Chemical characterization, antioxidant properties, anti-inflammatory activity, and enzyme inhibition of Ipomoea batatas L. leaf extracts

Ipomoea batatas L. is widely used as a functional food in many countries. In this work, I. batatas leaf extracts (Soxhlet extract, microwave [MW] extract, and decoction extract) were characterized for the first time, and their total flavonoid and phenolic compound contents were measured by spectrophotometric and chromatographic analyses. These extracts were investigated for their antioxidant activities (free radical scavenging and reducing power assays), enzyme inhibitory activities (cholinesterase, tyrosinase, α-amylase, and α-glucosidase) and effects on inflammation pathways. Various bioactive secondary metabolites were identified; among them, chlorogenic acid appeared to be the most abundant. The decoction extract displayed the highest level of phenolics (89.26 mg GAE/g extract) and thus exhibited stronger antioxidant ability than the Soxhlet and MW extracts. Each preparation was tested in in vitro enzymatic assays, which revealed that all three extracts exhibited interesting inhibitory activities against acetylcholinesterase, α-glucosidase, and α-amylase. Moreover, in vitro and ex vivo anti-inflammatory activities were observed for the decoction extract. Collectively, these results indicated that I. batatas leaf can be considered a potential candidate for the development of functional foods to combat the symptoms of metabolic disorders, such as type II diabetes mellitus.