Other antibacterial studies of plan

Other antibacterial studies of plant alkaloid extracts have shown similar MIC and MBC values
with variances according to bacteria and plant compounds. Extracts are classified as antimicrobials
on the basis of MICs in the range of 100–1000 g/mL [13]. Alkaloid extracts of the aerial part of
Sida acuta had MIC and MBC values against different clinical isolates of Staphylococcus that varied from
80 to >400 g/mL [14]. Berberine, jatrorrhizine and the crude extract of Mahonia aquifolium showed
activity against 20 clinical isolates of Propionibacterium acnes. The alkaloid extracts of Mahonia aquifolium
showed MIC values that varied from 100 to 500 g/mL against Staphylococcus epidermidis and from
250 to 500 g/mL against S. hominis [15].
In addition to the known antibacterial activity of berberine, jatrorrhizine and
tetrahydroberberine [6–8,12], the antibacterial activity of other pure alkaloids found in B. microphylla
alkaloid fractions have been previously reported. Protopine and allocryptopine, isolated from aerial
parts of Hypecoum erectum L., showed significant antibacterial activity (MIC 125 g/mL) against the
Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa and low antibacterial activity
(MIC > 500 g/mL) against the Gram-positive bacteria Staphylococcus aureus, Bacillus cereus and
B. subtilis [16]. Tetrandrine and demethyltetrandrine, two bisbenzylisoquinoline alkaloids isolated from
Stephania tetrandra S. Moore, related to calafatine, showed in vitro anti-MRSA and antibiotic synergistic
effects with four antibiotics: ampicillin, azithromycin, cefazolin and levofloxacin [17]. Also, reticuline
isolated from Annona salzmanni D.C. tested against the Gram-positive and Gram-negative bacteria:
Staphylococcus aureus, Bacillus cereus, B. subtilis, Escherichia coli and Pseudomonas aeruginosa showed to be inactive [18]. Protopine, allocryptopine, calafatine and reticuline are present in low proportion in
root alkaloid extracts, and stem alkaloid extracts contain only protopine and allocryptopine [6]. The
presence of these compounds in the root and stem alkaloid extracts of B. microphylla is not reflected in
significant changes of the MIC values of these fractions (Table2).