Analgesic, Anti-inflammatory and In-vitro Hyaluronidase Inhibitory Properties of the Leaf Extract and solvent fractions of Otostegia fruticosa (Forssk.) Schweinf. ex Penzig.

Otostegia fruticosa is traditionally used to treat tonsillitis, stomach ache, asthma, arthritis, and febrile illness in different parts of Ethiopia and other countries. In this experiment 70% ethanolic crude extract and fractions of the leaf of Otostegia fruticosa (Forssk.) Schweinf. ex Penzig were evaluated for their in-vivo anti-inflammatory and analgesic activities and in-vitro hyaluronidase inhibition properties at different concentrations. Tail immersion, acetic acid induced writhing and carrageenan-induced paw edema model were used to assess the in-vivo analgesic and anti-inflammatory activities, respectively. Swiss albino mice of either sex were randomly divided into five groups of six mice per group and for evaluation of the fractions randomly divided into six groups of six mice per group. The test groups were treated with hydroalcoholic extract of O. fruticosa at doses of 100, 200, and 400 mg/kg. The positive control groups received either pethidine 5 mg/kg or aspirin at 100 mg/kg or 150 mg/kg. The negative control groups were orally given sunflower oil. All the fractions were administered at the dose of 400 mg/kg. In all models, the higher dose (400 mg/kg) of the crude extract and chloroform fraction showed a significant central and peripheral analgesic and anti-inflammatory activities with comparable effects to standards used.  The hyaluronidase inhibition assay result showed that the test samples displayed concentration-dependent inhibitory activities. These findings indicate that 70% ethanol extract and organic solvent fractions of O. fruticosa leaves have potential analgesic, anti-inflammatory, and enzyme inhibitory activities.