A-53930A and B, novel N-type Ca2+ channel blockers

A-53930A, B and C, which inhibit N-type Ca2+ channels, were isolated from the culture broth of Streptomyces vinaceusdrappus SANK 62394. A-53930A and B were new compounds which contained a carbamoyl group on the 6-hydroxyl group of the D-gulosamine part of streptothricin. A-53930C was identical to streptothricin B. A-53930A, B and C inhibited [125I]omega-conotoxin MVIIA binding to N-type Ca2+ channels (IC50= 0.17, 0.091 and 0.071 microM), but did not inhibit [3H]PN200-110 binding to L-type Ca2+ channels (IC50 > 50 microM). These compounds also inhibited [3H]norepinephrine release from chick cerebral cortex synaptosomes (IC50=91.0, 20.6 and 39.5 microM), indicating these compounds selectively block N-type Ca2+ channels which are important for neurotransmitter release. It was also revealed that although A-53930C had antimicrobial activity against gram-negative and -positive bacteria and fungi, A-53930A and B showed weak activity only against gram-negative bacteria.