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7675560 
Journal Article 
Nematocidal effect of Piper retrofractum Vahl on morphology and ultrastructure of Strongyloides stercoralis third-stage infective larvae 
Riyong, D; Sangkhantree, C; Champakaew, D; Jitpakdi, A; Tippawangkosol, P; Junkum, A; Chaithong, U; Wannasan, A; Yasanya, T; Somboon, P; Pitasawat, B 
2020 
Yes 
Journal of Helminthology
ISSN: 0022-149X
EISSN: 1475-2697 
Cambridge University Press 
94 
e130 
English 
32103787 
WOS:000516620500001 
In a previous research work aimed at discovering natural helminthicides as alternatives to conventional synthetic drugs, Piper retrofractum fruit hexane extract (PHE) has been shown to possess promising nematocidal activity against the third-stage infective larvae of Strongyloides stercoralis. Thus, this study was designed to evaluate the chemical composition and the impact of PHE on symptom and structural alterations of S. stercoralis. Chemical analysis of PHE by gas chromatography-mass spectrometry demonstrated 26 different compounds, constituting 100% of the total composition. The main components were 4-acetylphenyl (4-benzoylphenoxy) acetate (14.86%) and octyl methoxycinnamate (12.72%). Nematocidal bioassays revealed promising potential of PHE against S. stercoralis larvae, with an LC50 value of 0.059 mg/ml, while the reference drug ivermectin exerted higher efficacy, with an LC50 value of 0.020 µg/ml. Behavioural observations under light microscopy revealed that PHE-treated S. stercoralis larvae moved slowly, became paralysed and eventually died during 24 h of incubation. The dead larvae appeared under light microscope as straight worms with unknown vacuoles of different sizes inside their internal bodies. Morphological alterations of the PHE-treated S. stercoralis larvae, such as straight bodies with swollen cuticle, faded transverse annulations and faded longitudinal striations, as well as shallow and smooth lateral longitudinal grooves, were seen clearly under scanning electron microscopy. Ultrastructural changes in the treated larvae, such as protruded lateral longitudinal grooves, loose muscle with vacuolation, dissociation between the hypodermis and cuticle and marked intracellular disorganization with vacuolation, were detected under transmission electron microscopy. The results of this study provide evidence that PHE is toxic against S. stercoralis and also a potential new alternative for anti-Strongyloides chemotherapy. 
natural anthelmintic; Piper retrofractum; plant extracts; Strongyloides stercoralis; ultrastructure