Synergetic Efficacy of Amending Pb-Polluted Soil with P-Loaded Jujube (Ziziphus mauritiana) Twigs Biochar and Foliar Chitosan Application for Reducing Pb Distribution in Moringa Leaf Extract and Improving Its Anti-cancer Potential

Soil polluted from Pb-acid batteries effluents (SPB) reduces the therapeutic potentials of Moringa oleifera, contaminates groundwater and surrounding soils via Pb transference. Amending SPB with P-loaded jujube twigs biochar (P-TB) can overcome these problems. Moreover, chitosan spray (CHs) on moringa, growing on SPB, can further biostimulate the production of essential phytochemicals and improve its anti-proliferative effects on human liver cancer cells (HePG2). In this pot experiment, moringa was grown on SPB (Pb = 639 mg kg(-1)) having control, CHs, TB, P-TB, TB+CHs, and P-TB+CHs treatments. Treatments effects on plant growth, Pb distribution in moringa leaf extract (MLE), shoots and roots, the status of plant phytochemicals and antioxidants, and concentrations of Pb and P in leachates were evaluated. Lastly, MLE was initially tested for its feasibility for human consumption through HEK 293 assay and later its antiproliferative efficacy on HePG2. Among all treatments, the P-TB+CHs exhibited the most significant results in compare to control. The P-TB+CHs resulted in the highest reduction of Pb concentrations in shoots, roots, and MLE by 79%, 70%, and 52%, whereas improved plant growth, phytochemicals, and antioxidants status. Interestingly, MLE at P-TB+CHs had Pb concentrations (3.27 mg L-1) below the critical limit [5 mg kg(-1), WHO/FAO, 2007], was safer for consumption (HEK 293 cells viability = 133.6%), and depicted the least proliferation of HepG2 cells (35.8%). In leachates of P-TB+CHs, the concentrations of Pb (5.26 mu g L-1) and P (0.021 mg L-1) were below the permissible limits for drinking water and preventing eutrophication, respectively. The lowest concentrations of Pb in MLE, plant parts, and leachates in P-TB+CHs were due to the formation of insoluble Pb-P compounds after Pb reacted with P present in P-TB and released P from P-TB. Hence, P-TB+CHs can remediate SPB, prevent groundwater contamination, avoid eutrophication, and boost the anti-cancer potential of moringa.