Processive kinetics in the three-step lanosterol 14α-demethylation reaction catalyzed by human cytochrome P450 51A1.

Cytochrome P450 (P450, CYP) family 51 enzymes catalyze the 14α-demethylation of sterols, leading to critical products used for membranes and the production of steroids, as well as signaling molecules. In mammals, P450 51 catalyzes the 3-step, 6-electron oxidation of lanosterol to form (4ß,5α)-4,4-dimethyl-cholestra-8,14,24-trien-3-ol (FF-MAS). P450 51A1 can also use 24,25-dihydrolanosterol (a natural substrate in the Kandutsch-Russell cholesterol pathway). 24,25-Dihydrolanosterol and the corresponding P450 51A1 reaction intermediates, the 14α-alcohol and -aldehyde derivatives of dihydrolanosterol, were synthesized to study the kinetic processivity of the overall 14α-demethylation reaction of human P450 51A1. A combination of steady-state kinetic parameters, steady-state binding constants, dissociation rates of P450-sterol complexes, and kinetic modeling of the time course of oxidation of a P450-dihydrolanosterol complex showed that the overall reaction is highly processive, with koff rates of P450 51A1-dihydrolanosterol and the 14α-alcohol and 14α-aldehyde complexes being 1 to 2 orders of magnitude less than the forward rates of competing oxidations. epi-Dihydrolanosterol (the 3α-hydroxy analog) was as efficient as the common 3ß-hydroxy isomer in the binding and formation of dihydro FF-MAS. The common lanosterol contaminant dihydroagnosterol was found to be a substrate of human P450 51A1, with roughly one-half the activity of dihydrolanosterol. Steady-state experiments with 14α-methyl deuterated dihydrolanosterol showed no kinetic isotope effect, indicating that C-14α C-H bond breaking is not rate-limiting in any of the individual steps. The high processivity of this reaction generates higher efficiency and also renders the reaction less sensitive to inhibitors.

Bioinspired Synthesis of Spirochensilide A from Lanosterol.

A bioinspired synthesis of spirochensilide A from commercially available lanosterol is reported. The synthesis features a directed C-H oxidation, a Wagner-Meerwein-type double methyl migration, a Meinwald rearrangement, and a double-bond isomerization/spiroketal formation cascade. The proposed biosynthetic speculation was modified by this synthetic sequence, which also served as a platform for the synthesis of other lanostanes with migrating methyl groups.

Synthesis and Antiproliferative Activity of Ester Derivatives of Mogrol through JAK2/STAT3 Pathway.

In attempt to enhance the antiproliferative activity of mogrol, two series of ester derivatives modified at C3 -OH and C11 -OH were designed and synthesized. The activity against human cancer cells including A549, NCI-H460 and CNE1 was screened by Cell Counting Kit-8 (CCK8) assay. According to the results, modifications of the mogrol core through introduction of different ester scaffolds drastically improved the cytotoxicity, and some of the derivatives exhibited even higher activity than the positive drug. Among them, compound M2h exhibited nearly 4 times more cytotoxic than 5-Fu against CNE1 cells, derivative M6c showed ten times higher activity with the IC50 value of 10.59 µM than mogrol against NCI-H460 cells, and compound M6a which contained one 1,2,3-triazole motif showed the strongest activity with an three folds lower IC50 value than mogrol. Furthermore, the most potent compound M2h could lead to cell cycle arrest at G2 phase on CNE1 cell lines and M6a induced G1 phase arrest on A549 cell lines. It was noteworthy that both M2h and M6a regulated signal transducer and activator of transcription 3 (STAT3) signal pathway through inhibiting phosphorylation of Janus Kinase 2 (JAK2) and STAT3, and simultaneously increasing the protein level of downstream cyclin p21.

PADI4 mediates autophagy and participates in the role of ganoderic acid A monomers in delaying the senescence of Alzheimer's cells through the Akt/mTOR pathway.

The effects of PADI4 and GAA on the senescence of Alzheimer's cells were explored in the present work. HT22 cells were treated with Aß25-35 to establish an Alzheimer's model and were then treated with different concentrations of GAA and transfected with a siPADI4 lentiviral vector. GAA could reverse the effects of Aß25-35 on inhibiting cell viability and promoting apoptosis and senescence. siPADI4 reduced Aß25-35-induced cell viability and upregulated Aß25-35-induced cell apoptosis and senescence, as well as partially reversed the effect of GAA on cells, and these results were confirmed by detecting the expressions of senescence- and apoptosis-related proteins. In addition, siPADI4 was found to promote the phosphorylation of Akt and mTOR, which was partially reversed by GAA. In conclusion, PADI4 mediates autophagy and participates in the role of GAA monomers in delaying the senescence of Alzheimer's cells through the Akt/mTOR pathway.

Protective effect of triterpenes of Ganoderma lucidum on lipopolysaccharide-induced inflammatory responses and acute liver injury.

Ganoderma lucidum is a popular medicinal mushroom, which has been used as therapeutic for centuries in traditional Chinese medicine. Although G. lucidum showed strong protective effects in prevention or treatment of a variety of inflammatory diseases, the mechanisms underlying the anti-inflammatory properties of triterpenes of G. lucidum remain undefined. In the current study, we demonstrated that ethanol extract and triterpenes of G. lucidum specifically suppressed LPS-mediated inflammatory responses. Notably, ganodermanontriol inhibited the expressions and interactions of TLR4 and MyD88, NF-κB translocation to nucleus and its DNA binding activity, phosphorylation of p38, ErK1/2 and JNK. In vivo, we showed that ganodermanontriol effectively prevented LPS/D-Galactosamine-induced liver injury by reducing TNF-α and IL-6 production, and decrease of ALT/AST release. Collectively, our results revealed a novel role in inhibition of inflammatory diseases for triterpenes that may act through potential inhibition of TLR4-MyD88-mediated NF-κB and MAPK signaling pathways.

Isolation and biological activity of agrostophillinol from kaffir lime (Citrus hystrix) leaves.

The leaves of the kaffir lime (Citrus hystrix) are commonly used in cuisine and folk medicine. The aim of this study was to isolate a bioactive compound in kaffir lime leaves and characterize its biological activity. The compound was isolated from a hexane fractional extract and identified as agrostophillinol. This is the first report of agrostophillinol isolated from kaffir lime leaves. In terms of cytotoxicity, agrostophillinol exhibited IC50 values of 36.27 ± 7.30 and 53.44 ± 10.63 µg/mL against EoL-1 and HL60 cells, respectively. Agrostophillinol also exhibited potent anti-inflammatory activity, significantly inhibiting IL-6 secretion.

Ganoweberianones A and B, Antimalarial Lanostane Dimers from Cultivated Fruiting Bodies of the Basidiomycete Ganoderma weberianum.

Two lanostane dimers, ganoweberianones A (1) and B (2), together with seven previously undescribed lanostanes, ganoweberianic acids A-G (3-9), and three known compounds (10-12), were isolated from the artificially cultivated fruiting bodies of the basidiomycete Ganoderma weberianum. Ganoweberianone A (1) exhibited significant antimalarial activity against Plasmodium falciparum K1 (multidrug-resistant strain) with an IC50 value of 0.050 µM. A method for semisynthesis of 1 by condensation of the corresponding lanostane monomers and acid-catalyzed intramolecular transesterification was demonstrated.

Steroid sulfatase inhibiting lanostane triterpenes - Structure activity relationship and in silico insights.

Steroid sulfatase (STS) transforms hormone precursors into active steroids. Thus, it represents a target of intense research regarding hormone-dependent cancers. In this study, three ligand-based pharmacophore models were developed to identify STS inhibitors from natural sources. In a pharmacophore-based virtual screening of a curated molecular TCM database, lanostane-type triterpenes (LTTs) were predicted as STS ligands. Three traditionally used polypores rich in LTTs, i.e., Ganoderma lucidum Karst., Gloeophyllum odoratum Imazeki, and Fomitopsis pinicola Karst., were selected as starting materials. Based on eighteen thereof isolated LTTs a structure activity relationship for this compound class was established with piptolinic acid D (1), pinicolic acid B (2), and ganoderol A (3) being the most pronounced and first natural product STS inhibitors with IC50 values between 10 and 16 µM. Molecular docking studies proposed crucial ligand target interactions and a prediction tool for these natural compounds correlating with experimental findings.

Highly oxygenated lanostane triterpenoids from Ganoderma applanatum as a class of agents for inhibiting lipid accumulation in adipocytes.

Ganoderma triterpenoids (GTs), a class of major active constituents in Ganoderma species, play an important role in the anti-obesity effect of Ganoderma fungi. In the study, seventeen new highly oxygenated lanostane triterpenoids, ganoapplanoids A-Q (1-17), together with five previously reported compounds (18-22), were isolated from the fruiting bodies of Ganoderma applanatum. Their structures were confirmed by comprehensive spectroscopic analyses, single-crystal X-ray diffraction and Mo2(OAc)4 induced CD cotton effect. Structurally, compound 6 represents the first example of 2-norlanostane triterpenoid possessing an unusual semiacetal moiety. Furthermore, isolates (1-5, 7-11, 13-22, 3a) were evaluated for regulatory effects on lipid accumulation by 3T3-L1 adipocytes model. Among them, compounds 11 and 17 exhibited significant potency in blunted adipogenesis activities dose-dependently. Meanwhile, compounds 11 and 17 reduced triglyceride (TG) and total cholesterol (TC) levels in the adipocytes. These results supported that the highly oxygenated lanostane triterpenoids from G. applanatum may serve as agents for inhibiting the lipid accumulation in adipocytes and the G. applanatum provided an important source for searching new drugs to treat obesity.

Modified lanostane-type triterpenoids with neuroprotective effects from the fungus Inonotus obliquus.

Six undescribed lanostane triterpenoids (1-6), together with three known compounds (7-9) were isolated from Inonotus obliquus. Compounds 3-5 are the rare natural compounds featuring a 4,5-seco-lanostane core with a 5,7,9-trien-21,24-cyclopentane moiety. The structure elucidation of the compounds was conducted by spectroscopic techniques and the ECD method. The absolute configuration of compound 1 was confirmed by single-crystal X-ray diffraction analysis. All isolated compounds were assayed for their neuroprotective activity against H2O2-induced cell injury using human neuroblastoma SH-SY5Y cells. Compound 9 exhibited the most potent neuroprotective activity and the flow cytometry analysis indicated that 9 could protect SH-SY5Y cells from oxidative damage by inhibiting cell apoptosis.

Ganoderic acid A protects neural cells against NO stress injury in vitro via stimulating ß adrenergic receptors.

Excessive nitric oxide (NO) causes extensive damage to the nervous system, and the adrenergic system is disordered in many neuropsychiatric diseases. However, the role of the adrenergic system in protection of the nervous system against sodium nitroprusside (SNP) injury remains unclear. In this study, we investigated the effect of ganoderic acid A (GA A) against SNP injury in neural cells and the role of adrenergic receptors in GA A neuroprotection. We found that SNP (0.125-2 mM) dose-dependently decreased the viability of both SH-SY5Y and PC12 cells and markedly increased NO contents. Pretreatment with GA A (10 µM) significantly attenuated SNP-induced cytotoxicity and NO increase in SH-SY5Y cells, but not in PC12 cells. Furthermore, pretreatment with GA A caused significantly higher adrenaline content in SH-SY5Y cells than in PC12 cells. In order to elucidate the mechanism of GA A-protecting SH-SY5Y cells, we added adrenaline, phentolamine, metoprolol, or ICI 118551 1 h before GA A was added to the culture medium. We found that addition of adrenaline (10 µM) significantly improved GA A protection in PC12 cells. The addition of ß1-adrenergic receptor antagonist metoprolol (10 µM) or ß2-adrenergic receptor antagonist ICI 118551 (0.1 µM) blocked the protective effect of GA A, whereas the addition of α-adrenergic receptor antagonist phentolamine (0.1 µM) did not affect GA A protection in SH-SY5Y cells. These results suggest that ß-adrenergic receptors play an important role in the protection of GA A in SH-SY5Y cells against SNP injuries, and excessive adrenaline system activation caused great damage to the nervous system.

Lanostane Triterpenoids from the Fruiting Bodies of Fomes officinalis and Their Anti-Inflammatory Activities.

In the current study, further chemical investigation of the fruiting bodies of Fomes officinalis led to isolate seven new 24-methyl-lanostane triterpenoids, named officimalonic acids I-O (1-7). Their structures were elucidated based on the analysis of spectroscopic data (HR-MS, 1D and 2D NMR, UV, IR). Compounds 1-3 possessed an unusual C-23 spirostructure moiety, while compounds 4-7 had 23,26-lactone unit. Anti-inflammatory assay revealed that compounds 3 and 5 exhibited significant inhibitory activities against NO production in LPS-induced RAW 264.7 cells and cyclooxygenase (COX-2).

A Lanosteryl Triterpene (RA-3) Exhibits Antihyperuricemic and Nephroprotective Effects in Rats.

Considering the global health threat posed by kidney disease burden, a search for new nephroprotective drugs from our local flora could prove a powerful strategy to respond to this health threat. In this study we investigated the antihyperuricemic and nephroprotective potential of RA-3, a plant-derived lanosteryl triterpene. The antihyperuricemic and nephroprotective effect of RA-3 was investigated using the adenine and gentamicin induced hyperuricemic and nephrotoxicity rat model. Following the induction of hyperuricemia and nephrotoxicity, the experimental model rats (Sprague Dawley) were orally administered with RA-3 at 50 and 100 mg/kg body weight, respectively, daily for 14 days. Treatment of the experimental rats with RA-3, especially at 100 mg/kg, effectively lowered the serum renal dysfunction (blood urea nitrogen and creatinine) and hyperuricemic (uric acid and xanthine oxidase) biomarkers. These were accompanied by increased antioxidant status with decrease in malondialdehyde content. A much improved histomorphological structure of the kidney tissues was also observed in the triterpene treated groups when compared to the model control group. It is evident that RA-3 possesses the antihyperuricemic and nephroprotective properties, which could be vital for prevention and amelioration of kidney disease.

Endogenous sterol intermediates of the mevalonate pathway regulate HMGCR degradation and SREBP-2 processing.

Sterol-regulated HMG-CoA reductase (HMGCR) degradation and SREBP-2 cleavage are two major feedback regulatory mechanisms governing cholesterol biosynthesis. Reportedly, lanosterol selectively stimulates HMGCR degradation, and cholesterol is a specific regulator of SREBP-2 cleavage. However, it is unclear whether other endogenously generated sterols regulate these events. Here, we investigated the sterol intermediates from the mevalonate pathway of cholesterol biosynthesis using a CRISPR/Cas9-mediated genetic engineering approach. With a constructed HeLa cell line expressing the mevalonate transporter, we individually deleted genes encoding major enzymes in the mevalonate pathway, used lipidomics to measure sterol intermediates, and examined HMGCR and SREBP-2 statuses. We found that the C4-dimethylated sterol intermediates, including lanosterol, 24,25-dihydrolanosterol, follicular fluid meiosis activating sterol, testis meiosis activating sterol, and dihydro-testis meiosis activating sterol, were significantly upregulated upon mevalonate loading. These intermediates augmented both degradation of HMGCR and inhibition of SREBP-2 cleavage. The accumulated lanosterol induced rapid degradation of HMGCR, but did not inhibit SREBP-2 cleavage. The newly synthesized cholesterol from the mevalonate pathway is dispensable for inhibiting SREBP-2 cleavage. Together, these results suggest that lanosterol is a bona fide endogenous regulator that specifically promotes HMGCR degradation, and that other C4-dimethylated sterol intermediates may regulate both HMGCR degradation and SREBP-2 cleavage.

Separation and purification of lanosterol, dihydrolanosterol, and cholesterol from lanolin by high-performance counter-current chromatography dual-mode elution method.

Lanosterol is a potential drug for cataracts treatment, which can reverse the aggregation of intracrystalline proteins. The low concentration in lanolin calls for high-performance separation methods. In this study, a counter-current chromatography dual-mode elution method was developed for the first time to separate and purify lanosterol from hexane extract of lanolin after saponification, in which the column was first eluted with the lower phase as mobile phase in head-to-tail mode, followed by the upper phase in the tail-to-head mode. High purity of lanosterol, dihydrolanosterol, and cholesterol can be obtained simultaneously. A solvent system composed of n-heptane/acetonitrile/ethyl acetate (5:5:1, v/v/v) was selected and optimized via partition coefficient determination. Compounds such as 111 mg lanosterol, 84 mg dihydrolanosterol, and 183 mg cholesterol with high purity of 99.77, 95.71, and 91.43%, respectively, analyzed by high-performance liquid chromatography were obtained within 80 min from 700 mg crude extract from 1.78 g lanolin. The method was also used to improve the purity of commercial lanosterol product from 66.97 to above 99%. Counter-current chromatography could serve as a potential and powerful technique for commercial production of highly pure lanosterol.

A Genome-Centric Approach Reveals a Novel Glycosyltransferase from the GA A07 Strain of Bacillus thuringiensis Responsible for Catalyzing 15-O-Glycosylation of Ganoderic Acid A.

Strain GA A07 was identified as an intestinal Bacillus bacterium of zebrafish, which has high efficiency to biotransform the triterpenoid, ganoderic acid A (GAA), into GAA-15-O-ß-glucoside. To date, only two known enzymes (BsUGT398 and BsUGT489) of Bacillus subtilis ATCC 6633 strain can biotransform GAA. It is thus worthwhile to identify the responsible genes of strain GA A07 by whole genome sequencing. A complete genome of strain GA A07 was successfully assembled. A phylogenomic analysis revealed the species of the GA A07 strain to be Bacillus thuringiensis. Forty glycosyltransferase (GT) family genes were identified from the complete genome, among which three genes (FQZ25_16345, FQZ25_19840, and FQZ25_19010) were closely related to BsUGT398 and BsUGT489. Two of the three candidate genes, FQZ25_16345 and FQZ25_19010, were successfully cloned and expressed in a soluble form in Escherichia coli, and the corresponding proteins, BtGT_16345 and BtGT_19010, were purified for a biotransformation activity assay. An ultra-performance liquid chromatographic analysis further confirmed that only the purified BtGT_16345 had the key biotransformation activity of catalyzing GAA into GAA-15-O-ß-glucoside. The suitable conditions for this enzyme activity were pH 7.5, 10 mM of magnesium ions, and 30 °C. In addition, BtGT_16345 showed glycosylation activity toward seven flavonoids (apigenein, quercetein, naringenein, resveratrol, genistein, daidzein, and 8-hydroxydaidzein) and two triterpenoids (GAA and antcin K). A kinetic study showed that the catalytic efficiency (kcat/KM) of BtGT_16345 was not significantly different compared with either BsUGT398 or BsUGT489. In short, this study identified BtGT_16345 from B. thuringiensis GA A07 is the catalytic enzyme responsible for the 15-O-glycosylation of GAA and it was also regioselective toward triterpenoid substrates.

A New Triterpenoid Glucoside from a Novel Acidic Glycosylation of Ganoderic Acid A via Recombinant Glycosyltransferase of Bacillus subtilis.

Ganoderic acid A (GAA) is a bioactive triterpenoid isolated from the medicinal fungus Ganoderma lucidum. Our previous study showed that the Bacillus subtilis ATCC (American type culture collection) 6633 strain could biotransform GAA into compound (1), GAA-15-O-ß-glucoside, and compound (2). Even though we identified two glycosyltransferases (GT) to catalyze the synthesis of GAA-15-O-ß-glucoside, the chemical structure of compound (2) and its corresponding enzyme remain elusive. In the present study, we identified BsGT110, a GT from the same B. subtilis strain, for the biotransformation of GAA into compound (2) through acidic glycosylation. BsGT110 showed an optimal glycosylation activity toward GAA at pH 6 but lost most of its activity at pH 8. Through a scaled-up production, compound (2) was successfully isolated using preparative high-performance liquid chromatography and identified to be a new triterpenoid glucoside (GAA-26-O-ß-glucoside) by mass and nuclear magnetic resonance spectroscopy. The results of kinetic experiments showed that the turnover number (kcat) of BsGT110 toward GAA at pH 6 (kcat = 11.2 min-1) was 3-fold higher than that at pH 7 (kcat = 3.8 min-1), indicating that the glycosylation activity of BsGT110 toward GAA was more active at acidic pH 6. In short, we determined that BsGT110 is a unique GT that plays a role in the glycosylation of triterpenoid at the C-26 position under acidic conditions, but loses most of this activity under alkaline ones, suggesting that acidic solutions may enhance the catalytic activity of this and similar types of GTs toward triterpenoids.

Identification of key amino acid residues determining product specificity of 2,3-oxidosqualene cyclase in Oryza species.

Triterpene synthases, also known as 2,3-oxidosqualene cyclases (OSCs), synthesize diverse triterpene skeletons that form the basis of an array of functionally divergent steroids and triterpenoids. Tetracyclic and pentacyclic triterpene skeletons are synthesized via protosteryl and dammarenyl cations, respectively. The mechanism of conversion between two scaffolds is not well understood. Here, we report a promiscuous OSC from rice (Oryza sativa) (OsOS) that synthesizes a novel pentacyclic triterpene orysatinol as its main product. The OsOS gene is widely distributed in indica subspecies of cultivated rice and in wild rice accessions. Previously, we have characterized a different OSC, OsPS, a tetracyclic parkeol synthase found in japonica subspecies. Phylogenetic and protein structural analyses identified three key amino acid residues (#732, #365, #124) amongst 46 polymorphic sites that determine functional conversion between OsPS and OsOS, specifically, the chair-semi(chair)-chair and chair-boat-chair interconversions. The different orientation of a fourth amino acid residue Y257 was shown to be important for functional conversion The discovery of orysatinol unlocks a new path to triterpene diversity in nature. Our findings also reveal mechanistic insights into the cyclization of oxidosqualene into tetra- and pentacyclic skeletons, and provide a new strategy to identify key residues determining OSC specificity.

Preparative isolation of ganoderic acid S, ganoderic acid T and ganoderol B from Ganoderma lucidum mycelia by high-speed counter-current chromatography.

Ganoderic acid S, ganoderic acid T and ganoderal B are the main bioactive triterpenes of Ganoderma lucidum. In this study, mycelia of G. lucidum were obtained by two-stage fermentation and then extracted by ethanol and petroleum ether sequentially to obtain crude triterpenes. The crude sample was further purified by recycling high-speed counter-current chromatography with n-hexane-ethyl acetate-methanol-water (7:12:11:5, v/v/v/v) as the optimized two-phase solvent system. A 16.4 mg aliquot of ganoderol B with a purity of 90.4% was separated from 300 mg of the crude sample in a single run. After employing the recycling elution mode of HSCCC with n-hexane-ethyl acetate-methanol-water (6:10:8:4.5, v/v/v/v) for five cycles, 25.7 mg ganoderic acid T and 3.7 mg ganoderic acid S with purities of 97.8 and 83.0%, respectively, were obtained. The purities of three compounds were determined by high-performance liquid chromatography and their chemical structures were identified by NMR and MS data.

Synthesis of Lanostane-Type Triterpenoid N-Glycosides and Their Cytotoxicity against Human Cancer Cell Lines.

Seventeen lanostane-type triterpenoid derivatives (2 - 18), including 11N-glycosides (8 - 18), were synthesized from the natural triterpenoid, lanosterol (1), and were evaluated for their cytotoxicity against the human cancer cell lines, HL-60, A549, and MKN45, as well as the normal human lung cells, WI-38. Among them, N-ß-d-2-acetamido-2-deoxyglucoside (10) showed cytotoxicity against HL-60, A549, MKN45, and WI-38 cells (IC50 0.0078 - 2.8 µm). However, N-ß-d-galactoside (12) showed cytotoxicity against HL-60 and MKN45 cells (IC50 0.0021 - 4.0 µm), but not the normal WI-38 cells. Furthermore, Western blot analysis suggested that 12 induces apoptosis by activation of caspases-3, 8, and 9. These results will be useful for the synthesis of other tetracyclic triterpenoids or steroid N-glycosides to increase their cytotoxicity and apoptosis-inducing activities.