Attenuation of reactive oxygen/nitrogen species with suppression of inducible nitric oxide synthase expression in RAW 264.7 macrophages by bark extract of Buchanania lanzan

Background: Oxidative stress is one of the most critical factors implicated in disease conditions. Buchanania lanzan Spr. (Anacardiaceae) bark powder preparation has been reported for treating an inflammatory condition in the Ayurvedic Pharmacopoeia of India. Objective: In the present study, we investigate the effect of the bark methanol extract (BLM) on reactive oxygen/nitrogen species (ROS/RNS), the expression of protein and mRNA of inducible nitric oxide synthase (iNOS) in RAW 264.7 macrophages stimulated with lipopolysaccharide (LPS) and sodium nitroprusside (SNP) to provide scientific validation of the above said medicinal property. Materials and Methods: The capacity to quench ROS and RNS was evaluated by 5-(and-6) chloromethyl-20,70-dichlorodihydrofluorescein diacetate acetyl ester fluorescence and nitrite estimations in LPS/SNP-stimulated macrophages respectively. The protein and transcript expression of iNOS was evaluated through Western Blot and reverse transcription-polymerase chain reaction (RT-PCR) analysis respectively. Results: Macrophages pretreated with BLM (>100 μg/mL) for 24 h, stimulated with LPS for the last 18 h of experimental duration recorded a significantly (P < 0.05) reduced levels of ROS (3.45-fold) against LPS-stimulated conditions (5.7-fold). SNP-stimulation resulted in increased NO accumulation (17-fold) which was neutralized by BLM at >100 μg/ml (1.6-fold) credited to a reduced protein and mRNA expression of iNOS as recorded by Western blots and RT-PCR results respectively. The reversed-phase liquid chromatography-diode array detection analysis identified the presence of 4-hydroxybenzoic acid, quercetin and p-coumaric acid (Rt values 5.444, 5.569 and 9.580 respectively). Conclusions: The potential of BLM inhibiting ROS/RNS production validates the medical use of bark, could find beneficial application under conditions of immune stimulation and/or bacterial infection.