The anthelmintic effect of plumbagin on Schistosoma mansoni

The anthelmintic effects of plumbagin (PB, 5-hydroxy-2-methyl-1,4-naphthoquinone) and praziquantel (PZQ) against adult Schistosoma mansoni in vitro were compared by estimating the relative motility (RM) values, survival indices (SI) and alterations of the tegument of flukes incubated in M-199 medium containing 1, 10 and 100 μg/ml of the drugs, at 1, 3, 6, 12 and 24 h. For the parasites incubated in 10 μg/ml, the RM values of the PB-treated group decreased at a more rapid rate than the PZQ-treated group. When incubated in 100 μg/ml all PB-treated flukes appeared immobile from 1 to 24 h when 91–100% died, while in the PZQ-treated group RM values were higher than that of PB and most flukes were still alive at 1–12 h, and at 24 h only 21% of flukes were killed. Furthermore, male parasites were more affected by PZQ than females as their RM values were significantly less than that of females at all doses. While in PB treatment, males and females showed less difference in response to the drug as their RM values were closer than those treated with PZQ. When observed by SEM, the tegument of untreated S. mansoni displayed no alteration, while in PB treated parasites it exhibited swelling, blebbing, loss of spines, disruption of tubercles and ridges, leading to erosion and lesion, exposure of the basal lamina, and sloughing of the tegument. PZQ induced similar tegumental changes as those observed in PB treatment but at longer incubation time and higher doses. These data indicated that PB had more anthelmintic effect on both sexes of adult S. mansoni than PZQ.

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► PB exhibited more anthelmintic effect against adult Schistosoma mansoni than PZQ with IC50 0.95 μg/ml versus 16.22 μg/ml.
► Both PB and PZQ exhibited more effect on male than female parasites.
► PB and PZQ caused similar sequences of tegumental damages.
► Mitochondria might be the major target of PB.