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Fig. 7 in Dimeric aporphine alkaloids from the twigs of Trivalvaria costata (Hook.f. & Thomson) I.M.Turner

Fig. 7. ECD spectra (MeOH) of compounds ()-(7), (+)-(7), (±)-8, (±)-9, (±)-10, ()-(11), (+)-(11), ()-(12), (+)-(12), ()-(13), (+)-(13), ()-(14), and (+)-(14).

Fig. 5 in Dimeric aporphine alkaloids from the twigs of Trivalvaria costata (Hook.f. & Thomson) I.M.Turner

Fig. 5. ECD spectra (MeOH) of compounds ()-(1), (+)-(1), ()-(2), (+)-(2), ()-(3), (+)-(3), (+)-(4), ()-(5), (+)-(5), ()-(6), and (+)-(6).

Fig. 8 in Structurally diverse alkaloids with nine frameworks from Zephyranthes candida and their acetylcholinesterase inhibitory and anti-inflammatory activities

Fig. 8. Experimental ECD spectra of zephyranines G–I (7–9), 6-O-ethylnerinine (10) and the calculated ECD spectra of zephyranine G (7), the aglycone of zephyranine H (8), zephyranine I (9), 6-O-ethylnerinine (10), and their enantiomers.

Fig. 7 in Structurally diverse alkaloids with nine frameworks from Zephyranthes candida and their acetylcholinesterase inhibitory and anti-inflammatory activities

Fig. 7. Experimental and calculated ECD spectra of zephyranines C F (3–6), isolated as mixtures of respective 6-epimers (d. r. 75: 25), and their enantiomers.

Fig. 7 in Alkaloids isolated from Tropaeolum tuberosum with cytotoxic activity and apoptotic capacity in tumour cell lines

Fig. 7. Effects of compounds on the apoptosis of different tumoral cells. Untreated cells as negative reference, with Dimethylenastron (CTK8F1368), as positive reference compound at IC50 = 0.23 μM, with compound 1 at IC50 = 29.06 μM and compound 2 at IC50 = 1.33 μM, for 72 h and were stained with fluorochromes Rho123 (Rhodamine 123) and IP (Propidium Iodide) and evaluated by flow cytometry. p <0.0001 (t Tukey, Two-way ANOVA).

Fig. 2 in Alkaloid chemophenetics and transcriptomics of the Nicotiana genus

Fig. 2. Euclidean-based hierarchical clustering of Nicotiana genus species. Prior to clustering mean root alkaloid biosynthesis gene expression as well as leaves and roots percentage alkaloid composition were subjected to log2 transformation. There are 3 black boxes enclosing species clustered together: first from top, 6 species from the Suaveolentes section; second, 9 species from the Suaveolentes section; and third, 4 species from the Rusticae section and 1 from the Undulatae section. Gene IDs and their acronyms (present in Table S2) together with alkaloid names are placed on the figure top. Clustering revealed transparent species segregation which corresponded to their sectional classification. Clusters where ≥50% of section species grouped together are enclosed by fade yellow dashed line, specifically: Tomentosae section (4/5), Paniculatae section (2/4), Suaveolentes section (17/21), Noctiflorae section (3/3), Rusticae section (4/5) and Repandae section (2/3).

Fig. 1 in Alkaloid chemophenetics and transcriptomics of the Nicotiana genus

Fig. 1. Current state-of-the-art picture of alkaloid biosynthesis in Nicotiana genus. Gene acronyms are provided in red next to the enzymatic steps they correspond to. Each gene acronym is explained in boxes with full gene names. Compound full names are provided in black, with additional 2D structure representation of alkaloids: anabasine, nicotine, nornicotine, anatabine, cotinine, myosmine as well as nicotinic acid. Additional 2D structures are also presented for alkaloids intermediates: Δ1-piperdiene, N-methyl-Δ1-pyrrolinium cation, 3,6-dihydronicotinic acid, and 2,5-dihydropyridine. In faded green, field steps of polyamine biosynthesis are presented, whereas the faded red field encloses steps limited to plastid and root tissue. Question marks are located next to enzymatic steps that are currently only hypothesized and have not yet been confirmed by independent studies. The figure is based on a review by Dewey and Xie (2013) and subsequent studies, that characterized the functions of further genes, namely LDC (Bunsupa et al., 2014) and NUP1 (Kato et al., 2015), in the alkaloid biosynthetic pathway.

Fig. 3 in Alkaloid chemophenetics and transcriptomics of the Nicotiana genus

Fig. 3. PCC matrix between gene expressions mean RPKM values and mean alkaloid accumulation metabolite data. Genes are presented with their Gene ID and Identifiers (full description of genes with names in Fig. 1 & Table S2). Six gene-specific comparisons were performed to calculate Pearson correlation coefficient, as presented in the table: leaf nornicotine to nicotine content ratio vs. leaf gene expression; total nicotine content (leaf and root) vs. root gene expression; total anatabine content (leaf and root) vs. root gene expression; root anatabine to nicotine and nornicotine content ratio vs. root gene expression; total anabasine content (leaf and root) vs. root gene expression; total alkaloid content leaf to root ratio vs. root gene expression. PCC values range from −1 to 1, with red white conditioning in negative to positive correlation. PCC values in bold and marked with thick borders represent correlations of significant importance.

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Fig. 5 in Macroline, talpinine, and sarpagine alkaloids from Alstonia penangiana. An NMR-based method for differentiating between A. penangiana and A. macrophylla

Fig. 5. Comparison of 1 H-NMR spectra (600 MHz) of alkaloid extracts (stem-bark) from A. penangiana (red markings correspond to resonances due to 10-methoxyaffinisine) and A. macrophylla (blue markings correspond to resonances due to villalstonine). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

opennotspecifiedJul 2020View details →

Fig. 3 in Gigantelline, gigantellinine and gigancrinine, cherylline- and crinine-type alkaloids isolated from Crinum jagus with anti-acetylcholinesterase activity

Fig. 3. Experimental ECD spectra of gigantelline (1) (black solid line), gigantellinine (2) (blue dotted line) and cherylline (5) (green dashed line) measured in methanol (ca. 3 mM, 0.1 cm cell). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3 in Alkaloid and iridoid glucosides from Palicourea luxurians (Rubiaceae: Palicoureeae) indicate tryptamine- and tryptophan-iridoid alkaloid formation apart the strictosidine pathway

Fig. 3. Most relevant correlations of isoalstrostine A (1) and dehydrorudgeifoline (2) indicated by correlation peaks in COSY (green), HMBC (red) and ROESY (blue), which are used for structure elucidation. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 2 in Alkaloid and iridoid glucosides from Palicourea luxurians (Rubiaceae: Palicoureeae) indicate tryptamine- and tryptophan-iridoid alkaloid formation apart the strictosidine pathway

Fig. 2. Structures of iridoids isolated from leaves and stem bark of Palicourea luxurians are asperuloside (6), secoxyloganin (7), demethylsecologanol (8), secologanic acid (9) and sweroside (10). Furthermore, the secologanin isolation artifacts (E)-aldosecologanin (11), secologanin dimethyl acetal (12), secologanin di-n-butyl acetal (13) as well as both diastereomeres of secologanin n-butyl methyl acetal (14a/14b) are shown. Compounds 6 and 7 have been isolated from the stem bark, all other compounds have been isolated from the leaves.

Fig. 1 in Alkaloid and iridoid glucosides from Palicourea luxurians (Rubiaceae: Palicoureeae) indicate tryptamine- and tryptophan-iridoid alkaloid formation apart the strictosidine pathway

Fig. 1. Structures of the isolated tryptamine-iridoid alkaloids and the tryptophan-iridoid alkaloid from leaves of Palicourea luxurians: Isoalstrostine A (1), dehydrorudgeifoline (2), alstrostine A (3), javaniside (4) and 5α-carboxystrictosidine (5). The glucoside moieties are shown as D-glycosides for compounds 1 to 5 as well as for all other isolated glycosides 6 to 14a/14b (Fig. 2), but have not been proven in all cases due to low available amounts.

Fig. 1 in Anti-inflammatory alkaloids from the root bark of Hernandia nymphaeifolia

Fig. 1. The chemical structures of previously undescribed compounds 1–4 isolated from H. nymphaeifolia.

Fig. 6 in Alkaloid and iridoid glucosides from Palicourea luxurians (Rubiaceae: Palicoureeae) indicate tryptamine- and tryptophan-iridoid alkaloid formation apart the strictosidine pathway

Fig. 6. Possible pathways, leading to alstrostine-type as well as to isoalstrostine-type alkaloid structures. In the first step (a) an alline-like intermediate with two secondary amine functions is generated by oxidation and cyclization of tryptamine (Nakagawa and Hino, 1977). Subsequent in step (b), two secologanin molecules react with both secondary amine functions gaining two enamine moieties. In the following steps (c1/c2) and (d1/d2), protonation of one of the two enamine functions leads to the formation of a sixmembered ring with an iminium ion moiety. Depending on the location of the initial protonation in step (d1/d2), the six-membered ring carries its substituents either in position 3′ (–CH2–R) and 14 (-R), or in position 3 (–CH2–R) and 14′ (-R), respectively. The final deprotonation (e1/e2) leads in both cases to the formation of the enamine and thus results in the alstrostine-type or the isoalstrostine-type structure, respectively. Structure of residue "R" is shown in the box. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 5 in Alkaloid and iridoid glucosides from Palicourea luxurians (Rubiaceae: Palicoureeae) indicate tryptamine- and tryptophan-iridoid alkaloid formation apart the strictosidine pathway

Fig. 5. Two possible pathways (a and b), both leading to javaniside (4) by a cyclization which is related to the Pictet-Spengler reaction. In pathway (a) tryptamine is oxidized to 2-oxo- tryptamine prior to enamine formation of the amine function with secologanin. In the following Pictet-Spengler reaction comparable rearrangement the spiro-cyclic system as well as the five membered ring are formed according to the mechanism described by Bailey (1987). Alternatively in the similar pathway (b) the enamine is formed prior to the Pictet Spengler-like reaction (Bailey, 1987). Subsequent the imine moiety is oxidized to gain the five membered lactam ring. The intermediate resulting from both possible pathways (a and b) is finally trans- formed to javaniside (4) by saponification and formation of the lactam ring. As no strictosidine or follow-up products have been detected in Palicourea luxurians, the enamine possibly occurring in pathway (b) has barely or not been accepted in a classic Pictet-Spenglerase catalyzed reaction, as indicated in hampered pathway c. Electron pair shifts and formations of new bonds are indicated with red arrows. For structure of the residue "R" see the box in Fig. 6. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

opennotspecifiedApr 2020View details →

Fig. 7 in Anti-inflammatory quinoline alkaloids from the root bark of Dictamnus dasycarpus

Fig. 7. Inhibitory effects on inflammatory cytokines of compound 15. (*, p <0.05; **, p <0.01; ###, ***, p <0.001; ####, ****, p <0.0001).

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Fig. 2 in Anti-inflammatory quinoline alkaloids from the root bark of Dictamnus dasycarpus

Fig. 2. Key HMBC (H C) and 1H–1H COSY (red thick lines) correlations of compounds 1–5. (For interpretation of the references to colour in this figure legend, the → reader is referred to the Web version of this article.)

opennotspecifiedApr 2020View details →

Fig. 3 in Anti-inflammatory quinoline alkaloids from the root bark of Dictamnus dasycarpus

Fig. 3. The chiral HPLC separation (A) and experimental and calculated ECD spectra (B, C) of compounds 1a and 1b.