Antischistosomal Activity of Calotropis procera Flower Ethanol Extract

Abstract

Schistosomiasis remains a major neglected tropical disease across sub-Saharan Africa, and control efforts rely almost entirely on a single drug, praziquantel, which has limited activity against juvenile schistosomes and no paediatric formulation. Medicinal plants therefore continue to be screened as potential sources of alternative or complementary antischistosomal agents. This study evaluated the phytochemical profile, chemical composition and antischistosomal potential of the flower of Calotropis procera, a plant widely used in African and Asian traditional medicine. Shade-dried, pulverised C. procera flowers were macerated in absolute ethanol and the crude extract was subjected to qualitative phytochemical screening, Gas Chromatography–Mass Spectrometry (GC–MS), Fourier Transform Infrared (FT–IR) and Ultraviolet–Visible (UV–Vis) spectroscopic analyses. Acute toxicity (LD50) and histopathological assessment were carried out in albino rats, and antischistosomal activity was evaluated in vitro (schistosome suspension exposed to graded extract concentrations) and in vivo (Schistosoma-infected albino mice dosed orally at 50–600 mg/kg/day, referenced against praziquantel). The extract (22% yield) tested positive for alkaloids, phenols, tannins, flavonoids and flavonol glycosides. GC–MS resolved 24 constituents, dominated by the fatty-acid methyl ester 9,12-octadecadienoic acid (Z,Z)-, methyl ester (31.57% relative peak area), together with 3-chloro-5-((dimethylamino)methyl)-4,5-dimethyl-2(5H)-furanone (13.68%) and 9,15-octadecadienoic acid (Z,Z)-, methyl ester (11.85%). FT–IR spectra showed O–H, C–H and C–O absorptions consistent with the identified metabolite classes, and UV–Vis analysis showed a dominant absorption maximum at 279 nm indicative of conjugated chromophores. The extract was well tolerated up to 2000 mg/kg body weight (no mortality), with only mild peri-portal infiltration on liver histology. In vitro, the extract produced dose- and time-dependent immobilisation and death of schistosomes, with the highest effect (75–100% mortality) recorded within 15 minutes at concentrations ≥500 mg/kg. In vivo, oral extract administration reduced worm burden by 18–52% across the dose range tested, compared with 73% for praziquantel. Calotropis procera flower extract shows measurable, dose-dependent antischistosomal activity and a favourable acute-toxicity profile, supporting its potential as a source of lead antischistosomal compounds. Bioassay-guided isolation of the major constituents and mechanistic and sub-chronic toxicity studies are recommended before any therapeutic application is considered.