Inorganic chemists working in India have made a series of ruthenium complexes that possess better antibacterial and antifungal properties than commercially available treatments. 

Sengottuvelan Balasubramanian and colleagues from the University of Madras, Chennai, used ruthenium complexes with functionalised terpyridine ligands - containing three pyridine groups - and investigated their antibacterial and antifungal activity against a range of human and plant pathogens in vitro.

Balasubramanian explained: 'Many metal complexes have been shown to possess bioactivity. Functionalised terpyridine complexes have found a wide range of uses, and are well suited to medicinal uses because of their rate of ligand exchange, range of accessible oxidation states, and the ability of ruthenium to mimic iron in binding to certain biological molecules.'

The activity of Balasubramanian's complexes was tested against four human pathogens including Pseudomonas aeruginosa and Escherichia coli and five plant pathogens. Balasubramanian said: 'They exhibited very good activity against most of the test pathogens and their activity is better than those of some of the commercially available antibiotics, such as tetracycline, and the fungicide carbendazim.' They found the effects of the test compounds to be dose dependent, working more efficiently at higher concentrations. 

'The ruthenium terpyridine complexes show promising antibiotic and antifungal activity in vitro and qualify for further investigation of their mode of action. This is an emerging field, as metal complexes may have specificity and resistance profiles different from those of organic drugs,' said Dirk Deubel, a theoretical chemist from the University of Marburg, Germany. Balasubramanian said he plans to extend the work to other ruthenium terpyridine complexes with such diverse applications as solar energy conversion and anticancer activity.

Michael Spencelayh