Objective: To investigate the effects of Gymnema montanum leaf extract against endoplasmic reticulum (ER) stress-induced toxicity in endothelial cells. Methods: The immortalized endothelial hybrid cell, EA.hy926 was treated with different concentrations of Gymnema montanum leaf extract (0-100 μg/mL) and the ER stress inducer, tunicamycin. The cytotoxicity was assessed by MTT as well as lactate dehydrogenase and malondialdehyde levels were determined. The levels of ER stress markers, GRP78 and CHOP were analysed by Western blot assay. The Gymnema montanum leaf extract-mediated activation of nuclear factor erythroid 2-related factor 2 (Nrf2) was assessed by cell-based luciferase enzyme fragment complementation assay and antioxidant responsive element driven luciferase reporter assay. The levels of phosphoproteins of the MAPK pathway were analyzed using the Bioplex system. Results: A dose-dependent cytoprotective effect of Gymnema montanum leaf extract was observed in tunicamycin-induced toxicity. Gymnema montanum leaf extract significantly reduced lactate dehydrogenase activity and malondialdehyde levels in ER stress-induced endothelial cells. It also suppressed ER stress markers dose dependently and inhibited the phosphorylation of JNK, ERK, MEK and p38 MAPK in tunicamycin-induced endothelial cells. Moreover, Gymnema montanum leaf extract increased the expression of Nrf2 and its downstream targets in endothelial cells. Conclusions: Gymnema montanum leaf extract attenuates ER stress by increasing the expression of Nrf2 and its downstream genes.

Objective: To assess the nuclear factor-erythroid 2-related factor-2 (Nrf2) modulatory effect of caffeic acid and protocatechuic acid and determine the anti-tumor activity of these phenolic compounds against Ehrlich ascites carcinoma growth in mice. Methods: Antioxidant activity of protocatechuic acid and caffeic acid was assessed using ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH). Nrf2 activation potential of phenolic compounds was tested by quantitative realtime polymerase chain reaction, and luciferase complementation reporter assays. In vivo efficacy was tested using the Ehrlich ascites carcinoma model. Results: FRAP and DPPH radical scavenging assays showed that caffeic acid and protocatechuic acid were more potent compared with cinnamic acid and benzoic acid. Luciferase complementation reporter assays identified caffeic acid and protocatechuic acid as the activators of Nrf2. Both caffeic acid and protocatechuic acid upregulated the expression of Nrf2 target genes heme oxygenase-1 (HO-1), glutamate-cysteine ligase catalytic subunit (GCLC), and glutamate-cysteine ligase modifier subunit (GCLM) and the activity of NAD(P)H:quinone oxidoreductase 1 (NQO1) when tested on HCT-116 cells using a cell-based assay system at 9 h. In addition, intraperitoneal administration of caffeic acid and protocatechuic acid to Ehrlich ascites carcinoma bearing mice suppressed tumor growth and angiogenesis. Conclusions: Caffeic acid and protocatechuic acid can modulate Nrf2 and inhibit Ehrlich ascites carcinoma cells.