Background: Blastocystosis is significantly implicated in irritable bowel disease, and its current available
drugs do not provide a complete cure and have several side effects.
Objective: In order to search for a safe natural alternative treatment for blastocystosis, the study
investigated both in vitro activity and in vivo effect of two natural medicinal plants extracts, Origanum
syriacum L. (Marjoram) and Ceratonia siliqua (Carob) on Blastocystis spp. isolated from symptomatic
patients.
Material and Methods: The ethanolic extracts of the two plants, O. syriacum L. and C. siliqua were prepared
in 3 concentrations (0.5, 2.5, 5.0 mg/ml), and screened phytochemically. Blastocystis-positive stool samples
from symptomatic patients were cultured in Jones medium. Cultured Blastocystis cysts were used to screen
the in vitro anti-Blastocystis activity of both plant extracts. Lab-bred mice were experimentally infected
with cultured Blastocystis and treated with different concentrations of the extract of both plants to assess
their in vivo effect. Metronidazole (MTZ) was used as a control drug in both in vitro and in vivo studies.
Results: Ethanolic extract of both plants showed dose and time dependent anti-Blastocystis effects both in
vitro and in vivo. C. siliqua at 5.0 mg/ml showed the highest anti-Blastocystis efficacy and had a maximum
significant growth inhibition rate compared to MTZ.
Conclusion: The ethanolic extract of C. siliqua is a promising, effective, safe, natural, environmentallyfriendly,
anti-Blastocystis alternative therapy. O. syriacum L. had a fair anti-Blastocystis effect and could be
used as a supportive additive.