GL-V9 is a prominent derivative of wogonin with a wide therapeutic spectrum and potent anti-tumor activity. The metabolism characteristics of GL-V9 remain unclear. This study aimed to clarify the metabolic pathway of GL-V9 and investigate the generation of its glucuronidation metabolites in vitro and in vivo. HPLC-UV-TripleTOF was used to identify metabolites. The main metabolite that we found was chemically synthesized and the synthetic metabolite was utilized as standard substance for the subsequent metabolism studies of GL-V9, including enzyme kinetics in liver microsomes of five different species and reaction phenotyping metabolism using 12 recombinant human UDP-glucuronosyltransferase (UGT) isoforms. Results indicated that the glucuronidation reaction occurred at C5-OH group, and 5-O-glucuronide GL-V9 is the only glucuronide metabolite and major phase II metabolite of GL-V9. Among 12 recombinant human UGTs, rUGT1A9 showed the strongest catalytic capacity for the glucuronidation reaction of GL-V9. rUGT1A7 and rUGT1A8 were also involved in the glucuronidation metabolism. Km of rUGT1A7-1A9 was 3.25 ± 0.29, 13.92 ± 1.05, and 4.72 ± 0.28 μM, respectively. In conclusion, 5-O-glucuronide GL-V9 is the dominant phase II metabolite of GL-V9 in vivo and in vitro, whose formation rate and efficiency are closely related to isoform-specific metabolism profiles and the distribution of UGTs in different tissues of different species.
GL-V9, a derivative of wogonin, has potent anti-cancer activity. The absorption and metabolism of this compound have not been investigated systematically. This study aims to illustrate the pharmacokinetic characters of GL-V9 by exploring its metabolic status under different administration routes. To further clarify the absorption mechanism of GL-V9, an in situ single-pass perfusion model and a Caco-2 cell monolayer model were used. Meanwhile, a microsomal incubation system was used to evaluate the enzyme kinetic parameters. In vivo, the obtained gastrointestinal availability (F a × F g ) was 21.28 ± 5.38%. The unmetabolized fraction in the gut wall (F gut wall ) was 98.59 ± 9.74%, while the hepatic bioavailability (F h ) was 29.11 ± 5.22%. These results indicated that poor absorption and extensive metabolism may contribute greatly to the low bioavailability of GL-V9. The effective permeability (P eff ) in the duodenum and jejunum was 1.34 ± 0.50 × 10 −4 and 0.90 ± 0.27 × 10 −4 cm/s, respectively. The high permeability of GL-V9 indicated that other unknown factors (such as metabolism) may account for its systemic exposure problem. Studies in rat liver microsomal (RLMs) confirmed this hypothesis, and the Cl int, CYP450s and UGT of GL-V9 was 0.20 ml/min/mg protein. In conclusion, these results suggest that GL-V9 possesses higher permeability than wogonin and the metabolism of GL-V9 is related to its disposition in rat intestine and liver.
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