چكيده لاتين :
Introduction: Nowadays, the use of herbal medicines for the treatment of many diseases has attracted the attention of scientists (Abdullaev et al., 2004; Samarghandian and Borji 2014). Turmeric is one natural plant, which has a bioactive ingredient called curcumin. It has many medicinal and food applications due to its biological properties. Yellow pigment curcumin is a polyphenol from the diaryl heptanoids group (Anuchapreeda et al., 2011). Curcumin has different application in industry as cosmetic creams, wound glues, capsules, herbal toothpaste, and soaps. It is also used in the food industry for the preparation of soups, drinks and even pastels (Prasad et al., 2014; yallapu et al., 2013). Curcumin metabolism indicated that it has low poor solubility in the aqueous media, dramatically reduces cellular uptake and so-called bioavailability. In addition, it causes many problems in adding this valuable bioactive ingredient to water-based food and drug formulations (Sreekanth et al., 2011; Pan et al., 2011). In recent decades, nanotechnology has been able to solve this problem with bioactive compounds. Prepared nanodispersions of bioactive compounds are suggested ways to overcome this problem with low water solubility and low bioavailability bioactive (Anton et al., 2007; Mora-Huertas et al., 2011). Conventional methods of preparing nanodispersions using organic solvents may have undesirable effects. Therefore, green technology has recently been developed. Nowadays, using novel methods has advantages to prepare nanodispersions of bio-friendly bioactive materials such as subcritical water. In this method, water are used as a solvent because of its unique physico-chemical properties (Ravber et al., 2015). The aim of this study is to prepare curcumin nanodispersions with very fine particle size and high antimicrobial properties using water in subcritical conditions, for the first time, and a solvent replacement method. Finally, Zeta potential and particle distribution index (PDI) were compared. Also, the antioxidant and antimicrobial effects of prepared curcumin nanodispersions using these two methods were investigated.
Material and methods: Curcumin (97% purity), poly ethylene glycol (PEG, 4000 Dalton) and Tween 20 were provided from Merck Company (Darmstadt, Germany). Ethyl acetate (99.7%) as solvent was prepared from Samchun Pure Chemical Company (Seoul, Korea). Escherichia coli (PTCC 1270) and Staphylococcus aureus (PTCC 1112) were purchased from microbial Persian type culture collection (PTCC, Tehran, Iran). Nutrient Agar (NA) was provided from Biolife Company (Milan, Italy). Double distilled water was used to prepare all nanodispersions. Curcumin nanodispersions were prepared using solvent displacement and subcritical water. In subcritical water method, 1.5 mg of Tween 20 was mixed with 20 mg of curcumin then was added into the water, placed in a sealed teflon autoclave and heated at 120 °C for 2 h in an oven (Behdad Medical Production Co., SP88, Tehran, Iran). The internal pressure of the autoclave was 1.5 bar. The Teflon autoclave with capacity of 100 mL, was designed and manufactured in our research laboratory. In solvent displacement method, 20 mg of curcumin was added into the ethyl acetate (10 mL) as solvent to produce the organic phase. On the other hand, 1.5 g Tween 20 was mixed into the distilled water (98.5 g) under a constant stirring (300 rpm) for 15 min to prepare aqueous solution. Organic phase was then slowly added into the aqueous solution and mixed using a conventional homogenizer at 300 rpm for 15 min. finally, the organic solvent was removed using a rotary evaporator (Eyela NE-1001, Tokya Rikakikai Co. Ltd, Tokyo, Japan) which it was adjusted at temperature, pressure and rotation speed of the 50 °C, 25 KPa and 100 rpm, respectively.
Results and discussion: Therefore, in the present study Curcumin nanodispersions using a novel subcritical water method and a traditional solvent displacement method using ethylacetate and utilizing Tween 20, as emulsifier, were prepared and the physico-chemical, rheological, stability, antioxidant and antimicrobial properties of the prepared Curcumin nanodispersions were evaluated. Dynamic Light Scattering analysis indicated that the produced nanodispersions using novel technique had minimum particle size (10.1 nm) and poly disperses index (0.06) and maximum conductivity (0.401 mS/cm) and zeta potential (-15.8 mV) values as compared to those of obtained by the solvent displacement method. The obtained results also indicated that the prepared pale yellow Curcumin nanodispersions (b=2.55) using subcritical water method had minimum turbidity (0.063 NTU) and viscosity. Furthermore, more stable (during three month) produced Curcumin nanodispersion using subcritical water method shown the highest antioxidant (57.6%) comparison to Curcumin in water (3%) and antibacterial activity against to the both studied Gram-positive and Gram-negative bacteria strains.
Conclusion: Curcumin nanodispersions were prepared using two methods as subcritical water and solvent displacement. The results showed a higher stability, lower viscosity, higher antioxidant and antimicrobial properties of curcumin nanodispersion prepared by the novel method as subcritical water. In addition to, organic solvents were eliminated in subcritical water method, also the amount of used emulsifier has decreased. Therefore, this method increases the economic justification of the process of production of curcumin nanodispersions then it decreases the concern about the health and environmental aspects of product consumption. Therefore, the use of this new method for preparing curcumin nanodispersions can be easily generalized and can be applied to prepare for other food and pharmaceutical nanodispersions.
