Researchers at the University of Ibadan have developed herbal soap formulations containing extracts from two medicinal plants traditionally used in African healthcare, with laboratory tests showing promising activity against selected bacteria and fungi associated with skin infections.
The study, titled “Formulation and Antimicrobial Assessment of Herbal Soap from Tetrapleura tetraptera and Ageratum conyzoides,” investigated whether extracts from the plants could retain their antimicrobial properties when incorporated into soap.
The findings showed that some formulations performed better than soap without plant extracts against selected microorganisms, including Staphylococcus aureus, Pseudomonas aeruginosa and Trichophyton rubrum.
The research adds to growing scientific interest in medicinal plants as potential sources of ingredients for pharmaceutical, cosmetic and personal-care products.
The study, in the Journal of Phytomedicine and Therapeutics, involved Iyamide Akinjo, Abraham O. Nkumah, Olufunke D. Akin-Ajani and Omonike O. Ogbole.
They examined Tetrapleura tetraptera, commonly known as Aridan in Nigeria, and Ageratum conyzoides, popularly called billy goat weed. Both plants have a history of use in traditional medicine.
Tetrapleura tetraptera is native to West and Central Africa. Its fruit is used as a spice in Nigerian cooking and has traditionally been used for various health complaints, including pain and inflammation. Ageratum conyzoides is a tropical herb also used in traditional remedies.
The researchers sought to determine whether extracts from the plants could be incorporated into soap while retaining properties that might inhibit selected bacteria and fungi.
For the study, the team collected plant materials from locations in Ibadan, dried and ground them, and extracted their chemical constituents. The extracts were then incorporated separately into soap formulations at different concentrations, using coconut, olive and almond oils in the soap base.
A formulation without plant extracts served as the control, allowing the researchers to compare the herbal soaps with conventional soap under laboratory conditions.
The finished products were assessed for characteristics such as appearance, texture, lather production and cleansing ability. Their ability to inhibit selected microorganisms was also tested.
One of the most promising findings involved the formulation containing five grammes of T. tetraptera extract. It showed notable activity against S. aureus, a bacterium associated with skin infections, and T. rubrum, a fungus that can cause infections affecting the skin, feet and nails.
The researchers reported that this formulation performed better than the control soap against both organisms in laboratory tests.
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Another formulation, containing 20 grammes of A. conyzoides extract, showed promising activity against P. aeruginosa, a bacterium that can cause infections, particularly in people with weakened defences or damaged skin.
Some T. tetraptera formulations also inhibited other bacteria, including Bacillus subtilis and Klebsiella pneumoniae. Tests against Candida albicans, a fungus that can cause infections under certain circumstances, produced encouraging results for some formulations containing the same plant extract.
However, the effects varied according to the plant, the concentration used and the microorganism tested.
An important finding was that increasing the amount of plant extract did not always produce stronger antimicrobial activity. The five-gramme T. tetraptera formulation performed particularly well against S. aureus and T. rubrum, while the formulation containing 20 grammes of A. conyzoides extract showed the strongest reported activity against P. aeruginosa.
The researchers also assessed the soaps’ lather production and cleansing performance. The formulation containing 10 grammes of T. tetraptera extract produced the highest foam level among the tested products, outperforming the control soap.
Meanwhile, the formulation containing 10 grammes of A. conyzoides extract performed particularly well in a laboratory cleansing test involving filter paper stained with engine oil, achieving complete stain removal under the test conditions.
Although the results suggest potential cleansing benefits, they do not establish that the formulation is superior for all personal-care applications.
The products also differed in colour, texture and hardness, indicating that further adjustments may be needed to ensure consistent quality. The researchers identified formulations containing 10 grammes of either plant extract as promising candidates when their physical and chemical characteristics were considered alongside their other performance measures.
The findings could contribute to efforts to develop products from locally available medicinal plants and create opportunities for innovation in Nigeria’s pharmaceutical and personal-care industries.
However, commercial development would require standardised extraction procedures, reliable sourcing of plant materials and quality-control measures to ensure consistent performance across production batches.
Safety is another important consideration. Further studies are needed to determine whether the extracts could cause skin irritation or allergic reactions, particularly with repeated use. Traditional use alone does not establish that a concentrated extract is safe for every user or suitable for all skin types.
The study also does not establish that the herbal soaps can prevent or treat skin infections in people. The experiments were conducted in the laboratory, and the researchers did not determine whether the observed antimicrobial effects would persist during normal washing, when soap is diluted with water and rinsed off after a short period.
The study shows that further research would be needed to assess the products under realistic conditions of use and determine whether they offer benefits beyond those of conventional soap. Human studies would also be required before claims that the formulations can prevent or treat specific infections could be substantiated.
For now, the findings provide a starting point for further investigation into T. tetraptera and A. conyzoides as potential ingredients in herbal soaps, while highlighting the need for additional safety assessments and product development before the formulations can be recommended for medical use.
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