Synthesis and discovery of 18α-GAMG as anticancer agent in vitro and in vivo via down expression of protein p65

18β-Glycyrrhetinic acid monoglucuronide (GAMG) alleviates single-walled carbon nanotubes (SWCNT)-induced lung inflammation and fibrosis in mice through PI3K/AKT/NF-κB signaling pathway

Carbon nanotubes (CNTs) have become far and wide used in a number of technical and merchant applications as a result of substantial advances in nanotechnology, therein single-walled carbon nanotubes (SWCNT) are one of the most promising nanoparticles. Inhaling CNTs has been linked to a variety of health problems, including lung fibrosis. Glycyrrhetinic acid 3-O-mono-β-D-glucuronide (GAMG), a natural sweetener, has anti-inflammatory and antioxidant capacities. The purpose of this study was to evaluate the potential for GAMG to alleviate SWCNT-induced lung inflammation and fibrosis. During days 3-28 after SWCNT intratracheal administration, we observed a remarkable increase of IL-1β, IL-6 and TNF-α in bronchoalveolar lavage fluid (BALF) on day 3 and collagen deposition on day 28. GAMG treatment remarkably ameliorated SWCNT-induced pulmonary fibrosis and attenuated SWCNT-induced inflammation and collagen deposition, and suppressed the activation of PI3K/AKT/NF-κB signaling pathway in the lungs. Therefore, GAMG has a therapeutic potential for the treatment of SWCNT-induced pulmonary fibrosis. Targeting PI3K/AKT/NF-κB signaling pathway may be a potential therapeutic approach to treat pulmonary fibrosis in mice with SWCNT.

Physiology-Based Pharmacokinetic Study on 18β-Glycyrrhetic Acid Mono-Glucuronide (GAMG) Prior to Glycyrrhizin in Rats

To understand that 18β-Glycyrrhetic acid 3-O-mono-β-D-glucuronide (GAMG) showed better pharmacological activity and drug-like properties than 18β-Glycyrrhizin (GL); a rapid and sensitive HPLC-MS/MS method was established for the simultaneous determination of GAMG and its metabolite 18β-Glycyrrhetinic acid (GA) in rat plasma and tissues after oral administration of GAMG or GL. This analytical method was validated by linearity, LLOQ, specificity, recovery rate, matrix effect, etc. After oral administration, GAMG exhibited excellent C_max (2377.57 ng/mL), T_max (5 min) and AUC_0-T (6625.54 mg/L*h), which was much higher than the C_max (346.03 ng/mL), T_max (2.00 h) and AUC_0-T (459.32 mg/L*h) of GL. Moreover, GAMG had wider and higher tissue distribution in the kidney, spleen, live, lung, brain, etc. These results indicated that oral GAMG can be rapidly and efficiently absorbed and be widely distributed in tissues to exert stronger and multiple pharmacological activities. This provided a physiological basis for guiding the pharmacodynamic study and clinical applications of GAMG.

Design and synthesis of novel glycyrrhetin ureas as anti-inflammatory agents for the treatment of acute kidney injury

To develop new anti-inflammatory drugs for the prevention and treatment of acute kidney injury, a series of novel glycyrrhetic ureas were designed, synthesized and evaluated for anti-inflammatory activity using RAW264.7 cells. Compounds 5r-5u (2.04, 2.50, 3.25 and 2.48 μM, respectively) with acidic or neutral amino acid showed potent anti-inflammatory activity (IC₅₀ = 2-3 μM for NO inhibition), amongst them, compound 5r also inhibited tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in a dose-dependent manner. In cisplatin-induced AKI mice model, compound 5r significantly reduced the level of pro-inflammatory factors, ameliorated the pathological damage of kidney tissue, and maintained the normal metabolic capacity.

18α-Glycyrrhetinic acid (GA) ameliorates fructose-induced nephropathy in mice by suppressing oxidative stress, dyslipidemia and inflammation

Excessive fructose (FRU) intake can result in insulin resistance and metabolic disorder, which are related to renal injury.18α-Glycyrrhetinic acid (GA) is a bioactive component mainly extracted from Glycyrrhiza radix, and has anti-oxidant and anti-inflammatory activities. However, its effects on FRU-induced renal injury still remain unclear. In this study, we found that 18α-GA treatments could significantly ameliorate the cell viability in FRU-treated tubule epithelial cells, accompanied with improved mitochondrial membrane potential. Furthermore, reactive oxygen species (ROS) accumulation in FRU-stimulated cells was markedly reduced by 18α-GA, which were associated with the activation of nuclear factor (erythroid-derived-2)-like 2 (Nrf-2) and the blockage of MAPKs signaling. Additionally, dyslipidemia detected in FRU-treated cells was greatly inhibited by 18α-GA. We also found that 18α-GA significantly ameliorated FRU-induced inflammation in cells through reducing the expression of pro-inflammatory cytokines and chemokine. The anti-inflammatory effects regulated by 18α-GA were mainly related to the repression of nuclear factor-κB(NF-κB) signaling. Furthermore, the protective effects of 18α-GA against ROS production, lipid accumulation and inflammation were verified in renal tissues from FRU-challenged mice, consequently improving metabolic disorder and kidney injury. Taken together, these findings demonstrated that 18α-GA exerted renal protective effects through reducing oxidative stress, lipid deposition and inflammatory response, and thus could be considered as a promising therapeutic strategy for metabolic stress-induced kidney injury.

Glycyrrhetic acid monoglucuronide: sweetness concentration-response and molecular mechanism as a naturally high-potency sweetener

Glycyrrhetic acid monoglucuronide (GAM) is obtained from the natural sweetener glycyrrhizin through enzymolysis. Its sweetness concentration-response (C-R) behavior in room-temperature in water was determined using two-alternative forced choice discrimination tests. The C-R equation of resultant hyperbolic curve relating sucrose equivalent (SE, %) to GAM concentration ([GAM], mg/L) was SE = 19.6 × [GAM]/(194.8 + [GAM]). From the C-R function, Pw (2) of GAM, relative to a 2% (w/v) sucrose reference, is more than 900, which has much higher potency than its precursor glycyrrhizin. Molecular modeling showed that GAM is finely bound into protein 1EWK through conventional hydrogen bonds, π-Alkyl interactions and Van der Waals bonds, which exhibited better protein inclusion than Glycyrrhizin. Thus, GAM could be developed as a new zero-calorie, naturally high-potency sweetener.

Identification of isoliquiritigenin as an activator that stimulates the enzymatic production of glycyrrhetinic acid monoglucuronide

Glycyrrhetinic acid monoglucuronide (GAMG) is a great value-added and has considerable commercial interest due to its strong pharmacological activities and functional low-calorie sweetener. However GAMG is quite rare in natural plants, and it must be prepared from glycyrrhizin (GL) by hydrolysing one terminal glucuronic acid. β-Glucuronidase is the key enzyme in the biotransformation of GL to GAMG, but its activities need to be enhanced to facilitate the industrial large-scale production of GAMG. In this study, we identified that isoliquiritigenin (ISL), as one of chemical compositions from the total flavonoids glycyrrhiza (TFG), can significantly enhance β-glucuronidase activity in vitro. Measurements using high-performance liquid chromatography (HPLC) showed that the activity of β-glucuronidase could be increased by 2.66-fold via the addition of ISL to a β-glucuronidase solution that contained GL at a 3:10 molar ratio of ISL to GL. ISL was concluded to be an activator because ISL could reduce the Km and Ea of β-glucuronidase reacting with GL. This study sheds new light on the mechanism of β-glucuronidase and helps to make industrial production of GAMG through fermentation feasible.

Novel unsaturated glycyrrhetic acids derivatives: Design, synthesis and anti-inflammatory activity

To develop novel anti-inflammatory agents, a series of unsaturated glycyrrhetic acids were designed, synthesized and evaluated for anti-inflammatory activity using RAW264.7 cells. The structure-activity relationship (SAR) of NO inhibitory activity was analyzed. α,β-Unsaturated glycyrrhetic acids showed better activity, among them, compounds 6k and 6l with piperazine unit exhibited the most potent nitric oxide (NO) and interleukin-6 (IL-6) inhibitory activity (IC₅₀ = 13.3 and 15.5 μM respectively). Furthermore, compound 6k could also significantly suppress LPS-induced iNOS and COX-2 expression and IL-6 production through MAPKs and NF-kB signaling pathway.

18α-Glycyrrhetinic acid monoglucuronide as an anti-inflammatory agent through suppression of the NF-κB and MAPK signaling pathway

Based on the SAR analysis of glycyrrhizin, 18α-glycyrrhetinic acid monoglucuronide (18α-GAMG) with strong inhibition against LPS-induced NO and IL-6 production in RAW264.7 cells was discovered. Western blotting and immunofluorescence results showed that 18α-GAMG reduced the expression of iNOS, COX-2, and MAPKs, as well as activation of NF-κB in the LPS-stimulated RAW264.7 cells. Further in vivo results showed that 18α-GAMG could significantly improve the pathological changes of CCl4-induced hepatic fibrosis.

Novel myricetin derivatives: Design, synthesis and anticancer activity

Telomere and telomerase were closely related to occurrence and development of some cancers. To enhance ability of myricetin moiety for inhibiting telomerase, we designed a series of novel myricetin derivatives based on reasonable analysis. The telomerase inhibition assay showed that compound 6d displayed the most potent inhibitory activity with IC50 value of 0.91 μM. The anticancer activity assay showed that 6d exhibited high activity against human breast cells MDA-MB-231. The docking simulation of compound 6d was performed to get the probable binding model, the results demonstrated that the furan ring inserted into the active site deeply and had hydrophobic interactions with residues of Phe 568, Pro 627, four methoxy groups had hydrophobic interactions with residues of Phe 568, Pro 627, Lys 902, Val 904 and Pro 929. Western blot results showed that expression of p65 and TERT protein was clearly down-regulated by compound 6d. These data support further studies for the rational design of more efficient p65 and TERT modulators.

Design and synthesis of celastrol derivatives as anticancer agents

A series of celastrol derivatives as potential telomerase inhibitors were designed and synthesized. The bioassays demonstrated that title compounds displayed potent anticancer activities against SGC-7901, SMMC-7721, MGC-803 and HepG-2 cell lines, among them, compounds 3c and 3d which containing hydrophilicity moieties exhibited high anti-proliferative activities (IC50 = 0.10-1.22 μM). The preliminary mechanism of antitumor action indicated that title compound 3c could induce significant SMMC-7721 cells apoptosis. A modified TRAP assay showed that compounds 3c and 3d displayed the most potent inhibitory activity with IC50 values at 0.11 and 0.34 μM, respectively. And there was a good correlation between telomerase inhibition and anti-proliferative inhibition of SMMC-7721 cells. Moreover, molecular docking indicated that the active compound 3c was nicely bound into the telomerase hTERT active site, hydrophobic, van der Waals and two hydrogen bond interactions with conserved residues ASP 628 and TYR 949 were found.