Heavy metals accumulation, distribution and gastrointestinal bioaccessibility in Chinese medicinal plant Panax notoginseng: Health Implications for human consumption

Panax notoginseng ( P . notoginseng ) is a valuable medicinal herb. Yunnan Province in China is the primary producing region, which is characterized by intensive mining activities and high geochemically background levels of metal(loid)s like arsenic (As), cadmium (Cd) and lead (Pb). However, whether and how much metal(loid)s can be accumulated and enter gastrointestinal tracts to induce health risk are still elusive. Therefore, paired P . notoginseng and soil samples (n = 140) were collected to investigate the transfer and risk of metal(loid)s within the soil- P . notoginseng -human continuum. The results showed that 45%, 15% and 9.29% of soil samples were polluted by As (11.9–231 mg kg –1 ), Cd (0.06–1.22 mg kg –1 ) and Pb (22–98.8 mg kg –1 ) (Pollution index, P i >1). Soil Cd showed higher availability (18.5%) than Pb (4.44%) and As (3.86%). After uptake by P . notoginseng , Cd was mainly accumulated in taproots, while As and Pb were translocated from taproot to leaf (TF=0.69 vs. 5.35 and 2.84). Besides, P . notoginseng showed higher bioaccumulation factor (BAF) for Cd than for As and Pb (BAF=1.07–6.38 vs. 0.01–0.09 and 0.03–0.19). As such, 23.6% of taproot Cd and 16.3–62.1% of leaf As/Pb contents failed the food safety standards (0.3, 1.5 and 2 mg kg –1 ). In taproots, metal(loid) bioaccessibility was higher in gastric phase (GP) than gastrointestinal phase (GI) (58.8–77.2% vs. 26.9–46%) due to metal(loid) precipitation under alkaline environment in intestinal phase (IP) (pH=7.0–8.0). Although total content-based assessment showed potential health risk (3.57% target hazard quotient THQ As ≥1 and 6.25% THQ Cd ≥1) in taproots, bioaccessible content-based assessment suggested negligible-to-low concern risk for adults. These findings highlight the necessity of incorporating bioaccessible fraction into risk assessment. The bioaccessible metal(loid)-based assay can provide more exposure-relevant risk predictions and informed consumption decisions.