Phytochemical composition of Urtica dioica essential oil with antioxidant and anti-inflammatory properties: In vitro and in vivo studies

Abstract

Background Urtica dioica (Urticaceae) is distinguished by its therapeutic medicinal and pharmacological properties from all over the world. This investigation was designed toassess the chemical composition, the total polyphenol and flavonoid content, antioxidant, anti-proliferative, and anti-inflammatory effects of Urtica dioica essential oil (UDEO). Methods GC/MS analysis was performed to assess the chemical composition, standard antioxidative test DPPH assay, reducing power assay, as well as the anti-proliferative capacities of UDEO against HeLa cell lines using the MTT test. In addition, the anti-inflammatory activities of UDEO were evaluated using paw thickness measurements in rats with carrageenan-induced paw edema and pathologic evaluation of inflammation in paw sections. Results GC/MS analysis revealed benzene dicarboxylic acid (14.69%), β-linalool (9.79%), phytol (9.52%), menthol (6.65%), borneol (6.45%), 3-Eicosene (E) (6.10%), 1-8 cineole (5.60%) and camphor (5.36%) as the major components of UDEO. In vitro results showed that UDEO contained 191±2.04 mg GAE/g of polyphenols and 83.59±4.7 mg CE/g of flavonoids. In addition, the UDEO showed radical scavenging activity with IC50 = 0.14±0.003 mg/mL and ferric reducing antioxidant power (FRAP) (optical density=0.556). A side from the UDEO's antioxidant properties, our findings revealed a reduction in ROS generation in the HeLa cell line. Furthermore, the anti-proliferative activity of UDEO is accompanied by acytotoxicity effect (IC50 at 3.20 µg ml-1). Data from inflammation models revealed that UDEO has an anti-inflammatory effect. The pretreatment with UDEO or Indomethacin (Ind) reduced significantly the volume of edema induced by Carr, the level of C-reactive protein (CRP), the reactive thiobarbituric acid (TBARS), the conjugated dienes (CD), the carbonyl proteins (CP) and the advanced protein oxidation products (AOPP). Furthermore, it restored the hematology parameters such as white blood cells (WBC), lymphocytes (LYM), and platelets (PLT). In addition, it increased the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). In UDEO-treated rats, the histopathological examinations of the paws revealed little infiltration of inflammatory cells. Conclusion The decrease in paw edema and human cell lines HeLa cytotoxicity showed that UDEO possesses anti-inflammatory and antioxidant properties, which could be attributed to the high amount of phenolic and flavonoid contents.

Keywords: GC/MS; Urtica dioica; anti-inflammatory; anti-proliferative; antioxidant; essential oil.