Synergistic antimalarial treatment of Plasmodium berghei infection in mice with dihydroartemisinin and Gymnema inodorum leaf extract

Abstract

Background: Chemotherapy is crucial in the fight against malaria. The rise of resistance to most antimalarial medicines has been a serious hurdle to effective treatment. Artemisinin-based combination therapies (ACTs) are currently the most effective antimalarial medication. Malaria parasites are growing more resistant to ACTs, particularly in Southeast Asia. As a result, effective alternative antimalarials are in high demand. The leaf extract of Gymnema inodorum (GIE) has previously shown promise as an effective antimalarial. Therefore, this study evaluated the antimalarial potential of combination dihydroartemisinin (DHA) and GIE therapy against Plasmodium berghei in a mouse model.

Methods: The medications were evaluated using the standard 4-day test for determining the 50% effective dosage (ED₅₀) of DHA and GIE on P. berghei ANKA (PbANKA). DHA and GIE were combined using a fixed-ratio approach, with DHA/GIE ED_50s of 100/0, 80/20, 60/40, 40/60, 20/80, and 0/100, respectively.

Results: The ED₅₀ against PbANKA was determined to be 2 mg/kg of DHA and 100 mg/kg of GIE. The 60/40 (DHA/GIE) ratio demonstrated significantly higher antimalarial activity than the other ratios (p < 0.001) against PbANKA, with 88.95% inhibition, suggesting synergistic efficacy (combination index (CI) = 0.68695). Furthermore, this ratio protected PbANKA-infected mice against loss of body weight and packed cell volume decline, leading to a longer survival time over 30 days.

Conclusion: Our results suggest that GIE could be an effective adjuvant to DHA that can enhance the antimalarial effects in the treatment of PbANKA-infected mice.

Keywords: Antimalarials; Dihydroartemisinins; Gymnema inodorum; Plasmodium berghei.

Fig. 1

PbANKA infection in BALB/c mice. The mice were infected with 1 × 10⁷ parasitized erythrocytes of PbANKA by IP injection. a Parasitemia (%), b body weight (g), c packed cell volume (%), and d mean survival time (days) were monitored. Results are presented as mean ± SEM (n = 5)

Fig. 2

Antimalarial activity of DHA and GIE against PbANKA in infected mice. BALB/c mice were infected with 1 × 10⁷ parasitized erythrocytes of PbANKA by IP injection and subsequently administered DHA (0.1, 1, 5, 10, or 20 mg/kg) and GIE (1, 10, 50, 100, or 200 mg/kg) by gavage for four consecutive days. On day 4, a parasitemia (%) was measured and b ED₅₀ values (mg/kg) were calculated. Results are presented as mean ± SEM (n = 5). DHA, dihydroartemisinin; GIE, Gymnema inodorum leaf extract; UN, untreated control. *p < 0.05, **p < 0.01, and ***p < 0.001, compared to untreated control

Fig. 3

Combined effects of DHA and GIE against PbANKA in infected mice. BALB/c mice were infected with 1 × 10⁷ parasitized erythrocytes of PbANKA by IP injection. They were given combinations between the ED₅₀ value of DHA and the ED₅₀ value of GIE (100/0, 80/20, 60/40, 40/60, 20/80, or 0/100) by oral gavage for four consecutive days. On day 4, a parasitemia (%) was measured, and b an interaction line was generated. Results are presented as mean ± SEM (n = 5). DHA, dihydroartemisinin; GIE, Gymnema inodorum leaf extract; UN, untreated control. *p < 0.05, **p < 0.01, and ***p < 0.001, compared to untreated control

Fig. 4

BW, PCV, and MST of PbANKA-infected mice treated with a combination of DHA and GIE. BALB/c mice were infected with 1 × 10⁷ parasitized erythrocytes of PbANKA by IP injection. They were given a combination of DHA and GIE between the ED₅₀ values of the two (DHA/GIE dosage ratios of 100/0, 80/20, 60/40, 40/60, 20/80, or 0/100) by oral gavage for four consecutive days. On day 4, a BW (g), b PCV (%), and c MST (day) were measured. Results are presented as mean ± SEM (n = 5). DHA, dihydroartemisinin; GIE, Gymnema inodorum leaf extract; H, healthy control; UN, untreated control. *p < 0.05 and **p < 0.01 compared to healthy control