Abstract

Osteosarcoma is a highly aggressive primary bone malignancy characterized by a poor prognosis due to treatment-related toxicity and chemoresistance. This clinical challenge has spurred growing interest in natural adjuncts, particularly plant-derived therapeutic agents. Azolla pinnata, an aquatic fern, is recognized for its potential antioxidant, anti-inflammatory, and anticancer properties. It is rich in bioactive constituents, including phenolics, flavonoids, tannins, and terpenoids. Key phytochemicals, such as gallic acid, kaempferol, and quercetin, have been shown to modulate redox balance and tumor suppression pathways. These compounds can induce cell-cycle arrest and trigger apoptosis through both extrinsic and intrinsic (mitochondrial) pathways—characterized by caspase-3/9 activation and BCL-2 downregulation—while concurrently inhibiting oncogenic signaling cascades, such as PI3K/AKT/mTOR, MAPK/ERK, and NF-κB. Furthermore, the modulation of VEGF, MMP-2, and MMP-9 suggests potential anti-angiogenic and anti-metastatic effects. The utilization of A. pinnata extracts in the green synthesis of CaO nanoparticles is proposed to offer therapeutic advantages, including pH-responsive dissolution, ROS generation, and bone-targeted delivery; however, these hypothesized effects require rigorous experimental validation. Despite promising preliminary data, significant hurdles remain, including inconsistent reproducibility in batch-to-batch green synthesis, a paucity of comprehensive in vivo toxicity data, and an incomplete understanding of the underlying molecular mechanisms. In summary, while current evidence suggests that A. pinnata and A. pinnata-derived CaO nanoparticles constitute promising theoretical platforms for osteosarcoma therapy, further in vivo validation, mechanistic elucidation, and translational development are critically warranted. Notably, the integration of A. pinnata bioactive compounds with CaO nanoparticles remains a conceptual framework, currently lacking direct experimental evidence to confirm synergistic efficacy.