Modifications in Lemongrass (Cymbopogon spp.) in response to green synthesized nano-selenium complex

•Selenium nano-complex improved the photosynthetic capacity and essential oil yield.•Application of selenium nano-complex increased the content of citral in EOs.•Se NC increased the antioxidant and antimicrobial activity of the essential oil. Selenium nanoparticles (Se-NPs) have different applications in various technologies due to their individual properties. In order to investigate the impacts of different concentrations of a green-synthesized selenium nano-complex (0, 20, 40, 60, and 80 mg L−1) on the chemical composition, antioxidant capacity and antimicrobial activity of lemongrass essential oil (EO), an experiment was designed as a completely randomized design (CRD) with four replications. The application of 40 mg L−1 selenium nano-complex caused the highest EO yield (3.96 ± 0.09%). The dominant compounds in EO, geranial (44.12 ± 1.22%) and neral (32.53 ± 1.08%), were achieved by the application of 60 mg L−1 selenium nano-complex. HPLC analysis indicated that the extracts were rich in 5-o-cafeoylquinicacid, luteolin 6-c-pentosyl-8-c-pentoside, and luteolin 2-o-deoxyhexosyl-6-c-glucoside. The extracts of lemongrass plants treated with 40 and 60 mg L−1 selenium nano-complex achieved the highest amount of 5-o-cafeoylquinicacid (25.29±1.31 and 24.16±1.26 µg mL−1, respectively). The highest antioxidant capacity was observed in the 40 mg L−1 selenium nano-complex treated plants. The minimum inhibitory concentration (MIC) of EO derived from the 60 mg L−1 selenium nano-complex treated lemongrass for Salmonella typhimurium, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Aspergillus niger and Candida albicans was 0.63±0.03, 1.84±0.1, 1.05±0.05, 0.008±0.01, 0.6±0.01 and 0.1±0.01 mg mL−1, respectively. It is expected that the selenium nano-complex would find a wide range of applications in medicine for its antioxidant and antimicrobial properties. It may also be applied to medicinal plants to enhance the quality and quantity of EOs.