Drying effects on antioxidant activity, enzyme activity, and phytochemicals of avocado ( Persea americana ) leaves

Abstract

In this study, avocado leaves were dried by five different drying treatments: oven‐drying at 50 and 100 °C, microwave‐drying, ambient air‐drying, and freeze‐drying. Investigation showed that oven‐drying and ambient air‐drying of leaves caused decrease in antioxidant properties while microwave‐drying and freeze‐drying preserved them. Polyphenol oxidase (PPO) and peroxidase (POD) activities decreased notably after drying in oven at 50 and 100°C, microwave, ambient air and blanching at 100°C. However, increase in PPO was observed in freeze‐dried leaves. Chlorogenic acid and rutin present in leaves showed varying decrease in drying processes except microwave‐drying, and freeze‐drying. Cellular antioxidant assay revealed reduced antioxidant activity in all drying treatments except for microwave‐drying. Factors that affected changes in antioxidant properties by various drying processes were identified and discussed. Microwave‐drying was considered to be the best drying method for avocado leaves as phenolic compounds were preserved and PPO and POD activities were deactivated. Practical applications Avocado leaves are used as herbal tea in traditional medicine and are reported to have medicinal properties such as antioxidant, anti‐viral, and anti‐inflammatory. Processing of fresh herbal tea leaves are required to preserve phenolic compounds and quality of the tea leaves. This study represents a comprehensive study on the effects of different drying treatments on the antioxidant activity using both in vitro and in vivo analysis and enzymatic changes of avocado leaves. The optimum drying condition found in this study will be beneficial to the tea processing industry.

Effect of Organic Solvents and Water Extraction on the Phytochemical Profile and Antioxidant Activity of Clitoria ternatea Flowers

“…The CAA assay of C. ternatea flower extracts was tested using RAW264.7 cells. 16 RAW264.7 cells at a density of 5 × 10 4 cells/well were seeded into a 96-well plate and incubated for 24 h. The growth medium was removed, and the wells were washed with phosphate-buffered saline (PBS). Triplicate wells were treated for 1 h with 100 μL of extracts mixed with 20 μM DCFH-DA dissolved in medium without FBS.…”

Comparison of Ethanolic and Aqueous Populus balsamifera L. Bud Extracts by Different Extraction Methods: Chemical Composition, Antioxidant and Antibacterial Activities

“…The drying process is critical, because it influences the antioxidant properties of the raw material, since the thermal decomposition and the action of oxidative enzymes are under way. Polyphenol oxidase is an oxidative enzyme which splits phenolic compounds, while peroxidase is associated with phytochemical splitting when hydrogen peroxide is present and plays an important role in splitting the phenolic compounds in the plant material, which are created by different drying methods [43]. The lower content of the active compounds in the extracts prepared from the fresh plant material may have been influenced by the fact that the fresh plant material usually has a higher moisture content [42].…”

Changes in the Content of Phenolic Compounds and Biological Activity in Traditional Mexican Herbal Infusions with Different Drying Methods

“…It is a critical process, given it is the process is known to affect the antioxidant properties of the leaves due to thermal degradation and/or the action of oxidative enzymes [21]. Polyphenol oxidase is the oxidative enzyme degrading phenolic compounds, while peroxidase is related to phytochemical degradation in the presence of hydrogen peroxide, which plays a role in the degradation of phenolic compounds in plant leaves produced by different types of drying [22].…”