New steroidal alkaloids from Buxus longifolia

Chemistry and bioactivities of natural steroidal alkaloids

Steroidal alkaloids possess the basic steroidal skeleton with a nitrogen atom in rings or side chains incorporated as an integral part of the molecule. They have demonstrated a wide range of biological activities, and some of them have even been developed as therapeutic drugs, such as abiraterone acetate (Zytiga^®), a blockbuster drug, which has been used for the treatment of prostate cancer. Structurally diverse natural steroidal alkaloids present a wide spectrum of biological activities, which are attractive for natural product chemistry and medicinal chemistry communities. This review comprehensively covers the structural classification, isolation and various biological activities of 697 natural steroidal alkaloids discovered from 1926 to October 2021, with 363 references being cited.

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.

New cholinesterase-inhibiting triterpenoid alkaloids from Buxus hyrcana

The current phytochemical investigation on Buxus hyrcana Pojark. has resulted in the isolation of the triterpenoid alkaloids 1-10. The structures of five new alkaloids, hyrcanone (1), hyrcanol (2), hyrcatrienine (3), N(b)-dimethylcycloxobuxoviricine (4), and hyrcamine (5), were elucidated by means of modern spectroscopic techniques, while the known alkaloids, buxidin (6), buxandrine (7), buxabenzacinine (8), buxippine-K (9) and E-buxenone (10), were identified by comparing their spectral data with those reported earlier. Compounds 1 and 3-9 were found to be acetyl- and butyrylcholinesterase inhibitors. The IC50 values were estimated to be in the range of 83.0-468.0 microM against AChE and 1.12-350.0 microM against BChE. The structure-activity relationship studies suggested that the presence of dimethylamino moieties at C(3) and C(20) is the most important factor influencing the activity of these compounds against the cholinesterase enzymes. All compounds were also evaluated for cytotoxicity on a fibroblast cell line with incubation of 24 h. No cytotoxic effects were exerted by any compound.