Nonaqueous Polyethylene Glycol as a Safer Alternative to Ethanolic Propolis Extracts with Comparable Antioxidant and Antimicrobial Activity.

Jelena Šuran,Božo Radić,Saša Radić,Ivana Tlak Gajger,Josipa Vlainić,Tomislav Mašek,Ivan Kosalec,Ivica Cepanec,Kristina Starčević,Mihaela Vranješ

doi:10.3390/antiox10060978

Abstract

We compared the chemical composition, antioxidant and antimicrobial activity of two propolis extracts: one obtained with nonaqueous polyethylene glycol, PEG 400 (PgEP), and the other obtained with ethanol (EEP). We analyzed the total phenolic content (TPC) and the concentrations of ten markers of propolis antioxidant activity with HPLC-UV: caffeic acid, p-coumaric acid, trans-ferulic acid, trans-cinnamic acid, kaempferol, apigenin, pinocembrin, chrysin, CAPE, and galangin. Antioxidant activity was tested using DPPH and FRAP assay, and antimicrobial activity was assessed through minimum inhibitory concentrations (MICs) and minimum biofilm eradication concentration (MBEC) determination. Maceration gave the yield of propolis of 25.2 ± 0.08% in EEP, and 21.5 ± 0.24% in PgEP. All ten markers of antioxidant activity were found in both extracts, with all marker concentrations, except kaempferol, higher in EEP. There was no significant difference between the TPC and antioxidant activity of the PgEP and the EEP extract; TPC of PgEP was 16.78 ± 0.23 mg/mL, while EEP had TPC of 15.92 ± 0.78 mg/mL. Both extracts had antimicrobial activity against most investigated pathogens and Staphylococcus aureus, Acinetobacter baumannii, and Escherichia coli biofilms. EEP was more effective against all tested susceptible pathogens, except E. coli, possibly due to higher content of kaempferol in PgEP relative to other polyphenols. Nonaqueous PEG 400 could be used for propolis extraction. It gives extracts with comparable concentrations of antioxidants and has a good antioxidant and antimicrobial activity. It is a safe excipient, convenient for pediatric and veterinary formulations.

Highlights

Propolis is a honey bee product known for its antioxidant, antimicrobial, and antiinflammatory properties [1,2]
There was no significant difference between the Total amount of phenolic compounds (TPC) and antioxidant activity of the PgEP and the extracted propolis with 70% ethanol (EEP) extract
Propolis extracts inhibit the generation of reactive oxygen species (ROS) through nuclear factor E2-related factor 2 (Nrf2) and activation of antioxidant response element (ARE), responsible for transcription of antioxidant enzymes [17,18]

Summary

Introduction

Propolis is a honey bee product known for its antioxidant, antimicrobial, and antiinflammatory properties [1,2] Over the centuries, it had a significant role in traditional medicine and is still used today as an antibiotic alternative due to the growing problem of Antioxidants 2021, 10, 978. Propolis is a honey bee product known for its antioxidant, antimicrobial, and of antiinflammatory properties [1,2] Over the centuries, it had a significant role in traditional medicine and is still used today as an antibiotic alternative due to the growing problem of antimicrobial resistance. Besides the the antibiotic resistance problem, natural products are are more valuable than synthetic ones due to their lower cytotoxicity [4].

Methods

Results

Discussion

Conclusion