The potential of plant-derived products or any other agents for uses as antiseptic,
disinfectant or antibiotic can be assessed in vitro using microbial test
organisms. Here we can broadly classify our interests into two; antibacterial and
antifungal assays and search for antiprotozoal agents.
Antibacterial and antifungal tests
For routine assessment of preliminary antimicrobial screening, the DISC-DIFFUSION METHOD
is highly recommended. Filter paper discs impregnated with variable
concentrations of the test agents are placed on agar plates inoculated with
micro-organisms. If the test micro-organisms are susceptible to the drug, they fail to grow around the filter paper disc
(see photograph) where the chemicals could reach
through diffusion. The zone of inhibition around the disc is dependent on the
ability of the chemical in question to diffuse through agar medium, the
thickness of the agar medium in the plate, the size of inoculums, time and
temperature of incubations, etc. Thus a good knowledge and experience on this
assay system is required to generate reproducible results using the disc-diffusion method.
Once the activity of the plant-derived product is established using the disc-diffusion
method, it is often necessary to record the activity of the substance through
experiments which are more quantifiable and reproducible. Here we use the Minimal Inhibitory
Concentration (MIC) which shows the lowest concentration of the test
that inhibit the growth of bacterial (or other test micro-organism) growth in vitro. The advantage of this
method is that the result is believed to correlate with the concentration of
the agent achievable in the blood. For this assay, we recommend the cheep macrotube
dilution technique that can easily be adopted in any microbiology lab.
There are a number of other techniques one could use to test
antibacterial/antifungal activity. For example, TLC based plates may be used to
quickly identify antimicrobial agents for both crude and purified samples. A
microtitre-based miniaturisation of the assay can also be adopted depending on
the need for the assay.
the site owner for further details of antibacterial/antifungal assays. The following
key references are also of interest:
See our article on antiviral
activity test: Álvarez,
Á.L, HABTEMARIAM, S, Juan-Badaturuge, M, Jackson,
C, Parra, F. (2011). In vitro anti HSV-1 and HSV-2 activity of
Tanacetum vulgare extracts and isolated compounds: An approach to their
mechanisms of action. Phytotherapy Research.
an overview of our Research on Tansy
recent media coverage of our findings...
|Antiprotozoal activity test:
Click here to see
our free full-text article on the subject.
List of Other Relevant Publications
Motlhanka, D.M.T., Houghton, P., HABTEMARIAM, S. (2008)
Antimicrobial activity of Clerodendrum uncinatum
from Botswana. Bots. J. Agric. App. Sci. 4(1),
D.M.T., Miljkovic-Brake, A., Houghton. P.J., ,
HABTEMARIAM, S., Hylands, P.J. (2005) Antibacterial
and Cytotoxic principles of Commiphora glandulosa
stem bark resin. J. Pharm. Pharmacol. 57(9),
antileishmanial effects of antibacterial diterpenes from
two Ethiopian Premna species: P. schimperi and
2003, 3:6 (The full text article can be
HABTEMARIAM, S., MacPherson, A.M. (2000).
Cytotoxicity and antibacterial activity of ethanolic
axtract from leaves of a herbal drug, Bonset (Eupatorium
perfoliatum). Phytotherapy Res. 14,
Gray, A.I., and Waterman, P.G. (1993). A novel
antibacterial sesquiterpene from Premna oligotricha
J. Nat. Prod. 56, 140-143.
Gray, A.I. and Waterman, P.G.(1992). Antibacterial
diterpenes from the aerial parts of Premna
oligotricha. Planta Med. 58, 109-110.
Gray, A.I., Lavaud, C., Massiot, G., Skelton, B.W.,
Waterman, P.G. and White, A.H. (1991). ent-12-Oxolabda-8,13(16)-dien-15-oic
acid and ent-8b,12a-epidioxy-12b-hydroxylabda-9(11),13-dien-15-oic
Two new diterpenes from the aerial parts of Premna
oligotricha. J. Chem. Soc. Perkin Trans. I
Gray, A.I., Halbert, G.W. and Waterman, P.G. (1990). A
novel antibacterial diterpene from Premna schimperi.
Planta Med. 56, 187-189.
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