Thermal Conversion of Cannabinoids in Hemp Flower: Decarboxylation Kinetics and Potential Accumulation of Δ9‑Tetrahydrocannabinol.

Carrera D.; Mazurov A.; Latino D.; George G.; Katsir L. · ACS omega · 2026

**Background & Methods** This review study investigated the thermal decarboxylation kinetics of cannabinoids in CBD-rich hemp flower under controlled dry-heat exposure at vaporization-relevant temperatures (up to 230°C) in a static, no-airflow environment. Cannabinoid transformations were analyzed across five hemp chemotypes and isolated cannabinoids using UHPLC-DAD and GC-FID analytical methods. **Key Findings** • CBDA decarboxylation was rapid and nearly complete at vaporization temperatures, achieving 99.96% conversion within 1 minute at 230°C; however, total CBD content declined progressively with increasing temperature, reaching approximately 58% relative loss at 230°C, with CBD isolate showing >30% decomposition under identical conditions. • Contrary to previous reports of CBD-to-THC conversion, no meaningful accumulation of Δ9-THC was detected across all five hemp chemotypes or isolated cannabinoids following heat treatment, indicating that the risk of unintended THC increase during vaporization is low. • CBN formation (up to 3% in THC-rich material) suggested that Δ9-THC generated via decarboxylation is thermally unstable and preferentially degrades to secondary products rather than accumulating or converting from CBD under realistic vaporization conditions. **Dosage & Administration** Not reported. Study evaluated temperature-dependent cannabinoid transformations rather than administered doses. **Safety & Adverse Effects** Not reported as direct clinical outcomes. However, findings indicate that under hemp flower vaporization conditions, the risk of unintended THC accumulation is low, supporting consumer safety and regulatory compliance. **Evidence Quality** As a laboratory-based review study using controlled in vitro conditions, this research provides mechanistic insights into cannabinoid thermal stability but lacks direct clinical or in vivo validation. Limitations include the static, no-airflow environment that may not fully replicate dynamic vaporization devices, reliance on whole-flower matrices from five chemotypes (potentially limited generalizability), and absence of human consumption studies. The findings contrast with some literature reports, suggesting potential artifacts from acidic conditions or GC-inlet effects in prior studies. Evidence quality is moderate, suitable for informing regulatory guidance and consumer safety assessments but requiring complementary real-world device studies.

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