Phytochemistry (v.97, #C)

Asparagusic acid by Stephen C. Mitchell; Rosemary H. Waring (5-10).
Asparagusic acid (1,2-dithiolane-4-carboxylic acid) is a simple sulphur-containing 5-membered heterocyclic compound that appears unique to asparagus, though other dithiolane derivatives have been identified in non-food species. This molecule, apparently innocuous toxicologically to man, is the most probable culprit responsible for the curious excretion of odorous urine following asparagus ingestion. The presence of the two adjacent sulphur atoms leads to an enhanced chemical reactivity, endowing it with biological properties including the ability to substitute potentially for α-lipoic acid in α-keto-acid oxidation systems. This brief review collects the scattered data available in the literature concerning asparagusic acid and highlights its properties, intermediary metabolism and exploratory applications.
Keywords: Asparagus; Asparagus officinalis L.; Asparagaceae family; Asparagusic acid; 1,2-Dithiolane-4-carboxylic acid; Sulphur heterocycle; Urine odour; Short review;

Production of barley endoprotease B2 in Pichia pastoris and its proteolytic activity against native and recombinant hordeins by Anne Lind Rosenkilde; Giuseppe Dionisio; Preben B. Holm; Henrik Brinch-Pedersen (11-19).
Barley endoprotease B2 was expressed in Pichia Pastoris. The endoprotease has preference for the hydrolysis of specific hordeins.Barley (Hordeum vulgare L.) cysteine proteases are of fundamental biological importance during germination but may also have a large potential as commercial enzyme. Barley cysteine endoprotease B2 (HvEPB2) was expressed in Pichia pastoris from a pPICZαA based construct encoding a HvEPB2 C-terminal truncated version (HvEPB2ΔC) and a proteolytic resistant His6 tag. Maximum yield was obtained after 4 days of induction. Recombinant HvEPB2ΔC (r-HvEPB2ΔC) was purified using a single step of Ni2+-affinity chromatography. Purified protein was evaluated by SDS–PAGE, Western blotting and activity assays. A purification yield of 4.26 mg r-HvEPB2ΔC per L supernatant was obtained. r-HvEPB2ΔC follows first order kinetics (K m  = 12.37 μM) for the substrate Z-Phe-Arg-pNA and the activity was significantly inhibited by the cysteine protease specific inhibitors E64 and leupeptin. The temperature optimum for r-HvEPB2ΔC was 60 °C, thermal stability T 50 value was 44 °C and the pH optimum was 4.5. r-HvEPB2ΔC was incubated with native purified barley seed storage proteins for up to 48 h. After 12 h, r-HvEPB2ΔC efficiently reduced the C and D hordeins almost completely, as evaluated by SDS–PAGE. The intensities of the B and γ hordein bands decreased continuously over the 48 h. No degradation occurred in the presence of E64. Recombinant hordeins (B1, B3 and γ1) were expressed in Escherichia coli. After 2 h of incubation with r-HvEPB2ΔC, an almost complete degradation of γ1 and partial digests of hordein B1 and B3 were observed.
Keywords: Hordeum vulgare; Pichia pastoris; Heterologous expression; Hordein degradation; Proteolytic resistant tag; Hordeum vulgare endoprotease B2;

Cereal grain, rachis and pulse seed amino acid δ15N values as indicators of plant nitrogen metabolism by Amy K. Styring; Rebecca A. Fraser; Amy Bogaard; Richard P. Evershed (20-29).
This investigation shows that AA δ15N values can provide insights into metabolic pathways influencing bulk plant protein δ15N values, and can aid understanding of plant N cycling in response to different sources of assimilated N.Natural abundance δ15N values of plant tissue amino acids (AAs) reflect the cycling of N into and within plants, providing an opportunity to better understand environmental and anthropogenic effects on plant metabolism. In this study, the AA δ15N values of barley (Hordeum vulgare) and bread wheat (Triticum aestivum) grains and rachis and broad bean (Vicia faba) and pea (Pisum sativum) seeds, grown at the experimental farm stations of Rothamsted, UK and Bad Lauchstädt, Germany, were determined by GC–C–IRMS. It was found that the δ15N values of cereal grain and rachis AAs could be largely attributed to metabolic pathways involved in their biosynthesis and catabolism. The relative 15N-enrichment of phenylalanine can be attributed to its involvement in the phenylpropanoid pathway and glutamate has a δ15N value which is an average of the other AAs due to its central role in AA–N cycling. The relative AA δ15N values of broad bean and pea seeds were very different from one another, providing evidence for differences in the metabolic routing of AAs to the developing seeds in these leguminous plants. This study has shown that AA δ15N values relate to known AA biosynthetic pathways in plants and thus have the potential to aid understanding of how various external factors, such as source of assimilated N, influence metabolic cycling of N within plants.
Keywords: Hordeum vulgare; Triticum aestivum; Vicia faba; Pisum sativum; Amino acids; Nitrogen; δ15N values;

The arbuscular mycorrhizal Rhizophagus irregularis activates storage lipid biosynthesis to cope with the benzo[a]pyrene oxidative stress by Maryline Calonne; Joël Fontaine; Djouher Debiane; Frédéric Laruelle; Anne Grandmougin-Ferjani; Anissa Lounès-Hadj Sahraoui (30-37).
This graphical abstract resume the impact of benzo[a]pyrene on [1-14C]acetate incorporation in the major lipid classes (sterols, phospholipids and triacylglycerols) of the arbuscular mycorrhizal fungus Rhizophagus irregularis.The phytoremediation assisted by arbuscular mycorrhizal fungi (AMF) could constitute an ecological and economic method to restore polycyclic aromatic hydrocarbon (PAH) polluted soils. Unfortunately, little is known about the PAH impact on the beneficial symbiotic AMF. Using radiolabelling experiments, our work aims to understand how benzo[a]pyrene (B[a]P), a representative of high molecular weight PAH, acts on the AMF lipid metabolism. Our results showed decreases in the sterol precursors as well as in total phospholipid quantities, in link with the [1-14C]acetate incorporation decreases in these lipids. Interestingly, a concomitant increase of [1-14C]acetate incorporation by 29.5% into phosphatidylcholine with its content decrease in Rhizophagus irregularis extraradical mycelium was observed, suggesting a membrane regeneration. A second concomitant increase (estimated to 69%) of [1-14C]acetate incorporation into triacylglycerols (TAG) with the content decrease was also observed. This suggests a fungal TAG biosynthesis activation probably to offset the decrease in storage lipid content when the fungus was grown under B[a]P pollution. In addition, our findings showed that lipase activity was induced by more than 3 fold in the presence of B[a]P in comparison to the control indicating that the drop in TAG content could be a consequence of their active degradation. Taken together, our data suggest the involvement of the fungal TAG metabolism to cope B[a]P toxicity through two means: (i) by providing carbon skeletons and energy necessary for membrane regeneration and/or for B[a]P translocation and degradation as well as (ii) by activating the phosphatidic acid and hexose metabolisms which may be involved in cellular stress defence.
Keywords: Arbuscular mycorrhizal fungi (AMF); Polycyclic aromatic hydrocarbons (PAH); Benzo[a]pyrene (B[a]P); Lipids; Extraradical mycelium; [1-14C]acetate;

Essential oils have been hydrodistilled and characterized from 21 populations of taxa currently assigned to the endemic Australian species Phebalium squamulosum (Rutaceae: Boronieae) using GC–MS, NMR and quantified using GC–FID. Essential oils were further examined using principle component analysis to distinguish chemotypes, then screened for antimicrobial activity using broth dilution and TLC-bioautography. Collections of subspecies of P. squamulosum, namely subsp. coriaceum, subsp. gracile, subsp. lineare, subsp. squamulosum, subsp. ozothamnoides and subsp. verrucosum, were made from the wild and one from a cultivated plant of known provenance within New South Wales. Results demonstrated considerable intra- and interspecific essential oil component variation, suggesting the existence of distinct chemotypes and supporting previously observed segregate species based on morphological evidence. Antimicrobial testing revealed moderate to high activity for all essential oils dominated by sesquiterpene alcohols; elemol and eudesmol isomers. Conversely, very low antimicrobial activity was observed from essential oils dominated by monoterpenes. This study constitutes the most exhaustive investigation of essential oils from P. squamulosum subspecies to date and provides the first report of antimicrobial activity.
Keywords: Chemotaxonomy; Bioactivity; Monoterpenes; Sesquiterpenes;

Diarylheptanoids from the bark of black alder inhibit the growth of sensitive and multi-drug resistant non-small cell lung carcinoma cells by Miroslav Novaković; Milica Pešić; Snežana Trifunović; Ivan Vučković; Nina Todorović; Ana Podolski-Renić; Jelena Dinić; Sonja Stojković; Vele Tešević; Vlatka Vajs; Slobodan Milosavljević (46-54).
Ten hitherto unknown and ten known diarylheptanoids were isolated from the Alnus glutinosa bark and exhibited significant cytotoxic activities against NCI-H460 and NCI-H460/R cancer cell lines.Display OmittedAn extended study of minor diarylheptanoids from the bark of black alder has resulted in the isolation of twenty diarylheptanoids, ten of which have not previously been reported (1418, 2024). The structures and configurations of all compounds were elucidated by NMR, HRESIMS, UV, IR, and CD. The anti-cancer potency of twenty diarylheptanoids and four previously isolated compounds (7, 10, 12, 13) was investigated in human non-small cell lung carcinoma cell lines (sensitive and multi-drug resistant variants) as well as in normal human keratinocytes. Diarylheptanoids with a p-coumaroyl group, 14 and 18, platyphylloside (1), platyphyllonol-5-O-β-d-xylopyranoside (2), alnuside B (4) and hirsutenone (9) exhibited strong anti-cancer activity, considerably higher than diarylheptanoid curcumin, which served as a positive control. Compounds 4, 9, 14, and 18 displayed significant selectivity towards the cancer cells. Structure/activity analysis of twenty-four closely related diarylheptanoids revealed a high dependence of cytotoxic action on the presence of a carbonyl group at C-3. Substitution of a heptane chain on C-5 and a number of hydroxyl groups in the aromatic rings also emerged as a significant structural feature that influenced their cytotoxic potential.
Keywords: Black alder; Diarylheptanoids; HPLC-DAD; NMR analysis; Anti-cancer activity; Multi-drug resistance;

Bicyclic and tetracyclic diterpenes from a Trichoderma symbiont of Taxus baccata by Emilie Adelin; Claudine Servy; Marie-Thérèse Martin; Guillaume Arcile; Bogdan I. Iorga; Pascal Retailleau; Mercedes Bonfill; Jamal Ouazzani (55-61).
Trichoderma atroviridae UB-LMA is an endophytic fungus isolated from Taxus baccata trees. Liquid-state fermentation coupled to in situ solid phase extraction provided three compounds belonging to the harziane tetracyclic diterpene family, and their potential bicyclic precursor. Trichoderma atroviridae UB-LMA is an endophytic fungus isolated from Taxus baccata trees. Liquid-state fermentation coupled to in situ solid phase extraction (SPE) was applied, and four compounds were discovered. Compounds 24 belong to the harziane tetracyclic diterpene family. Bicylic compound 1 may represent the biosynthetic precursor of this scarce family of compounds.
Keywords: Fungal secondary metabolites;

Classification of stilbenoid compounds by entropy of artificial intelligence by Gloria Castellano; Ana Lara; Francisco Torrens (62-69).
Stilbenoids are classified into a periodic system via information entropy. Eight characteristics classify stilbenoids. The former five mark the group while the latter three, the period in the periodic table. Stilbenoids in the same group/period present maximum resemblance. Stilbenoids are related to bioactivity and antioxidant properties in the literature.A set of 66 stilbenoid compounds is classified into a system of periodic properties by using a procedure based on artificial intelligence, information entropy theory. Eight characteristics in hierarchical order are used to classify structurally the stilbenoids. The former five features mark the group or column while the latter three are used to indicate the row or period in the table of periodic classification. Those stilbenoids in the same group are suggested to present similar properties. Furthermore, compounds also in the same period will show maximum resemblance. In this report, the stilbenoids in the table are related to experimental data of bioactivity and antioxidant properties available in the technical literature. It should be noted that stilbenoids with glycoxyl groups esterified with benzoic acid derivatives, in the group g11000 in the extreme right of the periodic table, show the greatest antioxidant activity as confirmed by experiments in the bibliography. Moreover, the second group from the right (g10111) contains E-piceatannol, which antioxidant activity is recognized in the literature. The experiments confirm our results of the periodic classification.
Keywords: Antioxidant activity; Information entropy; Molecular classification; Polycyclic compound; Stilbenoid;

Saponins with highly hydroxylated oleanane-type aglycones from Silphium asteriscus L. by Milena Masullo; Lalita Calabria; Dario Gallotta; Cosimo Pizza; Sonia Piacente (70-80).
Silphium asteriscus L., commonly known as starry rosinweed, is a plant found in prairies, glades, woodlands and savannas of the southeastern United States. The phytochemical investigation of the methanolic extract of S. asteriscus leaves led to the isolation of eighteen saponins with highly hydroxylated oleanane-type aglycones never reported before. Their structures were elucidated by extensive spectroscopic methods including 1D- (1H and 13C) and 2D-NMR (DQF-COSY, HSQC, HMBC, TOCSY and ROESY) experiments as well as ESIMS analysis. The antiproliferative activity of the isolated compounds was evaluated against three cancer cell lines including Hela (human epitheloid cervix carcinoma), Jurkat cells (leukaemic T-cell line) and DLD-1 (colorectal adenocarcinoma). Compounds 1, 5 and 17 displayed weak activity with IC50 values ranging from 50 to 75 μM.
Keywords: Silphium asteriscus; Oleanane-type saponins; Highly hydroxylated aglycones;

Cytotoxic non-aromatic B-ring flavanones from Piper carniconnectivum C. DC. by Giovana C. Freitas; João M. Batista; Gilberto C. Franchi; Alexandre E. Nowill; Lydia F. Yamaguchi; Janaina D. Vilcachagua; Denize C. Favaro; Maysa Furlan; Elsie F. Guimarães; Christopher S. Jeffrey; Massuo J. Kato (81-87).
Non-aromatic B-ring flavanones (1 and 2) were isolated from leaves of Piper carniconnectivum. The derivative 3 was obtained by hydrogenation of 1. The in vitro cytotoxicity assay indicated 1 as the most active.The EtOAc extract from the leaves of Piper carniconnectivum C. DC. was subjected to chromatographic separation to afford two non-aromatic B-ring flavanone compounds: 5-hydroxy-2-(1′-hydroxy-4′-oxo-cyclohex-2′-en-1′-yl)-6,7-dimethoxy-2,3-dihydro-4H-chromen-4-one (1) and 5-hydroxy-2-(1′,2′-dihydroxy-4′-oxo-cyclohexyl)-6,7-dimethoxy-2,3-dihydro-4H-chromen-4-one (2). The absolute configuration of (+)-1 was unambiguously determined as 2S,1′R by electronic circular dichroism (ECD) spectroscopy and comparison to simulated spectra that were calculated using time-dependent density functional theory (TDDFT). This methodology allowed the assignment of the absolute configuration of (+)-2 also as 2S,1′R, except for the stereogenic center at C-2′, which was assigned as R because of the evidence drawn from high resolution NMR experiments. The cytotoxic activity of both compounds and 3 (hydrogenated B-ring derivative of 1) was evaluated on twelve human leukemia cell lines, and the IC50 values (<10 μM) indicated the activity of 1 against seven cell lines.
Keywords: Piper carniconnectivum; Piperaceae; Non-aromatic B-ring flavanone; Cytotoxic;

Diterpenoid alkaloids and flavonoids from Delphinium trichophorum by Chao-Zhan Lin; Zhong-Xiang Zhao; Si-Min Xie; Ju-Hua Mao; Chen-Chen Zhu; Xiao-Hui Li; Zeren-dawa Bairi; Suolang-qimei Kangsa; Zhu Dun; Tian-Qin Xiong; Ai-Zhi Wu (88-95).
Six diterpenoid alkaloids, trichodelphinines A–F and three known flavonoids were isolated from Delphinium trichophorum. All the alkaloids showed cytotoxicity against A549 cells with IC50 values ranging between 12.03 and 52.79 μM.Five hetisane-type C20-diterpenoid alkaloids, trichodelphinines A–E, one delnudine-type C20-diterpenoid alkaloid, trichodelphinine F and three known flavonoids, quercetin, quercetin 3-O-β-d-glucopyranoside, and quercetin 3-O-β-d-glucopyranoside-7-O-α-l-arabinopyranoside, were isolated from whole plants of Delphinium trichophorum Franch. Their structures were elucidated on the basis of extensive spectroscopic analysis, including HSQC, HMBC, 1H–1H COSY, NOESY and X-ray crystallographic analysis, and from chemical evidence. The cytotoxic activities of the diterpenoid alkaloids were evaluated using the MTT method, and the IC50 values of their cytotoxicity against A549 cancer cells ranged from 12.03 to 52.79 μM.
Keywords: Delphinium trichophorum Franch; Ranunculaceae; Diterpenoid alkaloid; Hetisane-type diterpenoid alkaloid; Delnudine-type diterpenoid alkaloid;