This study examines the inhibitory effects of water extract from longan twigs (WLTs) on mutation and nitric oxide (NO) production. The results show that WLT inhibited the mutagenicity of 2-aminoanthracene (2-AA), an indirect mutagen, and 4-nitroquinoline-N-oxide (4-NQO), a direct mutagen toward Salmonella typhimurium TA 98 and TA 100. In addition, WLT in the range 0-0.6 mg/ml showed radical scavenging, reducing activities and chelating activity, as well as decreased lipid oxidative damage. Meanwhile, WLT also inhibited tyrosinase activity and NO generation in lipopolysaccharide (LPS) stimulated macrophages. High performance liquid chromatography analysis suggests that the major phenolic constituents in WLT are epicatechin, ellagic acid and gallic acid. These bioactive components may contribute to the protective effects of WLT. Our data suggests that WLT can be applied to antimutation, anti-inflammation and antityrosinase. (C) 2012 Elsevier Ltd. All rights reserved.