Researchers from the Xinjiang Institute of Ecology and Geography (XIEG) of the Chinese Academy of Sciences (CAS) have found that priming mungbean seeds with magnesium oxide nanoparticle (MgO-NP) prming can improve lead (Pb) tolerance and nutritional quality of the resulting sprouts through coordinated physiological and metabolic responses.

Led by Prof. WANG Lei and Associate Prof. Mohsin Tanveer, the study was published in Food Chemistry on September 9.

Soil salinization is a growing constraint on agricultural productivity in Xinjiang and other arid regions, where saline irrigation water and high evaporation can intensify salt accumulation in soils. Salinity not only limits crop growth but may also increase the mobility and bioavailability of heavy metals such as Pb, raising the risk of their accumulation in edible crops. Addressing both salinity-related constraints and heavy metal accumulation is therefore important for sustainable food production in Xinjiang and similar saline environments.

Against this backdrop, mungbean sprouts offer a promising perspective for resource-efficient food production. Mungbean seeds can be converted into nutrient-rich edible biomass within a short production cycle, providing a potential circular-economy pathway for generating value from plant-based resources.

However, because sprouts are consumed whole and with minimal processing, they are particularly vulnerable to Pb accumulation, which poses direct toxicological risks and reduces the nutritional quality of edible tissues. Ensuring nutritional quality and limiting the bioaccessibility of contaminants are therefore key considerations in developing such production systems for environmentally constrained regions.

"Understanding how MgO-NP priming influences Pb accumulation, antioxidant metabolism, and the bioaccessible fraction of Pb provides a more comprehensive basis for evaluating its potential application in edible sprouts," said Dr. Muhammad Saqib Bilal from XIEG, the first author of the study.

To investigate these effects, the researchers combined physiological and biochemical analyses, elemental profiling, untargeted metabolomics, weighted gene co-expression network analysis (WGCNA), and INFOGEST-based in vitro gastrointestinal digestion and compared the effects of MgO nanoparticles and bulk MgO on mungbean sprouts under Pb stress.

They found that under Pb stress, MgO-NP priming increased the germination rate to 93%, compared with 87% for bulk MgO, and promoted sprout growth. It also reduced Pb accumulation in edible sprout tissues by 62.5%, compared with a 36.4% reduction achieved with bulk MgO. MgO-NP priming further enhanced antioxidant capacity, increasing total antioxidant capacity by 138% compared with Pb stress alone. The treatment was also associated with greater accumulation of phenolic- and flavonoid-related metabolites.

To determine whether these effects could simply be attributed to the amount of MgO applied, the researchers conducted an additional dose-response experiment using bulk MgO. They found that even when its concentration was increased to 600 mg/L, bulk MgO did not reproduce the overall germination and growth response achieved with 100 mg/L MgO-NP.

Further metabolomic and WGCNA analyses pointed to coordinated changes in phenylpropanoid and flavonoid metabolism, along with increased phenylalanine ammonia-lyase activity. The researchers also assessed how much Pb could potentially become available for absorption during digestion. The INFOGEST-based digestion experiments showed that MgO-NP treatment reduced this potentially bioaccessible Pb fraction by 76.3% compared with Pb stress alone. Meanwhile, Mg bioaccessibility under Pb exposure reached 21% with MgO-NP treatment, compared with 18% with bulk MgO.

According to the researchers, the findings provide new insights into how MgO-NP priming affects mungbean sprouts under Pb stress and underscore the importance of considering gastrointestinal bioaccessibility when assessing the safety and nutritional quality of edible sprouts.

They said the approach may have potential for resource-efficient and stress-resilient food production in arid and saline regions and could provide a strategy for producing safer sprouts in Pb-contaminated environments.