Revisiting curcumin, an old ‘friend’ in the era of antimicrobial resistance

With antimicrobial resistance (AMR) an ever-present spectre and the prospect of 10 million deaths globally due to drug resistance by 2050 [1], scientists from various disciplines continue looking for alternate compounds to treat infections resistant to existing drugs. This includes re-evaluating natural products from plant extracts plus synthesising compounds based upon plant scaffolds. One such candidate is curcumin (Fig. 1), extracted from turmeric (Curcuma longa). With a long pedigree of historical medicinal use, from an activity perspective, one of the first published papers described curcumin’s antibacterial activity against Staphylococcus aureus, Salmonella paratyphi and Mycobacterium tuberculosis, although much subsequent research has concentrated on anticancer and anti-inflammatory properties due to issues with poor solubility and bioavailability [2]. Although curcumin shows promise against some difficult to treat bacterial species including MRSA and Clostridium difficile [3], curcumin derivatives have been synthesised with the aim to improve bioactivity. Curcuminoids synthesised and chemically characterised at Kingston University show minimum inhibitory concentrations between 5 and 20 μg/mL against staphylococci [4], close to that seen with vancomycin (4 mg/L) [5], with one derivative inhibiting biofilm formation at 40 μg/mL. Biofilms, bacterial communities attached to biotic and abiotic surfaces, are associated with numerous bacterial infections and provide a natural defence to bacterial cells within them, making them hard to remove. Such results support continued research on curcumin and its derivatives to treat bacteria of clinical importance.