Screening of isoquinoline alkaloids and their derivatives for antibacterial and antifungal activities.

A screening test of antimicrobial activities for some of the isoquinoline alkaloids and their first and second Hofmann elimination products was conducted in this study. Results showed that (+)-actinodaphnine (1), (+)-N-Me-actinodaphnine (2), (+)-anonaine (17), (-)-xylopine (19) and (-)-N-Me-xylopine MeI (20), had the strongest inhibitory activities against three G(+) bacteria (Bacillus cereus, Micrococcus sp. and Staphylococcus aureus) MIC greater than or equal to 50 micrograms/ml). Whereas anhydroushinsunine (34), anhydroushinsunine MeI (35), ushinsunine isomethine (38), dicentrine methine (23), roemerine methine (26), dicentrine bismethine (29) and O-Me-armepavine methine (48) also had antibacterial effects against these same three G(+) bacteria (MIC = 50-300 micrograms/ml). However, only (+)-actinodaphnine (1) and roemerine methine (26) showed weak effects against two G(-) bacteria (Escherichia coli and Klebsiella pneumonia) (MIC = 300 micrograms/ml). (+)-Actinodaphnine(1), (+)-N-Me-actinodaphnine (2), (+)-anonaine (17), anhydroushinsunine (34), anhydroushinsunine MeI (35), ushinsunine isomethine (38), O-Me-armepavine methine (48) and O,O-di-Et-N-Me-coclaurine methine (49) had potent antifungal activities against Candida albicans, Cryptococcus neoformans and other Candida species (MIC = 62.5-1000 micrograms/ml).