113-73-5

Gramicidin S was found in the culture broth of Bacillus brevis by Gause of the USSR Academy of Medical Sciences in 1944. It was later found by Otani of Osaka University in the cells of the Nagano strain of the same species. The antibiotic is a basic peptide showing strong activity against gram-positive bacteria and considerable activity against gramnegative cocci and Mycobacterium. Gramicidin S is rather toxic but is not absorbed orally; it is used topically as an ointment or as eye or ear drops in combination with other antibacterial drugs.

Gramoderm,Schering,US,1949

5 lb of acid precipitated solid (Hotchkiss, Advances in Enzymology, pages 157- 158) from 30 gal of tyrothricin fermentation liquor containing about 40 g (2%)of tyrothricin were extracted with 12 liters of absolute ethyl alcohol and filtered. The filtrate was evaporated in vacuo to 1 liter, and the concentrate extracted twice with 1 liter of pentane. The pentane layers were discarded.40 g of decolorizing charcoal were added to the pentane-extracted filtrate and filtered off.
To 500 ml of the charcoal-treated filtrate were added 200 ml benzene and 300 ml water, the whole shaken thoroughly, centrifuged, and the benzene layer separated. This treatment of the charcoal-treated filtrate was repeated twice, all benzene fractions were combined and evaporated in vacuo.
200 ml of absolute acetone were added to the residue and concentrated by boiling to 150 ml. The concentrate was refrigerated overnight. The crystals which had formed in the concentrate were filtered off, and the mother liquor concentrated first to 50 ml and then to 25 ml, the two concentrates refrigerated overnight, and the formed crystals filtered off. Total yield of crystalline gramicidin was 3.85 g = 19.2% of estimated tyrothricin in the initial material.
The combined crystal crops were redissolved in 50 ml absolute acetone, and the solution refrigerated overnight. After filtering, the formed crystals were dried in vacuo. The total yield of crystalline gramicidin thus obtained was 2.5 g.

Antibacterial

Gramicidin S crystallises from EtOH. The di-HCl crystallises from EtOH (+ few drops of HCl) with m 277-278o (see below). [NMR: Gibbons et al. Nature 227 840 1970, Beilstein 26 III/IV 4273.]