A tandem array of UDP-glycosyltransferases from the UGT73C subfamily glycosylate sapogenins, forming a spectrum of mono- and bisdesmosidic saponins

KEY MESSAGE

This study identifies six UGT73Cs all able to glucosylate sapogenins at positions 3 and/or 28 which demonstrates that B. vulgaris has a much richer arsenal of UGTs involved in saponin biosynthesis than initially anticipated. The wild cruciferous plant Barbarea vulgaris is resistant to some insects due to accumulation of two monodesmosidic triterpenoid saponins, oleanolic acid 3-O-β-cellobioside and hederagenin 3-O-β-cellobioside. Insect resistance depends on the structure of the sapogenin aglycone and the glycosylation pattern. The B. vulgaris saponin profile is complex with at least 49 saponin-like metabolites, derived from eight sapogenins and including up to five monosaccharide units. Two B. vulgaris UDP-glycosyltransferases, UGT73C11 and UGT73C13, O-glucosylate sapogenins at positions 3 and 28, forming mainly 3-O-β-D-glucosides. The aim of this study was to identify UGTs responsible for the diverse saponin oligoglycoside moieties observed in B. vulgaris. Twenty UGT genes from the insect resistant genotype were selected and heterologously expressed in Nicotiana benthamiana and/or Escherichia coli. The extracts were screened for their ability to glycosylate sapogenins (oleanolic acid, hederagenin), the hormone 24-epibrassinolide and sapogenin monoglucosides (hederagenin and oleanolic acid 3-O-β-D-glucosides). Six UGTs from the UGT73C subfamily were able to glucosylate both sapogenins and both monoglucosides at positions 3 and/or 28. Some UGTs formed bisdesmosidic saponins efficiently. At least four UGT73C genes were localized in a tandem array with UGT73C11 and possibly UGT73C13. This organization most likely reflects duplication events followed by sub- and neofunctionalization. Indeed, signs of positive selection on several amino acid sites were identified and modelled to be localized on the UGT protein surface. This tandem array is proposed to initiate higher order bisdesmosidic glycosylation of B. vulgaris saponins, leading to the recently discovered saponin structural diversity, however, not directly to known cellobiosidic saponins.

Pharmacogenomics of Chemically Distinct Classes of Keap1-Nrf2 Activators Identify Common and Unique Gene, Protein, and Pathway Responses In Vivo

The Kelch-like erythroid-associated protein 1 (Keap1)-NF-E2-related factor 2 (Nrf2) signaling pathway is the subject of several clinical trials evaluating the effects of Nrf2 activation on the prevention of cancer and diabetes and the treatment of chronic kidney disease and multiple sclerosis. 3H-1,2-dithiole-3-thione (D3T) and 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im) are representative members of two distinct series of Nrf2 chemical activators. Previous reports have described activator-specific effects on Nrf2-dependent gene regulation and physiologic outcomes. Here we used a robust chemical genomics approach to characterize expression profiles between D3T and CDDO-Im in livers from wild-type and Nrf2-null mice. At equally efficacious doses in wild-type mice, 406 genes show common RNA responses to both treatments. These genes enriched the Nrf2-regulated pathways of antioxidant defense and xenobiotic metabolism. In addition, 197 and 745 genes were regulated uniquely in response to either D3T or CDDO-Im, respectively. Functional analysis of the D3T-regulated set showed a significant enrichment of Nrf2-regulated enzymes involved in cholesterol biosynthesis. This result was supported by Nrf2-dependent increases in lanosterol synthase and CYP51 protein expression. CDDO-Im had no effect on cholesterol biosynthesis regardless of the dose tested. However, unlike D3T, CDDO-Im resulted in Nrf2-dependent elevation of peroxisome proliferator α and Kruppel-like factor 13, as well as the coactivator peroxisome proliferator γ coactivator 1β, together indicating regulation of β-oxidation and lipid metabolic pathways. These findings provide novel insights into the pharmacodynamic action of these two activators of Keap1-Nrf2 signaling. Although both compounds modify Keap1 to affect canonical cytoprotective gene expression, additional unique sets of Nrf2-dependent genes were regulated by each agent with enrichment of selective metabolic pathways.

Evaluation of seasonal changes of triterpenic acid contents in Viscum album from different host trees

CONTEXT

Viscum album L. (Loranthaceae) is a semi-parasitic plant used in pharmacy and medicine mostly for its hypotensive and anticancer activity. The effects may be related to the presence of triterpenic acids, such as betulinic (BA) and oleanolic (OA) acids.

OBJECTIVES

In our investigations the content of triterpenic acids in V. album from different host trees depending on the season of harvest was determined.

MATERIAL AND METHODS

V. album herb was dried and extracted with ethyl acetate using ultrasound energy. The reversed phase HPLC-PDA method was used for the analysis of triterpenic acids. The structure of the target components was confirmed by mass spectrometry with an electrospray ionization source.

RESULTS

Diversity in the content of both compounds was noted; however, OA was the dominant triterpenic acid and the amount thereof was ∼10 times higher than that of BA. The analysis of changes in the amount of triterpenic acids during the spring-winter period revealed the highest content of OA in summer (from 6.84 to 13.65 mg/g). In turn, in the other seasons of harvest, the content was in the range of 4.41-9.83, 6.41-9.56 and 5.59-12.16 mg/g for spring, autumn and winter, respectively. In most cases, a similar tendency was observed for BA.

DISCUSSION AND CONCLUSION

In most cases, the highest amount of the investigated compounds was found in summer; thus, this period seems to be optimal for acquisition of plant material rich in triterpenic acids.

In vitro inhibition of UGT1A3, UGT1A4 by ursolic acid and oleanolic acid and drug-drug interaction risk prediction

1. Ursolic acid (UA) and oleanolic acid (OA) may have important activity relevant to health and disease prevention. Thus, we studied the activity of UA and OA on UDP-glucuronosyltransferases (UGTs) and used trifluoperazine as a probe substrate to test UGT1A4 activity. Recombinant UGT-catalyzed 4-methylumbelliferone (4-MU) glucuronidation was used as a probe reaction for other UGT isoforms. 2. UA and OA inhibited UGT1A3 and UGT1A4 activity but did not inhibit other tested UGT isoforms. 3. UA-mediated inhibition of UGT1A3 catalyzed 4-MU-β-d-glucuronidation was via competitive inhibition (IC50 0.391 ± 0.013 μM; Ki 0.185 ± 0.015 μM). UA also competitively inhibited UGT1A4-mediated trifluoperazine-N-glucuronidation (IC50 2.651 ± 0.201 μM; Ki 1.334 ± 0.146 μM). 4. OA offered mixed inhibition of UGT1A3-mediated 4-MU-β-d-glucuronidation (IC50 0.336 ± 0.013 μM; Ki 0.176 ± 0.007 μM) and competitively inhibited UGT1A4-mediated trifluoperazine-N-glucuronidation (IC50 5.468 ± 0.697 μM; Ki 6.298 ± 0.891 μM). 5. Co-administering OA or UA with drugs or products that are substrates of UGT1A3 or UGT1A4 may produce drug-mediated side effects.

Antifungal activity of sterols and dipsacus saponins isolated from Dipsacus asper roots against phytopathogenic fungi

The in vivo antifungal activity of crude extracts of Dipsacus asper roots was evaluated against the phytopathogenic fungi Botrytis cinerea, Colletotrichum coccodes, Blumeria graminis f. sp. hordei, Magnaporthe grisea, Phytophthora infestans, Puccinia recondita and Rhizoctonia solani using a whole-plant assay method. Ethyl acetate and acetone extracts, at 1000μg/mL, suppressed the development of tomato gray mold (TGM) and tomato late blight (TLB) by 90%. Through bioassay-guided isolation, five antifungal substances were isolated from the D. asper roots and identified as β-sitosterol (1), campesterol (2), stigmasterol (3), cauloside A (4) and a novel dipsacus saponin, named colchiside (3-O-β-d-xylopyranosyl-23-O-β-d-glucopyranosyl-28-O-β-d-(6-O-acetyl)-glucopyranosyl hederagenin) (5). Of those, cauloside A (4) displayed the greatest antifungal efficacy against rice blast, TGM and TLB. Colchiside (5) moderately suppressed the development of TLB, but exhibited little effect against the other diseases. The synergistic effects of the isolated compounds against TLB were also assessed. Synergistic and additive interactions were observed between several of the sterol compounds. This study indicated that the crude extracts of, and bioactive substances from, the roots of D. asper suppress TGM and TLB. In addition, cauloside A (4) and colchiside (5) could be used as antifungal lead compounds.

Soyasapogenol B and Genistein Attenuate Lipopolysaccharide-Induced Memory Impairment in Mice by the Modulation of NF-κB-Mediated BDNF Expression

Lactobacillus plantarum C29-fermented defatted soybean (FDS), which contains soyasaponins such as soyasaponin I (SI) and soyasapogenol B (SB) and isoflavones such as genistin (GE) and genistein (GT), attenuated memory impairment in mice. Moreover, in the preliminary study, FDS and its soyasaponins and isoflavones significantly inhibited NF-κB activation in LPS-stimulated microglial BV2 cells. Therefore, we examined the effects of FDS and its constituents SI, SB, GT, and GE on LPS-induced memory impairment in mice. Oral administration of FDS (80 mg/kg), which has higher concentrations of SB and GE than DS, recovered LPS-impaired cognitive function in Y-maze (55.1 ± 3.5%) and passive avoidance tasks (50.9 ± 19.2 s) to 129.2% (74.1 ± 3.5%) and 114.2% (290.0 ± 22.4 s) of normal mice, respectively (P < 0.05). SB and GE (10 μM) also more potently attenuated LPS-impaired cognitive behavior than SI and GT, respectively. SB (10 mg/kg) was the most effective: treatment recovered LPS-impaired spontaneous alternation and latency time to 105.7% and 126.8% of normal control mice, respectively (P < 0.05). SB and GE significantly increased BDNF expression and CREB phosphorylation in LPS-treated mice and corticosterone-stimulated SH-SY5Y cells. Furthermore, SB and GE (10 μM) also significantly inhibited NF-κB activation in LPS-treated mice. These findings suggested that FDS and its constituent soyasaponins and isoflavones may attenuate memory impairment by the regulation of NF-κB-mediated BDNF expression.

Oleanolic acid and ursolic acid as potential inhibitors of human salivary α-amylase: insights from in vitro assays and in silico simulations

It is known that inhibiting α-amylase, an important enzyme in digestion of starch and glycogen, is a useful strategy for treating disorders in carbohydrate uptake. Two natural components distributed in many fruits and plants, oleanolic acid and ursolic acid, are endowed with important pharmacological activities and wide therapeutic possibilities. Until now, only a tiny fraction of their applications have been identified and exploited. Our in vitro inhibition studies demonstrated that oleanolic acid and ursolic acid non-competitively inhibit the activity and function of human salivary α-amylase. The molecular simulations revealed that oleanolic acid and ursolic acid interact with amino acid residues within the binding pocket of human salivary α-amylase, among which the side chain of Arg195 and Asp 197 was supposed to be important in imparting the inhibitory activity of triterpenoids. The present work will provide meaningful information for future development of functional drugs for the treatment of disorders in carbohydrate metabolism. Graphical abstract This work is valuable for providing a deeper insight into the interaction mechanism of oleanolic acid and ursolic acid with α-amylase.

Two CYP716A subfamily cytochrome P450 monooxygenases of sweet basil play similar but nonredundant roles in ursane- and oleanane-type pentacyclic triterpene biosynthesis

The medicinal plant sweet basil (Ocimum basilicum) accumulates bioactive ursane- and oleanane-type pentacyclic triterpenes (PCTs), ursolic acid and oleanolic acid, respectively, in a spatio-temporal manner; however, the biosynthetic enzymes and their contributions towards PCT biosynthesis remain to be elucidated. Two CYP716A subfamily cytochrome P450 monooxygenases (CYP716A252 and CYP716A253) are identified from a methyl jasmonate-responsive expression sequence tag collection and functionally characterized, employing yeast (Saccharomyces cerevisiae) expression platform and adapting virus-induced gene silencing (VIGS) in sweet basil. CYP716A252 and CYP716A253 catalyzed sequential three-step oxidation at the C-28 position of α-amyrin and β-amyrin to produce ursolic acid and oleanolic acid, respectively. Although CYP716A253 was more efficient than CYP716A252 for amyrin C-28 oxidation in yeast, VIGS revealed essential roles for both of these CYP716As in constitutive biosynthesis of ursolic acid and oleanolic acid in sweet basil leaves. However, CYP716A253 played a major role in elicitor-induced biosynthesis of ursolic acid and oleanolic acid. Overall, the results suggest similar as well as distinct roles of CYP716A252 and CYP716A253 for the spatio-temporal biosynthesis of PCTs. CYP716A252 and CYP716A253 might be useful for the alternative and sustainable production of PCTs in microbial host, besides increasing plant metabolite content through genetic modification.

Induction of intrinsic apoptosis in leukaemia stem cells and in vivo zebrafish model by betulonic acid isolated from Walsura pinnata Hassk (Meliaceae)

BACKGROUND

Leukaemia stem cells (LSC) have been associated with disease relapse and chemotherapy resistance. Betulonic acid (BA), a pentacyclic lupane-type triterpenoid, was reported to exhibit cytotoxicity toward various cancer cells and to be capable of inducing intrinsic apoptosis in solid tumours. However, the in vitro and in vivo apoptotic effects of BA against LSC remain unknown.

HYPOTHESIS/PURPOSE

We aimed to determine whether BA isolated from bark of Walsura pinnata Hassk (Meliaceae) has pro-apoptotic effects on LSC in in vitro and in vivo models.

STUDY DESIGN/METHODS

The population of high purity LSC was isolated from the Kasumi-1 cell line using magnetic sorting and characterised by flow cytometry. Cell viability was assessed using the MTS assay to examine dose- and time-dependent effects. The colony formation assay was performed in MethoCult® H4435 enriched media. Apoptosis was analysed using Annexin-V and propidium iodide staining, mitochondrial transmembrane potential was studied using JC-1 staining, and expression of apoptosis related genes (BAX, Bcl-2 and survivin) was evaluated by real time-polymerase chain reaction (RT-PCR). Caspase 3/7 and 9 activities were monitored through Promega Caspase-Glo® over a period of 24h. The in vivo antileukaemia activity was evaluated using LSC xenotransplanted zebrafish, observed for DNA fragmentation from apoptosis by TUNEL assay.

RESULTS

BA maintained its potency against the LSC population in comparison to parental Kasumi-1 cells (fold differences ≤ 1.94) over various treatment time points and significantly inhibited the formation of colonies by LSC. Apoptosis was triggered by BA through the upregulation of BAX and suppression of Bcl-2 and survivin genes with the loss of mitochondrial transmembrane potential, leading to the activation of caspase 9 followed by downstream caspase 3/7. BA was able to suppressed leukaemia formation and induced apoptosis in LSC xenotransplanted zebrafish.

CONCLUSIONS

The results demonstrate that BA inhibited the proliferative and colonogenic properties of LSC. BA induced apoptosis in LSC through the mitochondria pathway and was effective in the in vivo zebrafish model. Therefore, BA could be a lead compound for further development into a chemotherapy agent against LSC.

β-Amyrin synthase (EsBAS) and β-amyrin 28-oxidase (CYP716A244) in oleanane-type triterpene saponin biosynthesis in Eleutherococcus senticosus

Siberian ginseng (Eleutherococcus senticosus) is a woody medical shrub belonging to the Araliaceae family. E. senticosus contains various types of saponins, including oleanane, noroleanane, lupane, and 3,4-secolupane types, depending on the aglycone structure. Oleanane-type triterpenes are the major saponin components in E. senticosus. Two enzymes (β-amyrin synthase and β-amyrin 28-oxidase) are essential for oleanane-type saponin biosynthesis from 2,3-oxidosqualene. In the present study, two full-length cDNAs encoding EsBAS and CYP716A244 were isolated based on transcriptomics analysis of plant leaves. Both β-amyrin synthase (EsBAS) and β-amyrin 28-oxidase (CYP716A244), isolated from E. senticosus, were functionally characterised. β-amyrin production was confirmed by heterologous expression of the EsBAS gene in yeast and tobacco. Oleanolic acid production was confirmed by co-expression of both EsBAS and CYP716A244 in engineered yeast and transgenic tobacco.

Comparison of the interaction between lactoferrin and isomeric drugs

The binding properties of pentacyclic triterpenoid isomeric drugs, i.e. ursolic acid (UA) and oleanolic acid (OA), to bovine lactoferrin (BLF) have been studied by molecule modeling, fluorescence spectroscopy, UV-visible absorbance spectroscopy and infrared spectroscopy (IR). Molecular docking, performed to reveal the possible binding mode or mechanism, suggested that hydrophobic interaction and hydrogen bonding play important roles to stabilize the complex. The results of spectroscopic measurements showed that the two isomeric drugs both strongly quenched the intrinsic fluorescence of BLF through a static quenching procedure although some differences between UA and OA binding strength and non-radiation energy transfer occurred within the molecules. The number of binding sites was 3.44 and 3.10 for UA and OA, respectively, and the efficiency of Förster energy transfer provided a distance of 0.77 and 1.21nm for UA and OA, respectively. The conformation transformation of BLF affected by the drugs conformed to the "all-or-none" pattern. In addition, the changes of the ratios of α-helices, β-sheets and β-turns of BLF during the process of the interaction were obtained. The results of the experiments in combination with the calculations showed that there are two modes of pentacyclic triterpenoid binding to BLF instead of one binding mode only governed by the principle of the lowest bonding energy.

Metabolic switching of astringent and beneficial triterpenoid saponins in soybean is achieved by a loss-of-function mutation in cytochrome P450 72A69

Triterpenoid saponins are major components of secondary metabolites in soybean seeds and are divided into two groups: group A saponins, and 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP) saponins. The aglycone moiety of group A saponins consists of soyasapogenol A (SA), which is an oxidized β-amyrin product, and the aglycone moiety of the DDMP saponins consists of soyasapogenol B (SB). Group A saponins produce a bitter and astringent aftertaste in soy products, whereas DDMP saponins have known health benefits for humans. We completed map-based cloning and characterization of the gene Sg-5, which is responsible for SA biosynthesis. The naturally occurring sg-5 mutant lacks group A saponins and has a loss-of-function mutation (L164*) in Glyma15g39090, which encodes the cytochrome P450 enzyme, CYP72A69. An enzyme assay indicated the hydroxylase activity of recombinant CYP72A69 against SB, which also suggested the production of SA. Additionally, induced Glyma15g39090 mutants (R44* or S348P) lacked group A saponins similar to the sg-5 mutant, indicating that Glyma15g39090 corresponds to Sg-5. Endogenous levels of DDMP saponins were higher in the sg-5 mutant than in the wild-type lines due to the loss of the enzyme activity that converts SB to SA. Interestingly, the genomes of palaeopolyploid soybean and the closely related common bean carry multiple Sg-5 paralogs in a genomic region syntenic to the soybean Sg-5 region. However, SA did not accumulate in common bean samples, suggesting that Sg-5 activity evolved after gene duplication event(s). Our results demonstrate that metabolic switching of undesirable saponins with beneficial saponins can be achieved in soybean by disabling Sg-5.

β-Amyrin synthase from Euphorbia tirucalli L. functional analyses of the highly conserved aromatic residues Phe413, Tyr259 and Trp257 disclose the importance of the appropriate steric bulk, and cation-π and CH-π interactions for the efficient catalytic action of the polyolefin cyclization cascade

Many of the functions of the active site residues in β-amyrin synthase and its catalytic mechanism remain unclear. Herein, we examined the functions of the highly conserved Phe413, Tyr259, and Trp257 residues in the β-amyrin synthase of Euphorbia tirucalli. The site-specific mutants F413V and F413M [corrected] showed nearly the same enzymatic activities as the wild type, indicating that π-electrons are not needed for the catalytic reaction. However, the F413A [corrected] mutant yielded a large amount of the tetracyclic dammarane skeleton, with decreased production of β-amyrin. This indicates that the Phe413 [corrected] residue is located near the D-ring formation site and works to position the oxidosqualene substrate correctly within the reaction cavity. On the other hand, the major catalysis-related function of the Tyr259 and Trp257 residues is to yield their π-electrons to the cationic intermediates. The Y259F variant showed nearly equivalent activity to that of the wild type, but aliphatic mutants such as the Ala, Val, and Leu variants showed significantly decreased the activity and yielded the tetracyclic dammarane scaffold, strongly demonstrating that the Tyr259 residue stabilizes the baccharenyl secondary cation via cation-π interaction. The aliphatic variants of Trp257 exhibited remarkably decreased enzymatic activity, and lupeol was produced in a high production ratio, indicating that Trp257 stabilizes the oleanyl cation via cation-π interaction. The aromatic Phe and Tyr mutants exhibited high activities owing to their more increased π-electron density relative to that of the aliphatic mutants, but lupeol was produced in a significantly high yield besides β-amyrin. The Trp residue is likely to be responsible for the robust binding of Me-30 through CH-π interaction. The decreased π-electron density of the Phe and Tyr mutants compared to that of Trp would have resulted in the high production of lupeol.

Optimization of methyl jasmonate and β-cyclodextrin for enhanced production of taraxerol and taraxasterol in (Taraxacum officinale Weber) cultures

CONTEXT

Taraxacum officinale Weber (TO) commonly known as "dandelion", is a tropical Asian medicinal plant which contains taraxasterol (TX) and taraxerol (TA) in its roots, which are reported to be commercially important anticancer compounds.

OBJECTIVE

The main objective of the present study was to evaluate the increase in yield of TX and TA through elicitation by addition of abiotic elictors like methyl jasmonate (MJ) and β-cyclodextrin (CD), to the root callus suspension cultures of TO.

MATERIALS AND METHODS

The root callus suspension was maintained on Murashige and Skoog's (MS) medium MS + IAA + BA + 2, 4-D (0.5 ppm + 1 ppm + 0.5 ppm). The concentrations of the abiotic elicitors MJ and CD were optimized using central composite design (CCD) and quantification of TA and TX in elicited cultures was done by High Performance Liquid Chromatography (HPLC) analysis.

RESULT

It was observed that MJ at a concentration of 0.2 mM showed good increase in content of TX to 0.032% w/w and at concentrations 0.05 mM, 0.1 mM and 0.2 mM showed similar increase in TA content to 0.018% w/w, whereas CD at the concentration of 25 mM showed highest increase in TX content to 0.036% w/w and at the concentrations of 25 mM, 50 mM showed increase in TA content to 0.023% w/w as compared to the plant root (PR) which showed content of TX as 0.0299% w/w and TA as 0.0169% w/w.

DISCUSSION AND CONCLUSION

From the present investigation it was concluded that out of the two abiotic elicitors MJ and CD, CD was found to be more effective to increase TA and TX content in Dandelion cell cultures.

Factors affecting the content of the ursolic and oleanolic acid in apple peel: influence of cultivars, sun exposure, storage conditions, bruising and Penicillium expansum infection

BACKGROUND

For health promotion and as part of natural plant protection, it might be of interest to increase the content of oleanolic acid (OA) and ursolic acid (UA) by biofortification in breeding programs, although the extent of the influence of genetic and environmental factors needs to be clarified. The objective of this study was to determine the effect of cultivar, sun exposure, storage, bruising and fungal infection on the OA and UA content in apple peel.

RESULTS

Three apple cultivars with different ripening times--'Discovery' (early), 'Aroma' (middle) and 'Gloster' (late)--were investigated. The content of OA and UA was mainly influenced by cultivar and side subjected to sun exposure, and to a minor extent by storage and seasonal year. 'Gloster' had the highest OA and UA content of the investigated cultivars. OA and UA content on the shaded side was higher than that on the sun-exposed side in all three cultivars. Inoculation with Penicillium expansum did not have any consistent effect on OA or UA, except in a few cases where the levels decreased.

CONCLUSION

OA and UA content can be increased by choice of cultivar in the breeding process and to some extent by cultural practice.

Ultrasensitive Time-Resolved Fluoroimmunoassay for Saikosaponin a in Chaihu (Bupleuri Radix)

The aim of this study is to establish a time-resolved fluoroimmunoassay (TRFIA) system for quantitative analysis of saikosaponin a (SSa) in the crude drug of Chaihu (Bupleuri Radix). A 96-well microplate coated with rabbit anti-mouse IgG was incubated with the methanol extracts of Chaihu samples and a mouse anti-SSa monoclonal antibody, and a Eu3+-labeled SSa-human serum albumin conjugate was used as the tracer. The established competitive TRFIA showed a good fourth order polynomial fitting from 0.01 to 10.0 μg/mL for standard SSa sample with a detection limit of 0.006 μg/mL. The intra- and inter-assay coefficients of variation of the assay were 7.3% and 8.9%, respectively, and the average SSa recovery was 119.2%. For samples of Chaihu extract, the results of this assay showed a good correlation with those by enzyme-linked immunosorbent assay established previously. This TRFIA system is ultrasensitive for detecting SSa with a wide detection range and a good stability and represents the first attempt of using TRFIA for quality evaluation of the crude drug of Chaihu.

Identification and genome organization of saponin pathway genes from a wild crucifer, and their use for transient production of saponins in Nicotiana benthamiana

The ability to evolve novel metabolites has been instrumental for the defence of plants against antagonists. A few species in the Barbarea genus are the only crucifers known to produce saponins, some of which make plants resistant to specialist herbivores, like Plutella xylostella, the diamondback moth. Genetic mapping in Barbarea vulgaris revealed that genes for saponin biosynthesis are not clustered but are located in different linkage groups. Using co-location with quantitative trait loci (QTLs) for resistance, transcriptome and genome sequences, we identified two 2,3-oxidosqualene cyclases that form the major triterpenoid backbones. LUP2 mainly produces lupeol, and is preferentially expressed in insect-susceptible B. vulgaris plants, whereas LUP5 produces β-amyrin and α-amyrin, and is preferentially expressed in resistant plants; β-amyrin is the backbone for the resistance-conferring saponins in Barbarea. Two loci for cytochromes P450, predicted to add functional groups to the saponin backbone, were identified: CYP72As co-localized with insect resistance, whereas CYP716As did not. When B. vulgaris sapogenin biosynthesis genes were transiently expressed by CPMV-HT technology in Nicotiana benthamiana, high levels of hydroxylated and carboxylated triterpenoid structures accumulated, including oleanolic acid, which is a precursor of the major resistance-conferring saponins. When the B. vulgaris gene for sapogenin 3-O-glucosylation was co-expressed, the insect deterrent 3-O-oleanolic acid monoglucoside accumulated, as well as triterpene structures with up to six hexoses, demonstrating that N. benthamiana further decorates the monoglucosides. We argue that saponin biosynthesis in the Barbarea genus evolved by a neofunctionalized glucosyl transferase, whereas the difference between resistant and susceptible B. vulgaris chemotypes evolved by different expression of oxidosqualene cyclases (OSCs).

CYP72A67 Catalyzes a Key Oxidative Step in Medicago truncatula Hemolytic Saponin Biosynthesis

In the Medicago genus, triterpenic saponins are bioactive secondary metabolites constitutively synthesized in the aerial and subterranean parts of plants via the isoprenoid pathway. Exploitation of saponins as pharmaceutics, agrochemicals and in the food and cosmetic industries has raised interest in identifying the enzymes involved in their synthesis. We have identified a cytochrome P450 (CYP72A67) involved in hemolytic sapogenin biosynthesis by a reverse genetic TILLING approach in a Medicago truncatula ethylmethanesulfonate (EMS) mutagenized collection. Genetic and biochemical analyses, mutant complementation, and expression of the gene in a microsome yeast system showed that CYP72A67 is responsible for hydroxylation at the C-2 position downstream of oleanolic acid synthesis. The affinity of CYP72A67 for substrates with different substitutions at multiple carbon positions was investigated in the same in vitro yeast system, and in relation to two other CYP450s (CYP72A68) responsible for the production of medicagenic acid, the main sapogenin in M. truncatula leaves and roots. Full sib mutant and wild-type plants were compared for their sapogenin profile, expression patterns of the genes involved in sapogenin synthesis, and response to inoculation with Sinorhizobium meliloti. The results obtained allowed us to revise the hemolytic sapogenin pathway in M. truncatula and contribute to highlighting the tissue specificities (leaves/roots) of sapogenin synthesis.

Biotransformation of oleanolic and maslinic methyl esters by Rhizomucor miehei CECT 2749

The pentacyclic triterpenoids methyl oleanolate, methyl maslinate, methyl 3β-hydroxyolean-9(11),12-dien-28-oate, and methyl 2α,3β-dihydroxy-12β,13β-epoxyolean-28-oate were biotransformed by Rhizomucor miehei CECT 2749. Microbial transformation of methyl oleanolate produced only a 7β,30-dihydroxylated metabolite with a conjugated 9(11),12-diene system in the C ring. Biotransformation of the substrate with this 9(11),12-diene system gave the same 7β,30-dihydroxylated compound together with a 7β,15α,30-trihydroxyl derivative. The action of this fungus (R. miehei) on methyl maslinate was more varied, isolating metabolites with a 30-hydroxyl group, a 9(11),12-diene system, an 11-oxo group, or an 12-oxo group. Microbial transformation of the substrate with a 12β,13β-epoxy function resulted in the isolation of two metabolites with 12-oxo and 28,13β-olide groups, hydroxylated or not at C-7β, together with a 30-hydroxy-12-oxo derivative. The structures of these derivatives were deduced by extensive and rigorous spectroscopic studies.

Genome-scale transcriptome analysis in response to nitric oxide in birch cells: implications of the triterpene biosynthetic pathway

Evidence supporting nitric oxide (NO) as a mediator of plant biochemistry continues to grow, but its functions at the molecular level remains poorly understood and, in some cases, controversial. To study the role of NO at the transcriptional level in Betula platyphylla cells, we conducted a genome-scale transcriptome analysis of these cells. The transcriptome of untreated birch cells and those treated by sodium nitroprusside (SNP) were analyzed using the Solexa sequencing. Data were collected by sequencing cDNA libraries of birch cells, which had a long period to adapt to the suspension culture conditions before SNP-treated cells and untreated cells were sampled. Among the 34,100 UniGenes detected, BLASTX search revealed that 20,631 genes showed significant (E-values≤10-5) sequence similarity with proteins from the NR-database. Numerous expressed sequence tags (i.e., 1374) were identified as differentially expressed between the 12 h SNP-treated cells and control cells samples: 403 up-regulated and 971 down-regulated. From this, we specifically examined a core set of NO-related transcripts. The altered expression levels of several transcripts, as determined by transcriptome analysis, was confirmed by qRT-PCR. The results of transcriptome analysis, gene expression quantification, the content of triterpenoid and activities of defensive enzymes elucidated NO has a significant effect on many processes including triterpenoid production, carbohydrate metabolism and cell wall biosynthesis.

Comparative analysis of CYP93E proteins for improved microbial synthesis of plant triterpenoids

Cytochrome P450-dependent monooxygenases (P450s) belonging to the CYP93E subfamily catalyze the C-24 oxidation of the triterpene backbone during the biosynthesis of triterpenoid saponins, which are bioactive plant natural products. In our attempts to produce plant triterpenoids in the yeast Saccharomyces cerevisiae, we observed a poor in vivo catalytic efficiency of the Medicago truncatula CYP93E2. To overcome this biosynthetic bottleneck, we screened publicly available plant genome and transcriptome data for CYP93E subfamily members. Six CYP93E orthologs, exclusively from leguminous plant species, were identified and functionally characterized in S. cerevisiae. Despite the high degree of amino acid conservation, the CYP93E orthologs showed large variations in enzymatic efficiency in yeast. The CYP93E9 from Phaseolus vulgaris showed the highest activity and converted ∼80% of the accumulating in vivo produced substrate β-amyrin to the products olean-12-ene-3β,24-diol and probable 3β-hydroxy olean-12-en-24-oic acid, with a catalytic efficiency that was 61 times higher than that of the M. truncatula CYP93E2. In conclusion, we have expanded the list of functional CYP93E orthologs to a total of nine proteins and show that there are large variations in their catalytic efficiencies when expressed in a heterologous host. Although demonstrated here for the CYP93E family involved in triterpenoid saponin biosynthesis, this phenomenon is undoubtedly extendable to other enzyme families involved in natural product synthesis. Hence, screening for homologous enzymes may become a valuable synthetic biologist's tool for engineering superior production chassis.

[Effect of combined application of zinc, boron and molybdenum on yield and saikosaponin a, saikosaponin d contents of Bupleurum chinense]

This research use "3414" fertilizer effect experiments to handle zinc, boron and molybdenum trace element fertilizer, determined the dry matter accumulation and content of saikosaponion a and d, to investigate the different ratio of zinc, boron and molybdenum on yield and saikosaponin a, saikosaponin d contents of Bupleurum chinense. Found The suitable ratio of zinc, boron and molybdenum play an active role on dry matter accumulation and distribution, the treatment Zn2B2Mo3 is the best one to promote the dry matter accumulation and transfer to the underground part; in a certain range, only use zinc or molybdenum can promote the yield of B. chinense, the yield of treatment Zn2B2Mo1 is the highest one. According to the results of regression analysis: in accordance with Zn 48.45 g x hm(-2), B 355.05 g x hm(-2), Mo 86.40 g x hm(-2), can obtain the yield with 3313.05 kg x hm(-2); the treatment Zn2BMo2 is most effective to promote the total saikosaponin a and d accumulated, according to the results of regression analysis: in accordance with Zn 36.15 g x hm(-2), B 343.05 g x hm(-2), Mo 106.35 g x hm(-2), the content of total saikosaponin a and d can reach 1.23%. This research first discovered the suitable ratio of zinc, boron and molybdenum can promote the yield and saikosaponin a, saikosaponin d contents on B. chinense.

The molecular mechanisms underpinning the therapeutic properties of oleanolic acid, its isomer and derivatives for type 2 diabetes and associated complications

Recent research has uncovered the molecular mechanisms responsible for the therapeutic properties of oleanolic acid (OA), its isomer ursolic acid (UA), and derivatives. In particular, recent reports have highlighted the benefits of these compounds in the prevention and treatment of type 2 diabetes and associated life-threatening complications, such as nonalcoholic fatty liver disease, nephropathy, retinopathy, and atherosclerosis. The prevalence of type 2 diabetes is of major concern since it is reaching global epidemic levels. Treatments targeting the signaling pathways altered in type 2 diabetes are being actively investigated, and OA and UA in natural and derivative forms are potential candidates to modulate these pathways. We will explore the findings from in vitro and in vivo studies showing that these compounds: (i) improve insulin signaling and reduce hyperglycemia; (ii) reduce oxidative stress by upregulating anti-oxidants and; (iii) reduce inflammation by inhibiting proinflammatory signaling. We will discuss the molecular mechanisms underpinning these therapeutic properties in this review in order to provide a rationale for the future use of OA, UA, and their derivatives for the prevention and treatment of type 2 diabetes and associated comorbidities.

Investigation of triterpene synthesis and regulation in oats reveals a role for β-amyrin in determining root epidermal cell patterning

Sterols have important functions in membranes and signaling. Plant sterols are synthesized via the isoprenoid pathway by cyclization of 2,3-oxidosqualene to cycloartenol. Plants also convert 2,3-oxidosqualene to other sterol-like cyclization products, including the simple triterpene β-amyrin. The function of β-amyrin per se is unknown, but this molecule can serve as an intermediate in the synthesis of more complex triterpene glycosides associated with plant defense. β-Amyrin is present at low levels in the roots of diploid oat (Avena strigosa). Oat roots also synthesize the β-amyrin-derived triterpene glycoside avenacin A-1, which provides protection against soil-borne diseases. The genes for the early steps in avenacin A-1 synthesis [saponin-deficient 1 and 2 (Sad1 and Sad2)] have been recruited from the sterol pathway by gene duplication and neofunctionalization. Here we show that Sad1 and Sad2 are regulated by an ancient root developmental process that is conserved across diverse species. Sad1 promoter activity is dependent on an L1 box motif, implicating sterol/lipid-binding class IV homeodomain leucine zipper transcription factors as potential regulators. The metabolism of β-amyrin is blocked in sad2 mutants, which therefore accumulate abnormally high levels of this triterpene. The accumulation of elevated levels of β-amyrin in these mutants triggers a "superhairy" root phenotype. Importantly, this effect is manifested very early in the establishment of the root epidermis, causing a greater proportion of epidermal cells to be specified as root hair cells rather than nonhair cells. Together these findings suggest that simple triterpenes may have widespread and as yet largely unrecognized functions in plant growth and development.

Investigation of triterpene synthesis and regulation in oats reveals a role for β-amyrin in determining root epidermal cell patterning

Sterols have important functions in membranes and signaling. Plant sterols are synthesized via the isoprenoid pathway by cyclization of 2,3-oxidosqualene to cycloartenol. Plants also convert 2,3-oxidosqualene to other sterol-like cyclization products, including the simple triterpene β-amyrin. The function of β-amyrin per se is unknown, but this molecule can serve as an intermediate in the synthesis of more complex triterpene glycosides associated with plant defense. β-Amyrin is present at low levels in the roots of diploid oat (Avena strigosa). Oat roots also synthesize the β-amyrin-derived triterpene glycoside avenacin A-1, which provides protection against soil-borne diseases. The genes for the early steps in avenacin A-1 synthesis [saponin-deficient 1 and 2 (Sad1 and Sad2)] have been recruited from the sterol pathway by gene duplication and neofunctionalization. Here we show that Sad1 and Sad2 are regulated by an ancient root developmental process that is conserved across diverse species. Sad1 promoter activity is dependent on an L1 box motif, implicating sterol/lipid-binding class IV homeodomain leucine zipper transcription factors as potential regulators. The metabolism of β-amyrin is blocked in sad2 mutants, which therefore accumulate abnormally high levels of this triterpene. The accumulation of elevated levels of β-amyrin in these mutants triggers a "superhairy" root phenotype. Importantly, this effect is manifested very early in the establishment of the root epidermis, causing a greater proportion of epidermal cells to be specified as root hair cells rather than nonhair cells. Together these findings suggest that simple triterpenes may have widespread and as yet largely unrecognized functions in plant growth and development.

Secondary Metabolite Content in Fabiana imbricata Plants and in vitro Cultures

A rapid in vitro propagation system leading to the formation of shoots, calli, roots, cell suspensions and plantlets was developed for the Andean medicinal plant Fabiana imbricata (Solanaceae). Massive propagation of shoots and roots was achieved by the temporary immersion system (TIS), morphogenesis and maintenance of cell suspensions by standard in vitro culture techniques. Oleanolic acid (OA), rutin, chlorogenic acid (CA) and scopoletin content in aerial parts of wild growing Fabiana imbricata plants as well as in plantlets regenerated in vitro, callus cultures, cell suspensions and biomass, obtained by the TIS system was assessed by HPLC.

On a dry weight basis, the OA content in the aerial parts of the plant ranged between 2.26 and 3.47% while in vitro plantlets, callus and root cultures presented values ranging from not detected up to 0.14%. The rutin content of the samples presented a similar trend with maxima between 0.99 and 3.35% for the aerial parts of the plants to 0.02 to 0.20% for plantlets, 0.12% for cell suspensions and 0.28% for callus. Rutin was not detected in the roots grown by the TIS principle. The CA and scopoletin content in the aerial parts of F. imbricata ranged between 0.22-1.15 and < 0.01-0.55%, respectively. In the plantlets, the concentration of CA was 0.29 to 1.48% with scopoletin in the range 0.09 to 0.64% while in the callus sample, the CA and scopoletin content were 0.46 and 0.66%, respectively. A very different result was found in roots grown by TIS, where both OA and rutin were not detected and its main secondary metabolite, scopoletin was found between a range of 0.99 and 1.41% with CA between of 0.11 and 0.42%.

Hydroxylation of Oleanolic Acid to Queretaroic Acid by Cytochrome P450 fromNonomuraea recticatena

A gene for cytochrome P450 (moxA) from Nonomuraea recticatena, coexpressed with camAB for pseudomonad redox partners in Escherichia coli, hydroxylated oleanolic acid to produce queretaroic acid. When we used the P450-induced whole-cell as a catalyst, only a small amount of queretaroic acid was produced, probably due to poor permeability of oleanolic acid into the E. coli cell. In an alternative approach with the cell-free reaction system, the conversion ratio increased up to 17%.

Cloning and Characterization of Saponin Hydrolases fromAspergillus oryzaeandEupenicillium brefeldianum

We purified saponin hydrolases from Aspergillus oryzae PF1224 and Eupenicillium brefeldianum PF1226. It was confirmed that the enzymes from A. oryzae PF1224 (Sda1) and E. brefeldianum PF1226 (Sde1) are glycoproteins with molecular masses of 82 and 90 kDa respectively. The deduced amino acid sequences of each enzyme from the cloned genes (sda1 or sde1) showed approximately 50% homology with that of the saponin hydrolase Sdn1 from Neocosmospora vasinfecta var. vasinfecta PF1225 (DDBJ accession no. AB110615). When sda1 and sde1 were expressed in the host Trichoderma viride under the control of the cellobiohydrolase I gene promoter, recombinant proteins were secreted with molecular masses of 77 and 67 kDa respectively. These recombinant enzymes hydrolyzed soyasaponin I to soyasapogenol B and triose, and its substrate specificities for glycosides were similar to that of Sdn1, but the specific activities of these enzymes were lower than that of Sdn1.

Enhancing the accumulation of beta-amyrin in Saccharomyces cerevisiae by co-expression of Glycyrrhiza uralensis squalene synthase 1 and beta-amyrin synthase genes

Glycyrrhiza uralensis Fisch. ex DC is widely used in traditional Chinese medicine (TCM). Among its various active components, glycyrrhizic acid is believed to be the marker component. Squalene synthase (SQS) and beta-amyrin synthase (beta-AS) are key enzymes in the biosynthetic pathway of glycyrrhizic acid in G uralensis. To reveal the effects of co-expression of SQS1 and beta-AS genes on this pathway, 7 yeast expression vectors harboring different SQS1 variants and beta-AS were constructed and expressed in Saccharomyces cerevisiae as fusion proteins. TLC and GC-MS results showed that co-expression of SQS1 and beta-AS enhanced the accumulation of beta-amyrin. The effects of SQS12 were more obvious than the other two SQS1 variants. This study is significant for further investigations concerned with exploring the biosynthesis of glycyrrhizic acid in vitro and strengthening the efficacy of G. uralensis by means of increasing the content of glycyrrhizic acid.

Microbial transformation of oleanolic acid by Trichothecium roseum

Microbial transformation of the oleanolic acid (1) using Trichothecium roseum (pers.) Link (M 95.56) has resulted in the isolation of two new hydroxylated type metabolites, characterized as 15α-hydroxy-3-oxo-olean-12-en-28-oic acid (2) and 7β,15α-dihydroxy-3-oxo-olean-12-en-28-oic acid (3). The structure elucidation of these metabolites was based primarily on HR-EIMS, 1D NMR, and 2D NMR analyses.

Determination of triterpenic acids and screening for valuable secondary metabolites in Salvia sp. suspension cultures

Plant in vitro cultures are a prospective alternative for biochemicals production, for example the triterpenes oleanolic and ursolic acid present in plants and cell cultures of Salvia sp. Our objective was to develop a suitable analysis protocol for evaluation of triterpenic acid yield in plant raw material and in vitro cultures supporting selection processes. Moreover, valuable bioactive compounds had to be revealed. Thus, different strategies enhancing the separation for a sensitive and effective HPLC-UV method were investigated and the developed method was validated for linearity, precision, accuracy, limits of detection and quantification. A baseline separation of these isomers enabled detection limits of below 0.4 microg/mL and quantification limits of about 1.2 microg/mL. Over the tested concentration range a good linearity was observed (R2 > 0.9999). The variations in the method were below 6% for intra- and inter-day assays of concentration. Recoveries were between 85-98% for both compounds using ethanol as extraction solvent. Additionally, metabolite profiling of cell suspension culture extracts by GC-MS has shown the production variability of different plant metabolites and especially the presence of plant phenols and sterols. These studies provide a method suitable for screening plant and cell culture productivity of triterpenic acids and highlighted interesting co-products of plant cell cultures.

Biotransformation of oleanolic and maslinic acids by Rhizomucor miehei

Microbial transformation of oleanolic acid by Rhizomucor miehei produced three metabolites. A known compound, a 30-hydroxyl derivative (queretaroic acid), and two 7β,30- and 1β,30-dihydroxylated metabolites, respectively. The action of the same fungus (R. miehei) on maslinic acid produced an olean-11-en-28,13β-olide derivative, a metabolite hydroxylated at C-30, an 11-oxo derivative, and two metabolites with an 11α,12α-epoxy group, hydroxylated or not at C-30. Their structures were elucidated by extensive analyses of their spectroscopic data, and also by chemical correlations.

Antitrypanosomal triterpenoid with an ε-lactone E-ring from Salvia urmiensis

A new triterpenoid, urmiensolide (1), was isolated from Salvia urmiensis. The structure was elucidated by a combination of 1D and 2D NMR, HRESIMS, and X-ray crystallographic analyses. The absolute configuration was established by comparison of experimental and simulated ECD spectra. Urmiensolide is the first pentacyclic triterpenoid bearing a ε-lactone E-ring. The compound showed in vitro antitrypanosoal activity with an IC₅₀ value of 5.6 μM against the Trypanosoma brucei rhodesiense STIB 900 strain and a selectivity index of 33. A possible biosynthetic pathway of 1 from α-amyrin is proposed.

Optimisation of potassium chloride nutrition for proper growth, physiological development and bioactive component production in Prunella vulgaris L

Prunella vulgaris L. is an important medicinal plant with a variety of pharmacological activities, but limited information is available about its response to potassium chloride (KCl) supplementation. P. vulgaris seedlings were cultured in media with four different KCl levels (0, 1.00, 6.00 and 40.00 mM). Characteristics relating to the growth, foliar potassium, water and chlorophyll content, photosynthesis, transpiration, nitrogen metabolism, bioactive constituent concentrations and yield were determined after three months. The appropriate KCl concentration was 6.00 mM to result in the highest values for dry weight, shoot height, spica and root weight, spica length and number in P. vulgaris. The optimum KCl concentration resulted in a maximum net photosynthetic rate (Pn) that could be associated with the highest chlorophyll content and fully open stomata conductance. A supply of surplus KCl resulted in a higher concentration of foliar potassium and negatively correlated with the biomass. Plants that were treated with the appropriate KCl level showed a greater capacity for nitrate assimilation. The Pn was significantly and positively correlated with nitrate reductase (NR) and glutamine synthetase (GS) activities and was positively correlated with leaf-soluble protein and free amino acid (FAA) contents. Both KCl starvation (0 mM) and high KCl (40.00 mM) led to water loss through a high transpiration rate and low water absorption, respectively, and resulted in increased concentrations of ursolic acid (UA), oleanolic acid (OA) and flavonoids, with the exception of rosmarinic acid (RA). Moreover, the optimum concentration of KCl significantly increased the yields of RA, UA, OA and flavonoids. Our findings suggested that significantly higher plant biomass; chlorophyll content; Pn; stronger nitrogen anabolism; lower RA, UA, OA and flavonoid accumulation; and greater RA, UA, OA and flavonoid yields in P. vulgaris could be expected in the presence of the appropriate KCl concentration (6.00 mM).

Determination of soyasaponins I and βg in raw and cooked legumes by solid phase extraction (SPE) coupled to liquid chromatography (LC)-mass spectrometry (MS) and assessment of their bioaccessibility by an in vitro digestion model

Legumes contain a rich variety of phytochemicals as soyasaponins, triterpenoidal glycosides that possess multiple health-promoting properties, such as lowering of cholesterol. In this work, the quantification of soyasaponins I and βg in 60 raw and cooked legumes by using a solid phase extraction (SPE) coupled to a liquid chromatography (LC)-mass spectrometry (MS) method was carried out. Results showed that lentils are a good source of soyasaponins, with a content of soyasaponin I that ranged from 636 to 735 mg kg(-1) and of soyasaponin βg from 672 to 1807 mg kg(-1). The cooking process produced a small loss of soyasaponins in water, that is, 4.8-8.7%, and partially converted soyasaponin βg into soyasaponin I. In addition, the bioaccessibility of soyasaponins I in lentils was studied; the values ranged from 8.9 ± 0.3 to 10.6 ± 1.1% in the duodenal compartment. On the basis of these results, soyasaponins could be effective in lowering exogenous cholesterol.

Lancemaside A isolated from Codonopsis lanceolata and its metabolite echinocystic acid ameliorate scopolamine-induced memory and learning deficits in mice

The rhizome of Codonopsis lanceolata (family Campanulaceae), which contains lancemaside A as a main constituent, has been used as herbal medicine to treat inflammation, insomnia, and hypomnesia. Lancemaside A and echinocystic acid, which is its metabolite by intestinal microflora, potently inhibited acetylcholinesterase activity in a dose-dependent manner, with IC₅₀ value 13.6 μM and 12.2 μM, respectively. Its inhibitory potency is comparable with that of donepezil (IC₅₀=10.9 μM). Lancemaside A and echinocystic acid significantly reversed scopolamine-induced memory and learning deficits on passive avoidance task. Lancemaside A orally administered 5h before treatment with scopolamine reversed scopolamine-induced memory and learning deficits more potently than one orally administered 1h before. Echinocystic acid more potently reversed it than lancemaside A. Lancemaside A and echinocystic acid significantly reversed scopolamine-induced memory and learning deficits on the Y-maze and Morris water maze tasks. Lancemaside A and echinocystic acid also increased the expression of brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP response element binding protein (p-CREB). Based on these findings, orally administered lancemaside A may be metabolized to echinocystic acid, which may be absorbed into the blood and ameliorate memory and learning deficits by inhibiting AChE activity and inducing BDNF and p-CREB expressions.

Molecular characterization of the pentacyclic triterpenoid biosynthetic pathway in Catharanthus roseus

Catharanthus roseus is an important medicinal plant and the sole commercial source of monoterpenoid indole alkaloids (MIA), anticancer compounds. Recently, triterpenoids like ursolic acid and oleanolic acid have also been found in considerable amounts in C. roseus leaf cuticular wax layer. These simple pentacyclic triterpenoids exhibit various pharmacological activities such as anti-inflammatory, anti-tumor and anti-microbial properties. Using the EST collection from C. roseus leaf epidermome ( http://www.ncbi.nlm.nih.gov/dbEST ), we have successfully isolated a cDNA (CrAS) encoding 2,3-oxidosqualene cyclase (OSC) and a cDNA (CrAO) encoding amyrin C-28 oxidase from the leaves of C. roseus. The functions of CrAS and CrAO were analyzed in yeast (Saccharomyces cerevisiae) systems. CrAS was characterized as a novel multifunctional OSC producing α- and β-amyrin in a ratio of 2.5:1, whereas CrAO was a multifunctional C-28 oxidase converting α-amyrin, β-amyrin and lupeol to ursolic-, oleanolic- and betulinic acids, respectively, via a successive oxidation at the C-28 position of the substrates. In yeast co-expressing CrAO and CrAS, ursolic- and oleanolic acids were detected in the yeast cell extracts, while the yeast cells co-expressing CrAO and AtLUP1 from Arabidopsis thaliana produced betulinic acid. Both CrAS and CrAO genes show a high expression level in the leaf, which was consistent with the accumulation patterns of ursolic- and oleanolic acids in C. roseus. These results suggest that CrAS and CrAO are involved in the pentacyclic triterpene biosynthesis in C. roseus.

Metabolic fingerprinting by 1HNMR for discrimination of the two species used as Radix Bupleuri

Radix Bupleuri is a traditional Chinese medicine harvested from two Bupleurum species (B. chinense and B. scorzonerifolium). It is widely used and is sourced from different regions of China. 1H NMR spectroscopy and multivariate data analysis were applied to 67 Radix Bupleuri samples to discriminate the two species, and explore the influences of habitat and culture method on the quality of Radix Bupleuri based on their metabolomics profiles. Metabolites responsible for the differences between the two species were higher levels of arginine, citric acid, sucrose, saikosaponin b1/b2 analogs, volatile oil with an (E)-2-olefin aldehyde fragment, and fatty acids in B. scoreonerifolium, and more saikosaponin a/c/d analogs in B. chinense. The variances of two cultivation areas were observed due to the higher amount of saikosaponins a/c/d in samples from Shaanxi and lipidsin samples from Shanxi. No obvious difference was detected between cultivars and wild type. 1HNMR metabolomics can simultaneously detect saikosaponins and hydrocarbon aldehydes, and also differentiate the two main saikosaponin skeletons, making it a suitable tool for the species discrimination and quality evaluation of Radix Bupleuri.

Study on the noncovalent interactions of saikosaponins and cytochrome c by electrospray ionization mass spectrometry

RATIONALE

The study of interactions between protein and pharmaceutical molecules including natural extracts has become of increasing interest in biological and biomedical research. An investigation of the interaction between saikosaponins and cytochrome c (Cyt c) by electrospray ionization mass spectrometry (ESI-MS) is described in this study. Saikosaponins are found in Bupleurum falcatum (a flowering plant), and they are glycosides that consist of saccharides and the sapogenins of triterpenoids.

METHODS

Seven model molecules of saccharides and triterpenes, namely maltose (Mal II), maltotriose (Mal III), raffinose (Raf), and stachyose (Sta), glycyrrhetinic acid (Gly), ursolic acid (Urs) and oleanic acid (Ole), were chosen to perform a series of ESI-MS control experiments for the exploration of the interaction groups in saikosaponins with Cyt c. The dissociation constants of detected noncovalent complexes were determined by using a direct ESI-MS assay.

RESULTS

We have observed in the ESI mass spectra the formation of Cyt c complexes with saikosaponins a and c, and these saccharides, with 1:1 and 1:2 stoichiometry. Our results showed that no complex ions of triterpenes and Cyt c were detected in the ESI-MS and similar Kd values were obtained for the Cyt c complexes of saikosaponins and saccharides. This demonstrates that the glycosyl moiety in the saikosaponins is the effective interaction group with Cyt c. We propose that saikosaponins and saccharides interact with Cyt c by hydrogen bonds. The binding affinity of these six ligands with Cyt c is shown to be in the order Ssa > Ssc > Raf, Mal III > Sta ≥ Mal II.

CONCLUSIONS

The ESI-MS methodology presented in this study enables us to investigate the interactions of saikosaponins with Cyt c, and allows the direct determination of binding constants. These results could guide further research for providing insights into the structure-binding relationship of ligands with Cyt c.

Response surface methodology to optimize enzymatic preparation of Deapio-Platycodin D and Platycodin D from Radix Platycodi

In the present work, we reported the enzymatic preparation of deapio-platycodin D (dPD) and platycodin D (PD) optimized by response surface methodology (RSM) from Radix Platycodi. During investigation of the hydrolysis of crude platycosides by various glycoside hydrolases, snailase showed a strong ability to transform deapio-platycoside E (dPE) and platycoside E (PE) into dPD and PD with 100% conversion. RSM was used to optimize the effects of the reaction temperature (35-45 °C), enzyme load (5-20%), and reaction time (4-24 h) on the conversion process. Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of dPD and PD conversion yield. The optimum preparation conditions were as follows: temperature, 43 °C; enzyme load, 15%; reaction time, 22 h. The biotransformation pathways were dPE→dPD3→dPD and PE→PD3→PD, respectively. The determined method may be highly applicable for the enzymatic preparation of dPD and PD for medicinal purposes and also for commercial use.

CYP716A subfamily members are multifunctional oxidases in triterpenoid biosynthesis

Triterpenoids are a diverse group of secondary metabolites that are associated with a variety of biological activities. Oleanolic acid, ursolic acid and betulinic acid are common triterpenoids in plants with diverse biological activities, including antifungal, antibacterial, anti-human immunodeficiency virus (HIV) and/or antitumor activities. In the present study, using the gene co-expression analysis tool of Medicago truncatula, we found a strong correlation between CYP716A12 and β-amyrin synthase (bAS), which encodes the enzyme responsible for the initial cyclization of 2,3-oxidosqualene to β-amyrin (the basic structural backbone of most triterpenoid saponins). Through an in vitro assay, we identified CYP716A12 as a β-amyrin 28-oxidase able to modify β-amyrin to oleanolic acid (through erythrodiol and, possibly, oleanolic aldehyde). We also confirmed its activity in vivo, by expressing CYP716A12 in transgenic yeast that endogenously produce β-amyrin. In addition, CYP716A12 was evaluated for its potential α-amyrin- and lupeol-oxidizing activities. Interestingly, CYP716A12 was able to generate ursolic acid (through uvaol and, possibly, ursolic aldehyde) and betulinic acid (through betulin). Hence, CYP716A12 was characterized as a multifunctional enzyme with β-amyrin 28-oxidase, α-amyrin 28-oxidase and lupeol 28-oxidase activities. We also identified homologs of CYP716A12 in grape (CYP716A15 and CYP716A17) that are involved in triterpenoid biosynthesis, which indicates the highly conserved functionality of the CYP716A subfamily among plants. These findings will be useful in the heterologous production of pharmacologically and industrially important triterpenoids, including oleanolic acid, ursolic acid and betulinic acid.

Proteomic analysis shows synthetic oleanane triterpenoid binds to mTOR

New multifunctional drugs that target multiple disease-relevant networks offer a novel approach to the prevention and treatment of many diseases. New synthetic oleanane triterpenoids (SO), such as CDDO (2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid) and its derivatives, are multifunctional compounds originally developed for the prevention and treatment of inflammation and oxidative stress. However, the protein binding partners and mechanisms of action of these SO are not yet fully understood. Here we characterize the putative target profile of one SO, CDDO-Imidazolide (CDDO-Im), by combining affinity purification with mass spectroscopic proteomic analysis to identify 577 candidate binding proteins in whole cells. This SO pharmaco-interactome consists of a diverse but interconnected set of signaling networks; bioinformatic analysis of the protein interactome identified canonical signaling pathways targeted by the SO, including retinoic acid receptor (RAR), estrogen receptor (ER), insulin receptor (IR), janus kinase/signal transducers and activators of transcription (JAK/STAT), and phosphatase and tensin homolog (PTEN). Pull-down studies then further validated a subset of the putative targets. In addition, we now show for the first time that the mammalian target of rapamycin (mTOR) is a direct target of CDDO-Im. We also show that CDDO-Im blocks insulin-induced activation of this pathway by binding to mTOR and inhibiting its kinase activity. Our basic studies confirm that the SO, CDDO-Im, acts on a protein network to elicit its pharmacological activity.

Investigation of the potential for triterpene synthesis in rice through genome mining and metabolic engineering

The first committed step in sterol biosynthesis in plants involves the cyclization of 2,3-oxidosqualene by the oxidosqualene cyclase (OSC) enzyme cycloartenol synthase. 2,3-Oxidosqualene is also a precursor for triterpene synthesis. Antimicrobial triterpenes are common in dicots, but seldom found in monocots, with the notable exception of oat. Here, through genome mining and metabolic engineering, we investigate the potential for triterpene synthesis in rice. The first two steps in the oat triterpene pathway are catalysed by a divergent OSC (AsbAS1) and a cytochrome P450 (CYP51). The genes for these enzymes form part of a metabolic gene cluster. To investigate the origins of triterpene synthesis in monocots, we analysed systematically the OSC and CYP51 gene families in rice. We also engineered rice for elevated triterpene content. We discovered a total of 12 OSC and 12 CYP51 genes in rice and uncovered key events in the evolution of triterpene synthesis. We further showed that the expression of AsbAS1 in rice leads to the accumulation of the simple triterpene, β-amyrin. These findings provide new insights into the evolution of triterpene synthesis in monocots and open up opportunities for metabolic engineering for disease resistance in rice and other cereals.

Neuroprotective effect of Nrf2/ARE activators, CDDO ethylamide and CDDO trifluoroethylamide, in a mouse model of amyotrophic lateral sclerosis

Oxidative damage, neuroinflammation, and mitochondrial dysfunction contribute to the pathogenesis of amyotrophic lateral sclerosis (ALS), and these pathologic processes are tightly regulated by the Nrf2/ARE (NF-E2-related factor 2/antioxidant response element) signaling program. Therefore, modulation of the Nrf2/ARE pathway is an attractive therapeutic target for neurodegenerative diseases such as ALS. We examined two triterpenoids, CDDO (2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid) ethylamide and CDDO trifluoroethylamide (CDDO-TFEA), that potently activate Nrf2/ARE in a cell culture model of ALS and in the G93A SOD1 mouse model of ALS. Treatment of NSC-34 cells stably expressing mutant G93A SOD1 with CDDO-TFEA upregulated Nrf2 expression and resulted in translocation of Nrf2 into the nucleus. Western blot analysis showed an increase in the expression of Nrf2/ARE-regulated proteins. When treatment started at a "presymptomatic age" of 30days, both of these compounds significantly attenuated weight loss, enhanced motor performance, and extended the survival of G93A SOD1 mice. Treatment started at a "symptomatic age," as assessed by impaired motor performance, was neuroprotective and slowed disease progression. These findings provide further evidence that compounds that activate the Nrf2/ARE signaling pathway may be useful in the treatment of ALS.

Oleanolic and ursolic acids influence affect the expression of the cysteine regulon and the stress response in Escherichia coli

The pentacyclic triterpenoids, oleanolic, and ursolic acids, affect peptidoglycan metabolism, altering bacterial morphology, and inhibit the growth and survival of several bacterial species, including pathogenic ones. We investigated the effect of subinhibitory concentrations of these compounds on the expression of three operons from the E. coli cysteine regulon, cysPTWA, cysJIH, and cysB, by using transcriptional fusions with the lacZ reporter gene. An inhibitory effect on β-galactosidase expression directed by all three chromosomal fusions was observed with both compounds. In addition, oleanolic acid, but not ursolic acid, caused a weak increase in DnaK synthesis, suggesting moderate ability of inducing heat-shock response.

Biotransformation of oleanolic acid by Alternaria longipes and Penicillium adametzi

Microbial transformation of oleanolic acid (1) was carried out. Six transformed products (2-7) from 1 by Alternaria longipes and three transformed products (8-10) from 1 by Penicillium adametzi were isolated. Their structures were elucidated as 2α,3α,19α-trihydroxy-ursolic acid-28-O-β-d-glucopyranoside (2), 2α,3β,19α-trihydroxy-ursolic acid-28-O-β-d-glucopyranoside (3), oleanolic acid 28-O-β-d-glucopyranosyl ester (4), oleanolic acid-3-O-β-d-glucopyranoside (5), 3-O-(β-d-glucopyranosyl)-oleanolic acid-28-O-β-d-glucopyranoside (6), 2α,3β,19a-trihydroxy-oleanolic acid-28-O-β-d-glucopyranoside (7), 21β-hydroxyl oleanolic acid-28-O-β-d-glucopyranoside (8), 21β-hydroxyl oleanolic acid (9), and 7α,21β-dihydroxyl oleanolic acid (10) based on the extensive NMR studies. Among them, 10 was a new compound and compounds 5 and 8-10 had stronger cytotoxic activities against Hela cell lines than the substrate. At the same time, it was reported for the first time in this paper that the skeletons of compounds 2 and 3 were changed from oleanane to uranane and seven glycosidation products were obtained by biotransformation.

Biotransformation using Mucor rouxii for the production of oleanolic acid derivatives and their antimicrobial activity against oral pathogens

The goal of this study is to produce oleanolic acid derivatives by biotransformation process using Mucor rouxii and evaluate their antimicrobial activity against oral pathogens. The microbial transformation was carried out in shake flasks at 30°C for 216 h with shaking at 120 rpm. Three new derivatives, 7β-hydroxy-3-oxo-olean-12-en-28-oic acid, 7β,21β-dihydroxy-3-oxo-olean-12-en-28-oic acid, and 3β,7β,21β-trihydroxyolean-12-en-28-oic acid, and one know compound, 21β-hydroxy-3-oxo-olean-12-en-28-oic acid, were isolated, and the structures were elucidated on the basis of spectroscopic analyses. The antimicrobial activity of the substrate and its transformed products was evaluated against five oral pathogens. Among these compounds, the derivative 21β-hydroxy-3-oxo-olean-12-en-28-oic acid displayed the strongest activity against Porphyromonas gingivalis, which is a primary etiological agent of periodontal disease. In an attempt to improve the antimicrobial activity of the derivative 21β-hydroxy-3-oxo-olean-12-en-28-oic acid, its sodium salt was prepared, and the minimum inhibitory concentration against P. gingivalis was reduced by one-half. The biotransformation process using M. rouxii has potential to be applied to the production of oleanolic acid derivatives. Research and antimicrobial activity evaluation of new oleanolic acid derivatives may provide an important contribution to the discovery of new adjunct agents for treatment of dental diseases such as dental caries, gingivitis, and periodontitis.

Two oxidosqualene cyclases responsible for biosynthesis of tomato fruit cuticular triterpenoids

The first committed step in triterpenoid biosynthesis is the cyclization of epoxysqualene into various triterpene alcohol isomers, a reaction catalyzed by oxidosqualene cyclases (OSCs). The different OSCs have characteristic product specificities, which are mainly due to differences in the numbers of high-energy intermediates the enzymes can stabilize. The goal of this investigation was to clone and characterize OSCs from tomato (Solanum lycopersicum), a species known to accumulate δ-amyrin in its fruit cuticular wax, in order to gain insights into the enzymatic formation of this particular triterpenoid. We used a homology-based approach to isolate two tomato OSCs and tested their biochemical properties by heterologous expression in yeast as well as overexpression in tomato. One of the enzymes was found to be a product-specific β-amyrin synthase, while the other one was a multifunctional OSC synthesizing 48% δ-amyrin and six other products. The product spectra of both OSCs together account for both the range and the relative amounts of the triterpenoids found in the fruit cuticle. Both enzymes were expressed exclusively in the epidermis of the tomato fruit, indicating that their major function is to form the cuticular triterpenoids. The relative expression levels of both OSC genes, determined by quantitative reverse transcription-polymerase chain reaction, were consistent with product profiles in fruit and leaves of the tomato cultivar MicroTom. However, the transcript ratios were only partially consistent with the differences in amounts of product triterpenoids between the tomato cultivars MicroTom, M82, and Ailsa Craig; thus, transcriptional control of the two OSCs alone cannot explain the fruit triterpenoid profiles of the cultivars.

Biotransformation of 3-oxo-oleanolic acid by Absidia glauca

3-Oxo-oleanolic acid (1) was biotransformed in growing cultures of the fungus Absidia glauca, resulting in three novel hydroxylated metabolites, identified as 1β-hydroxy-3-oxo-olean-11-en-28,13-lactone (2), 1β,11α-dihydroxy-3-oxo-olean-12-en-28-oic acid (3), and 1β,11α,21β-trihydroxy-3-oxo-olean-12-en-28-oic acid (4).

Synthetic triterpenoids target the Arp2/3 complex and inhibit branched actin polymerization

Synthetic triterpenoids are anti-tumor agents that affect numerous cellular functions including apoptosis and growth inhibition. Here, we used mass spectrometric and protein array approaches and uncovered that triterpenoids associate with proteins of the actin cytoskeleton, including actin-related protein 3 (Arp3). Arp3, a subunit of the Arp2/3 complex, is involved in branched actin polymerization and the formation of lamellipodia. 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO)-Im and CDDO-Me were observed to 1) inhibit the localization of Arp3 and actin at the leading edge of cells, 2) abrogate cell polarity, and 3) inhibit Arp2/3-dependent branched actin polymerization. We confirmed our drug effects with siRNA targeting of Arp3 and observed a decrease in Rat2 cell migration. Taken together, our data suggest that synthetic triterpenoids target Arp3 and branched actin polymerization to inhibit cell migration.