Pyrrolizidine alkaloids and fatty acids from the endemic plant species Rindera umbellata and the effect of lindelofine-N-oxide on tubulin polymerization

Rinderidine and oblongifolidine new pyrrolizidine alkaloids from Rindera oblongifolia M. Popov and their absolute configurations

The alkaloid composition of Rindera oblongifolia was studied, in which the pyrrolizidine alkaloids echinatine and trachelanthamine N-oxide, as well as two new quaternary salts namely rinderidine and the oblongifolidine were isolated. The structures of the isolated new alkaloids were elucidated by NMR spectroscopy. The absolute configuration of lindelofine, trachelanthamine N-oxide, rinderidine and oblongifolidine was established by single crystal X-ray diffraction as: 1 R, 4 R, 8 R, 2'S, 3'R; 1 R, 4S, 8S, 2'S, 3'R; 4 R, 7S, 8 R, 2'S, 3'S; 4 R, 7S, 8 R, 2'S, 3'S (7''S, 8''R) respectively. Both new pyrrolizidine alkaloids showed no cytotoxicity against four cancer cell lines such as HeLa, НEр-2, HBL-100 and CCRF-CEM.

Multifaceted Anticancer Potential of Gnidia glauca (Fresen.) Gilg Leaf Alkaloids: Impact on Multiple Cellular Targets

Gnidia glauca (Fresen.) Gilg has demonstrated significant anticancer potential through multiple mechanisms, including apoptosis induction, as shown by the TUNEL assay against MCF-7 cells, modulation of tubulin polymerization, preservation of mitochondrial function indicated by the JC-1 assay, and inhibition of DNA polymerase α and β activities. Rationale for the present study is to investigate the potential anticancer properties of G. glauca leaf alkaloid extract. Fresh and healthy G. glauca leaves were cleaned, shade-dried, and the powder was defatted, extracted with 10% acetic acid in ethanol, and subjected for alkaloid extraction. The partially purified G. glauca leaf alkaloid extract was evaluated for its effects on tubulin polymerization, DNA polymerase activity, mitochondrial membrane potential, and apoptosis studies using human breast cancer (MCF-7) cells by flow cytometry. The extract was found to affect microtubule assembly in a concentration-dependent manner (15.125-250 μg/mL), indicating presence of alkaloids that function as spindle poison agents. Leaf alkaloid extract of G. glauca was also found to affect the mitochondrial membrane potential with IC50 value 144.51 μg/mL, and inhibited DNA polymerase α and β activities dose dependently, thus potentially interfering with DNA replication and repair processes. Leaf alkaloid extract also showed the potential to induce DNA damage of 53.6%, albeit somewhat less than the standard drug camptothecin (64.94%) as confirmed by the TUNEL assay. Additionally, the GgLAE (IC50 144.51 μg/mL) showed significant inhibition of MCF-7 cells proliferation after 24 h, revealing phase arrests in sub G0/G1, S, and G2/M. These findings suggest that G. glauca leaf alkaloid extract contains alkaloids that possess anticancer properties with multiple targets, making the plant a natural source for a promising phytochemical drug candidates for further evaluation in pre-clinical and clinical studies. Further investigations are warranted to determine the efficacy, safety, identification and characterization of the alkaloids, and evaluate and determine their potential applications in cancer therapy.

HPLC-PDA-ESI-HRMS-Based Profiling of Secondary Metabolites of Rindera graeca Anatomical and Hairy Roots Treated with Drought and Cold Stress

To cope with environmental harmful conditions, plant cells developed adaptive strategy that involves production of a wide variety of complex secondary metabolites. The spectrum and quantity of biosynthesized compounds in specific plant species is determined by its genotype, tissue, developmental and physiological stage and environmental factors. This phenomenon was used to exploit the potential of anatomical and hairy root cultures of Rindera graeca to produce bioactive compounds. Cultivated in vitro roots were subjected to abiotic stresses i.e., drought or coldness. Next the extract profiling was performed using HPLC-PDA-ESI-HRMS method, as well quantitative determination of caffeic, rosmarinic and lithospermic B acids, that were present in all root extracts. Phenolic acids, flavonoids and iridoids represent the major groups of compounds detected in chemical profiles growing under various conditions roots. The highest number of phytochemicals was determined in roots subjected to coldness. Lithospermic B acid proved to be the most abundant compound in all investigated extracts. Among applied abiotic stress factors it was demonstrated that coldness affected to the most secondary metabolites production. The results of current study suggest that root cultures of R. graeca could serve as a new and abundant source of lithospermic B acid.

Chemical Profile and Screening of Bioactive Metabolites of Rindera graeca (A. DC.) Bois. & Heldr. (Boraginaceae) In Vitro Cultures

Rindera graeca is a rare endemic plant where in vitro culture has been used in order to investigate bioactive metabolites. Phytochemical study of the in vitro shoots and hairy roots led to the isolation of seven phenolic derivatives and the unusual furano-naphthoquinone rinderol. R. graeca was also analyzed for its pyrrolizidine alkaloids content by LC-MS, and it was found to contain echinatine together with echinatine and rinderine N-oxides. Rinderol, isolated only from in vitro hairy root culture for the first time in the genus, revealed promising bioactivities. It was evaluated in vitro against a panel of microorganisms, showing very strong activity specifically against Gram-positive bacteria (MIC values 0.98 × 10-2-1.18 µg/mL) as well as very interesting antiproliferative effect against the human non-small-cell bronchopulmonary carcinoma cell line NSCLC-N6-L16 and the epidermoid lung cancer cell line A549. These findings were compared with the chemical profile of the plant from nature, while this study is the first to report on the effects of R. graeca extracts obtained from in vitro culture, providing a valuable contribution to the scientific community towards this sustainable method of production of potential bioactive molecules.

Rindera graeca (Boraginaceae) Phytochemical Profile and Biological Activities

Rindera graeca is a Greek endemic plant of the Boraginaceae family which has never been studied before. Consequently, this study attempted to phytochemically examine the aerial parts of this species. Nine phenolic secondary metabolites were identified, consisting of seven caffeic acid derivatives and two flavonol glucosides, namely rutin and quercetin-3-rutinoside-7-rhamnoside. These flavonoids, together with rosmarinic acid, were isolated via column chromatography and structurally determined through spectral analysis. Quercetin-3-rutinoside-7-rhamnoside is an unusual triglycoside, which is identified for the first time in Rindera genus and among Boraginaceae plants. This metabolite was further examined with thermal analysis and its 3D structure was simulated, revealing some intriguing information on its interaction with biological membrane models, which might have potential applications in microcirculation-related conditions. R. graeca was also analyzed for its pyrrolizidine alkaloids content, and it was found to contain echinatine together with echinatine N-oxide and rinderine N-oxide. Additionally, the total phenolic and flavonoid contents of R. graeca methanol extract were determined, along with free radical inhibition assays. High total phenolic content and almost complete inhibition at experimental doses at the free radical assays indicate a potent antioxidant profile for this plant. Overall, through phytochemical analysis and biological activity assays, insight was gained on an endemic Greek species of the little-studied Rindera genus, while its potential for further applications has been assessed.

Design and Antiproliferative Evaluation of Novel Sulfanilamide Derivatives as Potential Tubulin Polymerization Inhibitors

A series of sulfanilamide-1,2,3-triazole hybrids were designed by a molecular hybridization strategy and evaluated for antiproliferative activity against three selected cancer cell lines (MGC-803, MCF-7 and PC-3). The detailed structure-activity relationships for these sulfanilamide-1,2,3-triazole hybrids were investigated. All these sulfanilamide-1,2,3-triazole hybrids exhibited moderate to potent activity against all cell lines. In particular 4-methyl-N-((1-(3-phenoxybenzyl)-1H-1,2,3-triazol-4-yl)methyl)benzenesulfonamide (11f) showed the most potent inhibitory effect against PC-3 cells, with an IC₅₀ value of 4.08 μM. Furthermore, the tubulin polymerization inhibitory activity in vitro of compound 11f was 2.41 μM. These sulfanilamide hybrids might serve as bioactive fragments for developing more potent antiproliferative agents.

Pyrrolizidine alkaloids: occurrence, biology, and chemical synthesis

Covering: 2013 up to the end of 2015This review covers the isolation and structure of new pyrrolizidines; pyrrolizidine biosynthesis; biological activity, including the occurrence of pyrrolizidines as toxic components or contaminants in foods and beverages; and formal and total syntheses of naturally-occurring pyrrolizidine alkaloids and closely related non-natural analogues.

Chemotaxonomic perspectives of the Paracaryum (Cynoglosseae, Boraginaceae) taxa based on fruit fatty acid composition

Paracaryum is a medium sized genus in Cynoglosseae. This study represents the most comprehensive phytochemical investigation of Paracaryum to date. The fatty acid compositions of the fruits of ten Paracaryum taxa belonging to three different subgenera were investigated for chemotaxonomic allocation using gas chromatography. The fatty acid profiles of seven Paracaryum taxa, five of which are endemic to Turkey, were recorded for the first time. Among the twenty-two analysed fatty acids, oleic, linoleic and α-linolenic acids were the major fatty acids represented. The oleic acid content ranged from 22.1% in P. hirsutum to 51.7% in P. lithospermifolium subsp. cariense var. erectum; linolenic acid content ranged from 8.6% in P. lithospermifolium subsp. cariense var. erectum to 20.7% in P. erysimifolium; α-linolenic acid content ranged from 7.5% in P. lithospermifolium subsp. cariense var. erectum to 13.5% in P. cristatum subsp. cristatum; gamma linolenic acid content ranged from 2.8% in P. erysimifolium to 6.0% in P. hirsutum. Additional fatty acids also displayed varying levels in different species; palmitic acid content accounted for 17.7% in P. erysimifolium, erucic acid content was 8.73% in P. strictum, eicosenoic acid content was 6.0% in P. cristatum subsp. cristatum, eicosadienoic acid content was 4.4% in P. hirsutum, and stearic acid content was 4.3% in P. erysimifolium. The classification of the tribe Cynoglosseae remains controversial despite the many intensive morphological and phylogenetic investigations that have been carried out. Our fatty acid data from Paracaryum were analysed together with previously recorded fatty acid data from Cynoglosseae s.l. taxa to examine the chemotaxonomic contribution to the classification among taxa in Cynoglosseae by multivariate methods, including the unweighted pair group method with arithmetic mean and principal component analysis. An assessment of these chemometrics data supported the chemotaxonomic position of the genus Paracaryum in the tribe Cynoglosseae. While the principal component graphic did not depict clear separation of the three subgenera of Paracaryum, the principal component analysis revealed the chemotaxonomic significance of palmitic, linoleic, capric, and oleic acids.

Optimisation of isolation procedure for pyrrolizidine alkaloids from Rindera umbellata Bunge

Procedure for isolation of pyrrolizidine alkaloids (PAs) from Rindera umbellata Bunge plant species was optimised. Different extraction media (methanol, ethanol and sulphuric acid), concentration and volume of sulphuric acid, pH of PA solution for alkaline extraction, extraction time and techniques (maceration, ultrasonic and overhead rotary mixer assisted extraction) were investigated. The yields of six PAs (7-angeloyl heliotridane, 7-angeloyl heliotridine, lindelofine, 7-angeloyl rinderine, punctanecine and heliosupine) were monitored by GC-MS/FID. The best results for the isolation all of six PAs were obtained when the extraction was performed with 1 M sulphuric acid (30 mL per 1.00 g of dried sample) by overhead rotary mixer during three days. Optimal pH value for alkaline extraction of PAs with CH₂Cl₂ was 9, and the extraction should be performed with four portions of 30 mL of CH₂Cl₂. This procedure could be also useful for a plant sample preparation for GC and LC analyses of PAs.

Diversity of Pyrrolizidine Alkaloids in the Boraginaceae Structures, Distribution, and Biological Properties

Among the diversity of secondary metabolites which are produced by plants as means of defence against herbivores and microbes, pyrrolizidine alkaloids (PAs) are common in Boraginaceae, Asteraceae and some other plant families. Pyrrolizidine alkaloids are infamous as toxic compounds which can alkylate DNA und thus cause mutations and even cancer in herbivores and humans. Almost all genera of the family Boraginaceae synthesize and store this type of alkaloids. This review reports the available information on the present status (literature up to early 2014) of the pyrrolizidine alkaloids in the Boraginaceae and summarizes the topics structure, distribution, chemistry, chemotaxonomic significance, and biological properties.