Fig 1: The percentage inhibition of PTP1B (a) and TCPTP (b–f) activity. Compound 3 is used as a control to validate the inhibition assay targeting PTP1B (a) and TCPTP (b). Four lupane triterpenes are tested for the inhibition potency of TCPTP: (c) Lupeol; (d) Lupenone; (e) Betulin; and (f) Betulinic acid.