Anti-malarial activities of Andrographis paniculata and Hedyotis corymbosa extracts and their combination with curcumin

Abstract

Background: Herbal extracts of Andrographis paniculata (AP) and Hedyotis corymbosa (HC) are known as hepato-protective and fever-reducing drugs since ancient time and they have been used regularly by the people in the south Asian sub-continent. Methanolic extracts of these two plants were tested in vitro on choloroquine sensitive (MRC-pf-20) and resistant (MRC-pf-303) strains of Plasmodium falciparum for their anti-malarial activity.

Methods: Growth inhibition was determined using different concentrations of these plant extracts on synchronized P. falciparum cultures at the ring stage. The interactions between these two plant extracts and individually with curcumin were studied in vitro. The performance of these two herbal extracts in isolation and combination were further evaluated in vivo on Balb/c mice infected with Plasmodium berghei ANKA and their efficacy was compared with that of curcumin. The in vivo toxicity of the plant derived compounds as well as their parasite stage-specificity was studied.

Results: The 50% inhibitory concentration (IC50) of AP (7.2 microg/ml) was found better than HC (10.8 microg/ml). Combination of these two herbal drugs showed substantial enhancement in their anti-malarial activity. Combinatorial effect of each of these with curcumin also revealed anti-malarial effect. Additive interaction between the plant extracts (AP + HC) and their individual synergism with curcumin (AP+CUR, HC+CUR) were evident from this study. Increased in vivo potency was also observed with the combination of plant extracts over the individual extracts and curcumin. Both the plant extracts were found to inhibit the ring stage of the parasite and did not show any in vivo toxicity, whether used in isolation or in combination.

Conclusion: Both these two plant extracts in combination with curcumin could be an effective, alternative source of herbal anti-malarial drugs.

Figure 1

A flowering plant of Andrographis paniculata (A), Flower of Andrographis paniculata (B). A flowering plant of Hedyotis corymbosa (C), A twig of Hedyotis corymbosa showing the arrangement of flowers. Andrographis paniculata is an herb, usually 30–90 cm in height and commonly found in plains all over India, China and other subtropical countries in South East Asia. Hedyotis corymbosa is a small herb, 5–30 cm long, distributed through out India and other subtropical countries. Both of these plants can grow between 25 to 40°C temperatures and at any soil texture.

Figure 2

In vitro interaction of plant extracts studied in choloroquine resistant strains (MRC-pf-303) of P. falciparum. Representative isobolograms of the interaction of Andrographis paniculata with Hedyotis Corymbosa (A), Andrographis paniculata with curcumin (B), Hedyotis corymbosa with curcumin (C).

Figure 3

In vivo efficacy of the extracts of Andrographis paniculata (AP), Hedyotis corymbosa (HC) in isolation and in combination (AP+HC) compared with curcumin (CUR) in P. berghei ANKA infected mice.