Zin, Nik Nor Imam Nik Mat
(2021)
Antimalarial activity, toxicity and phytochemical screening of quercus infectoria gall crude extracts.
Masters thesis, Universiti Sains Malaysia.
Abstract
The reduced efficacy of the mainstay antimalarial drugs due to widespread
of drug-resistant Plasmodium falciparum has necessitated efforts to discover new
antimalarial drugs with new targets. Quercus infectoria galls have been used
traditionally as a herbal remedy for post-partum medication and treatment of parasitic
diseases. However, the antimalarial activity of the galls has not been reported. Thus,
this study was aimed at evaluating the in vitro antimalarial activity of Q. infectoria gall
crude extracts. This study was also designed to evaluate the toxicity profiles and screen
the phytochemical constituents. The antimalarial potential of acetone, methanol,
ethanol and aqueous extracts against the chloroquine-sensitive strain (3D7) of P.
falciparum was assessed via malarial SYBR Green-I fluorescence-based (MSF) assay.
Only acetone and methanol extracts showed a promising antimalarial activity with
50% inhibitory concentration (IC50) of 5.86 (1.64) and 10.31 (1.90) μg/mL,
respectively. The cytotoxicity of the extracts was evaluated against mouse fibroblast
cell (NIH/3T3), monkey kidney epithelial cell (Vero) and primary human umbilical
vein endothelial cell (HUVEC) via 3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide (MTT) assay. The acetone and methanol extracts showed
50% cytotoxicity concentration (CC50) ranged from moderate toxic to non-toxic
against all tested normal cells. The cytotoxicity evaluation using a brine shrimp
lethality test (BSLT) showed that all extracts were non-toxic according to Meyer’s
toxicity index. In addition to the haemolytic assay, a 2,2-diphenyl-1-picrylhydrazyl
(DPPH)-based antioxidant assay of the extracts was performed to observe its
connection with haemolysis of human erythrocytes (A+, B+, AB+ and O+ blood groups).
No haemolytic effect was observed on the erythrocytes treated with all extracts. All
extracts exhibited excellent DPPH radical scavenging activities. The concentration of
heavy metals (lead, zinc, chromium, copper and cadmium) analysed with atomic
absorption spectroscopy (AAS) in all extracts was below the permissible level
according to WHO guidelines. The phytochemical screening revealed the presence of
tannins and flavonoids, and high amount of total phenolic content (TPC) and total
flavonoid content (TFC) in all extracts. The effect of acetone extract which previously
exhibited the most promising antimalarial activity and have satisfactory selectivity
index (SI) values on the pH of the parasite’s digestive vacuole was examined using a
ratiometric fluorescent probe, fluorescein isothiocyanate (FITC)-dextran incorporated
into mid trophozoite stage-infected erythrocytes and analysed by flow cytometry. The
pH of the digestive vacuole of acetone extract-treated parasites was significantly
altered in a concentration-dependent manner compared to the untreated parasites (p <
0.001). Overall, this study provides valuable insights of Q. infectoria gall capability as
a safer and promising antimalarial candidate.
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