The stem and root bark of Anthostema aubryanum (Baill, family, Euphorbiaceae) are extensively used in African ethnomedicine for treating and managing a number of disease conditions which include inflammation, pain, wounds, boil, dyspepsia and a variety of other disease conditions. Although the chemistry and pharmacology of many phytoconstituents isolated from the family are fairly established, the plant has not yet been investigated. In the present study, an alkaloidal extract of the root bark was demonstrated to display a time- and dose (30-300 mg/Kg p.o.)-dependent anti-inflammatory effect in rats (ED50=13.84±0.011) compared to diclofenac (ED50=1.994±0.002). Comprehensive chromatographic and spectroscopic analyses have led to the isolation and characterization of two major anti-inflammatory and antioxidant alkaloids as 5-methoxycanthin-6-one and canthin-6-one. The dose (10-100 mg/Kg p.o.)-dependent anti-inflammatory effects of the 5-methoxycanthin-6-one (ED50=60.84±0.010) and canthin- 6-one (ED50=96.64±0.012) were either comparable or significant as the positive control, diclofenac. The radical scavenging activity of the alkaloidal extract (IC50=23.12±0.010), 5-methoxycanthin-6-one (IC50=27.62±0.090) and canthin-6-one (IC50=33.60±0.011) was also significantly comparable to Vitamin E (IC50=8.605±0.002) used as positive control. Canthinone alkaloids are well-known constituents of the Simaroubaceae and Rutaceae and display a wide range of biological activities. However, they are being reported as constituents of the Euphorbiaceae here for the first time.
