Ethanolic leaf extract from Strophanthus gratus (Hook.) Franch. (Apocynaceae) exhibits anti-inflammatory and antioxidant activities

Abstract

Chronic inflammation is associated with many diseased conditions. In particular, free radicals and oxidative stress play a major role in the development of tissue damage and some pathological events which result in inflammation. Plant extracts have widespread folkloric use in the management of various diseased conditions. One of such plants used in Ghana for managing inflammation-related conditions is Strophantus gratus. This study evaluated the anti-inflammatory and antioxidant activities of the ethanolic extract of the leaves of Strophantus gratus. Crude ethanolic leaf extract was obtained by Soxhlet extraction. The crude extract was then fractionated to obtain hexane, ethyl acetate, and butanol fractions. Anti-inflammatory activity of the extract and fractions were evaluated using carrageenan-induced paw edema model in 7-day old chicks. Phosphomolybdenum assay was used to assess the total antioxidant activity of the extracts. The concentration of the crude extract required to reduce the induced inflammation by 50% (ED₅₀) was determined to be 129.7 ± 10.5 mg/kg. The ethyl acetate fraction produced a similar ED₅₀ value (133.5 ± 14.7 mg/kg). The ED₅₀ values of the hexane and butanol fractions were however greater than 1000 mg/kg, indicating that the activity of the crude extract was concentrated in the ethyl acetate fraction. The total antioxidant capacity of the crude extract and the ethyl acetate fraction was determined to be 6.7 ± 1.0 g/100g and 8.3 ± 1.4 g/100g ascorbic acid equivalent respectively. Taken together, the results provide scientific validation for the use of Strophantus gratus in managing inflammation associated ailments in traditional herbal medicine.