Impact of curcumin nanoformulation on its antimicrobial activity

Background: Curcumin is a yellow-orange, hydrophobic compound extracted from Curcuma longa and widely used by oriental cultures. It displays numerous biological activities and shows antimicrobial activity against both Gram-positive and Gram-negative bacteria, as well as yeasts and molds. However, its low water solubility decreases its bioavailability and hinders its industrial use. Curcumin may be modified by micro/nanoencapsulation or nanonization (transformation in nanometric crystals) techniques, to improve its water solubility and dispersibility and potentiate its biological properties. Furthermore, encapsulated curcumin may be applied to foods as a preservative, to increase the product's shelf life. Scope and approach: In this work, the recent developments in the antimicrobial activity of micro- and nano-formulations (nano/microparticles, capsules and nanocrystals) of curcumin are comprehensively reviewed. Also, the most common methods applied for antimicrobial determination are listed and discussed, highlighting the conflicting results of inhibitory concentration that may be found by each technique. Key findings and conclusions: When evaluating the antimicrobial properties of curcumin, it becomes important to determine the actual gains from encapsulation because these techniques are usually expensive and may lead to the degradation of curcumin during the encapsulation steps. Attention must be paid when choosing the most suitable experimental method to determine the antimicrobial activity of encapsulated curcumin because minimum inhibitory concentration values may vary significantly.