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 electronic circular dichroism (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 μmol·L⁻¹ and 5.87±1.58 μmol·L⁻¹ (MDA-MB-231), and 2.21±1.38 μmol·L⁻¹ and 3.52±1.55 μmol·L⁻¹ (MCF-7), respectively. Western blotting and flow cytometry analyses demonstrated that 8 and 9 dose-dependently induced apoptosis in MDA-MB-231 cells by up-regulating BAX, activating caspase-3 and down-regulating BCL-2. Additionally, compound 8 affected autophagy-related proteins, increasing the ratio of LC3-II/LC3-I and Beclin-1 levels to inhibit MDA-MB-231 cell proliferation. Moreover, anti-inflammatory studies indicated that 2, 3, 7, 13, 14, and 18 moderately inhibited tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and nitric oxide (NO) release.