Health risk evaluation of heavy metals in Azadirachta indica leaves and phytochemical profiling

Abstract

As reliance on medicinal plants continues to grow worldwide, more scientific attention has been given to the safety and therapeutic effects of medicinal plant species. This comprehensive study evaluates the toxicological risk, antioxidant capacity, and solvent-dependent phytochemical profiles of Azadirachta indica (neem) leaves from Gampaha District, Sri Lanka. No prior study has assessed health risks along with solvent-specific bioactive profiles of neem leaves simultaneously. In the present study, methanol, dichloromethane, and hexane extracts of A. indica leaves were analyzed. The mean concentrations of all metal(loid)s were within the regulatory thresholds established by WHO and US FDA, with lead (Pb) being the highest at 0.92 ± 0.09 mg kg-1. Although all hazard quotient values were below the risk threshold of 1.0, the carcinogenic risk (CR) for chromium exceeded acceptable limits. The methanol extract showed substantial in vitro antioxidant activity with the highest phenolic and flavonoid levels. GC-MS analysis revealed important compounds such as phytol (0.75%), neophytadiene (5.23%), and hexadecanoic acid (2.83%), with notable therapeutic effects. These results substantiate the safe and effective use of neem leaves from the Gampaha region in herbal medicine, emphasizing the need for further studies on therapeutic efficacy in medicinal applications and regular monitoring of metal(loid) concentrations in this species.