AimsThis study aims to evaluate the antioxidant activity of oral Lactobacillus strains invitro. Methods and ResultsA total of 201 Lactobacillus strains were investigated for antioxidant activities: free radical scavenging (DPPH), inhibition of linoleic acid peroxidation (TAA(LA)), superoxide dismutase (SOD) and glutathione (GSH). Resistance to reactive oxygen species was also assessed. Results showed that there was a wide range of individual antioxidant properties of DPPH, TAA(LA), SOD and GSH between/within the species of Lactobacillus strains. Generally, all tested Lactobacillus, except L. oris and L. gasseri, showed relatively high antioxidative parameters indicating that antioxidative properties are strain specific. Lactobacillus fermentum, L. paracasei and L. rhamnosus strains with high DPPH and TAA(LA) activities (>60%) could survive under oxidative stress (incubated in 10mmoll(-1) hydrogen peroxide for 8h or 10mmoll(-1)hydroxyl radicals for 1h) better than L. salivarius, L. oris and L.gasseri strains. It was also observed that there were significant differences in all antioxidative parameters tested, except DPPH, between the strains from caries-free subjects and those from subjects with caries. ConclusionsThe different antioxidants were found among Lactobacillus strains. The strains with high antioxidants could tolerate well under the oxidative stress. Significance and Impact of the StudyThis is the first study to investigate the antioxidant properties of human oral Lactobacillus strains. Significant results found that certain Lactobacillus strains exhibited relatively high antioxidative parameters. Further studies are needed to examine whether there would be any antioxidant effect on oral health.