Synthesis, pH dependent, plasma and enzymatic stability of bergenin prodrugs for potential use against rheumatoid arthritis

Publication date: Available online 10 August 2017
Source:Bioorganic & Medicinal Chemistry
Author(s): Rohit Singh, Vikas Kumar, Sonali S. Bharate, Ram A. Vishwakarma
Bergenin is a unique C-glycoside natural product possessing anti-inflammatory and anti-arthritic activity. It is hydrophilic molecule and stable under acidic conditions however is unstable at neutral-basic pH conditions. The rate of degradation is directly proportional to the increase in pH which might be one of the reasons for its low oral bioavailability. Thus, herein our objective was to improve its stability using prodrug strategy. Various ester and ether prodrugs were synthesized and studied for lipophilicity, chemical stability and enzymatic hydrolysis in plasma/ esterase. The stability of synthesized prodrugs was evaluated in buffers at different pH, in biorelevant media such as SGF, SIF, rat plasma and in esterase enzyme. All prodrugs displayed significantly improved lipophilicity compared with bergenin, which was in accordance with the criteria of drug-like compounds. Acetyl ester 4a2 appeared to be the most promising prodrug as it remained stable at gastric/intestinal pH and was completely transformed to the parent compound bergenin in plasma as desired for an ideal prodrug. The data presented herein, will help in designing stable prodrugs of unstable molecules with desired physicochemical properties in structurally similar chemotypes.

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