In-vivo and In-vitro Activities of Medicinal Plants on Ecto, Endo and Haemoparasitic Infections: A Review
Abstract:
Crude methanol, pet. ether, ethyl acetate, n-hexane, dichloromethane and
aqueous extracts of various species of medicinal plants have shown
significant in-vivo and in-vitro pharmacological activities against
ecto, endo and haemoparasites. The scientific evaluations of the use of
the
plants as antiparasitic agents were based on the claims of folklore
drawn from traditional healers from various communities across the
world. The pharmacological activities of these plants were associated
with the presence of various bioactive compounds such as alkaloids,
flavonoids, saponins,
glycosides, allicinine, harmala, harmaline, harman, tetrahydroharman,
ursolic acid, terapines, tannins, phenolic compounds, embelin and
brucine. These compounds were either found in the leaves, seeds, bulbs,
flowers, stem, root barks or entire plant. In the in-vivo studies, plant
extracts
were tested using animal models such as mice, sheep, goats, cattle and
dogs. The in-vivo anthelmintic activities of the plants were assessed by
faecal egg out puts and post-mortem worm counts which in most instances
achieved 70-90% priori levels with some of the plants. For
haemoparasitic
infections, parasitaemia clearance levels were used, while larvae and
adult deaths were used to measure the activity of the plants against
ectoparasites. For in-vitro activities, inhibitory concentration IC50
values using the brine lethality test, micro dilution, flow cytometery
and larval
packet test were used to assess the efficacy of the plant extracts on
the parasites in various cell cultures. Significant in-vitro activity of
99.8% at 3.1mg/ml was achieved with the ethanolic extract of
Azadirachta indica. Many of the plants were found to be more potent and
possessed similar
mechanism of action as their novel synthetic drugs. Such breakthroughs
have led to the development of less toxic, cheaper and readily available
drugs. Worthy of note is the use of the fruit of the Thai plant Piper
longum (PIPERACEAE) as part of a drug formulation used in India for the
treatment
of clinical giardiosis in human patients.
