Identification of Major α-Glucosidase Inhibitors from Stem Bark of Panamanian Mangrove Plant Pelliciera rhizophorae

Abstract

In our continuous search for α-glucosidase inhibitors, three active pentacyclic triterpenes were isolated from stem bark samples of the Panamanian mangrove Pelliciera rhizophorae Triana & Planchon. These compounds were identified by both spectroscopic and spectrometric analysis. Of the isolated compounds, only betulinic acid has been previously isolated from P. rhizophorae leaves while both betulin (IC 50 2.09 µM) and lupeol (IC 50 0.58 µM) were isolated from this plant for the first time. All three pentacyclic triterpenes inhibited the α‑glucosidase enzyme in a concentration‑dependent manner, and their inhibitory activity was higher than that of the antidiabetic drug acarbose (IC 50 241.6 µM). Kinetic analysis established that betulin and lupeol acted as competitive inhibitors. Finally, docking analysis suggested that all three triterpenes bind at the same site as acarbose does in the human intestinal α‑glucosidase (PDB: 3TOP). This work contributes further evidence similar to previous studies that point out that the aerial parts of P. rhizophorae might be potential agents in controlling hyperglycemia in diabetic persons.