Anti-cancer and anti-inflammatory effects of flavan-4-ol and flavan glycosides from the roots of Pronephrium penangianum

Five new flavan-4-ol glycosides jixueqiosides A-E (1-5) and two new flavan glycosides jixueqiosides F and G (6 and 7), along with twelve known flavan-4-ol glycosides (8-19) were isolated from the roots of Pronephrium penangianum. Comprehensive spectral analyses, X-ray single crystal diffraction, and theoretical ECD calculations established structures and absolute configurations. A single crystal structure of flavan-4-ol glycoside (14) was reported for the first time, while the characteristic ECD and NMR data for all isolated flavan-4-ol glycosides (1-5, 8-19) were analyzed, establishing a set of empirical rules. Activity screening of these isolates showed that 8 and 9 could inhibit the proliferation of MDA-MB-231 and MCF-7 cells with IC₅₀ values of 7.93±2.85 μM and 5.87±1.58 μM (MDA-MB-231), and 2.21±1.38 μM and 3.52±1.55 μM (MCF-7), respectively. Western blot and flow cytometry experiments showed that 8 and 9 could dose-dependently induce apoptosis in MDA-MB-231 cells by up-regulating Bax, activating caspase-3 and down-regulating BCL-2. In addition, compound 8 could affect autophagy-related proteins, such as increasing the ratio of LC3-II/LC3-I and Beclin-1 levels to inhibit the proliferation of MDA-MB-231 cells. Furthermore, anti-inflammatory studies revealed that 2, 3, 7, 13, 14 and 18 could moderately inhibit TNF-α, IL-6, and NO (nitric oxide) release.