Tan Xue Fei, Uddin Zia, Park Chanin, Song Yeong Hun, Son Minky, Lee Keun Woo, Park Ki Hun
Division of Applied Life Science (BK21 Plus), IALS, Gyeongsang National University, Jinju 52828, Republic of Korea.
Division of Applied Life Science (BK21 Plus), PMBBRC, RINS, Gyeongsang National University, Jinju 52828, Republic of Korea.
Bioorg Med Chem. 2017 Apr 15;25(8):2498-2506. doi: 10.1016/j.bmc.2017.03.010. Epub 2017 Mar 6.
Protein tyrosine phosphatase 1B (PTP1B) plays important role in diabetes, obesity and cancer. The methanol extract of the gum resin of Garcinia hanburyi (G. hanburyi) showed potent PTP1B inhibition at 10µg/ml. The active compounds were identified as prenylated caged xanthones (1-9) which inhibited PTP1B in dose-dependent manner. Carboxybutenyl group within caged motif (A ring) was found to play a critical role in enzyme inhibition such as 1-6 (ICs=0.47-4.69µM), whereas compounds having hydroxymethylbutenyl 7 (IC=70.25µM) and methylbutenyl 8 (IC>200µM) showed less activity. The most potent inhibitor, gambogic acid 1 (IC=0.47µM) showed 30-fold more potency than ursolic acid (IC=15.5µM), a positive control. In kinetic study, all isolated xanthones behaved as competitive inhibitors which were fully demonstrated with K, V and K/K ratio. It was also proved that inhibitor 1 operated under the enzyme isomerization model having k=0.0751µMS, k=0.0249µMS and K=0.499µM. To develop a pharmacophore model, we explored the binding sites of compound 1 and 7 in PTP1B. These modeling results were in agreement with our findings, which revealed that the inhibitory activities are tightly related to caged motif and prenyl group in A ring.
蛋白酪氨酸磷酸酶1B（PTP1B）在糖尿病、肥胖症和癌症中发挥着重要作用。藤黄树脂的甲醇提取物在10μg/ml时表现出强大的PTP1B抑制作用。活性化合物被鉴定为异戊烯基笼形呫吨酮（1 - 9），它们以剂量依赖性方式抑制PTP1B。发现笼形基序（A环）内的羧丁烯基在酶抑制中起关键作用，如化合物1 - 6（IC50 = 0.47 - 4.69μM），而具有羟甲基丁烯基的化合物7（IC50 = 70.25μM）和甲基丁烯基的化合物8（IC50>200μM）活性较低。最有效的抑制剂藤黄酸1（IC50 = 0.47μM）的效力比阳性对照熊果酸（IC50 = 15.5μM）高30倍。在动力学研究中，所有分离出的呫吨酮均表现为竞争性抑制剂，这通过Km、Vmax和Ki/Km比值得到充分证明。还证明抑制剂1在酶异构化模型下发挥作用，其k1 = 0.0751μM-1S-1，k-1 = 0.0249μM-1S-1，K1 = 0.499μM。为了建立药效团模型，我们探索了化合物1和7在PTP1B中的结合位点。这些建模结果与我们的发现一致，表明抑制活性与A环中的笼形基序和异戊烯基密切相关。
