Protective effect of gallic acid and Syzygium cumini extract against oxidative stress-induced cellular injury in human lymphocytes

Context: Syzygium cumini (Myrtaceae) presents antioxidant, anti-inflammatory, hypoglycemic and antibacterial effects; however, the cellular and molecular mechanisms of action in the immune system are not yet completely elucidated. Objective: This study evaluates the in vitro effect of gallic acid and aqueous S. cumini leaf extract (ASc) on adenosine deaminase (ADA) and dipeptidyl peptidase IV (DPP-IV) activities, cell viability and oxidative stress parameters in lymphocytes exposed to 2, 2 '-azobis-2-amidinopropane dihydrochloride (AAPH). Materials and methods: Lymphocytes were incubated with ASc (100 and 500 mu g/ml) and gallic acid (50 and 200 mu M) at 37 degrees C for 30 min followed by incubation with AAPH (1 mM) at 37 degrees C for 2 h. After the incubation time, the lymphocytes were used for determinations of ADA, DPP-IV and lactate dehydrogenase (LDH) activities, lipid peroxidation, protein thiol (P-SH) group levels and cellular viability by colorimetric methods. Results: (i) HPLC fingerprinting of ASc revealed the presence of catechin, epicatechin, rutin, quercitrin, isoquercitrin, quercetin, kaempferol and chlorogenic, caffeic, gallic and ellagic acids; (ii) for the first time, ASc reduced the AAPH-induced increase in ADA activity, but no effect was observed on DPP-IV activity; (iii) ASc increased P-SH groups and cellular viability and decreased LDH activity, but was not able to reduce the AAPH-induced lipid peroxidation; (iv) gallic acid showed less protective effects than ASc. Discussion and conclusion: ASc affects the purinergic system and may modulate adenosine levels, indicating that the extract of this plant exhibits immunomodulatory properties. ASc also may potentially prevent the cellular injury induced by oxidative stress, highlighting its cytoprotective effects.