Discovery of new homologous pamamycins by mass spectrometry and post mortem inhibitory action on autolysis of chicken embryo chorioallantoic membrane blood vessels.

protonophoric agents10). The structural diversity of most of the published pamamycins has been ascribed to the substitution of protons or methyl groups at both parts of the macrodiolide ring by ethyl groups (see c. f. R1, R2, R3, R4 and R5 in Fig. 1)1,2,11). However, variations of the length of the nitrogen-containing side chain at the left side of the pamamycin skeleton (see c. f. R6 in Fig 1) have been reported for pamamycins-621 and -6354,5) harbouring the same ring structure as was shown for pamamycin-607 (R1=R2=R3=R4=R5=CH3)3). The homologous mixtures of pamamycins are difficult to separate owing to their high degree of chemical similarity. Structural assignment of the known individual components has employed chemical derivatizations4,10) in addition to spectroscopic methods. In the course of screening for embryotoxic compounds, an extract of Streptomyces sp. HKI-0118 was found to prevent post mortem the autolysis of the chorioallantoic membrane blood vessel tissues of 15-day-old embryonated chicken eggs. This effect was also observed in presence of the above extract when the mortalization of the embryo was induced by ergotamine tartrate. Here we report the occurence of new pamamycins with molecular weights of 663, 677, 691 and 705 Da in extracts of Streptomyces sp. HKI-0118 as constitutive parts of a mixture of homologous pamamycins containing also pamamycins-607, -621, -635 and -649. Due to the possibility of daughter-ion generation from the single [M+H]+ ions of a mixture, triple-quadrupole mass spectrometry (CID-MS/MS) appeared as a promising tool for the analysis of the new pamamycin complex.