A wealth of empirical data exists for the medicinal use of goldenseal; however, much of the research has been conducted using the chief constituent berberine. It is recommended that goldenseal products be standardised to contain at least 8 mg/mL of berberine and 8 mg/mL of hydrastine (Bone 2003). ANTIMICROBIAL
In vitro testing has demonstrated antibacterial activity of both the whole extract of goldenseal and the major isolated alkaloids (berberine, beta-hydrastine, canadine and canadaline) against Staphylococcus aureus, Streptococcus sanguis, Escherichia coli and Pseudomonas aeruginosa (Scazzocchio et al 2001). In one recent study, two flavonoids isolated from goldenseal were shown to exhibit antibacterial activity against the oral pathogens Streptococcus mutans and Fusobacterium nucleatum (Hwang et al 2003). An added antimicrobial effect against 5. mutans was noted with the addition of berberine.
The methanolic extract of the rhizome inhibited the growth of 1 5 strains of Helicobacter pylori in vitro (Mahady et al 2003). The authors identified berberine and beta-hydrastine as the main active constituents.
Berberine alone, and in combination with both ampicillin and oxacillin, has demonstrated strong antibacterial activity against all strains of MRSA in vitro (Yu et al 2005); 90% inhibition was demonstrated with 64^g/mL or less of berberine. Berberine was also found to enhance the effectivness of ampicillin and oxacillin against MRSA in vitro.
Many of the Berberís spp. contain the flavonolignan 5'-methoxyhydnocarpin, which inhibits the expression of the multidrug resistant efflux pumps (Musumeci et al 2003, Stermitz et al 2000a, b); however, it is unknown whether goldenseal contains this compound.
Berberine inhibits the adherence of streptococci to host cells by aiding the release of an adhesin lipoteichoic acid (an acid that is responsible for the adhesion of the bacteria to the host tissue) from the streptococcal cell surface (Sun 1998). Berberine is also able to dissolve lipoteichoic acid-fibronectin complexes once they have been formed. Berberine displays well-defined antimicrobial properties against certain bacteria and such data suggests that it may also be able to prevent adherence and destroy already formed complexes. Goldenseal 631
Berberine destroys cell wall and sterol biosynthesis in Candida spp. in vitro (Park et al 1999).
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