Inhibitory effects of phenolic compounds from Artocarpus styracifolius on respiratory burst of rat neutrophils

Abstract

Context: Searching for polymorphonuclear neutrophils (PMNs) respiratory burst inhibitors is an important topic in the treatment of human diseases associated with inflammation. Objective: To investigate the inhibitory effects of phenolics isolated from Artocarpus styracifolius Pierre (Moraceae) on respiratory burst induced by phorbol myristate acetate (PMA). Materials and methods: The anti-respiratory burst activities of eight phenolics (20μM) were assessed by determining luminol-dependent chemiluminiscence in rat PMNs. Cytotoxicity of active compounds (1-1000μM) was assayed by Trypan blue dye exclusion method. Cell-free models were employed to evaluate scavenging capacity of active compounds (20μM) against reactive oxygen species. Results: The PMA-induced respiratory burst was significantly inhibited (p<0.05) by six isoprenylated phenolics (AS1-6) at the concentration of 20μM (below the toxic concentration) with the inhibition rate ranging from 25.0 to 99.6%. The inhibitory potency estimated by IC50 was in the order of AS1 (3.1μM) >AS6 (5.9μM) >AS2 (9.1μM) >AS3 (10.0μM) >AS5 (29.7μM) >AS4 (57.7μM). AS1-4, four isoprenylated flavones, potently quenched superoxide anion, hydroxyl radical, and hydrogen peroxide at the concentration of 20μM with their scavenging rates in the range of 30.1-78.1%, 35.4-69.7%, and 65.5-86.3%, respectively. In contrast, AS5-6, two isoprenylated 2-arylbenzofurans, showed less effect than that exhibited by AS1-4. Conclusion and discussion: The isoprenylated phenolics from A. styracifolius can potently inhibit PMA-induced respiratory burst in rat neutrophils without showing cytotoxicity. The inhibitory effects of these isoprenylated phenolics on the respiratory burst might depend on their different types of structure. © 2014 Informa Healthcare USA, Inc.