The distribution of indole alkaloids in the leaves, stems and roots of 10 African mainland RAUVOLFIA species is summarised and the interrelationships of the alkaloid types discussed.

The occurrence of alkaloids in Rauwolfia caffra SOND. was investigated using thin layer chromatography and a colorimetric assay of the eluted alkaloids. It was noted that the nitrous acid colorimetric assay devised by Szalkowski and Mader (1956) yielded high results unrelated to pharmacological activity unless the alkaloids were separated and estimated individually. The weakly basic alkaloids are usually a minor component of the total alkaloids of R. caffra root, the principal alkaloids being ajmaline and raucaffricine.

The indole alkaloids ajmalicine, ajmaline, rescinnamine, reserpiline, reserpine, a-yohimbine, another yohimbine isomer, renoxydine and serpentine were de-' tected in the root bark of R. oreogiton MGF. Reserpiline, reserpine and ajmaline were the principal alkaloids. Confusion concerning the identities of Rauwolfia volkensii STAPF and R. oreogiton M G F. resulted in the assumption that the species were synonymous because silviculturists regarded the species as doubtfully distinct (WILLAN, 1960). &lore recent communications with the East African Herbarium, Nairobi, Kenya, inform us that the specimens ,,Semsei 2827" and ,,Semsei 2948" supplied as R. volkensii should be renamed R. oreogiton. Thus earlier publications (COURT, 1961, 1964, 1968) refer to R. oreogiton. R. oreogiton is a shrub growing to a height of about 2 m and indigenous to Tanzania, occurring at an elevation in excess of 1260 m (FEUELL, 1955; COURT, 1966). Local enquiries in Tanzania indicated that the roots are used in the treatment of gonorrhoea and snakebite, and to increase lactation in nursing mothers (WOOD, 1964). R. oreogiton has been shown by chromatography to contain the indole alkaloids ajmaline, reserpine, reserpiline and serpentine (COURT, 1968). More detailed work using improved techniques has enabled us to demonstrate the occurrence of nine alkaloids in R. oreogiton root bark. Experimental Plant material R. oreogiton roots collected by the Forest Department, Lushoto, Tanzania and vouched for by the East African Herbarium, Nairobi, from botatlical specimens sent under collector's num

11 indole alkaloids were isolated from Rauwolfia oreogiton roots and identified. The alkaloids comprised dihydroindole, heteroyohimbine, oxindole, yohimbine and 18-hydroxy-yohimbine ester types. Chromatographic comparison of alkaloidal extracts from Rauwolfia oreogiton and Rauwolfia volkensii roots revealed no basis for chemical differentiation of the species.

The morphology of the leaves of R a u w o l f i a c a f f r a , a potential source of indole alkaloids, has been described. Diagnostic features include straight-walled epidermal cells, paracytic stomata, laticiferous canals, unlignified fibres, calcium oxalate prisms and clusters and the absence of sclereids and trichomes.