Bioaccessibility of Heavy Metals in Raw and Processed Alternanthera sessilis and Centella asiatica: An In vitro Study

Heavy metals pose significant risks to food safety because of their persistence in the environment and their ability to accumulate in the food chain. Even small amounts of these metals can harm human health upon consumption. This study assessed the in vitro bioaccessibility of Ni, Cd, Cr, Pb, and Cu in two commonly consumed green leafy vegetables in Sri Lanka, Alternanthera sessilis and Centella asiatica. Composite samples of A. sessilis and C. asiatica were randomly collected from the Western Province, Sri Lanka. The edible portions of each sample were divided into three 200 g test portions and subjected to the following treatments: Treatment 1 - raw sample, Treatment 2 - cooked sample, and Treatment 3 - stir-fried sample. The in vitro bioaccessibility of heavy metals in raw, cooked, and stir-fried samples was determined using a physiology-based extraction test (PBET). In contrast to the overall concentrations of heavy metals in A. sessilis and C. asiatica, the bioaccessible fractions were significantly lower in raw, cooked, and stir-fried samples (P<0.05). Moreover, significant differences were observed in metal concentrations between the intestinal and gastric stages. The average bioaccessibility (%) of Cu was considerably higher in the intestinal stage, whereas Cr, Cd, Pb, and Ni were higher (P<0.05) in the gastric stage. Additionally, cooking and stir-frying reduced the bioaccessibility of metals compared with the raw samples.