Nanoencapsulation of Tomentosin-Rich Pulicaria crispa Fraction in MIL-53(Fe) Improves the Release Profile and In Vitro Anti-Colorectal Cancer Activity.

Background/Objectives: Plant-derived bioactives offer pharmacological potential but are often limited by poor delivery and selectivity. The Pulicaria crispa dichloromethane fraction (DCMF) shows potent but non-selective antiproliferative activity. This study aimed to engineer a functional nanoformulation using a MIL-53(Fe) metal-organic framework (MOF) to achieve sustained release and improve in vitro potency and selectivity against colorectal cancer cells. Methods: DCMF was phytochemically profiled by GC-MS. A DCMF@MIL-53(Fe) nanocomposite was synthesized and characterized for particle size, zeta potential, and entrapment efficiency. In vitro release kinetics were evaluated. Anticancer activity and selectivity were assessed in HCT-116 cells. Mechanistic studies included cell-cycle analysis, cell-death assays, and molecular docking. Results: Tomentosin was identified as the predominant constituent (28.82%). The nanocomposite displayed suitable physicochemical properties (mean size: 218 nm; entrapment efficiency: 83.6%) and a clear transition from burst to sustained drug release over 48 h. Nanoencapsulation resulted in a 53-fold increase in cytotoxic potency, calculated on a DCMF-equivalent basis (IC50 = 0.40 µg/mL), compared with free DCMF (IC50 = 21.51 µg/mL), along with a modest improvement in selectivity. Enhanced activity was associated with G0/G1 cell cycle arrest and a shift toward necrotic, non-apoptotic cell death. Docking of the predominant constituent, tomentosin, supported plausible interactions with CDK4/Cyclin D3 and the MDM2-p53 axis, providing structural context for G1/S checkpoint disruption. Conclusions: MIL-53(Fe) nanoencapsulation converted a non-selective plant extract into a sustained-release formulation with improved in vitro efficacy and selectivity. These findings provide proof-of-concept that rational nano-delivery strategies can mitigate key pharmaceutical limitations of plant-derived fractions and enhance the anticancer potential of traditional medicinal resources.