Bitterness values for traditional tonic plants of southern Africa

Bitterness values have been determined for southern African plant species that are traditionally used as tonics (imbizas or ’musa-pelo) to alleviate the symptoms of stress and a variety of ailments related to the digestive system. To measure and present, for the first time, the bitterness values of 15 of the best-known and most widely used tonic plants in southern Africa in order to find a rationale for their traditional use in improving appetite and treating digestive ailments. Most of the plants were found to be very bitter, with bitterness values comparable to those reported for internationally well-known bitter tonics such as Artemisia absynthium L. and Gentiana lutea L. The relatively high bitterness values obtained for all of the plants indicate that their alleged value in improving digestion and appetite may at least be partly ascribed to the bitter tonic (amarum) effect, i.e., the stimulation of gastric juices via the nervus vagus. It may be interesting to examine the chemical compounds responsible for the bitter taste, as well as the possible links between bitterness and the anecdotal anti-stress properties ascribed to these species. All 15 traditional southern African tonic plants examined are bitter. Five of them are extremely bitter, with average bitterness values above 10 000 (Aloe ferox, Artemisia afra, Dicoma capensis, Sutherlandia microphylla and Vernonia oligocephala), four are very bitter, with bitterness values between 5000 and 10 000 (Arctopus monacanthus, Dicoma anomala, Muraltia heisteria and Ziziphus mucronata) and six are moderately bitter, with values between 2000 and 5000 (Agathosma betulina, Balanites maughamii, Harpagophytum procumbens, Hypoxis hemerocallidea, Warburgia salutaris and Withania somnifera). [Display omitted]