In Vitro Antimalarial and Toxicological Activities of Quercus infectoria (Olivier) Gall Extracts

Abstract

Background: The spread of Plasmodium falciparum resistance in common antimalarial drugs, including artemisinin-based combination therapies, has necessitated the discovery of new drugs with novel mechanisms of action. In the present study, the in vitro antimalarial and toxicological activities of acetone, methanol, ethanol and aqueous extracts of Quercus infectoria (Q. infectoria) galls were investigated.

Methods: The extracts were assessed for the antimalarial potential using a malarial SYBR Green I fluorescence-based (MSF) assay, while the toxicity was screened by using brine shrimp lethality test (BSLT), haemolytic assay, and cytotoxicity assay against normal embryo fibroblast cell line (NIH/3T3) and normal kidney epithelial cell line (Vero).

Results: The acetone extract showed the highest antimalarial activity (50% inhibitory concentration, IC₅₀ = 5.85 ± 1.64 μg/mL), followed by the methanol extract (IC₅₀ = 10.31 ± 1.90 μg/mL). Meanwhile, the ethanol and aqueous extracts displayed low antimalarial activity with IC₅₀ values of 20.00 ± 1.57 and 30.95 μg/mL ± 1.27 μg/mL, respectively. The significant antimalarial activity was demonstrated in all extracts and artemisinin (P < 0.05). All extracts were non-toxic to brine shrimps (50% lethality concentration, LC₅₀ > 1000 ppm). Furthermore, no occurrence of haemolysis (< 5%) was observed in normal erythrocytes when treated with all extracts compared to Triton X-100 that caused 100% haemolysis (P < 0.05). The acetone and methanol extracts were non-toxic to the normal cell lines and statistically significant to artemisinin (P < 0.05).

Conclusion: Taken together with satisfactory selectivity index (SI) values, the acetone and methanol extracts of Q. infectoria galls could serve as an alternative, promising and safe antimalarial agents.

Keywords: 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay; Quercus infectoria; antimalarial activity; brine shrimp lethality test; haemolytic assay; malarial SYBR Green I fluorescencebased assay; toxicological activity.

Figure 1

The haemolytic effect of the Q. infectoria crude extracts on normal fresh erythrocytes (n = 4) after 45 min of incubation. The data represent the mean (SD) of three independent experiments of different blood groups (A⁺, B⁺, O⁺, AB⁺). Mean values were tested for normality before proceeding to the parametric test; one-way ANOVA followed by Tukey multiple comparisons at 95% confidence. Triton-X in 1% (TX-100) and PBS were used as positive and negative controls, respectively. Value of P < 0.05 was considered to be statistically significant. The haemolytic activity of the gall extracts was not concentration-dependent. Letter ‘a’ indicates that there was statistical significance between the mean values of the gall extracts (concentrations between 1.56 μg/mL–400 μg/mL) with the positive control. No statistical significance was shown in all extracts when compared with the negative control