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Purpose. This study describes the antibacterial effect of extracts and compounds isolated from the aerial part of Chelidonium majus Linn. (Papaveraceae) acting against clinical strains of methicillin-resistant Staphylococcus aureus (MRSA). Methods. The activities were evaluated by using the macrobroth dilution method and reported as the MICs/MBCs. Results. Bioassay-guided fractionation of the most active extract from the aerial parts (EtOAc) led to the isolation of benzo[c]phenanthridine-type alkaloids 8-hydroxydihydrosanguinarine (hhS), 8-hydroxydihydrochelerythrine (hhC), which were potently active against MRSA strains. Conclusions. The selective antibacterial activity reported in this paper for 8-hydroxylated benzo[c]phenanthridine-type alkaloids isolated from C.majus opens the possibility that they could be helpful for the developing of new antibacterial agents for treating the infection of MRSA which has created nosocomial problem worldwide.

In a bioassay-guided search for acetylcholinesterase (AChE) inhibitors from Chinese natural resources, eight isoquinoline alkaloids, tetrahydropalmatine (1), corydaline (2), protopine (3), berberine (4), palmatine (5), jatrorrhizine (6), coptisine (7) and dehydrocorydaline (8), were isolated from the methanolic extract of the tubers of Corydalis yanhusuo. Structures of these compounds were identified by spectroscopic techniques. Compounds 4-8 inhibited AChE activity in a dose-dependent manner, and the IC₅₀ values were 0.47 ± 0.01, 0.74 ± 0.06, 2.08 ± 0.09, 1.01 ± 0.03 and 0.62 ± 0.05 µM, respectively. Structure-activity relationship analysis suggested that aromatisation at ring C, as well as substitutions at C-2, C-3, C-9, C-10 and C-13 affect the AChE activity of protoberberine alkaloids.