Inhibitors of recombinant protein-tyrosine phosphatase 1B (PTP1B) from Khaya senegalensis: Towards a strategic target for therapeutic intervention in trypanosomiasis

• Published in: Phytomedicine Plus : International journal of phytotherapy and phytopharmacology 2022-08, Vol.2 (3), p.100325, Article 100325
• Main Authors: Adamude, Fatima Amin, Ezeaku, Ikenna Nnamdi, Ubhenin, Abraham Ehinomhen, Onyeka, Ifeanyi Peter, Ambi, Ahmad Adamu, Uroko, Ikechukwu Robert, Dingwoke, Emeka John
• Format: Article
• Language: English
• Subjects: Cell signaling; Human African Trypanosomiasis; Inhibition, myristic acid analog; Procyclic trypanosome; Protein-tyrosine phosphatase; Trypanosome differentiation
• ISSN: 2667-0313; 2667-0313
• DOI: 10.1016/j.phyplu.2022.100325

•Protein-tyrosine phosphatase is an important regulator of trypanosome differentiation and, as such, a promising therapeutic target for trypanosomiasis.•In an active fraction of Khaya senegalensis stem bark, potent inhibitors of recombinant human protein-tyrosine phosphatase (PTP1B) were discovered.•Three of the seven compounds in the active fraction (n-tridecanoic acid, n-hexadecanoic acid, and 14-pentadecenoic acid) were analogs of myristic acid with the general formula R-(CH2)n-COOH.•These are PTP1B inhibitors that are both potent and naturally occurring, with a low inhibitor binding constant (Ki). Background: Tyrosine dephosphorylation, catalyzed by protein-tyrosine phosphatase (PTP), prevents trypanosome differentiation to a procyclic form that lacks diverse mechanisms for survival within the mammalian host's bloodstream. Thus, differentiation to a procyclic form in the mammalian host's bloodstream would be potentially lethal to the parasite. This demonstrates that PTP is a critical regulator of trypanosome differentiation, making it a strategic therapeutic target for trypanosomiasis. Purpose: The in vitro inhibitory effect of seven compounds from the active fraction of Khaya senegalensis stem bark (4‑hydroxy-2-butanone, 1,3-butanediol, 2-methylpropyl butanoate, n-tridecanoic acid (CH3-(CH2)11-COOH), n-tetratriacontane, n-hexadecanoic (CH3-(CH2)14-COOH), and 14-pentadecenoic acid (CH2=CH-(CH2)12-COOH)) on the enzymatic activity of recombinant human PTP1B (MBL-SE332–0050) was investigated in this study. Method: The inhibition study was performed according to the standard procedure for analytical experiment and was monitored spectrophotometrically. PTP1B was assayed with 10 mM of p-nitrophenylphosphate. Bioassay-guided fractionation of methanol stem bark extract from K. senegalensis yielded the potent PTP1B inhibitors. Sodium orthovanadate was used as the positive control for inhibition. The kinetic parameters were determined by Lineweaver-Burk plots and calculated using Sigma Plot (SPCC Inc., Chicago, IL, USA) Results: The active fraction that contains the seven compounds inhibited PTP1B dose-dependently with an IC50 of 1.32 µM. Lineweaver-Burk plots revealed that PTP1B was inhibited non-competitively with a Ki of 0.46 ± 0.03 mg/ml, while sodium orthovanadate inhibited the enzyme competitively with an IC50 of 1.02 µM and Ki of 0.26 ± 0.01 mg/ml. Cleavage of the substrate para-Nitrophenylphosphate (pNPP) by PTP1B showed a KM of 4.99 mM and Vmax of 0.053