Elephantorrhiza elephantina (Ee) and Pentanisia prunelloides (Pp) are two medicinal plants which are widely used by traditional healers to remedy various ailments including diarrhoea, dysentery, inflammation, fever, rheumatism, heartburn, tuberculosis, haemorrhoids, skin diseases, perforated peptic ulcers and sore joints in Southern Africa (South Africa, Swaziland, Botswana and Zimbabwe). Often, decoctions and infusions from these two plants are used in combination, specifically for stomach ailments. The following study was conducted to explore the possible mechanism underlying the synergistic interactions of the joint application of these two medicinal plant species.The checkerboard micro-dilution technique was used to determine the efficacy of (-)-epicatechin (EC): palmitic acid (PA) and (-)-epicatechin: E. elephantina or P. prunelloides combinations on five selected pathogenic bacteria. The results demonstrated that the combination of EC and PA exhibit either additive or synergistic but no antagonistic interactions. Of the 35 administered combinations, 11 were synergistic, 10 additive and 14 indifferent. The fractional inhibitory concentrations (FIC) indices for the combination of EC and E. elephantina for the three pathogens tested exhibited indifferent interactions with all FIC values above 1 while the FIC indices for the 1:1 combinations of EC and P. prunelloides exhibited additive interactions (FIC values between 1 and 0.50). This is the first report to explore the possible explanation underlying the synergistic interactions exhibited by the two medicinal plants.
Key words: Elephantorrhiza elephantina, Pentanisia prunelloides, (-)-epicatechin, palmitic acid, efficacy, fractional inhibitory concentrations (FIC) index
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