# Benzimidazole-Quinoline Hybrids: Synthesis and Antimicrobial Properties

## TL;DR

This paper reviews the synthesis and antimicrobial properties of benzimidazole-quinoline hybrid compounds, highlighting their potential as effective and low-toxicity antimicrobial agents.

## Contribution

The paper provides a comprehensive review of recent synthetic methods and antimicrobial activities of benzimidazole-quinoline hybrids.

## Key findings

- Hybrids with halogen substitution and specific linker structures show enhanced antimicrobial activity.
- Some hybrids exhibit low MICs (1–8 µg/mL) and low cytotoxicity, indicating strong antimicrobial potential.
- Incorporating a five-membered heterocycle improves the therapeutic properties of these hybrids.

## Abstract

Background: Heterocyclic compounds are particularly important in medicinal chemistry. With a range of therapeutic uses, benzimidazoles and quinolines are both key heterocycles in medicinal chemistry. A number of hybrid heterocyclic compounds have been reported in recent years because they typically have better therapeutic properties than single heterocyclic rings. Methods: A literature search was conducted across relevant scientific literature from peer-reviewed sources, using keywords, including “benzimidazole”, “quinoline”, “benzimidazole-quinoline hybrids”, “antibacterial”, “antifungal”, “antimalarial” and “hybrid complexes”. Results: This review summarizes the synthetic methodologies for benzimidazole–quinoline hybrids, benzimidazole– quinolinones, and benzimidazole–quinoline metal complexes, along with their antimicrobial and antimalarial activities and the reported structure–activity relationship (SAR) studies. The importance of halogen substitution, particularly with chlorine and fluorine atoms, as well as the structure of the linker between the benzimidazole and quinoline rings—specifically chain length, the presence of oxygen, sulfur, or nitrogen atoms, and heterocyclic moieties—is highlighted. A series of benzimidazole–quinoline hybrids exhibit antimalarial and antitrypanosomal activities or show enhanced antimicrobial properties due to the incorporation of a five-membered heterocycle in addition to the two existing heterocyclic rings. Notably, several hybrids from different compound series exhibit very low minimum inhibitory concentrations (MICs) in the range of 1–8 µg/mL, along with low cytotoxicity, supporting their potential for further investigation as antimicrobial agents. Conclusions: This review summarizes the synthetic methods, medicinal properties, and structure–activity relationship (SAR) studies of benzimidazole–quinoline hybrids reported between 2002 and 2026.