Global health organisations are faced with tough challenges in treating diseases caused by pathogenic micro-organisms due to the resistance that many strains have developed to available medicinal drugs. Researchers around the world are now interested in the natural medicinal properties of plants in the hope of discovering new and effective drugs that are less toxic than synthetic pharmaceuticals. In South Africa, recent studies have shown that certain invasive plant species could be administered for the treatment of sexually transmitted infections (STIs).
By Lesibana Petrus Maema
The medicinal use of various invasive (non-native) plants in South Africa has encouraged scientists to investigate their efficacy in tackling sexually transmitted infections (STIs). The corresponding study on the antimicrobial activity of seven invasive plant species against fungal and gonorrhoeal pathogens was recently published in the Journal of Complimentary and Integrative Medicine.
Madagascar periwinkle (Catharanthus roseus) is native to Madagascar and was imported to South Africa as a garden ornamental © Warayoo/Getty Images
The researchers used a disc diffusion model to test various plant extracts against fungal pathogens. In this model, a small circular wafer containing the plant extract is placed on an agar plate that has been covered with a fungal pathogen. If the plant extract has antimicrobial properties, a visible ring will form around this wafer in which the pathogen is unable to grow.
Madagascan periwinkle extract inhibits the activity of Neisseria gonorrhoea (A) and Cryptococcus neoformans (B), sisal plant and earleaf nightshade extracts show anti-Candida albicans activity (C)
Sisal plant (Agave sisalana), Madagascan periwinkle (Catharanthus roseus), castor oil plant (Ricinus communis) and African senna (Senna didymobotrya) showed promising antifungal activity against various fungal pathogens. With the use of microdilution plates the researchers found that the most active plant extracts were from Madagascan periwinkle and African senna, with both showing excellent inhibitory effects on Candida glabrata, a strain of yeast.
Cryptococcus neoformans was defenceless against an extract of prickly pear (Opuntia ficus–indica), castor oil plant and African senna. Prickly pear, Madagascan periwinkle and castor oil plant revealed noteworthy anti-gonococcal (gonorrhea-causing bacterium) inhibition.
Senna didymobotrya (also known as African senna or Peanut Butter casia) is native to Eastern Africa and regarded as an invasive species in South Africa. The plant can form dense impenetrable thickets, which affect the growth and regeneration of native plants and the movement of wildlife. © nurulanga/Getty Images
According to the researchers, the use of invasive plant species by traditional health practitioners plays an important role in the conservation of indigenous plants, as they provide an alternative medicinal source. This research highlights that certain invasive plants contain medicinal compounds that warrant further pharmacological investigation in order to isolate pure compounds and perform standard safety tests.
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