Among all the extracts studied, the 100 μg of the ethanolic extract of Cortex Magnoliae Officinalis loaded on the filter paper disc demonstrated the most robust antimicrobial activities against S. aureus, B. subtilis, M.smegmatis and C. albicans, equivalent to at least 50% of the activities of the standard antibiotics. Among the test organisms, it was most active against M.smegmatis, 20% more than the standard antibiotic, streptomycin 10 μg (Student's t-test, P = 0.001) ( Table 2 ). The boiled extract of Cortex Magnoliae Officinalis had comparable antimicrobial activities to those of streptomycin 10 μg (Student's t-test, P = 0.279). These data suggest that Cortex Magnoliae Officinalis may be a potential agent to treat infections caused by M. smegmatis and Mycobacterium tuberculosis [40] . It was reported that magnolol and honokiol exhibited antibacterial activities against methicillin-resistant S. aureus and vancomycinresistant enterococci [33] , Propionibacterium sp [32] and periodontal pathogens [34] . Therefore, disk diffusion test was carried out on magnolol and honokiol individually and in combination ( Table 2 ). The one way ANOVA on the four treatment groups namely streptomycin, honokiol, magnolol and combination of magnolol and honokiol (1:1) demonstrated a significant difference between groups (P = 0.001). Bonferroni post-hoc test showed that honokiol and magnolol had comparable activities (P = 1.000) against M. smegmatis, accounting for 83.58 ± 3.06% (P = 0.015) and 82.09 ± 6.51% (P = 0.006) of those of Streptomycin 10 μg respectively. In terms of antibacterial activities, the combination of magnolol and honokiol (1:1) was comparable to the reference antibiotic (P = 1.000) but higher than either magnolol (P = 0.007) or honokiol (P = 0.017) alone. These results suggest a new discovery of synergism between magnolol and honokiol.