Isolation and Characterization of α,β-Unsaturated γ-Lactono-Hydrazides from <i>Streptomyces</i> sp.

Abstract

Two novel α,β-unsaturated γ-lactono-hydrazides, geralcin A (<b>2</b>) and geralcin B (<b>3</b>), were isolated from <i>Streptomyces</i> sp. LMA-545. This unusual scaffold consists of the condensation of alkyl-hydrazide with an α,β-unsaturated γ-lactone, 3-(5-oxo-2<i>H</i>-furan-4-yl)­propanoic acid (<b>1</b>), which was isolated from the same broth culture. Amberlite XAD-16 solid-phase extraction was used during the cultivation step, and the trapped compounds (<b>1</b>–<b>3</b>) were eluted from the resin with methanol. The structures were elucidated using ¹H, ¹³C, and ¹⁵N NMR spectroscopic analysis and high-resolution mass spectrometry. Geralcin B (<b>3</b>) was cytotoxic against MDA231 breast cancer cells with an IC₅₀ of 5 μM