Effects of Different Drying Methods on the Antioxidant and Antidiabetic Activities of Peppermint (Mentha Piperita L.) Leaf Extract

Chua, Jia Xi (2026) Effects of Different Drying Methods on the Antioxidant and Antidiabetic Activities of Peppermint (Mentha Piperita L.) Leaf Extract. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

For decades, aromatic plants are recognized as valuable sources of natural bioactive compounds, particularly phenolic compounds. Among these, peppermint (Mentha piperita L.) is one of the most utilised herbs, known for its medicinal and culinary applications. Its leaves are rich in diverse classes of phenolic compounds. Drying serves as an important preservation method for herbs by reducing moisture content, thereby inhibiting microbial growth, and slowing down undesirable chemical changes during storage. However, drying has been reported to induce alterations in quality, particularly in terms of their bioactive properties. This study aims to determine the effects of oven drying, microwave drying, and sun drying on the antioxidant and antidiabetic activity of peppermint leaf extracts. The peppermint leaves were subjected to three drying methods while fresh peppermint leaves act as control. The extracts were produced by soaking the ground leaves in 80% ethanol, followed by shaking, stirring, and filtering. TPC and TFC were conducted to evaluate the phytochemical constituents of extracts. DPPH and FRAP were applied to study the antioxidant activity. Also, α-amylase inhibition assay was carried out to determine the antidiabetic activity of the extracts. Results obtained indicate that fresh leaf extract had the highest TPC and TFC, followed by MD, SD, and OD leaf extracts. MD increased the antioxidant activity of extracts, while SD and OD leaf extracts exhibit lower antioxidant activities. Fresh extract had the highest α-amylase inhibition activity, followed by MD, OD, and SD leaf extracts. Although drying appeared to reduce the α-amylase inhibition activity, there were no significant differences between the inhibition activity of all extracts. In conclusion, MD leaf extract displays the most promising antioxidative and antidiabetic activities, making it a potential pharmaceutical candidate for preventing oxidative damage and diabetes.