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Preparative-scale separation of colistin sulphate bulk sample was carried out on a preparative poly(styrene-divinylbenzene) stationary phase. Isocratic elution with acetonitrilesodium sulphate solution (0.7% m/v; pH adjusted to 2.5 with TFA) -water (16 : 50 : 34, % v/v/v) was carried out at a flow rate of 4.0ml min"1. Six colistin componentswere isolated and characterized using *H and 13C NMR.The molecular weights were confirmed by mass spectrometry. The structures of 2 components were determined for the first time. Polymyxin E7 was identified as having the same composition as polymyxin E1? except that the fatty acid moiety was 7-methyloctanoic acid. Isoleucine polymyxin E8 was characterized as having the same composition as isoleucine polymyxin Ex with 7-methylnonanoic acid as the fatty acid moiety.Colistin, also known as polymyxin E, is a complex mixture of closely related polypeptides isolated from Bacillus polymyxa var. colistinus.Colistin

Ajuga remota is the most frequently used medicinal herb for malaria treatment in Kenya. Its two known isolates ajugarin-1 (1) and ergosterol-5,8-endoperoxide (3) and a new isolate 8-O-acetylharpagide (2) were evaluated for their in vitro antiplasmodial activity. Ajugarin-1 was moderately active, with an IC(50) of 23.0 +/- 3.0 microM, as compared to chloroquine (IC(50) = 0.041 +/- 0.003 microM) against the chloroquine-sensitive (FCA 20/GHA) strain of Plasmodium falciparum. Ergosterol-5,8-endoperoxide was about 3x as potent (IC(50) = 8.2 +/- 1.1 microM), while 8-O-acetylharpagide, whose structure was established by spectroscopic evidence, was inactive. Both ajugarin-1 and ergosterol-5,8-endoperoxide did not exhibit cytotoxicity against A431 (skin carcinoma) cell line, but 8-O-acetylharpagide was significantly cytotoxic. This iridoid glucoside, which has been formerly isolated from Ajuga decumbens, was identified in A. remota for the first time.