Phenolic content of hydroponically grown sweet basil inoculated with endophytic bacteria and their antioxidant activity in model systems.

Basil is one of the vegetables grown hydroponically for sustainability purposes. In this soil-less technique, plants grow in the absence of bacteria that inhabit them such as endophytes. Research showed that endophytic bacteria enhance nutrients, phytochemical compounds, and antioxidant activities in vegetables. The use of endophytic bacteria in hydroponic sweet basil may then improve their phytochemical contents and antioxidant capacities compared to soil growth. The aim of this study was to determine in a hydroponic system, the effect of different bacterial endophytes on the accumulation of polyphenols in sweet basils and their antioxidant properties.Bacterial strains were P. flavus (SB1), P. flavus (SB2), C. flaccumfaciens (SB3), M. oryzae (SB4), S. medicae (SB5), Consortium (SB6: SB1 + SB2), R. selenireductens (SB7), C. herbarum (SB8), B. toyonensis (SB9), and B. fluminis (SB10) previously isolated from healthy basils. Data showed that five out of the eleven endophytes exhibited a significant increase in total phenolic contents, ranging from 4.5±0.3 to 5.8±1.2 mg GAE/g f.w., compared to 3.1 ± 0.5 mg GAE/g for the control basils. The increase was due to hydroxycinnamic (HCAs) derivatives but not to total flavonoids. HPLC analysis showed that the most increased HCAs were chicoric acid and rosmarinic. Significant changes were observed for the flavonoids quercetin and luteolin. Endophytes that showed the greatest effects were strains SB3, SB4, SB7, and SB9. In the antioxidant assays, endophytes SB7 and SB9 scavenged hydroxyl radicals by 87.6% and 82.9%, respectively, while SB2 and SB5, demonstrated the highest iron chelating capacity (56.89% and 54.15%). Overall, all strains retarded linoleic acid oxidation by reducing hydroperoxides (LOOH) values, relative to control oil.In the lipid peroxidation, there was an increase of 10-fold in LOOH concentration in the absence of basil extract. Control basil only increase LOOH by 1.5-fold but there was a complete inhibition by strains SB2 and SB5.-