Figure 1.

(a) Chromatogram showing purification of andrographolide (AND, retention time, 3.776) from crude bark extracts of Andrographis paniculata. (b) Chromatogram showing the peaks for andrographolide (retention time, 3.757) in standard andrographolide. (c) Structure of andrographolide. (d) Structure of curcumin, (e) and (f) Representative isobolograms of the interactions between andrographolide with curcumin (e) and andrographolide with artesunate (f) against chloroquine-resistant strains (MRC-pf-303) of P. falciparum. The values in X- and Y-axes of the isobolograms represent the FIC₅₀ values of andrographolide-curcumin and andrographolide-artesunate, respectively, at different concentration ratios (1 : 5, 1 : 2, 2 : 1, and 5 : 1). (g) In vivo efficacy of andrographolide (AND), curcumin (CUR) and artesunate (AS), tested in isolation and combination in Plasmodium berghei ANKA-infected mice.