Comparisons of Ethanol Extracts of Chinese Propolis (Poplar Type) and Poplar Gums Based on the Antioxidant Activities and Molecular Mechanism

Abstract

The biological activities of propolis are varied from plant sources and the prominent antioxidant effects of Chinese propolis (poplar type) have been extensively reported. Oxidative stress is associated with inflammation and induces many diseases. In the study, to evaluate antioxidant capacities and clarify the underlying molecular mechanisms of ethanol extracts of Chinese propolis (EECP) and ethanol extracts of poplar gums (EEPG), we analyzed their compositions by HPLC, evaluating their free radical scavenging activities and reducing power by chemical analysis methods. Moreover, we studied the roles of EECP and EEPG on the elimination of ROS and expressions of antioxidant genes (HO-1, TrxR1, GCLM, and GCLC) in RAW264.7 cells. We further investigated the effects of MAPKs on the antioxidant genes expression by specific inhibitors. The nucleus translocation effects of Nrf2 were also measured by confocal microscopy analysis. The results indicated that EECP had higher TPC and FDC values but regarding TFC values were not significant. EECP also possessed more contents of 11 compounds than EEPG. Both phytochemical analysis and cell experiment reflected that EECP exerted stronger antioxidant activities than EEPG. EECP and EEPG enhanced endogenous antioxidant defenses by eliminating reactive oxygen species directly and activating Erk-Nrf2-HO1, GCLM, and TrxR1 signal pathways.

In VitroIon Chelating, Antioxidative Mechanism of Extracts from Fruits and Barks ofTetrapleura tetrapteraand Their Protective Effects against Fenton Mediated Toxicity of Metal Ions on Liver Homogenates

“…All the extracts from T. tetraptera may act as antioxidant by scavenging free radicals. This result corroborates previous studies which demonstrated that plant phenolic compounds could act as radical chelator [41]. …”

Characterization of bioactive compounds in the biomass of black locust, poplar and willow

“…The same method for the TAC determination of methanol-water extracts from the black locust and poplar leaves was used by Tálos-Nebehaj et al (2017) as well as of water extracts from willow bark by Durak et al (2015) and Durak and Gawlik-Dziki (2014). The results of ABTS test of poplar buds and willow bark were also expressed as the IC 50 value (Zaiter et al 2016;Zhang et al 2015b). Todaro et al (2017) determined TAC in terms of radical scavenging ability using the stable DPPH.…”

“…TACs of willow and poplar leaves (Tálos-Nebehaj et al 2017), willow leaves, bark and catkins (Enayat and Banerjee 2009;Zaiter et al 2016), as well as poplar buds and Fig. 5 The structures of lignans present in willow wood poplar-type propolis (Zhang et al 2015b) were evaluated. The wavelength at which the absorbance was measured was generally 515 or 517 nm.…”

“…A variation of FRAP assay is reducing power assay (FRAP-RP assay), based on the ability of plant polyphenols to reduce Fe(III) to Fe(II), which was used to determine TAC of ethanolic extracts of poplar buds and poplar-type propolis (Zhang et al 2015b) as well as water extracts of willow bark (Durak and Gawlik-Dziki 2014). Poplar buds extracts had an oxidant activity of 1.55, whereas poplar-type propolis had 2.08 mmol TE/g.…”

“…In addition to ABTS, DPPH and FRAP, ORAC assay is a very useful method. This method was used to assess the antioxidant activity of black locust wood (Sergent et al 2014) and poplar buds (Zhang et al 2015b). In both studies, Trolox was used as a standard.…”