Quaternary alkaloids of two Kenyan medicinal plants belonging to the genus Zanthoxylum, Z. usambarense and Z. chalybeum, were examined using ion-pair HPLC. Both plants contained similar alkaloids, but colored protoberberines were found only in Z. chalybeum. From the stems of Z. usambarense a new alkaloid named usambanoline (1) was isolated and characterized.

Ion‐pair and ion‐suppression mode high performance liquid chromatography was conducted on the alkaloidal constituents of the roots of Artabotrys monteiroae, an important medicinal plant in Kenya having analgesic and anti‐inflammatory action. Use of sodium perchlorate as an ion‐pair reagent led to excellent separation. In the ion‐suppression system containing ammonium acetate, the separation was rather poor, but liquid chromatography‐mass spectrometry was possible, which was not the case in the ion‐pair system. Four aporphines, (‐)‐asimilobine, (+)‐wilsonirine, (+)‐norisoboldine and anonaine, and a benzylisoquinoline, (+)‐reticuline, were identified after isolation by preparative thin layer chromatography.

Quaternary alkaloids of the stem of Zanthoxylum usambarense, an important medicinal plant in Kenya utilized for the treatment of pneumonia and rheumatism, were examined by a combination of ion‐pair extraction and preparative ion‐pair high performance liquid chromatography (HPLC), in which sodium perchlorate was used as an ion‐pair reagent. Quaternary bases were extractable from aqueous solution into 1,2‐dichloroethane in the presence of perchlorate in acidic conditions. The phenomenon is explained in terms of ion‐pair extraction between alkaloidal cation and perchlorate anion. The quaternary alkaloidal fraction thus obtained was well separated by means of ion‐pair HPLC in which sodium perchlorate was also utilized. Furthermore, the solvent system was easily applied to preparative HPLC, yielding the pure perchlorate of each alkaloid. Eight quaternary bases in Z. usambarense were thus obtained and their structures were elucidated. One of them was a new quaternary base of the tetrahydroprotoberberine type, which was named (‐)‐usambarine.

Mefloquine pharmacokinetics were studied in Kenyan African normal volunteers and in patients with severe acute attack of Plasmodium falciparum malaria. Peak concentrations were achieved in both groups at 20-24 hours. The mean half-life of elimination was 385 +/- 150 hours (mean +/- SD) in normal subjects while in severe malaria it was 493 +/- 215 hours which was significantly longer (P less than or equal to 0.001). The volume of distribution was significantly smaller in severe malaria where it was 30.76 +/- 10.50 l/kg (mean +/- SD) while in the normal subjects it was 40.90 +/- 20.70 l/kg (mean +/- SD) (P less than or equal to 0.001). The total body clearance in severe malaria was 3.75 +/- 1.51 l/h (mean +/- SD). This was significantly lower than in the normal subjects where it was 5.15 +/- 1.50 l/h (mean +/- SD) (P less than or equal to 0.001).

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