Enhanced production of glycyrrhetic acid 3-O-mono-β-D-glucuronide by fed-batch fermentation using p H and dissolved oxygen as feedback parameters

Glycyrrhetic acid 3-O-mono-β-D-glucuronide （GAMG）, the major functional ingredient in licorice, has widespread applications in food, pharmacy and cosmetics industry. The production of GAMG through Penicillium purpurogenum Li-3 cultivation was for the first time performed through both batch and fed-batch processes in bioreactors. In batch process, under optimal conditions （pH 5.0, temperature 32℃, agitation speed 100 r. rain 1）, 3.55 g. L^-1 GAMG was obtained in a 2.5 L fermentor. To further enhance GAMG production, a fine fed-batch process was developed by using pH and DO as feedback parameters. Starting from 48 h, 100 m190 g-L 1 substrate Glycyrrhizin （GL） was fed each time when pH increased to above 5.0 and DO was increased to above 80%. This strategy can significantly enhance GAMG production： the achieved GL conversion was 95.34% with GAMG yield of 95.15%, and GAMG concentration was 16.62 g. L^-1 which was 5 times higher than that of batch. Then, a two-step separation strat- egy was established to separate GAMG from fermentation broth by crude extraction of 15 ml column packed with D10I resin followed by fine purification with preparative C18 chromatography. The obtained GAMG purity was 95.79%. This study provides a new insight into the industrial bioprocess of high-level GAMG production.

Rapid and Sensitive Liquid Chromatography-Tandem Mass Spectrometry for Quantification of Glycyrrhetic Acid in Human Plasma

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometry（LC-MS/MS） for the determination of glycyrrhetic acid in human plasma with ginsenoside Rh2 as internal standard was developed and validated. The plasma samples were prepared via liquid-liquid extraction with ethyl acetate. Chromatographic separation was accomplished on a Venusil MP-C18（50 mm×2.1 mm, 5 μm i.d.） column at 25 °C. The mobile phase consisted of acetonitrile/5 mmol？L-1 ammonium acetate（10：90, volume ratio） at a flow rate of 0.4 mL/min. Negative electrospray ionization was utilized as the ionization source. Glycyrrhetic acid and internal standard were determined via the mutiple reaction monitoring of precursor→production ion transitions at m/z 469→425, 409 and m/z 621→161, respectively. Each sample was chromatographed within 2.5 min. The lower limit of quantification was 0.50 ng/mL for 200 μL of plasma sample and the linear range was from 0.50 ng/mL to 800 ng/mL. The intra- and inter-day precisions were less than 8.76% in terms of relative standard deviation（RSD）, and the accuracy was within a range of -3.25%-1.32% in terms of relative error（RE）. The method was successfully applied to the pharmacokinetic studies of glycyrrhetic acid in healthy male Chinese volunteers after a single oral administration of 75 mg of glycyrrhizin.

A method for the quantitative determination of glycyrrhetic acid in plasma by LC-MS/MS and its application in a pharmacokinetic study of ammonium glycyrrhetate

A simple and rapid liquid chromatography-tandem mass spectrometry（LC-MS/MS）method was developed and validated for the quantitative determination of glycyrrhetic acid（GA）,metabolite of glycyrrhizin and glycyrrhetate,in human plasma.GA and internal standard（IS,thiamphenicol）were separated on a C_（18）column by elution with acetonitrile-ammonium acetate solution（5 mmol/L）（70：30,v/v）after a simple liquid-liquid extraction with ethyl acetate.The flow rate was 0.8 mL/min. They were detected by tandem mass spectrometry in the negative ion multiple reaction monitoring（MRM）mode with ion transitions of m/z 469.3→355.3 for GA and m/z 354.1→185.0 for IS.The calibration curve was linear over GA concentration range of 0.5-500 ng/mL（r^20.99）,with intra-and inter-day precisions（RSD）of less than 7.1%,and mean extraction recovery of 74.3%. The method was used for the pharmacokinetic study of ammonium glycyrrhetate after its oral administration of a single dose of 75 mg ammonium glycyrrhetate tablet in humans.The main pharmacokinetic parameters of GA were as follows：AUC_（0-t） （3457.26±1999.01）ng·h/mL;AUC_（0-∞）（3708.85±2428.36）ng·h/mL;MRT_（0-t）（19.69±4.03）h;MRT_（0-∞）（22.83±8.45）h;t_（1/2）Z （11.71±7.77）h;T_（max）（13.40±4.84）h;CLz/F（29.17±19.82）L/h;Vz/F（487.38±518.07）L;C_（max）（215.85±99.88）ng/mL.

In vitro Metabolism of Strychnine by Human Cytochrome P450 and Its Interaction with Glycyrrhetic Acid

Objective To investigate the metabolism of strychnine(STN)and the metabolic interaction between STN and glycyrrhetic acid(GA)in vitro.Methods Human liver microsomes(HLM)and human recombinant cytochrome P450(CYP)isoforms were employed to study the metabolism of STN and the metabolic interaction of STN with GA in vitro.Results In HLM,the Km,Vmax,and clearance of STN were 88.50μmol/L,0.88 nmol/(mg·min),and 9.93 mL/(mg·min),respectively.STN was metabolized mainly by CYP3A4.However,STN noncompetitively inhibited CYP3A4-catalyzed testosterone 6β-hydroxylation with IC50 value of 5.9μmol/L and Ki value of 5.5 μmol/L.Moreover,GA competitively inhibited STN metabolism with IC50 value of 10.6μmol/L and Ki value of 17.7μmol/L.Conclusion Although STN is mainly metabolized by CYP3A4 in vitro,STN has noncompetitive inhibition on CYP3A4-catalyzed testosterone 6β-hydroxylation.Moreover,GA could competitively inhibit STN metabolism.The present work is helpful to elucidate the metabolic interaction between STN and GA.

O-glycosyltransferases from Homo sapiens contributes to the biosynthesis of Glycyrrhetic Acid 3-O-mono-β-D-glucuronide and Glycyrrhizin in Saccharomyces cerevisiae

Glycyrrhizin(GL)and Glycyrrhetic Acid 3-O-mono-β-D-glucuronide(GAMG)are the typical triterpenoid glycosides found in the root of licorice,a popular medicinal plant that exhibits diverse physiological effects and pharmacological manifestations.However,only few reports are available on the glycosylation enzymes involved in the biosynthesis of these valuable compounds with low conversion yield so far.In mammals,glycosyltransferases are involved in the phase II metabolism and may provide new solutions for us to engineer microbial strains to produce high valued compounds due to the substrate promiscuity of these glycosyltransferases.In this study,we mined the genomic databases of mammals and evaluated 22 candidate genes of O-glycosyltransferases by analyzing their catalytic potential for O-glycosylation of the native substrate,glycyrrhetinic acid(GA)for its glycodiversification.Out of 22 selected glycosyltransferases,only UGT1A1 exhibited high catalytic performance for biosynthesis of the key licorice compounds GL and GAMG.Molecular docking results proposed that the enzymatic activity of UGT1A1 was likely owing to the stable hydrogen bonding interactions and favorite conformations between the amino acid residues around substrate channels(P82~R85)and substrates.Furthermore,the complete biosynthesis pathway of GL was reconstructed in Saccharomyces cerevisiae for the first time,resulting in the production of 5.98±0.47 mg/L and 2.31±0.21 mg/L of GL and GAMG,respectively.

Development of a validated UPLC-qTOF-MS/MS method for determination of bioactive constituent from Glycyrrhiza glabra

An ultra-performance liquid chromatography quadrupole time of flight mass spectrometry （UPLC-qTOF-MS/MS） method was developed and validated for the simultaneous determination of glycyrrhizin and glycyrrhetic acid. These analytes were separated on a reverse phase C18 column using a mobile phase of acetonitrile：2% acetic acid in water （75：25, v/v） with a flow rate of 200 μL/min. The qTOF-MS was operated under multiple reaction monitoring （MRM） mode using the electrospray ionization （ESI） technique with positive ion polarity. A comparison of three different extraction techniques i.e. accelerated solvent extraction （ASE）, extraction under ultrasonic waves （USW） and the classical extraction by percolation （CE） method was done and quantification of these extracts was also carried out by the proposed method.

Enhanced production of β-glucuronidase from Penicillium purpurogenum Li-3 by optimizing fermentation and downstream processes

β-Glucuronidase from Penicillium purpuro- genum Li-3 （PGUS） can efficiently hydrolyze glycyrrhizin into the more valuable glycyrrhetic acid monoglucuronide. However, a low productivity of PGUS and the lack of an effective separation strategy have significantly limited its industrial applications. Therefore, the production of PGUS has been improved by optimizing both the fermentation and purification strategies. A two-stage fermentation strategy was developed where PGUS was first grown with glucose and then PGUS was produced in the presence of glycyrrhizin as an inducer. By using this strategy, the biomass was increased 1.5 times and the PGUS activity increased 5.4 times compared to that when glycyrrhizin was used as the sole carbon source. The amount of PGUS produced was increased another 16.6% when the fermentation was expanded to a 15-L fermenter. An effective protocol was also established to purify the PGUS using a sequential combination of hydrophobic, strong anionexchange and gel filtration chromatography. This protocol had a recovery yield of 6% and gave PGUS that was 39 times purer than the crude PGUS. The purified PGUS had a specific activity of 350 U. mg-1.

Effect of strychnine hydrochloride on liver cytochrome P450 mRNA expression and monooxygenase activities in rat

Strychnos nux-vomica L.has been frequently used in traditional Chinese medicine but has high acute toxicity.It is commonly taken with Glycyrrhizae radix to decrease its toxicity but the mechanism of this interaction is unknown.In this work,the mRNA expression and the activity of four cytochrome P450(CYP)enzymes representative of four subfamilies(CYP1A,CYP3A,CYP2C and CYP2E)were determined ex vivo in rat livers from groups of Wistar rats orally administered strychnine hydrochloride(SH)at three doses(0.1,0.3 and 0.9 mg/kg/day)alone and,at the highest dose,in combination with glycyrrhetinic acid(GA,25 mg/kg/day)or liquiritin(LQ,20 mg/kg/day)once a day for 7 consecutive days.Compared to control,the mRNA expressions of CYP3A1,1A2 and 2E1 were higher in rats receiving the highest dose of SH but lower for CYP3A1 and CYP2E1 in rats receiving the SH+GA and SH+LQ combinations.CYP2E1 activity was higher and CYP2C,CYP3A and CYP1A2 activities were lower in rats receiving the highest dose of SH.In contrast CYP1A2 and CYP2C activities were higher and CYP2E1 and CYP3A activities lower in rats receiving the SH+GA combination.CYP2E1 and CYP3A activities were also lower in rats receiving the SH+LQ combination.The results show that treatment with SH for 7 days affects the expression and the activity of CYP enzymes and that coadministration of GA and LQ modulates these effects.This modulation may explain the role of Glycyrrhizae radix in reducing the acute toxicity of Strychnos nux-vomica L.CYPs enzymes.