beta-Amyrin and alpha-amyrin acetate isolated from the stem bark of Alstonia boonei display profound anti-inflammatory activity

Context: Alstonia boonei De Wild (Apocyanaceae) is used in ethnomedicine for the management of malaria, ulcer, rhematic pain, toothache, and inflammatory disorders.

Objective: To investigate the anti-inflammatory potential of β-amyrin and α-amyrin acetate isolated from the stem bark of Alstonia boonei using animal models.

Materials and methods: Chromatographic purification of the crude methanol extract led to the isolation and structure elucidation of β-amyrin and α-amyrin acetate. Their anti-inflammatory activities were evaluated in rodents using egg albumen-induced paw edema and xylene-induced ear edema models. The gastric ulcerogenic, in vivo leucocyte migration, and RBC membrane stabilization tests were also investigated.

Results: α-Amyrin acetate at 100 mg/kg showed significant (p < 0.05) inhibition of egg albumen-induced paw edema with % inhibition of 40 at the 5th hour. Oral administration up to 100 mg/kg did not produce significant (p > 0.01) irritation of the gastric mucosa while significant (p < 0.01) ulceration was recorded for indomethacin at 40 mg/kg compared with the negative control. At 100 μg/mL, both β-amyrin and α-amyrin acetate inhibited heat-induced hemolysis to as much 47.2 and 61.5%, respectively, while diclofenac sodium (100 μg/mL) evoked only 40.5% inhibition. Both compounds at 100 µg/ear produced significant (p < 0.01) inhibition of ear edema in mice by 39.4 and 55.5%, respectively. Also at 100 mg/kg (p.o.) α-amyrin acetate evoked 60.3% reduction in total leucocyte count and significant (p < 0.05) suppression (47.9%) of neutrophil infiltration.

Discussion and conclusion: This study generally provided evidence of profound anti-inflammatory activity of β-amyrin and α-amyrin acetate isolated from the Alstonia boonei stem bark.