Flavonoids and Terpenoids with PTP-1B Inhibitory Properties from the Infusion of Salvia amarissima Ortega.

An infusion prepared from the aerial parts of Salvia amarissima Ortega inhibited the enzyme protein tyrosine phosphatase 1B (PTP-1B) (IC50~88 and 33 μg/mL, respectively). Phytochemical analysis of the infusion yielded amarisolide (1), 5,6,4'-trihydroxy-7,3'-dimethoxyflavone (2), 6-hydroxyluteolin (3), rutin (4), rosmarinic acid (5), isoquercitrin (6), pedalitin (7) and a new neo-clerodane type diterpenoid glucoside, named amarisolide G (8a,b). Compound 8a,b is a new natural product, and 2-6 are reported for the first time for the species. All compounds were tested for their inhibitory activity against PTP-1B; their IC50 values ranged from 62.0 to 514.2 μM. The activity was compared to that of ursolic acid (IC50 = 29.14 μM). The most active compound was pedalitin (7). Docking analysis predicted that compound 7 has higher affinity for the allosteric site of the enzyme. Gas chromatography coupled to mass spectrometry analyses of the essential oils prepared from dried and fresh materials revealed that germacrene D (15) and β-selinene (16), followed by β-caryophyllene (13) and spathulenol (17) were their major components. An ultra-high performance liquid chromatography coupled to mass spectrometry method was developed and validated to quantify amarisolide (1) in the ethyl acetate soluble fraction of the infusion of S. amarissima.