Limoniastrum guyonianum prevents H2O2-induced oxidative damage in IEC-6 cells by enhancing enzyamtic defense, reducing glutathione depletion and JNK phosphorylation.

Limoniastrum guyonianum is used in several regions of North Africa as a folk medicine. The objective of this study was to determine the in vitro antioxidant activities of L. guyonianum roots and their cytoprotective action on H2O2-challenged rat small intestine epithelial cells (IEC-6 cells). To assess the cytoprotective effect of L. guyonianum extract (LGE), IEC-6 cells were pre-incubated with different LGE concentrations. Then, IEC-6 cultures were exposed to 40μM H2O2 during 4h. Modulation of endogenous antioxidant system including SOD, CAT, MDA, GSH and the expression of possibly involved MAPKs was evaluated. Main results reported that L. guyonianum was rich in polyphenols and exhibited an important antioxidant activity as revealed by different tests (DPPH Assay, IC50=1.6μg/mL; ABTS+ test, IC50=27μg/mL; Fe-reducing power, EC50=44μg/mL). HPLC analysis showed that quercetin, catechin, and isorhamnetin-3-O-rutinoside were major phenolics. The exposure of IEC-6 cells to 40μM H2O2 during 4h resulted in oxidative stress manifested by (i) over 70% cell mortality, (ii) over-activity of CAT (246%), (iii) decrease in GSH level (10.4nmol/mg), (iv) excess in MDA content (18.4nmol/mg), and (v) a trigger of JNK phosphorylation. Pretreatment with LGE, especially at 0.25μg/mL, restored cell viability to 100%, and normal cell morphology in H2O2-chalenged cells. In addition, this extract maintained a high CAT activity, enhanced SOD capacity (120%) and increased GSH level (45.5nmol/mg). Furthermore, reducing cell death seems to be due to dephosphorylated JNK MAPK exerted by L. guyonianum bioactive compounds. In all, L. guyonianum components provided a cross-talk between regulatory pathways, implying their role as cytoprotector against oxidative stress.