Oral Lymphatic Transport Is an Underused Design Space for Lipophilic Natural Products with Poor Aqueous Solubility and Extensive First-Pass Loss

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Poor aqueous solubility and extensive presystemic metabolism frequently constrain the oral development of lipophilic natural products, yet formulation strategies are commonly evaluated through dissolution and plasma exposure without explicitly considering whether intestinal lymphatic transport could become a design variable. This translational framework examines when oral lymphatic delivery should be considered during natural-product lead selection and formulation development rather than treated as an incidental pharmacokinetic phenomenon. Current evidence indicates that intestinal lymphatic transport depends on coordinated gastrointestinal solubilization, epithelial uptake, intracellular lipid processing, association with chylomicron-related pathways, lacteal access, and formulation-specific behavior. High lipophilicity is therefore permissive rather than sufficient: intestinal instability, inadequate lipid association, inappropriate dose or vehicle composition, and inefficient chylomicron incorporation can prevent meaningful lymphatic exposure. Conversely, lipid vehicles, nanostructured carriers, and lipid-mimetic prodrug strategies can alter pathway engagement and, in selected cases, reduce initial hepatic first-pass delivery. The framework proposed here distinguishes intrinsic from engineered lymphatic eligibility and organizes development around exposure liabilities, pathway compatibility, formulation leverage, route-specific evidence, and translational verification. It further separates increased systemic exposure from demonstrated lymphatic transport and treats computational or in-vitro prediction as prioritization evidence rather than mechanistic proof. The principal implication is that lymphatic delivery should be evaluated selectively, where chemical and biopharmaceutical liabilities plausibly align with lipid-mediated intestinal transport. Species differences, physiological variability, formulation dependence, limited predictive datasets, and difficult route attribution remain major boundaries requiring prospective experimental validation.