Fructus Psoraleae contains natural compounds with potent inhibitory effects towards human carboxylesterase 2

Effects of Psoralen as an Anti-tumor Agent in Human Breast Cancer MCF-7/ADR Cells

Psoralen is a major active component of Psoralea corylifolia. In the present study, we analyzed psoralen-induced changes in human breast cancer MCF-7/ADR cells and investigated the underlying mechanisms of the anticancer effect on MCF-7/ADR cells. We measured cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to evaluate the cytotoxicity and multidrug resistance (MDR) reversal activity of psoralen. The cell cycle distribution and apoptosis, accumulation and efflux of rhodamine123 (Rh123), and P-glycoprotein (P-gp) expression levels of MCF-7/ADR cells treated with psoralen were all detected by flow cytometry (FCM). We assessed P-gp ATPase activity by monitoring ATP consumption. We evaluated the activity of nuclear factor-kappaB (NF-κB) and the expression of E-cadherin, vimentin and α-smooth muscle actin (SMA) involved in regulating epithelial-mesenchymal transition (EMT). The results showed that psoralen inhibited the proliferation of MCF-7/ADR cells as shown by G0/G1 phase arrest rather than encouraging apoptosis. It was also observed that psoralen reversed MDR through inhibiting ATPase activity rather than reducing P-gp expression. Our results further showed that psoralen inhibited the migration abilities of MCF-7/ADR cells by repressing EMT possibly through inhibiting the activation of NF-κB. Our findings provided a systematic and detailed description of the anti-cancer effect of psoralen on MCF-7/ADR cells for the exploration of natural compounds as novel anticancer agents.

Protostane Triterpenoids from the Rhizome of Alisma orientale Exhibit Inhibitory Effects on Human Carboxylesterase 2

Twelve new and 10 known protostane triterpenoids were isolated from the rhizome of Alisma orientale. Their structures were elucidated based on physical data analyses, including UV, HRESIMS, NMR experiments ((1)H, (13)C NMR, (1)H-(1)H COSY, HSQC, HMBC, and NOESY), and induced electronic circular dichroism. New compounds 1-12 were classified as protostanes (1-10), 29-norprotostane (11), and 24-norprotostane (12) by structure analyses. Furthermore, the inhibitory effects on human carboxylesterases (hCE-1, hCE-2) of compounds 1-22 were evaluated. Compounds 2, 6, 9, and 11 showed moderate inhibitory activities and were selective toward hCE-2 enzymes, with IC50 values of 8.68, 4.72, 4.58, and 2.02 μM, respectively. The inhibition kinetics of compound 11 toward hCE-2 were established, and the Ki value was determined as 1.76 μM using a mixed inhibition model. The interaction of bioactive compound 11 with hCE-2 was shown using molecular docking.

Glucuronidation of bavachinin by human tissues and expressed UGT enzymes: Identification of UGT1A1 and UGT1A8 as the major contributing enzymes

Bavachinin (BCI), a major bioactive compound in Chinese herbal Psoralea corylifolia, possesses a wide range of biological activities. In this study, the glucuronidation pathway of BCI was characterized for the first time, by using pooled human liver microsomes (HLM), pooled human intestine microsomes (HIM) and recombinant human UDP-glucosyltransferases (UGTs). One mono-glucuronide was detected in HLM in the presence of uridine-diphosphate glucuronic acid (UDPGA), and it was biosynthesized and well-characterized as BCI-4'-O-glucuronide (BCIG). Reaction phenotyping assay showed that UGT1A1, UGT1A3 and UGT1A8 were involved in BCI-4'-O-glucuronidation, while UGT1A1 and UGT1A8 displayed the higher catalytic ability among all tested UGT isoforms. Kinetic analysis demonstrated that BCI-4'-O-glucuronidation in both HLM and UGT1A1 followed sigmoidal kinetic behaviors and displayed much close Km values (12.4 μM in HLM & 9.7 μM in UGT1A1). Both chemical inhibition assays and correlation analysis demonstrated that UGT1A1 displayed a predominant role in BCI-4'-O-glucuronidation in HLM. Both HIM and UGT1A8 exhibited substrate inhibition at high concentrations, and Km values of HIM and UGT1A8 were 3.6 and 2.3 μM, respectively. Similar catalytic efficiencies were observed for HIM (199.3 μL/min/mg) and UGT1A8 (216.2 μL/min/mg). These findings suggested that UGT1A1 and UGT1A8 were the primary isoforms involved in BCI-4'-O-glucuronidation in HLM, and HIM, respectively.