Certain plant phytochemicals have been shown to inhibit RV activity through inhibition of viral penetration and viral replication. Some flavonoids were shown to inhibit penetration of RV in rhesus monkey epithelial cell line (MA104) [31] , while others have an effect on the viruses or on the enzymes responsible for their replication [40] . These effects could not be singly demonstrated in this study; further work on these possible mechanisms of antiviral effects of T. esculentum extracts is, therefore, encouraged. The observed antirotaviral effects can be attributed to the high phenolic acid content (especially gallic acid), in bean cotyledons, among other components (Marama II report, unpublished). Gallic acid was previously shown to prevent viral replication, inhibition of virus attachment to and penetration into cells, and virucidal effects [41] . Interference with attachment and penetration into cells could not be proved in this study. Tylosema esculentum tubers may contain some yet to be determined phenolics (Marama II report, unpublished). Ethanolic extracts had notably higher antiviral activity than aqueous bean and tuber extracts (Figures 3  and 6 ). Some essential oils as found in T. esculentum beans may contribute towards the observed antiviral effects; similar findings were reported by Astani et al. [42] using essential oils extracted from Melaleuca alternifolia. Moreover, recently, a Kunitz-type inhibitor, distinct from other known plant serine protease inhibitors and shown to be specific for elastase, was isolated in T. esculentum beans [43] . The quantity of this elastase inhibitor present in T. esculentum beans is many times greater than in soybean or any other bean or nut source reported to date [43] . Certain protease inhibitors have been shown to impart high antienteroviral effects through interference with proteolytic cleavage during the replication process [44] . The high phytosterol content of T. esculentum bean oil 4-desmethylsterols (75%) and 4.4-dimethylsterols and 4-monomethylsterols (15.72%) [4] could also contribute to the high antiviral activity in bean extracts. Phytosterols have been determined to have antihuman cytomegalovirus (HCMV) and antiherpes simplex virus (HSV) effects [45] . The antiviral activity of phytosterols is through the blocking effect on immediate-early antigen expression in fibroblast cells and blocking of virus-cell interaction and/or virus multiplication [45] .