Proline influences the antioxidant capacity of Quelite (Amaranthus hybridus L.) and promotes its nutraceutical value

Resumen

Objective: To identify the proline content and antioxidant capacity in quelites of crop fields and marginal lands, for the delimitation of collection sites of plants with superior nutraceutical quality.

Design/ Methodology/ Approach: Plants of Mexican quelite (Amaranthus hybridus L.) in the fruiting stage were collected in two contrasting site conditions. The variables measured were plant height, number of lateral branches, and (visible) damage caused by insects. Aqueous extracts were obtained to measure the concentration of proline by the Bates free proline extraction method, to estimate antioxidant capacity as a percentage of inhibition of the DPPH radical.

Results: Results express average proline concentrations, 34.34 mg L^-1 in plants exposed to unfavorable conditions and 32.93 mg L^-1 in those associated with agricultural crops, this difference was significant (p ≤ 0.05). Proline content was higher in plants subjected to stress. Regarding the percentage of inhibition of the DPPH radical with Ellagic Acid as a reference, in extracts of plants collected under marginal conditions, the average value was 22% (5.06 mg L^-1 EAeq), while in extracts of plants collected under favorable conditions it was 15.8% (0.98 mg L^-1 of EAeq). This is, plant extracts from sites with unfavorable conditions had a greater antioxidant capacity, which is related directly to proline.

Limitations/ Implications of the study: The sample size of the quelite collections was small, even for non-parametric statistical tests. It is important to increment sample size to adequately measure the metabolites content of this plant with nutraceutical potential. High contents of proline, a bioactive compound with therapeutic properties place quelites, until now considered as weeds, as a functional food with the potential to improve human health.

Findings/ Conclusions: The significant differences in proline concentration between sites, and the relationship of this aminoacid with the antioxidant capacity of quelite, highlight that site conditions increase the nutraceutical potential of these edible wild plants. This fact can lead to public health and food safety criteria for the sustainable use of marginal lands.