Exploring the Antioxidant and Antimicrobial Properties of Mentha piperita (Peppermint)

Publication Date

Spring 4-1-2026

Presentation Length

15 minutes

College

College of Sciences & Mathematics

Department

Chemistry and Physics, Department of

Student Level

Undergraduate

Faculty Mentor

Kimberlee Entsminger

Presentation Type

Talk/Oral

Summary

Mentha piperita (peppermint) is widely used for its therapeutic properties, though its antioxidant and antimicrobial properties depend on extraction methods and solvent polarity. This study evaluated the antioxidant and antimicrobial properties of peppermint essential oil and solvent based extracts prepared using 70% ethanol, methanol, and a 1:1 methanol-ethanol mixture. Antioxidant activity was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, with 𝐼𝐶50 values calculated relative to solvent controls and validated using gallic acid. Methanol extracts exhibited the strongest antioxidant activity (𝐼𝐶50 ≈10.7mg/mL), followed by the 1:1 methanol-ethanol extract (𝐼𝐶50 ≈8.88mg/mL) and the ethanol extract (𝐼𝐶50 ≈ 19.3mg/mL). Antimicrobial activity was evaluated using an agar diffusion assay against Escherichia coli, where peppermint essential oil and higher concentration extracts produced limited zones of inhibition, while solvent controls showed no activity and ampicillin produced clear inhibition. Overall, these results indicate that peppermint shows solvent dependent antioxidant activity, while antimicrobial effects against gram-negative bacteria are limited and primarily associated with essential oil, suggesting greater potential for antioxidant-based applications.

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