Antioxidant activity and protective effect of ethanolic extract from Phlomis umbrosa Turcz. roots on H2O2- and PM2.5-induced oxidative stress in respiratory cells

This study was conducted to evaluate the in vitro antioxidant activity and cellular protective effect of 20% ethanolic extract from Phlomis umbrosa Turcz. roots (EPT) on hydrogen peroxide (H2O2) and particulate matter (PM)2.5-induced oxidative stress in human nasal epithelial RPMI 2650 and human lung epithelial A549 cells. EPT showed high total phenolic and flavonoid contents, with 42.92 mg of GAE/g and 45.35 mg of RE/g. EPT presented antioxidant activity by measuring 2,2’-azino-bis (3-ethyl benzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidant power (FRAP), and malondialdehyde (MDA) inhibitory effect. Moreover, EPT exhibited inhibitory effects on α-glucosidase activity and advanced glycation end-products (AGEs) formation. Furthermore, EPT showed significant cellular protective effects by decreasing intracellular reactive oxygen species (ROS) and increasing cell viability on H2O2- and PM2.5-induced oxidative stress in RPMI 2650 and A549 cells. In addition, EPT decreased the expression levels of inflammatory proteins such as TLR-4, MyD88, p-JNK, p-NF-κB, and iNOS on PM2.5-induced oxidative stress in A549 cells. Finally, the bioactive compounds of EPT were identified as chlorogenic acid and ferulic acid through quantitative analysis using high-performance liquid chromatography.