Ph.D. (Chemistry) / The following study was conducted to explore the in vitro antimicrobial and synergistic properties of the two medicinal plants (Elephantorrhiza elephantina, Fabaceae and Pentanisia prunelloides, Rubiaceae), which are widely used in southern Africa. These two plant species are used to remedy various ailments including diarrhoea, dysentery, inflammation, fever, rheumatism, heartburn, tuberculosis, haemorrhoids, skin diseases, perforated peptic ulcers and sore joints. The cytotoxicity of the aqueous and methanol extracts and fractions of both species was studied using the brine shrimp lethality tests for the first time. The results demonstrated that the lethality (LC₅₀) for crude extracts for both plants ranged between 1.8 and 18 μg/mL which was relatively greater than the fractions of the extracts. This suggested that crude extracts were more potent than their respective fractions which further implied that the different fractions of phytochemicals in these plant species work jointly (In synergy) to exert their therapeutic efficacy. The antimicrobial activity of methanol and aqueous extracts of rhizomes was investigated by means of a checkerboard micro-dilution technique in a bid to validate possible synergistic interactions between the two plants...