Anti-inflammatory, Antinociceptive, Antipyretic and Antioxidant Activities and Phenolic Constituents from Loranthus regularis Growing in Saudi Arabia

Loranthus regularis Steud. ex Sprague (Loranthaceae) aerial part is widely used for medicinal purposes. The present work was undertaken to evaluate the anti-inflammatory, antinociceptive, antipyretic and in vitro antioxidant potential and to isolate and characterize the responsible constituents. To evaluate the anti-inflammatory, antinociceptive and antipyretic activities, two concentrations (250 and 500 mg/kg, p.o.) of the extract and its fractions were tested in carrageenan-induced rat paw edema, hot-plate test model in mice and brewer's yeast-induced pyrexia in mice. Moreover, the antioxidant power of the extract, its fractions and isolated compounds has been studied using two in vitro assays, scavenging activity of DPPH radical and β-carotene/linoleic acid tests. The methanol extract showed significant anti-inflammatory, antinociceptive, antipyretic and antioxidant activity. Moreover, the ethyl acetate fraction of the methanol extract was found to be the most active fraction and exhibited the highest inhibition of inflammation (67%) and the highest inhibition of oxidation of β-carotene (92%). Thus, a bioassay-guided fractionation of the active ethyl acetate fraction has been carried out and finally three flavonoid glycosides were isolated for the first time from this species. The structures were elucidated by using mass, 1D and 2D NMR spectroscopic studies as (1) quercetin 3-O-β-D-galactopyranoside, (2) quercetin 3-O-β-L-arabinopyranoside and (3) quercetin 3-O-α-L-rhamnopyranoside. The present results confirmed the traditional use of L. regularis and clearly indicate that the plant could be a potential source for using as anti-inflammatory and antioxidant agent.

Acknowledgements: The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding the work through the research group project No. (RGP-VPP-073).