Analysis of heavy metals, bioactive components, and non-carcinogenic and carcinogenic health risk assessment based on drying methods in medicinal plants of Bangladesh

Traditional medicinal plants are widely used for therapeutic, nutritional, and cosmetic applications, yet their safety and quality remain major concerns due to possible contamination and processing related degradation. This study evaluates the physicochemical properties, antioxidant activity, and heavy metal-associated health risks of nine medicinal plant species commonly used in Bangladesh-ILCR, Phyllanthus emblica , Withania somnifera (leaf and root), Terminalia arjuna , Justicia adhatoda , Ocimum sanctum Linn. , Hibiscus rosa-sinensis , Psidium guajava Linn. , and Azadirachta indica processed through heat pump and traditional sun drying methods. Moisture, protein, and total phenolic contents were determined alongside DPPH radical scavenging activity to assess bioactive compound preservation. Heavy metal concentrations (Pb, Cd, Cr, Mn, As, Ni, and Se) were quantified via Graphite Furnace Atomic Absorption Spectroscopy (GF-AAS), and non-carcinogenic (HQ, HI) and carcinogenic (ILCR) health risks were estimated following USEPA guidelines. Results revealed that heat pump drying significantly enhanced protein and phenolic retention while reducing residual moisture compared to sun drying. DPPH assays confirmed superior antioxidant activity (up to 88% scavenging at 200 µg/mL) in heat pump dried samples. Heavy metal concentrations in all samples were below permissible limits, with HQ, HI, and ILCR values indicating negligible non-carcinogenic and carcinogenic risks. Heat pump drying demonstrated enhanced preservation efficiency of nutritional and bioactive components while minimizing contamination risks. These findings provide strong scientific evidence supporting the adoption of controlled heat pump drying for safer, higher-quality, and more efficacious herbal product development in Bangladesh and beyond.