Detection of cysteine-rich peptides in Tragia benthamii Baker (Euphorbiaceae) and in vivo antiinflammatory effect in a chick model

Abstract

Abstract Tragia benthamii (TBM) commonly called the climbing nettle is a tropical plant claimed to have numerous anti inflammatory effects in sub Saharan African ethnomedicine which lacks scientific evidence. Aqueous extracts of TBM were further prepurified on a RP-C18 parked solid phase system to obtain 20% aqueous fraction. This fraction was enzymatically and chemically analyzed (by MALDI TOF MS and MS/MS) to contain interesting low molecular weight cysteine-rich stable peptides within the range of 2.5–3.2 KDa. The 20% aqueous fraction was further tested in vivo using carrageenan-induced foot edema (acute inflammation) in seven-day old chicks with diclofenac as reference drug. The cytotoxicity of this active fraction was investigated using the brine shrimp lethality assay. The brine shrimp cytotoxicity assay produced LC50 above 1000 μg/mL. Pretreatment with the TBM extract (30–300 mg/kg, i.p) dose dependently (P<0.01) reduced foot edema with maximal inhibition of 0.253 ± 0.180 (84.3%) at 300 mg/kg body weight, which was comparable to that of diclofenac with inhibition (P<0.05) of 0.410 ± 0.271 (74.5%) at 10 mg/kg body weight. The study has therefore shown for the first time, the detection of cysteine-rich biologically active peptides in T. benthamii and the stable peptide extracts from this ethnomedicinal plant, which is not toxic to Artemia salina, exhibits anti inflammatory activity in a chick in vivo model. This may provide scientific evidence for its use in the treatment of inflammation and pain in traditional medicine. Further in-depth vivo and in vitro studies will be required to investigate its anti inflammatory activity including effect on HUVEC-TERT, the possible inhibition of ICAM-1 surface expression and the mechanism of the anti inflammatory effect.