Magnolia bark fights ‘super bug’



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January 4, 2009  
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CM NEWS – Among eight popular Chinese medicinal plants used by Asians, magnolia bark has the best antimicrobial and antioxidant results, including fighting against MRSA, or the “Super Bug”, according to a study done at the National University of Singapore.

The eight plants chosen by the researchers are:

  1. Cortex Magnoliae Officinalis (Houpo) ??
  2. Herba Polygonis Hydropiperis (Laliaocao) ???
  3. Folium Murraya Koenigii (Jialiye, “curry leaves”) ???
  4. Rhizoma Arachis Hypogea (Huashenggen) ???
  5. Herba Houttuyniae (Yuxingcao) ???
  6. Epipremnum pinnatum (Qilinwei) ???
  7. Rhizoma Typhonium Flagelliforme (Shuibanxia) ???
  8. Rhizoma Imperatae (Baimaogen) ???

The traditional method for Chinese medicine preparation is to boil the medicinal plants in water for 20 minutes to one hour. The present study aims to test the effectiveness of traditional herb preparation methods for antimicrobial and antioxidant treatments.

Four strains of bacteria and one strain of yeast were used for antimicrobial tests. The test bacteria included Gram-positive Staphylococcus aureus — or the “Super Bug” — and Bacillus subtilis (under most conditions the organism is not biologically active and is one of the most widely used bacteria for the production of enzymes and specialty chemicals), Gram-negative Pseudomonas aeruginosa and acid-fast Mycobacterium smegmatis (the mycobacteria which cause tuberculosis and leprosy). Candida albicans was used as a representative of yeast.

What is “Super Bug”? Methicillin-resistant Staphylococcus aureus (MRSA, often pronounced “mersa”) is a bacterium responsible for difficult-to-treat infections in humans. It may also be referred to as multiple-resistant Staphylococcus aureus or oxacillin-resistant Staphylococcus aureus (ORSA). MRSA is by definition a strain of Staphylococcus aureus that is resistant to a large group of antibiotics called the beta-lactams, which include the penicillins and the cephalosporins.

The Super Bug is easily picked up by hospital patients with weaker immunity.

What is Pseudomonas aeruginosa? P. aeruginosa typically infects the pulmonary tract, urinary tract, burns, wounds, and also causes other blood infections. It is the most common cause of burn and external ear infections, and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.

Three extraction methods were employed: (1) boiling in water for 1 hour, (2) maceration for 24 hours in water or (3) 80% ethanol at room temperature.

Among all the extracts studied, the ethanolic extract of houpu, or magnolia bark, demonstrated the most robust antimicrobial activities against the four tested viruses, equivalent to at least 50% of the activities of the standard antibiotics.

Houpu was most active against M. smegmatis, 20% more than the standard antibiotic streptomycin. The boiled extract of houpu had comparable antimicrobial activities to those of streptomycin.

These data suggest that houpu may be a potential agent to treat infections caused by M. smegmatis (such as tuberculosis and leprosy) and Mycobacterium tuberculosis. It was reported that magnolol and honokiol exhibited antibacterial activities against methicillin-resistant S. aureus and vancomycin-resistant enterococci – the “Super Bug”. These results suggest a new discovery of synergism between magnolol and honokiol.

Honokiol (???) and magnolol (????) are the main constituents simultaneously identified in the barks of Magnolia officinalis, which have been used in traditional Chinese medicine to treat a variety of respiratory and intestinal disorders. (see Magnolia bark acts like antidepressant)

The high antioxidant activities of the boiled and ethanolic extracts of the leafy materials were probably due to the extracted tannins and photosynthetic pigments. Houpu is a rich source for antioxidative compounds, such as biphenols, polyphenols and tannins.

The strongly aromatic plant materials, such as Herba Polygonis Hydropiperis, curry leaves and houpu, exhibited a broad spectrum of antimicrobial activities. One possible reason is the presence of essential oils and active polyphenolic compounds which possess antimicrobial activities.

In conclusion, the researchers discovered that (a) the ethanolic extract of houpu had 20% greater antimicrobial activities against M. smegmatis than streptomycin; (b) the boiled extract of houpu demonstrated comparable activities to streptomycin (c) the synergism of magnonol and honokiol had comparable effects to those of streptomycin; (d) the aerial parts of rodent tuber had antimicrobial activities against S. aureus. Among the tested 107 extracts, houpu had (1) potent antimicrobial activities against S. aureus, B. subtilis, M. smegmatis and C. albicans and (2) highest antioxidant activities in DPPH assay regardless extraction methods.

As such, houpu is likely a potential medicinal plant resource for developing effective antimicrobials and antioxidants.

[Chinese Medicine 2008, 3:15]