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Bacterial γ-glutamyltranspeptidases (γ-GT) is a well-known metabolic enzyme, which could cleave the γ-glutamyl amide bond of γ-glutamyl analogues. As a key metabolic enzyme of bacteria and a virulence factor for the host, bacterial γ-GT was determined to be a novel pharmaceutical target for new antibiotics development. However, there is no efficient method for the sensing of γ-GT activity in bacteria and the recognition of γ-glutamyltransferase rich-bacteria. In the present work, a dicyanoisophorone derivative (ADMG) has been designed and developed to be a sensitive and selective near-infrared fluorescent probe for the sensing of bacterial γ-GT. ADMG not only sensed bacterial γ-GT in vitro, but also imaged intestinal bacteria in vivo. More interesting, the intestinal bacteria existed in the duodenum section of mouse displayed significant fluorescence emission. Under the guidance of the sensing of γ-GT using ADMG, three intestinal bacteria strains K. pneumoniae CAV1042, K. pneumoniae XJRML-1, and E. faecalis were isolated successfully, which expressed the bacterial γ-GT. Therefore, the fluorescent probe ADMG not only sensed the endogenous bacterial γ-GT and imaged the intestinal bacteria but also guided the isolation of intestinal bacteria possessing γ-GT efficiently, which suggested a novel biological tool for the rapid isolation of special bacteria from a mixed sample.

Alismanin A (1), a novel aromatic triterpenoid with a C 34 skeleton, was isolated from Alisma orientale together with a rearranged nor-triterpenoid (2) and a 13,17-seco triterpenoid (3). Their structures were determined by a combination of HRESIMS, 2D NMR spectra, electronic circular dichroism (ECD), theoretical calculations, and X-ray diffraction analysis. Compounds 1 and 2 displayed significant activation effects on pregnane X receptor (PXR) at 10 nM. A plausible biosynthetic pathway for 1-3 is also discussed.