Phytochemical and biological characterization of methanolic extracts from Tunisian Rumex algeriensis and Rumex tunetanus

Local environmental resources derived from plants play an important role not only for the provision of foods but also for their content of bioactive compounds useful for human wellbeing. The Rumex species, belonging to the Polygonaceae family, comprise about 200 species widely distributed around the World, including North Africa regions. Some species have been used traditionally, besides that as vegetable foods, also for their medicinal properties. The extracts of these plants, and compounds isolated from them, have been demonstrated to possess various pharmacological activities, including anti-inflammatory, antioxidant, antitumour, antibacterial, antiviral and antifungal properties, both in in vitro and in vivo studies. In the context of a research project aimed to investigate plants from North Africa as potential sources of bioactive product useful for healthy purposes, we have studied the phytochemical profile and the biochemical properties of methanolic extracts from different parts (flowers, leaves and stems) of Tunisian Rumex algeriensis and Rumex tunetanus. In fact Tunisia flora is known for its diversity of medicinal plants, but phytochemical and biological of these two Rumex species, endemic in Tunisia, have not been deeply investigated up today. The phytochemical analyses were performed using standard colorimetric procedures (total flavonoids, total flavonols, total tannins, hydrolysable tannins, condensed tannins) and HPLC-DAD and HPLC-DAD-ESI-MS. Then, several in vitro cell-free assays have been used to estimate the antioxidant/free radical scavenging capability of the extracts (total polyphenols, DPPH, TEAC, ORAC, FRAP, β-carotene bleaching, NO scavenging-activity, SOD-like activity, HOCl-induced albumin degradation). Moreover, cell culture tests have been performed to evaluate the biocompatibility (on NIH/3T3 fibroblast cells) and the anti-inflammatory potential (on THP-1 cells) of the extracts under investigation. All extracts appeared particularly rich in phenolic compounds, being flowers and leaves richer than stems for both Rumex species. The main compounds were respectively: catechin, quercetin glycoside methyl derivatives, epicatechingallate for Rumex algeriensis flowers; dicaffeoylquinic and caffeoylquinic acids, epicatechingallate, quercetin glucoside methyl derivatives, quercitrin for Rumex algeriensis stems; quercetin glucoside methyl derivatives, catechin, quercetin hexoside deoxyhexoside, epicatechingallate for Rumex tunetanus flowers; quercetin glucoside methyl derivatives, quercetin hexoside deoxyhexoside, epicatechingallate, catechin for Rumex tunetanus stems; quercetin glucoside methyl derivatives, quercetin hexoside deoxyhexoside, kaempferol 3-O-glucoside, kaempferol hexoside deoxyhexoside, chlorogenic acid for Rumex tunetanus leaves. All extracts appeared endowed with excellent antioxidant/free radical scavenging properties. In particular the extracts from both Rumex algeriensis and tunetanus flowers and the extract from Rumex algeriensis stems are characterized by a remarkable SOD-like and NO-scavenging activity, as well as by the capability to protect albumin against degradation. Taking into account also the results concerning the cytotoxicity on NIH/3T3 cells, the anti-inflammatory properties of these extracts have been confirmed on THP-1 cells. In conclusion, Rumex algeriensis and tunetanus flowers and stems showed to be a potential source of bioactive products, to be used, due to their significant antioxidant properties, as nutraceuticals as well as in the food industry.