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.

Keywords:

• total antioxidant capacity
• carrageenan-induced paw edema
• phosphomolybdenum assay
• solvent fractionation
• inflammation

PUBLIC INTEREST STATEMENT

Many plants are used in herbal formulations to treat various diseases. In Ghana, Strophantus gratus is used to treat diseases which has inflammation as one of the symptoms. However, there is no scientific proof that validates the use of this plant in managing inflammation related conditions. This research work showed that the leaf extracts of Strophantus gratus do indeed possess anti-inflammatory capabilities and can also neutralize reactive oxidant species.

Acknowledgements

The authors are grateful to the Departments of Chemistry and Pharmacology for the use of their facilities for this study. Bernard Ussher, Mr. Gyan, Michael Konney Laryea, Jennifer Amo-Mensah, and Michel Selassie Doetse, all of KNUST are acknowledged for technical support. Mr Edward Ntim Gasu is also appreciated for help with data analysis.

Competing interests

The authors declare that there were no competing financial, professional, or personal interests that might have influenced the performance or presentation of the work described in this manuscript.

Author contributions

LSB conceived the study. All experiments were designed by LSB and SOB. Sample collection and all experimental procedures were carried out by SOB. Data analysis was by SOB and LSB. The initial manuscript was drafted by SOB and edited by LSB. All authors read and approved the final manuscript.

Data availability

All data generated or analyzed during this study are included in this published article.

Ethics

The project proposal and procedures were reviewed and approved by the Institution Ethics Review Board for Animal Use at the Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.

Additional information

Funding

No direct funding was received for this research. The rotary evaporator used for the study was purchased with an International Foundation for Science (IFS) Collaborative Research Grant to LSB.

Notes on contributors

Samuel Ofori – Baah

Samuel Ofori – Baah was an undergraduate Chemistry student who did his final year research project in the Borquaye Research Group.

Lawrence Sheringham Borquaye is a bioorganic chemist at the Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana and leader of the Borquaye Research Group. His research focuses on science at the interface of chemistry and biology. He has been exploring biologically active natural products from plants and marine organisms. Other research interests include the development of methods for the analysis of pharmaceutical and personal care products in the environment and the characterization of plant volatiles (essential oils). Visit us at www.borquayelab.com for more information about our research group.