrasound-assisted extraction is an effective approach for recovering its bioactive constituents.