Polyphenolic composition and antioxidant capacity of legume-based swards are affected by light intensity in a Mediterranean agroforestry system.

BACKGROUND: In Mediterranean grazed woodlands, microclimate changes induced by trees influence the growth and development of the understory, although very little is known about its polyphenolic composition in relation to light intensity. We investigated the bioactive compounds and antioxidant capacity of different legume-based swards and variations as a result of full sunlight and partial shade. The research was carried out in a cork oak agrosilvopastoral system in Sardinia. RESULTS: The highest values of (1,1-diphenyl-2-picrylhydrazyl) (DPPH) reached 7 mmol Trolox equivalent antioxidant capacity 100 g-1 dry weight (DW), total phenolics 67.1 g gallic acid equivalent kg-1 DW and total flavonoids 7.5 g catechin equivalent kg-1 DW. Compared to full sunlight, partial shade reduced DPPH values by 29% and 42%, and the total phenolic content by 23% and 53% in 100% legume mixture and semi-natural pasture, respectively. Twelve phenolic compounds were detected: chlorogenic acid in 80% legume mixture (partial shade) and verbascoside in pure sward of bladder clover (full sunlight) were the most abundant. CONCLUSION: Light intensity significantly affected antioxidant capacity, composition and levels of phenolic compounds. The results of the present study provide new insights into the effects of light intensity on plant secondary metabolites from legume-based swards, highlighting the important functions provided by agroforestry systems. © 2018 Society of Chemical Industry.