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Table 2 Highlight features of chemical groups relate to the correlation between anti-hemozoin and in vitro antimalarial activity

From: Correlation between anti-malarial and anti-haemozoin activities of anti-malarial compounds

Chemical groups Characteristics
Quinoline Strong correlations between anti-haemozoin and in vitro anti-malarial activity, against sensitive strain (NF54), r = 0.919 (p = 0.003). Logarithm manner of the correlation observed between BHIA50 and normalized-IC50 values of in vitro anti-malarial activity in strain 3D10 (R2 = 0.83, Spearman ρ = 0.919)
There were three compounds (with hydro-, hydroxyl-, and acetyl-radicals at 7-position) were removed from the analysis, because they had very weak anti-malarial activity (IC50 ranging from 448 to 3017 nM) and non-detectable anti-haemozoin activity
Strong affinity with haem
Quinoline (chloroquinoline) Quite good or strong correlation between anti-haemozoin and in vitro anti-malarial activity, against sensitive strains 3D7 (R2 = 0.92–0.96, Spearman ρ = 0.464–0.595), resistant strain W2 (R2 = 0.93–0.95, Spearman ρ = 0.821–0.976). The good correlations between these two activities on 3D7 strain might be fortuitous
Poorer correlations recorded for resistant strain K1 (Spearman ρ = 0. 571–0.643)
A compound was removed from this analysis due to its inactivation of haemozoin formation, despite it might have good anti-malarial effect
Quinoline (Reversed chloroquinoline) Pretty good correlation observed when normalizing the IC50 values of in vitro anti-malarial activity, against sensitive strain D6 (R2 = 0.66, Spearman ρ = 0.476 (p = 0.233)), and resistant strain Dd2 (Spearman ρ = 0.574 (p = 0.183))
Poorer correlation observed on resistant strain 7G8 (Spearman ρ = 0.333 (p = 0.42))
A compound which had strong anti-malarial activity (IC50 = 2 nM) was removed from the analysis due to its insoluble form in anti-haemozoin test
Xanthone Good correlation between anti-haemozoin and in vitro anti-malarial activity in strain D6 (Spearman ρ = 0.886 (p = 0.019))
Strong affinity with haem
Position 4-, and 5- in xanthone scaffold were favored to the good correlation
Three compounds were removed from the analysis, namely 2-hydroxanthone, 1,3-dihydroxyxanthone, 2,3,4,5,6- pentaacetylxanthone. They were active against P. falciparum D6 strain (IC50 ranged from 0.075 to 75 µM) but did not possess the anti-haemozoin activity (IC50 > 1000 µM)
Quinoline (biquinoline) Modest correlation with pooled data for strains W2, D6 (R = 0.57, Spearman ρ = 0.519 (p = 0.013))
Poor correlation for strain D6 (R = 0.29, Spearman ρ = 0.376 (p = 0.254))
Pyrazoline Modest correlation (r = 0.54–0.62)
Logarithm manner of the correlation observed between normalized-IC50 values of in vitro anti-malarial activity (MRC-02 strain and RKL9 strain) and BHIA50. Lower correlation values happened when adding chloroquine
Acridine No correlation observed on strains 3D7, W2, FCR3, Bre1 (Spearman ρ = 0.095, 0.299, 0.381, 0.261, respectively)