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Evidence-Based Complementary and Alternative Medicine
Volume 2015 (2015), Article ID 307594, 15 pages
Research Article

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

1College of Animal Science, Zhejiang University, Hangzhou 310058, China
2Husbandry and Veterinary Technical Popularization Center of Zhejiang Province, Hangzhou 310020, China

Received 9 October 2014; Revised 12 December 2014; Accepted 18 December 2014

Academic Editor: Valério Monteiro-Neto

Copyright © 2015 Jianglin Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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.