In Vitro Anti-Proliferative, and Kinase Inhibitory Activity of Phenanthroindolizidine Alkaloids Isolated from Tylophora indica

Medicinal Plants: Advances in Phytochemistry and Ethnobotany

Prance once defined Ethnobotany as an interdisciplinary Science combining Anthropology and Botany [...].

Phenanthroindolizidine Alkaloids Secondary Metabolites Diversity in Medicinally Viable Plants of the Genus Tylophora

Plants of the genus Tylophora have commonly been used in traditional medicine in various communities, especially in the tropical and subtropical regions of climatic zones. Of the nearly 300 species reported in the Tylophora genus, eight are primarily used in various forms to treat a variety of bodily disorders based on the symptoms. Certain plants from the genus have found use as anti-inflammatory, anti-tumor, anti-allergic, anti-microbial, hypoglycemic, hypolipidemic, anti-oxidant, smooth muscle relaxant, immunomodulatory, and anti-plasmodium agents, as well as free-radical scavengers. Pharmacologically, a few plant species from the genus have exhibited broad-spectrum anti-microbial and anti-cancer activity, which has been proven through experimental evaluations. Some of the plants in the genus have also helped in alcohol-induced anxiety amelioration and myocardial damage repair. The plants belonging to the genus have also shown diuretic, anti-asthmatic, and hepato-protective activities. Tylophora plants have afforded diverse structural bases for secondary metabolites, mainly belonging to phenanthroindolizidine alkaloids, which have been found to treat several diseases with promising pharmacological activity levels. This review encompasses information on various Tylophora species, their distribution, corresponding plant synonyms, and chemical diversity of the secondary metabolic phytochemicals as reported in the literature, together with their prominent biological activities.

Phenanthroindolizidine Alkaloids Isolated from Tylophora ovata as Potent Inhibitors of Inflammation, Spheroid Growth, and Invasion of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC), representing the most aggressive form of breast cancer with currently no targeted therapy available, is characterized by an inflammatory and hypoxic tumor microenvironment. To date, a broad spectrum of anti-tumor activities has been reported for phenanthroindolizidine alkaloids (PAs), however, their mode of action in TNBC remains elusive. Thus, we investigated six naturally occurring PAs extracted from the plant Tylophora ovata: O-methyltylophorinidine (1) and its five derivatives tylophorinidine (2), tylophoridicine E (3), 2-demethoxytylophorine (4), tylophoridicine D (5), and anhydrodehydrotylophorinidine (6). In comparison to natural (1) and for more-in depth studies, we also utilized a sample of synthetic O-methyltylophorinidine (1s). Our results indicate a remarkably effective blockade of nuclear factor kappa B (NFκB) within 2 h for compounds (1) and (1s) (IC50 = 17.1 ± 2.0 nM and 3.3 ± 0.2 nM) that is different from its effect on cell viability within 24 h (IC50 = 13.6 ± 0.4 nM and 4.2 ± 1 nM). Furthermore, NFκB inhibition data for the additional five analogues indicate a structure–activity relationship (SAR). Mechanistically, NFκB is significantly blocked through the stabilization of its inhibitor protein kappa B alpha (IκBα) under normoxic as well as hypoxic conditions. To better mimic the TNBC microenvironment in vitro, we established a 3D co-culture by combining the human TNBC cell line MDA-MB-231 with primary murine cancer-associated fibroblasts (CAF) and type I collagen. Compound (1) demonstrates superiority against the therapeutic gold standard paclitaxel by diminishing spheroid growth by 40% at 100 nM. The anti-proliferative effect of (1s) is distinct from paclitaxel in that it arrests the cell cycle at the G0/G1 state, thereby mediating a time-dependent delay in cell cycle progression. Furthermore, (1s) inhibited invasion of TNBC monoculture spheroids into a matrigel®-based environment at 10 nM. In conclusion, PAs serve as promising agents with presumably multiple target sites to combat inflammatory and hypoxia-driven cancer, such as TNBC, with a different mode of action than the currently applied chemotherapeutic drugs.