Several species of the Rumex (Polygonaceae) genus have been used in traditional medicine, although their high
oxalic acid content has been implicated in oxalic intoxication, mainly in children. Rumex induratus Boiss. & Reuter is an endemic Iberian herb that prefers rocky habitats of the
thermo Mediterranean region. It grows spontaneously in Northeast Portugal, where its
leaves are highly consumed in salads. Phenolic compounds and organic acids, known
to influence the organoleptic properties of plant foods, have been successfully used
in their quality control. On the other hand, antioxidants present in fruits and vegetables,
including those belonging to these two phtyochemical classes, are associated with
oxidative damage prevention.
The chemical composition of aqueous extracts of R. induratus leaves, in terms of phenolic compounds and organic acids, and its antioxidant activity
against the DPPH radical, a Reactive Oxigen Species, hypochlorous acid, and a Reactive
Nitrogen Species, nitric oxide, were studied. The samples were collected in several
locations, seasons and in different stages of development. The phenolic compounds
identified by HPLC/DAD were: caffeoyl-hexoside, p-coumaroyl-hexoside, feruloyl-hexoside, sinapoyl-hexoside, 6-C-hexosyl-quercetin, 8-C-hexosyl-luteolin, 6-C-hexosyl-luteolin, 6-C-hexosyl-apigenin, 3-O-hexosyl-quercetin, 3-O-rutinosyl-quercetin, 7-O-hexosyl-diosmetin and 3-O-rutinosyl-isorhamnetin. Oxalic, citric, malic, ascorbic and shikimic acid were identified
using HPLC-UV. Total amount of phenolic compounds and organic acids were affected
by growing conditions and developmental phase. The aqueous extract exhibits a dose
related activity against all tested radicals.
Acknowledgements: Fundação para a Ciência e a Tecnologia (POCI/AGR/57399/2004), Luís
Guerra. Fundação Calouste Gulbenkian, Patrícia Valentão.
