Soil-to-Plant Transfer of Potentially Toxic Elements and Bioactive Profiles of Petroselinum crispum and Lactuca sativa Grown Under Controlled Conditions

The accumulation of essential and potentially toxic elements in leafy vegetables, together with their phytochemical composition, represents an important aspect of horticultural quality. This study comparatively evaluated parsley (Petroselinum crispum) and lettuce (Lactuca sativa) cultivated under controlled environmental conditions using a common initial soil substrate. Elemental concentrations of cadmium (Cd), nickel (Ni), iron (Fe), zinc (Zn), copper (Cu), and lead (Pb) were determined in soil and edible plant tissues by flame atomic absorption spectrometry (soil Fe as the DTPA-extractable), while phytochemical composition, antioxidant activity, and colorimetric properties were assessed using spectrophotometric and instrumental methods. In the edible leaves of both species, the quantified elements followed the order Fe > Zn > Cu > Ni; Pb was below the detection limit and Cd below the quantification limit of the method. Parsley contained markedly more Fe, Zn and Cu, whereas lettuce contained slightly more Ni. Expressed on a fresh-weight basis, Cd, Pb and Ni in both species were below the EU maximum levels. Parsley exhibited higher total carotenoid (2.19 mg/g DW), β-carotene equivalents (spectrophotometric estimate, 1.54 mg/g DW), and total chlorophyll (4.09 mg/g DW) contents, whereas lettuce showed higher total phenolic (6.68 mg GAE/g DW) and total flavonoid (3.66 mg CE/g DW) contents. Antioxidant activity differed between species, with parsley exhibiting higher ABTS radical-scavenging activity (42.62 µmol TE/g DW) and lettuce higher DPPH radical-scavenging activity (38.44 µmol TE/g DW). Colorimetric analysis revealed higher lightness (L* = 51.04) and chroma (C* = 28.12) in lettuce than in parsley (L* = 41.11; C* = 24.79). Soil-to-plant bioaccumulation factors (BAF) also differed between species, with higher values in parsley for Zn (0.539 vs. 0.123) and Cu (0.146 vs. 0.069); the ratio of leaf Fe to DTPA-extractable soil Fe was 2.544 in parsley and 0.224 in lettuce. These results show distinct element accumulation and phytochemical profiles in the two leafy vegetables grown in the same soil under controlled conditions. Combining soil-to-plant transfer indicators with phytochemical and colorimetric measurements provides a useful comparative characterisation of leafy vegetable quality.