Rachmaniah et al. / Malaysian Journal of Fundamental and Applied Sciences Vol. 16, No. 5 (2020) 514-518 514 Orchidea Rachmaniah * , Galang Ramdhani Fitra Gama, Zandhika Alfi Pratama, Muhammad Rachimoellah Department of Chemical Engineering, Faculty of Industrial Technology, Institut Teknologi Sepuluh Nopember, 60111 Sukolilo, Surabaya, Indonesia * Corresponding author: orchidea@its.ac.id Article history Received 8 April 2019 Revised 21 February 2020 Accepted 30 April 2020 Published Online 15 October 2020 Graphical abstract Abstract An antimicrobial photodynamic therapy (aPDT) is a local antimicrobial treatment which utilizes a photosensitizer dye, visible light, and oxygen. It is considered as an alternative treatment for bacterial or fungal resistance. In this treatmetn, a pure, stable and non-toxic natural photosensitizer compound as a host cell which soluble in water and capable of producing reactive photoproducts is required. Curcumin as a natural yellow-orange photosensitizer dye with anti-inflammatory, anti-carcinogenic, anti-bacterial, and anti-infection activities is believed to be safe for human consumption. Combining curcuminoids as a photosensitizer dye with NADES as solvent instead of solving the low solubility drawback of curcuminoids in water, as well as becoming a potential candidate of aPDT. However, an antimicrobial effect of dissolved curcuminoids in NADES need to be studied first. Antimicrobial tests of curcuminoids to both of Escherichia coli and Staphylococcus aureus using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods were conducted. Three NADES i.e. malic acid-sucrose-water (MAS-H2O = 1:1:18); fructose-glucose-water (FG-H2O = 1:1:1); and fructose-sucrose-water (FS-H2O = 2:1:15) were tested by applying nine different concentrations of curcuminoids (2.00-4.00 mM). A blank of sample (no dissolved curcuminoids) as well as a pure solution of each constituent compounds of NADES such sucrose, malic acid, fructose, and glucose were also applied. Bacterial suspension approx. 10 8 cells/mL of 1 mL (24 h incubated at 37 o C) was used for the test. MAS-H2O (1:1:18) shown the most effective antimicrobial activity compared to both of FG-H2O (1:1:1) and FS-H2O (2:1:15). The toxicity of MAS-H2O (1:1:18) to both E. coli and S. aureus may due to the low pH condition of NADES itself since malic acid has high acidity (pH <3). Meanwhile, both other NADES contains sugars, i.e. fructose, glucose, and sucrose, showing lower pH value (pH >5). Both on the concentration of the curcuminoids and bacteria effects the observed toxicity. Keywords: Antibacterial, curcuma, deep eutectic solvent, ionic liquid © 2020 Penerbit UTM Press. All rights reserved INTRODUCTION Staphylococcus aureus strain has shown high resistance against each new class of licensed antibiotics. It is recently reported that a strain of S. aureus is resistant to vancomycin, a glycopeptide antibiotic considered as a last line generation of antibiotics. The problem is made more severe by social factors such as an inappropriate prescription of antibiotics, or an excessive prescription of antibiotics leading to either bacterial or fungal resistance. Moreover, more and more frequent transmissions of microorganisms occur due to global traveling, expansion of poverty among the population of the third world countries, and by the large variety of mechanisms adopted by microbial cells, thus increasing the resistance of the bacteria to external insults. This results in a thickening of their outer wall, encoding of new proteins which prevent the penetration of drugs, onset of mutants deficient in those porin channels allowing the influx of externally added chemicals, among others (Heger et al., 2014). Therefore, a comprehensive strategy is required to resolve this problem, such as an alternative solution to inactivate pathogens or bacteria. A photochemical reaction among a photosensitizer (PS) or a dye, visible light, and oxygen produces reactive oxygen species (ROS) which is applied in antimicrobial photodynamic therapy (aPDT). The produced ROS, free radicals and/or other reactive photoproducts may cause damage to bacterial cell structures, which ultimately results in bacterial inactivation. An alternative way to combat bacteria resistances (Kumavat et al., 2013) is by overcoming the antibiotic resistances. A visible light at an appropriate wavelength is used to excite the PS molecule to produce superoxide radicals (type 1 reaction) or generate singlet oxygen (type 2 reaction) (Kumavat et al., 2013) which subsequently lead to the destruction of the bacterial cells by an oxidative burst (Cieplik et al., 2018) of biomolecules such proteins, lipids, and nucleic acids (Hamblin, 2016). It has been reported the effectiveness of aPDT against Gram-positive, such Staphylococcus aureus and Bacillus subtilis, and Gram-negative bacteria, such RESEARCH ARTICLE Antimicrobial effect of dissolved curcuminoid in natural deep eutectic solvents (NADES) to Escherichia coli and Staphylococcus aureus: A promising candidate for antimicrobial photodynamic therapy (aPDT)