Dolabellane-type diterpene alkaloids from Nigella glandulifera

Screening of Monoamine Oxidase Inhibitors from Seeds of Nigella glandulifera Freyn et Sint. by Ligand Fishing and Their Neuroprotective Activity

Nigella glandulifera is a traditional medicinal plant used to treat seizures, insomnia, and mental disorders among the Tibetan and Xinjiang people of China. Recent pharmacological research indicates that the seeds of this plant have a neuroprotective effect; however, the chemical components responsible for this effect are unknown. Monoamine oxidase B (MAO-B) has been recognized as a target for developing anti-Parkinson's disease drugs. In this work, MAO-B functionalized magnetic nanoparticles were used to enrich the enzyme's ligands in extracts of N. glandulifera seeds for rapid screening of MAO-B inhibitors coupled with HPLC-MS. Tauroside E and thymoquinone were found to inhibit the enzyme with IC₅₀ values of 35.85 μM and 25.54 μM, respectively. Both compounds exhibited neuroprotective effects on 6-OHDA-induced PC-12 cells by increasing the cell viability to 52% and 58%, respectively, compared to 50% of the injured cells. Finally, molecular docking indicated strong interactions of both inhibitors with the enzyme. This work shows that MAO-B functionalized magnetic nanoparticles are effective for rapid screening of anti-PD inhibitors from complex herbal mixtures and, at the same time, shows the promising potential of this plant's seeds in developing anti-PD drugs.

Chemical constituents from the seeds of Nigella glandulifera and their hypoglycemic activities

The seeds of Nigella glandulifera Freyn et Sint. are traditional Uygur medicine used for the treatment of diabetes. However, the active anti-diabetic constituents in the seeds of N. glandulifera remain unclear. In the present study, a new delabellane-type diterpene, 8-denicotinoylnigellamine A1 (1), and a new acyclic sesquiterpene, 2,6,10-trimethyl-6,7,12-trihydroxy-dodec-2-ene (3), together with eight known compounds including alkaloids (2 and 7), triterpenoid saponins (4–6), and phenolic compounds (8–10), were isolated from the seeds of N. glandulifera. Their structures were determined by extensive spectroscopic analyses and quantum chemical calculations. We evaluated the potential protective effects of the isolated compounds on an insulin resistant HepG2 (IR-HepG2) cell model. The results showed that compounds 2, 4–8, and 10 could promote the consumption of glucose in IR-HepG2 cells. Those compounds might be responsible for the anti-diabetic effects of the seeds of N. glandulifera.

The seed of Nigella glandulifera Freyn et Sint. is a traditional Uygur medicine used for the treatment of diabetes.

The ethnobotany, phytochemistry, and biological properties of Nigella damascena - A review

This review is a systematic scientific work on medicinal and traditional use, on the chemical composition of specialized metabolites, volatile and non-volatile, on aspects related to toxicology and phytotherapy of Nigella damascena L. The genus Nigella (Ranunculaceae) is distributed throughout the Mediterranean basin, extending to northern India, and has been divided into three sections. Nigella damanscena L. is traditionally used as an ingredient in food, for example, as flavouring agents in bread and cheese, but is also known in folk medicine, used to regulate menstruation; for catarrhal affections and amenorrhea; as a diuretic and sternutatory; as an analgesic, anti-oedematous, and antipyretic; and for vermifuge and its disinfectant effects. This paper reviews the most dated to the latest scientific research on this species, highlighting the single isolated metabolites and exploring their biological activity. Fifty-seven natural compounds have been isolated and characterised from the seeds, roots, and aerial parts of the plant. Among these constituents, alkaloids, flavonoids, diterpenes, triterpenes, and aromatic compounds are the main constituents. The isolated compounds and the various extracts obtained with solvents of different polarities presented a diverse spectrum of biological activities such as antibacterial, antifungal, antitumour, antioxidant, anti-inflammatory, antipyretic, anti-oedema, and antiviral activities. Various in vitro and in vivo tests have demonstrated the pharmacological potential of β-elemene and alkaloid damascenin. Unfortunately, the largest number of biological studies on this species and its metabolites have been conducted in vitro; therefore, further investigation is necessary to evaluate the toxicological aspects and real mechanisms of action of crude extracts to confirm the therapeutic potential of N. damascena.

Structural diversity, bioactivities, and biosynthesis of natural diterpenoid alkaloids

Covering: 2009 to 2018. Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, are a diverse class of compounds having complex structural features with many stereocenters. The important pharmacological activities and structural complexity of the diterpenoid alkaloids have long interested scientists due to their medicinal uses, infamous toxicity, and unique biosynthesis. Since 2009, 373 diterpenoid alkaloids, assigned to 46 skeletons, have been isolated and identified from plants mostly in the Ranunculaceae family. The names, classes, molecular weight, molecular formula, NMR data, and plant sources of these diterpene alkaloids are collated here. This review will be a detailed update of the naturally occurring diterpene alkaloids reported from the plant kingdom from 2009-2018, providing an in-depth discussion of their diversity, biological activities, pharmacokinetics, toxicity, application, evolution, and biosynthesis.

Nigegladines A-C, Three Thymoquinone Dimers from Nigella glandulifera

Nigegladines A-C (1-3), three thymoquinone dimers, were isolated from the seeds of Nigella glandulifera. Racemic 1 possesses a unique tricyclo[5.4.0.1^2,6]dodecane carbon skeleton, and compounds 2 and 3 are two unusual diterpenoid alkaloids with indole cores. Their structures were determined by extensive spectroscopic analyses, and that of 1 was confirmed by single-crystal X-ray diffraction. Both (+)-1 and (-)-1 exhibited significant protective effects against hypoxia/reoxygenation-induced H9c2 myocardial cell injury.

Three new alkaloids from the seeds of Nigella glandulifera

Three new alkaloids namely 8-(4-hydroxyphenyl)-6-methoxy-3,4-dihydroisoquinolin-1(2H)-one (1), 4-aminonigellidine (2), and N-[(4-hydroxy-2-isopropyl-5-methyl)]phenylurea (3), along with six known ones (4-9), were isolated from the seeds of Nigella glandulifera. The structures of 1-3 were determined through spectroscopic analyses (HRESIMS, 1D/2D NMR). Compound 1 was a rare isoquinolinone alkaloid with phenyl substituted at C-8.

New phenolic compounds from the seeds of Nigella glandulifera and their inhibitory activities against human cancer cells

Four phenolic compounds, including two new ones, Nigephenol A and B (1-2), and a new natural product, Nigephenol C (3), were isolated from the seeds of Nigella glandulifera. Their structures were elucidated on the basis of spectroscopic analyses using HR-ESI-MS, 1D and 2D NMR spectra. All compounds were evaluated by MTT method for in vitro cytotoxicity against four human cancer cell lines (Bel7402, HepG2, HCT-8 and A549). The results revealed that Compounds 1-4 showed more selective activities against HepG2 cells, and that Compound 2 showed significant inhibitory effects against four human tumor cell lines with IC50 values comparable to those of 5-fluorouracil.

Highly conjugated norditerpenoid and pyrroloquinoline alkaloids with potent PTP1B inhibitory activity from Nigella glandulifera

Three norditerpenoid alkaloids, nigelladines A-C (1-3), and one pyrroloquinoline alkaloid, nigellaquinomine (4), all possessing new skeletons with highly conjugated systems, were isolated from Nigella glandulifera. The 8aS-configuration for 1 and 2 was determined by comparison of the experimental and calculated electronic circular dichroism spectra. These alkaloids exhibited potent protein tyrosine phosphatase 1B (PTP1B) inhibitory activity but are devoid of cytotoxicity against the A431 cell line at 100 μM.

A Spotlight on Chemical Constituents and Pharmacological Activities ofNigella glanduliferaFreyn et Sint Seeds

Plants belonging to the Ranunculaceae family, and particularly their seeds, have been a hot research topic in numerous pharmacognosy laboratories.Nigella glanduliferaFreyn et Sint (NG) is one of the promising, but relatively insufficiently studied, plants from this family. In this review, we summarize the recently isolated chemical constituents from the seeds of this plant including alkaloids, flavonol glycosides, isobenzofuranone derivatives, saponins, terpenes, terpenoids, and fatty acids. We put also a spotlight on the recently studied therapeutic potentials of such amazing herb seeds as antidiabetes, melanogenesis inhibition, anticancer, anti-inflammatory, antithrombosis, and antiplatelet aggregation effects. Herein, we illustrate certain properties and potentials via selected examples, and thus we suggest more studies to confirm the therapeutic hypotheses, find out new compounds, and eventually to discover novel properties.