Antischistosomal activity, immunomodulation, safety and phytochemical composition of bridelia micrantha, ocimum americanum and chenopodium ambrosoides extracts.

Abstract

Schistosomiasis is among the most common, debilitating disease of humans caused by several species of digenetic blood trematodes of the genus Schistosoma. It is estimated that 200 million people are infected with approximately 600 million at risk. The disease manifests itself as acute schistosomiasis which occurs relatively early in the infection and the more severe chronic schistosomiasis after a number of years following infection. Praziquantel which is effective against adult worm stages is the only commercially available antischistosomal drug after oxamniquine and metrifonate production was discontinued. Extracts of three plants shown in preliminary studies to have antischistosomal activity were initially validated in mice model followed by gross pathology, histopathology and immune reaction studies. Acute and sub-chronic toxicity of the extracts was determined and finally headspace GCMS analysis was performed to determine chemical compounds. Worm reduction efficacy percentages were 35% for C. ambrosoides methanol extract, 33% for C. ambrosoides water extract, 36% for B. micrantha water extract, 17% for O. americanum water extract, 31% for O. americanum hexane extract against the adult worm while for the juvenile worm it was 37%, 33%, 11%, 44%, and 39% respectively. Praziquantel which served as a positive control had efficacy of 81% and 77% against the adult and juvenile worm respectively. The extracts were also observed to have immunomodulation properties suggesting they play a role in disease pathology which is the more important aspect of schistosomiasis. Toxicity studies showed that B. micrantha water extract was toxic and was therefore excluded from subsequent studies, progressing with the relatively non-toxic O. americanum and C. ambrosoides extracts.