Discovery and characterization of pentacyclic triterpenoid acids in Styrax as potent and reversible pancreatic lipase inhibitors

Abstract

• Styrax extract was found with strong pancreatic lipase (PL) inhibition activity. • Bioactivity and LC-MS guided fractionation strategy was used to identify naturally occurring PL inhibitors in Styrax. • Oleanonic acid (ONA) and betulonic acid (BNA) potently inhibit PL, with IC 50 values less than 1.5 μM. • Inhibitory mechanisms of ONA and BNA against PL were investigated by inhibition kinetic analyses and in silico analysis. Pancreatic lipase (PL) inhibitor therapy is one of the most effective ways to treat obesity and obesity-associated metabolic disorders. Herein, bioactivity and liquid chromatograph-mass spectrometer (LC-MS) guided fractionation strategy was used to identify the naturally occurring PL inhibitors in Styrax, a popular folk medicine in Asia and Turkey. The results clearly showed that five pentacyclic triterpenoid acids in Styrax displayed strong inhibition on PL, with IC 50 values ranging from 0.49 µM to 6.35 µM. Further investigations demonstrated that oleanonic acid and betulonic acid (the most two potent PL inhibitors in Styrax) potently inhibited PL in a reversible and mixed inhibition manner, while molecular dynamics simulations showed that these two agents could stably bind at the entrance to the active site of PL. Collectively, our findings revealed the molecular basis for the anti-obesity effects of Styrax, while the newly identified PL inhibitors in this herb could be used for development of novel anti-obesity agents.