Antiplasmodial sesquiterpene alkaloids from the roots of Maytenus mekongensis

Densely Functionalized Macrocyclic Sesquiterpene Pyridine Alkaloids from Maytenus austroyunnanensis

Eleven densely functionalized new dihydro-β-agarofuran sesquiterpenoid derivatives, named maytenoids A-K (1-11), as well as one known analog, were isolated and characterized from Maytenus austroyunnanensis. Their structures were assigned based on analysis of spectroscopic data and X-ray crystallography. Compounds 1-9 are macrocyclic sesquiterpene pyridine alkaloids generated by the respective acylation of the hydroxy groups at C-3 and C-13 of dihydro-β-agarofuran sesquiterpenoids via diverse pyridine dicarboxylic acids. Compounds 1, 2, 5-10, and 12 exhibited significant inhibitory effects on NO production at 10 μM in lipopolysaccharide (LPS)-stimulated BV2 cells.

Synthesis and Antimicrobial Activity Evaluation of Homodrimane Sesquiterpenoids with a Benzimidazole Unit

Herein we report a feasible study concerning the synthesis and the in vitro antimicrobial activity of some new homodrimane sesquiterpenoids with a benzimidazole unit. Based on some homodrimane carboxylic acids, on their acyl chlorides and intermediate monoamides, a series of seven N-homodrimenoyl-2-amino-1,3-benzimidazoles and 2-homodrimenyl-1,3-benzimidazoles was synthesized. The syntheses involved the decarboxylative cyclization and condensation of the said acids or acyl chlorides with o-phenylendiamine and 2-aminobenzimidazole, as well as the p-TsOH-mediated cyclodehydration of the said monoacylamides. The structures of the synthesized compounds have been fully confirmed, including by the X-ray diffraction. Their biological activities were evaluated on five species of fungi (Aspergillus niger, Fusarium solani, Penicillium chrysogenum, P. frequentans, and Alternaria alternata) and two strains of bacteria (Bacillus sp. and Pseudomonas aeruginosa). Compounds 7 and 20 showed higher antifungal (MIC = 0.064 and 0.05 μg/mL) and antibacterial (MIC = 0.05 and 0.032 μg/mL) activities compared to those of the standards: caspofungin (MIC = 0.32 μg/mL) and kanamycin (MIC = 2.0 μg/mL), and compounds 4, 10, 14, and 19 had moderate activities.

A Review on Phytochemicals of the Genus Maytenus and Their Bioactive Studies

The genus Maytenus is a member of the Celastraceae family, of which several species have long been used in traditional medicine. Between 1976 and 2021, nearly 270 new compounds have been isolated and elucidated from the genus Maytenus. Among these, maytansine and its homologues are extremely rare in nature. Owing to its unique skeleton and remarkable bioactivities, maytansine has attracted many synthetic endeavors in order to construct its core structure. In this paper, the current status of the past 45 years of research on Maytenus, with respect to its chemical and biological activities are discussed. The chemical research includes its structural classification into triterpenoids, sesquiterpenes and alkaloids, along with several chemical synthesis methods of maytansine or maytansine fragments. The biological activity research includes activities, such as anti-tumor, anti-bacterial and anti-inflammatory activities, as well as HIV inhibition, which can provide a theoretical basis for the better development and utilization of the Maytenus.

Natural Nitrogenous Sesquiterpenoids and Their Bioactivity: A Review

Nitrogenous sesquiterpenoids fromnatural sourcesare rare, so unsurprisingly neither the potentially valuable bioactivity nor thebroad structural diversity of nitrogenous sesquiterpenoids has been reviewed before. This report covers the progressduring the decade from 2010 to February 2020 on the isolation, identification, and bioactivity of 391 nitrogen-containing natural sesquiterpenes from terrestrial plant, marine organisms, and microorganisms. This complete and in-depth reviewshouldbe helpful for discovering and developing new drugs of medicinal valuerelated to natural nitrogenous sesquiterpenoids.

A MDR transporter contributes to the different extracellular production of sesquiterpene pyridine alkaloids between adventitious root and hairy root liquid cultures of Tripterygium wilfordii Hook.f

TwMDR1 transports sesquiterpene pyridine alkaloids, wilforine and wilforgine, into the hairy roots of T. wilfordii Hook.f. resulting in low secretion ratio of alkaloids. Hairy roots (HRs) exhibit high growth rate and biochemical and genetic stability. However, varying secondary metabolites in HR liquid cultures mainly remain in root tissues, and this condition may affect cell growth and cause inconvenience in downstream extraction. Studies pay less attention to adventitious root (AR) liquid cultures though release ratio of some metabolites in AR liquid cultures is significantly higher than that of HR. In Tripterygium wilfordii Hook.f., release ratio of wilforine in AR liquid cultures reached 92.75 and 13.32% in HR on day 15 of culture. To explore potential roles of transporters in this phenomenon, we cloned and functionally identified a multidrug resistance (MDR) transporter, TwMDR1, which shows high expression levels in HRs and is correlated to transmembrane transportation of alkaloids. Nicotiana tabacum cells with overexpressed TwMDR1 efficiently transported wilforine and wilforgine in an inward direction. To further prove the feasibility of genetically engineered TwMDR1 and improve alkaloid production, we performed a transient RNAi experiment on TwMDR1 in T. wilfordii Hook.f. suspension cells. Results indicated that release ratios of wilforine and wilforgine increased by 1.94- and 1.64-folds compared with that of the control group, respectively. This study provides bases for future studies that aim at increasing secretion ratios of alkaloids in root liquid cultures in vitro.

Dimacrolide Sesquiterpene Pyridine Alkaloids from the Stems of Tripterygium regelii

Two new dimacrolide sesquiterpene pyridine alkaloids (DMSPAs), dimacroregelines A (1) and B (2), were isolated from the stems of Tripterygium regelii. The structures of both compounds were characterized by extensive 1D and 2D NMR spectroscopic analyses, as well as HRESIMS data. Compounds 1 and 2 are two rare DMSPAs possessing unique 2-(3′-carboxybutyl)-3-furanoic acid units forming the second macrocyclic ring, representing the first example of DMSPAs bearing an extra furan ring in their second macrocyclic ring system. Compound 2 showed inhibitory effects on the proliferation of human rheumatoid arthritis synovial fibroblast cell (MH7A) at a concentration of 20 μM.

Bioactive Dihydro-β-agarofuran Sesquiterpenoids from the Australian Rainforest Plant Maytenus bilocularis

Chemical investigations of the CH2Cl2 extract obtained from the leaves of the Australian rainforest tree Maytenus bilocularis afforded three new dihydro-β-agarofurans, bilocularins A-C (1-3), and six known congeners, namely, celastrine A (4), 1α,6β,8α-triacetoxy-9α-benzoyloxydihydro-β-agarofuran (5), 1α,6β-diacetoxy-9α-benzoyloxy-8α-hydroxydihydro-β-agarofuran (6), Ejap-10 (11), 1α,6β-diacetoxy-9β-benzoyloxydihydro-β-agarofuran (12), and Ejap-2 (13). The major compound 1 was used in semisynthetic studies to afford four ester derivatives (7-10). The chemical structures of 1-3 were elucidated following analysis of 1D/2D NMR and MS data. The absolute configurations of bilocularins A (1) and B (2) were determined by single-crystal X-ray diffraction analysis. All compounds were evaluated for cytotoxic activity against the human prostate cancer cell line LNCaP; none of the compounds were active. However, several compounds showed similar potency to the drug efflux pump inhibitor verapamil in reversing the drug resistance of the human leukemia CEM/VCR R cell line. In addition, similar to verapamil, compound 5 was found to inhibit leucine uptake in LNCaP cells (IC50 = 15.5 μM), which was more potent than the leucine analogue 2-aminobicyclo[2.2.1]heptane-2-carbocyclic acid. This is the first report of secondary metabolites from Maytenus bilocularis.

Untargeted analysis of sesquiterpene pyridine alkaloids from the dried roots of Tripterygium wilfordii using high-performance liquid chromatography/electrospray ionization tandem mass spectrometry

RATIONALE

Sesquiterpene pyridine alkaloids are a large group of highly oxygenated sesquiterpenoids that have attracted attention in the fields of medicine because of their significant biological activities.

METHODS

Reference compounds including 14 sesquiterpene pyridine alkaloids and one dihydroagarofuran ester were analyzed by collision-induced dissociation tandem mass spectrometry (CID-MS/MS). A high-performance liquid chromatography/electrospray ionization (HPLC/ESI)-MS/MS method at two collision energies was adopted to investigate the botanical extracts of Tripterygium wilfordii.

RESULTS

For 15 reference compounds, in the high mass range, the product ions were formed by the loss of side chains or H2 O. In the low mass range, the high-abundance product ions at m/z 206, 204, or 194 were the characteristic ions of the pyridine moiety. The characteristic product ion at m/z 310 was formed through an ion-neutral complex intermediate. Fifty-four sesquiterpenoid derivatives, including 50 sesquiterpene pyridine alkaloids, were identified or tentatively characterized in botanical extracts of T. wilfordii based on their elemental constituents, characteristic fragmentation patterns, and the major product ion profiles of the reference compounds ascertained with HPLC/ESI-MS/MS at two collision energies. It seems that isocratic energy was appropriate for the untargeted analysis of compounds with molecular weights exceeding 800 Da, whereas a linear gradient energy vs molecular weight was suitable for those compounds with molecular weights below 800 Da.

CONCLUSIONS

The HPLC/ESI-MS/MS method, combining characteristic fragmentation patterns and the profiles of the product ions generated at different collision energies, is an effective technique for characterizing untargeted compounds.

β-Agarofurans and Sesquiterpene Pyridine Alkaloids from Maytenus spinosa

Nine new β-dihydroagarofurans (1-9) and four new sesquiterpene pyridine alkaloids (10-13) were isolated from the leaves of Maytenus spinosa. Their structures were determined mainly by 1D- and 2D-NMR spectroscopic studies. The absolute configuration of compound 6 was established using CD spectroscopy. Several derivatives (14-20) were prepared from the sesquiterpene 13. Most of the sesquiterpenoids were tested for anti-HIV activity, but only compound 1 was found to be active.

Nitrogen-containing dihydro-β-agarofuran derivatives from Tripterygium wilfordii

Thunder god vine, the dried roots of Tripterygium wilfordii, is a widely used traditional Chinese medicine. More than 200 bioactive complex natural products have been isolated from this herb. Inspired by the diversity of chemical structures and bioactivities of the components of this herb, the investigation to mine new chemical entities as potential drug leads led to the identification of 36 nitrogen-containing compounds. Among them, 18 new dihydro-β-agarofuran alkaloids (tripterygiumines A-L (1-12), M-Q (22-26), and R (33)) were identified from the spectroscopic data and chemical degradation studies. Tripterygiumine Q (26) exhibited immunosuppressive activity against human peripheral mononuclear cells with an IC50 value of 8.67 μM and showed no cytotoxicity, even at 100 μM, indicating that 26 may represent a novel scaffold for the development of new immunosuppressants.

Dihydroagarofuran derivatives from the dried roots of Tripterygium wilfordii

Five new sesquiterpene derivatives, including dihydroagarofuran pyridine macrolides 1-4 and dihydroagarofuran ester 18, and 13 known dihydroagarofuran derivatives were isolated from the aqueous EtOH extract of the dried roots of Tripterygium wilfordii. An in vitro antiherpetic activity assay indicated that compounds 11 and 17 displayed weak and moderate inhibition against herpes simplex virus type II, respectively.