Inclusion of endophytes in hydroponic cultivation of basils enhances hydroxycinnamic acid levels and antioxidant capacity.

Abstract

The lack of microorganisms in soil-less hydroponic farming can limit the accumulation of nutrients and secondary metabolites. This work was then aimed for the first time, to identify and quantify polyphenols, determine antioxidant properties of hydroponically grown basils, and assess the effects of endophytic bacteria. Data showed that of the eleven endophytes investigated, five increased (p < 0.05) total phenolic contents to 4.5 ± 0.3-5.8 ± 1.2 mg GAE/g F.W. relative to 3.1 ± 0.5 mg GAE/g for the control basils. The increase was due to the enhanced biosynthesis of hydroxycinnamic acid derivatives (r = 0.65, p = 0.028) but not to total flavonoids (r = 0.188). HPLC analysis showed that hydroxycinnamic compounds with the greatest increase were chicoric and rosmarinic acids. Significant changes were observed for the flavonoids quercetin and luteolin. The endophytes that had the greatest effects were Curtobacterium flaccumfaciens (SB3), Methylobacterium oryzae (SB4), Rizhobium selenireductens (SB7), and Bacillus toyonensis (SB9). In the antioxidant assay, two of the best endophytes (SB7 and SB9) scavenged hydroxyl radicals by 87.6% and 82.9%, respectively. Additionally, inoculation increased iron-chelating capacity by 40% and fully inhibited lipid oxidation, indicating, overall, the benefits of the inoculation of endophytes during the hydroponic growth of basils.