RESUMEN
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 (20 µM) were assessed by determining luminol-dependent chemiluminiscence in rat PMNs. Cytotoxicity of active compounds (1-1000 µM) was assayed by Trypan blue dye exclusion method. Cell-free models were employed to evaluate scavenging capacity of active compounds (20 µM) 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 20 µM (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 (3.1 µM) >AS6 (5.9 µM) >AS2 (9.1 µM) >AS3 (10.0 µM) >AS5 (29.7 µM) >AS4 (57.7 µM). AS1-4, four isoprenylated flavones, potently quenched superoxide anion, hydroxyl radical, and hydrogen peroxide at the concentration of 20 µM 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.