The Potent Inhibitors of Protein Tyrosine Phosphatase 1B from the Fruits of Melaleuca leucadendron

Background: Melaleuca leucadendron (Myrtaceae) is a kind of fruit used as Indonesian medicinal component and recorded in Jamu (tonic made of medical herbs) prescription records for the diabetes treatment. Its methanol extract exhibited a strong inhibitory activity with the half maximal inhibitory concentration (IC₅₀) value of 2.05 μg/mL, while it is the same value with positive control RK‑682. Objective: To isolate the chemical constituents of M. leucadendron and to evaluate their activity against protein tyrosine phosphatase 1B (PTP1B). Further, determine their toxicity potential against T‑cell protein tyrosine phosphatase (TCPTP). Materials and Methods: Methanol extract was fractionated using silica column chromatography, and the obtained fraction was purified using Sephadex 20‑LH. The structure of isolated compounds was identified based on 1H and 13Nuclear Magnetic Resonance Spectrometry. Furthermore, the compounds were examined against PTP1B and TCPTP. Results: Methanol extract of M. leucadendron (Myrtaceae) afforded two triterpenes: Betulinic acid and ursolic acid in high quantities. Both compounds exhibited a strong inhibitory activity against PTP1B inhibition with IC50 value of 1.5 and 2.3 μg/mL, respectively (positive control RK‑682, IC50 = 2.05 μg/mL). Their activity toward TCPTP, on the other hand, were at 2.4 and 3.1 μg/ mL, respectively. Based on this purification work, betulinic acid and ursolic acid presented 7.6% and 2.4%, respectively, as markedly M. leucadendron most potential for betulinic acid source among Indonesian plants. The result should have demonstrated that the antidiabetes of M. dendron could be through the inhibition of PTP1B.