Stevia Polyphenols, Their Antimicrobial and Anti-Inflammatory Properties, and Inhibitory Effect on Digestive Enzymes

Polyphenols from stevia leaves (PPSs) are abundant byproducts from steviol glycoside production, which have been often studied as raw extracts from stevia extracts for their bioactivities. Herein, the PPSs rich in isochlorogenic acids were studied for their antimicrobial and anti-inflammatory properties, as well as their inhibitory effects on digestive enzymes. The PPSs presented stronger antibacterial activity against E. coli, S. aureus, P. aeruginosa, and B. subtilis than their antifungal activity against M. furfur and A. niger. Meanwhile, the PPSs inhibited four cancer cells by more than 60% based on their viability, in a dose-dependent manner. The PPSs presented similar IC₅₀ values on the inhibition of digestive enzyme activities compared to epigallocatechin gallate (EGCG), but had weaker anti-inflammatory activity. Therefore, PPSs could be a potential natural alternative to antimicrobial agents. This is the first report on the bioactivity of polyphenols from stevia rebaudiana (Bertoni) leaves excluding flavonoids, and will be of benefit for understanding the role of PPSs and their application.