Traditional dietary additives of the Maasai are antiviral against the measles virus.

Although ethnopharmacological investigations emphasize the importance of medicinal plants in developing countries, species used regularly with diet are under-investigated and potentially make greater contributions to health. Thirteen traditional plants most commonly added to milk/soups by the Maasai for perceived health benefits were tested for activity against measles virus (MV) using non-medicinal plants as controls. Antiviral effects of plant extracts were sought using a modified neutralization assay. Methanolic extracts of medicinal species exhibited significantly greater activity neutralizing MV in vitro in comparison to non-medicinal extracts (p<0.02). Four of 13 (31%) medicinal species versus 0/13 controls had measurable effects against MV in vitro. Olinia rochetiana (Olkirenyi) and Warburgia ugandensis (Osokonoi) extracts were most potent with the number of plaque forming units reduced 37- and 34-fold, respectively. Given the importance of monocytes in the dissemination of MV, we assessed the capacity of a subset of plant extracts to inhibit MV growth in monocytoid cell line, U937. MV output from U937 cells was significantly reduced by four of seven medicinal plant extracts (mean reduction 48 h: 39.0+/-26.0%, range 3.5-87%; 72 h: 56.4+/-29.5%, range 14.1-103.1%) (p<0.05). This study provides evidence that medicinal plants added to the Maasai diet may contribute to the modulation of viral infections.