Extraction of active constituents from Amaranthus retroflexus and its effect on wheat thermotolerance
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Graphical Abstract
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Abstract
Previous studies showed that the extract of Amaranthus retroflexus could significantly enhance the heat stress resistance of wheat seedlings, but the active components responsible for this activity are still unknown. In this study, five compounds were isolated from the roots of A. retroflexus by using a bioassay-guided method. They were identified as p-hydroxybenzoic acid (1), 14-hydroxymyristic acid (2), p-methoxybenzoic acid (3), 3-hydroxyacetyl-indole (4), and 3-indole formaldehyde (5) by nuclear magnetic resonance spectroscopy and mass spectrometry analysis. p-Hydroxybenzoic acid, p-methoxybenzoic acid, and 14-hydroxymyristic acid could enhance the tolerance of wheat seedlings to heat stress with p-methoxybenzoic acid showing the highest activity. Under high-temperature stress, the fresh weight and length of aboveground, and root length of the wheat seedlings treated with 100 μg/mL p-methoxybenzoic acid increased by 56.44%, 30.03%, and 38.71% compared with the control. The changes in relevant physiological and biochemical indicators were determined in wheat seedlings treated with 50 μg/mL p-methoxybenzoic acid and subjected to high-temperature stress for 1, 3, 5, and 7 days. The results showed that the malondialdehyde content in the plant decreased by 32.59%, 50.27%, 57.53%, and 33.64% compared with the control, respectively. The proline content increased by 28.57%, 50.00%, and 29.87% on days 1, 3, and 5, respectively, and then decreased by 5.16% on day 7. The soluble sugar content increased by 39.76%, 35.93%, 41.33%, and 12.50%. Superoxide dismutase enzyme activity increased by 39.48%, 41.63%, 26.09% and 25.27%. Peroxidase enzyme activity increased by 11.19%, 32.05%, 32.54%, and 26.90%. Catalase enzyme activity increased by 35.62%, 50.97%, 22.82%, and 25.89%, respectively. Collectively, p-methoxybenzoic acid can significantly improve wheat resistance to high-temperature stress.
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