Doctoral Thesis
Antiparasitic potential of medicinal plants: In vitro evidence on common gastrointestinal parasites
Doctor of Philosophy (PhD), Murdoch University
2022
Abstract
This thesis is a multidisciplinary approach to investigating the effective alternative therapy for human gastrointestinal (GI) parasites with particular emphasis on Cryptosporidium parvum and Giardia duodenalis, the most common cause of protozoal diarrhoea, worldwide. Several classes of drugs with good efficacy are available for G. duodenalis, but reduced compliance and drug resistance are evident. There is no effective specific chemotherapeutic intervention for C. parvum. This project aimed to upgrade existing knowledge on plant antiparasitics and to explore in vitro cytotoxic profiles and antiparasitic potential of thirteen plant extracts against two protozoan parasites C. parvum and G. duodenalis.
A systematic review and a meta-analysis were designed to explore medicinal plants and their compounds, which may have antiparasitic activity against human GI parasites. The results revealed that a large part of the current evidence on the antiparasitic potential of plants is based on experimental studies rather than clinical trials. Entamoeba histolytica and G. duodenalis were the most studied protozoan parasites in vitro and in vivo. However, studies focused on C. parvum were limited. Results of the meta-analyses suggested that Lepidium virginicum L. is effective for intestinal protozoan parasite Entamoeba histolytica with pooled mean IC50 of 198.6 μg/mL.
The cytotoxicity of all plant extracts in human ileocecal adenocarcinoma (HCT-8) cells was determined before evaluating their antiparasitic effects using a fluorometric assay (CellTiter-Blue®). No apparent cytotoxicity was detected in HCT-8 cells incubated with a 3-fold dilution (2–500 μg/mL) of plant extracts for up to 72 h.
The efficacy of plant extracts against C. parvum was detected and quantified using quantitative (q)PCR and immunofluorescence assays. All plant extracts tested against C. parvum have shown varying inhibition activities in vitro. Four plant species with the strongest evidence of activity against C. parvum were Curcuma longa, Piper nigrum, Embelia ribes, and Nigella sativa, with a dose-dependent efficacy. The efficacy of plant extracts against G. duodenalis was evaluated by resazurin reduction assay. None of the extracts demonstrated antigiardial efficacy at the tested concentration. Additionally, plant extracts were assessed against three bacterial pathogens affecting humans. Boswellia serrata oleo-gum resin extract showed potency against Methicillin-resistant Staphylococcus pseudintermedius (MRSP).
This research successfully demonstrated the in vitro antiparasitic potential of selected medicinal plant extracts. The results of this research can be adopted to design future studies to characterise the bioactive compounds. Their mode of action could lead to the identification of novel drug targets.
Details
- Title
- Antiparasitic potential of medicinal plants: In vitro evidence on common gastrointestinal parasites
- Authors/Creators
- Sandamalie S Ranasinghe Liyanage
- Contributors
- Amanda Ash (Supervisor) - Murdoch University, Centre for Biosecurity and One HealthAlan Lymbery (Supervisor) - Murdoch University, Centre for Sustainable Aquatic EcosystemsAnthony Armson (Supervisor)Ali Zahedi Abdi (Supervisor) - Murdoch University, Centre for Biosecurity and One HealthSasha Aspinall (Supervisor) - Murdoch University, School of Allied Health
- Awarding Institution
- Murdoch University; Doctor of Philosophy (PhD)
- Identifiers
- 991005588666907891
- Murdoch Affiliation
- Centre for Biosecurity and One Health; Harry Butler Institute; School of Medical, Molecular and Forensic Sciences
- Resource Type
- Doctoral Thesis
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