Cardenolides and dihydro-β-agarofuran sesquiterpenes from the seeds of Salacia staudtiana

Research Progress on Plant-Derived Cardenolides (2010-2023)

Cardenolides are a class of steroidal glycoside compounds that are mainly distributed in plants, have significant physiological activity in the heart, and have been used clinically for over 200 years. To provide a reference for further research and development of these compounds, the phytochemical and biological properties of natural cardenolides (295 compounds in total) isolated between 2010 and 2023 from 17 families and hundreds of species belonging to 70-80 genera were reviewed. In vitro and in vivo studies have indicated that antitumor, antibacterial, and antiviral activities are the most commonly reported pharmacological properties of cardenolides. Antitumor activities have been thoroughly studied to understand their structure-activity relationships, revealing numerous potential anticancer molecules that lay the theoretical foundation for further development of traditional Chinese medicinal herbs and the creation of new drugs.

Cytotoxic Compounds from the Stem Bark of Two subsp. of Bersama abyssinica

Three new bufadienolides, namely, paulliniogenin A (1), paulliniogenin B (2), and 16β-formyloxybersamagenin 1,3,5-orthoacetate (3), together with two known bufadienolides and six known phenolic substances, were isolated from the stem bark of Bersama abyssinica subsp. abyssinica and B. abyssinica subsp. paullinioides. The structures of the compounds were elucidated based on their NMR and HRMS data analyses. The relative configurations were defined by single-crystal X-ray crystallography and NOESY correlations. Cytotoxicity against the L929 and KB3.1 cancer cell lines of the isolated compounds was investigated using an MTT assay. Paulliniogenin A (1) and 16β-hydroxybersamagenin-1,3,5-orthoacetate (4) showed cytotoxicity against the KB3.1 cell line with IC₅₀ values of 1.4 ± 0.77 and 1.6 ± 0.81 μM, respectively. Moreover, paulliniogenin A (1) and paulliniogenin B (2) demonstrated weak activity against Staphylococcus aureus.

Cytotoxic bufadienolides from the leaves of a medicinal plant Melianthus comosus collected in South Africa

From the leaves of South African medicinal plant Melianthus comosus, four previously undescribed bufadienolides, 16β-formyloxymelianthugenin (1), 2β-acetoxymelianthusigenin (2), 2β-hydroxy-3β,5β-di-O-acetylhellebrigenin (3), and 2β-acetoxy-5β-O-acetylhellebrigenin (4) were isolated together with two known bufadienolides. The structural elucidation of the compounds was based on 1D and 2D NMR spectroscopy, high-resolution mass spectrometry, and other spectroscopic methods. The relative configurations were determined by single-crystal X-ray crystallography analysis and NOESY correlations. The isolated compounds displayed strong cytotoxicity against MCF-7 breast cancer cells, sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells. Compound 1 showed the most potent activity, with IC₅₀ values of 0.07 μM towards CCRF-CEM, 0.06 μM towards CEM/ADR5000 and 0.36 μM towards MCF-7 followed by compound 4 with IC₅₀ values of 0.13 μM towards CCRF-CEM, 0.08 μM towards CEM/ADR5000 and 0.53 μM towards MCF-7.

Cytotoxic Bufadienolides from the Leaves of Melianthus major

Melianthus major is a medicinal plant endemic to South Africa. Its leaf extract led to the isolation of five new bufadienolides, 2β-acetoxy-3,5-di-O-acetylhellebrigenin (1), 2β-acetoxy-3-O-acetylhellebrigenin (2), 2β-acetoxy-14-deoxy-15β,16β-epoxymelianthugenin (4), 2β-acetoxy-14-deoxy-15β,16β-epoxymelianthusigenin (5), and 2β-hydroxymelianthusigenin (6), and four known analogues. The structures of the compounds were elucidated using NMR and HRESIMS data analyses. The relative configurations were defined by single-crystal X-ray crystallography and NOESY correlations. The isolated compounds exhibited strong cytotoxicity against MCF-7 breast cancer cells and sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells. Compound 1 showed the most potent activity, with IC₅₀ values of 0.1 μM toward CCRF-CEM and CEM/ADR5000 and 0.3 μM toward MCF-7.