Identification of naturally occurring inhibitors in Xian-Ling-Gu-Bao capsule against the glucuronidation of estrogens

Abstract

Xian-Ling-Gu-Bao (XLGB) capsule, a well-known traditional Chinese medicine prescription, is widely used for the treatment of osteoporosis. It could significantly increase the levels of estrogen in ovariectomized rats and mice. However, this working mechanism has not been well elucidated. Considering that UDP-glucuronosyltransferase (UGT) enzymes are the important enzymes that inactivate and regulate estrogen activity in vivo, this study aimed to identify the bioactive compounds from XLGB against the glucuronidation of estrogens. First, thirty compounds were considered as candidate bioactive compounds based on our previous studies including pharmacological evaluation, chemical profiles, and metabolic profiles. Second, the characteristics of estrogen glucuronidation by uridine diphosphate glucuronic acid (UDPGA)-supplemented human liver microsomes (HLM), human intestine microsomes (HIM), and expressed UGT enzymes were determined, and the incubation systems of their key UGT enzymes were optimized. Then, inhibitory effects and mechanisms of XLGB and its main compounds toward the key UGT isozymes were further investigated. As a result, estrogen underwent efficient glucuronidation by HLM and HIM. UGT1A10, 1A1, and 2B7 were mainly responsible for the glucuronidation of estrone, β-estradiol, and estriol, respectively. For E1 and E2, UGT1A10 and 1A1 tended to mediate estrogen-3-O-glucuronidation, while UGT2B7 preferred catalyzing estrogen-16-O-glucuronidation. Furthermore, the incubation system for active UGT isoforms was optimized including Tris-HCl buffer, detergents, MgCl2 concentration, β-glucuronidase inhibitors, UDPGA concentration, protein concentration, and incubation time. Based on optimal incubation conditions, eleven, nine, and nine compounds were identified as the potent inhibitors for UGT1A10, 1A1, and 2B7, respectively (IC50 < 4.97 μM and Ki < 3.35 μM). Among them, six compounds (bavachin, isobavachin, isobavachalcone, neobavaisoflavone, corylifol A, and icariside II) simultaneously demonstrated potent inhibitory effects against these three active enzymes. Prenylated flavanols from Epimedium brevicornu Maxim., prenylated flavonoids from Psoralea corylifolia L., and salvianolic acids from Salvia miltiorrhiza Bge. were characterized as the most important and effective compounds. The identification of potent natural inhibitors of XLGB against the glucuronidation of estrogen laid an important foundation for the pharmacodynamic material basis.

Targeting the PANoptosis signaling pathway for myocardial protection: therapeutic potential of Xian Ling Gu Bao capsule

“…XLGB, a well-known traditional Chinese medicine prescription, is known for its effects in nourishing yin and blood, promoting blood circulation, resolving blood stasis, regulating the immune system, and enhancing bone density (He et al, 2022). Numerous studies have found that XLGB has a variety of active ingredients, including flavonoids, terpenes, and phenylpropanoids, etc., (Guan et al, 2011;Tang et al, 2020).…”

Corylifol A ameliorates muscle atrophy by inhibiting TAOK1/p38‐MAPK/FoxO3 pathway in cancer cachexia

“…BuGuZhi is popularly used in the treatment of patients with inflammatory diseases or malignancy at late stages 6–8 . CYA had been reported to exhibit inhibitive effects on glucuronidation of estrogens, 9 STAT3 activation 10 as well protective effects against ionizing radiation injury 11 and dexamethasone‐induced muscle atrophy 12 . However, the effects of CYA on cancer cachexia have not been reported before.…”