Screening for anti-inflammatory activity of extract and fractions of Morinda lucida stem bark and detection of bioactive secondary metabolite

Morinda lucida Benth (Rubiaceae) is a versatile plant used in traditional medicine for the treatment of a variety of ailments and the claims of its efficacy are particularly remarkable in the treatment of infections and immuno-inflammatory disorders. This study evaluates the anti-inflammatory properties of methanolic stem bark extract and fractions of M. lucida and also identifies the phytochemicals responsible for its anti-inflammatory activity. The crude extract was subjected to liquid- liquid partitioning successively with n- hexane, ethylacetate, butanol and water. High performance liquid chromatography (HPLC) of the four fractions and Vacuum Liquid Chromatography fraction (VLC) of the promising fraction was evaluated. The effect of the fractions on egg albumen induced rat paw oedema were also evaluated. Anti-inflammatory activity of the fractions was further screened using xylene induce ear oedema models and human red blood cell membrane stabilization test. Ulcerogenic test on the normal stomach mucosa was also evaluated. The result of the egg albumen induced rat paw oedema showed that the butanol fractions maximally inhibited egg albumen induced effect at 400 mg/kg (70%) and 200mg/kg (67.5%) after 180 minutes compared to the positive control, ibuprofen (20mg/kg) with 100% inhibition after 180 minutes. The result of the xylene induced ear oedema showed that the inhibition produced by 100 µg/ear of the Butanol fraction (BF) was 56.67 % and was greater than inhibition produced by 200 µg/ear of ibuprofen (38.89 %). HPLC analysis of the fractions revealed the following phytocompounds; Cytreo- a-pyrone, Cytosporin- J and Waol A. Ulcerogenic test was negative at the doses of 200 mg/kg and 400 mg/kg of the fractions when compare with the indomethacin (positive control) at dose of 50 mg/kg. Human red blood cell membrane stabilization assay showed that BF-VLC 2 (Dichloromethane: methanol (8:2) VLC of Butanol fraction) exhibited concentration dependent inhibition of heat-induced haemolysis while other extract showed a non- concentration dependent inhibition of haemolysis when compared to the standard, ibuprofen. These findings suggest that the stem bark of M. lucida possess promising anti-inflammatory phytocompounds which justify its use in ethno-medicine.