Overcoming the "Bioavailability" Barrier: Novel Delivery Systems for Oral Cancer

Abstract

Background: Oral squamous cell carcinoma (OSCC) accounts for over 90% of oral malignancies, with a five-year survival rate persistently below 50% despite surgical, chemo-, and radiotherapeutic advances.Curcumin, the principal curcuminoid (~77%) of turmeric (Curcuma longa L.), has demonstrated preclinical activity against OSCC through inhibition of NF-κB, STAT3, VEGF, and apoptotic pathways. However, its clinical translation is severely restricted by less than 1% oral bioavailability, rapid metabolic degradation, and instability at neutral and alkaline pH. Turmeric contains two additional pharmacologically active curcuminoids — demethoxycurcumin (DMC, ~18%) and bisdemethoxycurcumin (BDMC, ~5%) — both of which possess demonstrably greater chemical stability and superior pharmacokinetic profiles compared to curcumin, owing to the absence of one or both methoxy groups. Despite established mechanistic evidence of their activity in OSCC-relevant protein targets, DMC and BDMC remain systematically absent from OSCC-targeted drug delivery research.

Objective: This review presents, for the first time, a structured evidence synthesis mapping the mechanistic activity of DMC and BDMC against specific OSCC protein targets across ten established drug delivery platforms, and explicitly identifies the translational gaps created by their systematic exclusion from OSCC delivery research.

Methods: A comprehensive, PubMed-indexed literature review was conducted across ten delivery subtopics — mucoadhesive buccal patches,nano-liposomal encapsulation, pH-responsive nanoparticles, photodynamic therapy (PDT), niosomes, exosome-based carriers, in situ gelling systems, piperine-curcumin synergistic complexes, and clinical translation pathways — evaluating available mechanistic, pharmacokinetic, in vitro, and in vivo evidence for Biopress Journal of Drug Chemistry and Quality Control Vol. 1 Issue. 2 (2026) 28 DMC and BDMC specifically in oral cancer contexts. All included references are peer-reviewed and directly traceable to cited sources.

Key Findings: DMC was identified as the single most effective anti-tumour compound among 639 natural products screened against OSCC cells, operating via USP13-mediated stabilisation of PTEN and consequent suppression of the PTEN/Akt/HK2 glycolytic axis — a mechanism not reported for curcumin in OSCC. DMC additionally induces G2/M arrest and caspase-mediated apoptosis via the p38 MAPK–HO-1 axis in HSC-3 and SCC-9 tongue carcinoma cell lines, suppressing cIAP1 and XIAP — key mediators of cisplatin resistance — and demonstrating synergy with gefitinib in OSCC.DMC further inhibits NF-κB-driven apoptotic signalling in FaDu pharyngeal squamous carcinoma cells and overcomes cisplatin resistance via ERCC1 suppression through the PI3K-Akt-Snail pathway when delivered in chitosan nanoparticles. BDMC demonstrated superior anti-invasion and anti-angiogenic activity compared to curcumin in head and neck squamous carcinoma models through simultaneous suppression of NF-κB, STAT3, VEGF, MMP-9, TGF-β, and multiple EMT regulators. BDMC also suppressed Bcl-2 and XIAP while upregulating BAX and caspase-3 in glioblastoma xenograft models,inhibited NF-κB-mediated invasion via GRB2/RhoA/uPA in cervical carcinoma,and suppressed GPR161/mTOR-driven EMT in triple-negative breast cancer. Critically, BDMC has been confirmed to generate reactive oxygen species — hydroxyl radicals and singlet oxygen — under blue light irradiation, establishing proof-of-concept for its application as a photosensitiser in OSCC-directed PDT.

Gaps Identified: Across all ten delivery subtopics reviewed, neither DMC nor BDMC has been incorporated into a delivery system specifically designed for OSCC. No mucoadhesive buccal film or patch, pH-responsive nanoparticle, noisome, liposome,exosomal carrier, or in situ gel has been formulated with either molecule as the active payload for oral cancer. No BDMC-PDT study exists in any human cancer cell line,[ and no DMC-PDT study exists in any model. The piperine–DMC/BDMC pharmacokinetic interaction is entirely unstudied. No comparative pharmacokinetic study of all three curcuminoids exists in an OSCC-relevant oral delivery model.The complete clinical translation pathway — from OSCC-specific in vitro validation through Phase I trials — is absent for both molecules. Exosomal delivery, pH-responsive nanoparticles, and PDT applications represent the three highest-priority unstudied combinations based on mechanistic rationale and platform suitability. DMC and BDMC represent a neglected pharmacological resource in OSCC therapy development.This review establishes the evidence-based framework for redirecting OSCC curcuminoid delivery research from its current curcumin-centric focus toward the more potent, more stable, and mechanistically distinctive minor curcuminoids. Immediate research priorities include OSCC-specific in vitro validation of BDMC in HSC-3, SCC-9, and CAL-27 cell lines, DMC/BDMC formulation into established OSCC delivery platforms,and initiation of BDMC-PDT studies— steps with direct implications for the field’s ability to translate preclinical curcuminoid activity into effective oral cancer therapeutics.