In vitro anti dengue viral activity of Aegle marmelos (Beal) dried flower aqueous extract

Abstract

Introduction and Objectives Dengue is an arboviral disease of global concern. No specific anti-dengue viral agent exists. We investigated the in-vitro anti-dengue viral activity of Aegle marmelos (AM; Common name: Bael) dried flowers, which is used as a fever remedy in traditional medicine. Method: Cytotoxicity of AM for Vero cells was tested using 4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) to identify the maximum non-toxic dose (MNTD) and the 50% cytotoxic concentration (CC50) at 37°C in 5% carbon dioxide. Chloroquine diphosphate (CQ) was used as the control drug. Plaque reduction assay for quantifying infectious viral particles was used to determine the half-maximum inhibitory concentration (IC50). Vero cells were infected using dengue virus types 1 (DV1), 2 (DV2), 3 (DV3) and 4 (DV4) and treated with AM extracts at concentrations of 2.08-33.32 µg/ml. Dose-response curve was plotted using GraphPad Prism (9.0.0) software. Selectivity Index (SI) was calculated as the ratio of CC50/IC50. Results MNTD and CC50 of AM were 33.32 µg/ml and 455.0 (CI 371.8- 564.8) µg/ml respectively. IC50 values of AM for dengue serotypes were, DV1 30.16 (CI 24.97-39.08) µg/ml, DV2 8.64 (CI 6.99-10.72) µg/ml, DV3 36.60 (CI 31.93-44.42) µg/ml and DV4 9.36 (CI 6.94-12.81) µg/ ml respectively. SI values were DV1 15.09, DV2 52.67, DV3 12.43 and DV4 48.59. MNTD and CC50 of CQ was 10 µg/ml and 17.03 (CI 15.74-18.36) µg/ml respectively, while IC50 values were DV1 2.48 (CI 2.20-2.80) µg/ml, DV2 7.98 (CI 6.11-11.74) µg/ml, DV3 2.41(CI 2.11-2.74) µg/ml. CQ did not inhibit DV4. SI values of CQ were DV1 6.86, DV2 2.13, DV3 7.06.Conclusions and recommendations A. marmelos dried flower aqueous extract inhibited all four dengue viruses in vitro displaying moderate cytotoxicity to Vero cells. Inhibitory activity was serotype dependant. DV2 and DV4 IC50 values indicated good inhibitory activity (<10 µg/ml) and DV1 and DV3 demonstrated moderate inhibitory activity (10-50 µg/ml). Compared to chloroquine, SI values for all four dengue serotypes were higher and were >10, indicating that this plant extract should be investigated further to identify biologically active compounds with good anti-dengue viral activity