*Review* **Silver Camphor Imine Complexes: Novel Antibacterial Compounds from Old Medicines**

#### **Jorge H. Leitão 1,\*, Silvia A. Sousa 1, Silvestre A. Leite 1,2 and Maria Fernanda N. N. Carvalho 2,\***


Received: 12 June 2018; Accepted: 24 July 2018; Published: 26 July 2018

**Abstract:** The emergence of bacterial resistance to available antimicrobials has prompted the search for novel antibacterial compounds to overcome this public health problem. Metal-based complexes have been much less explored than organic compounds as antimicrobials, leading to investigations of the antimicrobial properties of selected complexes in which silver may occupy the frontline due to its use as medicine since ancient times. Like silver, camphor has also long been used for medicinal purposes. However, in both cases, limited information exists concerning the mechanisms of their antimicrobial action. This work reviews the present knowledge of the antimicrobial properties of camphor-derived silver complexes, focusing on recent research on the synthesis and antimicrobial properties of complexes based on silver and camphor imines. Selected examples of the structure and antimicrobial activity relationships of ligands studied so far are presented, showing the potential of silver camphorimine complexes as novel antimicrobials.

**Keywords:** silver; camphor derivatives; silver camphorimine complexes; antimicrobial activity
