Buxus steroidal alkaloids: chemistry and biology

Structurally diverse alkaloids from Buxus sempervirens with cardioprotective activity

Extensive phytochemical study of the methanol extract of twigs and leaves of Buxus sempervirens resulted in the identification of 17 Buxus alkaloids, including 12 new ones, namely buxusemines A-L (1-12). Their structures were delineated by detailed analysis of the HRESIMS and NMR data, as well as quantum chemical NMR calculations. Buxusemine A (1) represents the second Buxus alkaloid with a unique spiro[4.6]undecatriene moiety, buxusemines B-C (2-3) are a rarely occurring class of Buxus alkaloids featured with an additional five-membered ring through the ether or lactone linkage between C-10 and C-23, and buxusemines D-F (4-6) are another rare type of Buxus alkaloids with an epoxy motif. In the assessment of their bioactivities, buxusemine F (6) and buxanoldine (17) displayed more potent protective effects than the positive control cyclovirobuxinum D in the doxorubicin-induced cardiac injury model.

Natural and synthetic drugs used for the treatment of the dementia

This review is devoted to comparative pharmacological analysis of synthetic drugs such as memantine and its isomers, as well as tacrine, velnacrine, rivastigmine, and donepezil, with natural alkaloids, terpenoids, and triterpenoid peroxides, which are used to treat dementia, Alzheimer's and Parkinson's diseases, myasthenia gravis and other neurodegenerative diseases. Recently discovered by French scientists from Marseille triterpenoid hydroperoxides demonstrate high activity as potential therapeutic agents for the treatment of dementia. The information presented in this review is of great interest to pharmacologists, medical chemists, physiologists, neurologists and doctors, as well as for the pharmaceutical industry.

Anandins A and B, Two Rare Steroidal Alkaloids from a Marine Streptomyces anandii H41-59

Anandins A (1) and B (2), two rare steroidal alkaloids, were isolated from the fermentative broth of a marine actinobacteria Streptomyces anandii H41-59. The gross structures of the two alkaloids were elucidated by spectroscopic methods including HR-ESI-MS, and NMR. Their absolute configurations were confirmed by single-crystal X-ray diffraction analysis and comparison of their experimental and calculated electronic circular dichroism spectra, respectively. Anandin A exhibited a moderate inhibitory effect against three human cancer cell lines MCF-7, SF-268, and NCI-H460 with IC₅₀ values of 7.5, 7.9, 7.8 μg/mL, respectively.

Terminamines K-S, Antimetastatic Pregnane Alkaloids from the Whole Herb of Pachysandra terminalis

Nine new pregnane alkaloids (1-9), together with eight known alkaloids (10-17), were isolated from the whole herb of Pachysandra terminalis. Their structures were elucidated on the basis of spectroscopic analyses. In addition, the isolates were examined for their ability to inhibit the migration of MDA-MB-231 cells induced by the chemokine epidermal growth factor (EGF). Alkaloids 1, 5, 7, 9, 12, and 17 presented significant anti-metastasis activities compared with the positive reagent, LY294002.

Quantification of steroidal alkaloids in Buxus papillosa using electrospray ionization liquid chromatography-triple quadrupole mass spectrometry

Buxus papillosa is one of the most extensively studied species of the genus Buxus known to possess steroidal alkaloids which can be used for assessing the various pharmacological activities of this plant. This paper describes the liquid chromatography-electrospray ionization triple quadrupole mass spectrometry (LC-ESI-QQQ-MS) method for the quantification of six steroidal alkaloids as chemical markers in the extracts of leaves, roots and stems of B. papillosa. Quantitative MS/MS analysis was carried out by optimization of the most sensitive transition for each analyte. This has yielded detection and quantification limits of 0.486-8.08 ng/mL and 1.473-24.268 ng/mL, respectively for all analytes. Linearity of response was also achieved and the regression coefficient found to be >0.99 for all analyzed compounds. The newly developed MRM (Multiple Reaction Monitoring) method showed excellent sensitivity for the quantification of steroidal alkaloids within 15 min run time. This paper describes the application of LC-QQQ-MS technique for steroidal alkaloids analysis in plant samples.

Antiprotozoal activity of Buxus sempervirens and activity-guided isolation of O-tigloylcyclovirobuxeine-B as the main constituent active against Plasmodium falciparum

Buxus sempervirens L. (European Box, Buxaceae) has been used in ethnomedicine to treat malaria. In the course of our screening of plant extracts for antiprotozoal activity, a CH₂Cl₂ extract from leaves of B. sempervirens showed selective in vitro activity against Plasmodium falciparum (IC₅₀ = 2.79 vs. 20.2 µg/mL for cytotoxicity against L6 rat cells). Separation of the extract by acid/base extraction into a basic and a neutral non-polar fraction led to a much more active and even more selective fraction with alkaloids while the fraction of non-polar neutral constituents was markedly less active than the crude extract. Thus, the activity of the crude extract could clearly be attributed to alkaloid constituents. Identification of the main triterpene-alkaloids and characterization of the complex pattern of this alkaloid fraction was performed by UHPLC/+ESI-QTOF-MS analyses. ESI-MS/MS target-guided larger scale preparative separation of the alkaloid fraction was performed by ‘spiral coil-countercurrent chromatography’. From the most active subfraction, the cycloartane alkaloid O-tigloylcyclovirobuxeine-B was isolated and evaluated for antiplasmodial activity which yielded an IC₅₀ of 0.455 µg/mL (cytotoxicity against L6 rat cells: IC₅₀ = 9.38 µg/mL). O-tigloylcyclovirobuxeine-B is thus most significantly responsible for the high potency of the crude extract.

Terpenoid-Alkaloids: Their Biosynthetic Twist of Fate and Total Synthesis

Terpenes and alkaloids are ever-growing classes of natural products that provide new molecular structures which inspire chemists and possess a broad range of biological activity. Terpenoid-alkaloids originate from the same prenyl units that construct terpene skeletons. However, during biosynthesis, a nitrogen atom (or atoms) is introduced in the form of β-aminoethanol, ethylamine, or methylamine. Nitrogen incorporation can occur either before, during, or after the cyclase phase. The outcome of this unique biosynthesis is the formation of natural products containing unprecedented structures. These complex structural motifs expose current limitations in organic chemistry, thus providing opportunities for invention. This review focuses on total syntheses of terpenoid-alkaloids and unique issues presented by this class of natural products. More specifically, it examines how these syntheses relate to the way terpenoid-alkaloids are made in Nature. Developments in chemistry that have facilitated these syntheses are emphasized, as well as chemical technology needed to conquer those that evade synthesis.

Triterpenoidal alkaloids from Buxus natalensis and their acetylcholinesterase inhibitory activity

Acetylcholinesterase (AChE) inhibition-directed phytochemical studies on the methanolic extract of Buxus natalensis, collected in South Africa, resulted in the isolation of 12 compounds: O(2)-natafuranamine (1), O(10)-natafuranamine (2), cyclonataminol (3), 31-demethylbuxaminol A (4), buxaminol A (5), buxafuranamide (6), buxalongifolamidine (7), buxamine A (8), cyclobuxophylline K (9), buxaminol C (10), methyl syringate (11), and p-coumaroylputrescine (12). Compounds 1-4 were new alkaloids, and compound 5 was isolated for the first time as a natural product. Their structures were elucidated with the aid of extensive NMR and mass spectroscopic studies. Compounds 1 and 2 are members of a rarely occurring class of Buxus alkaloids, having a tetrahydrofuran ring incorporated in their structures. Compounds 1-12 exhibited strong to moderate AChE inhibitory activity.