Effect drying process of white turmeric herb (Curcuma mangga) on antioxidant activity

Curcuma mangga is one of the herbal rhizome plants. It has good benefits as Curcuma longa, and it has advantage of having aroma like a mango. This study aims to determine the effect of drying process of Curcuma mangga herb toward antioxidant activity. There are eight drying variations (oven drying at 50, 60, 70, 80 and 90°C, sun drying, room temperature, and freeze drying). Extraction of Curcuma mangga powder was carried out by maceration using aquadest, this study didn’t used organic solvents because the solvent for herbal drink is water (aquadest). Curcuma mangga extract was analysed for its stability in room temperature, FTIR analysis, and antioxidant activity analysis using 0.02% DPPH. The entire process in this research was replicated three times and average results were obtained. Based on the results, it can be seen that Curcuma mangga extracts are not stable at room temperature (maximum at 6 hours). Based on spectra FTIR results, Curcuma mangga extracts have polar functional group because the solvent used for extraction is aquadest which is polar solvent. The best antioxidant activity results (%AA) of Curcuma mangga is vacuum freeze drying process with an IC50 value 106.95 ppm, it was classified as a moderate antioxidant.


Introduction
Turmeric is a plant that widely used as herbal medicine / herbal functional drink.Turmeric belongs to the Zingiberacheae family [1].The object of this research is white turmeric.White turmeric was chosen because it has beautiful color (yellowishwhite color).Beside of that, white turmeric is still not widely used as yellow turmeric.White turmeric consists of two species, namely Curcuma amada Roxb.and Curcuma zedoaria.Both of them have the similar rhizome shapes and colors, but different in scent.Curcuma zedoaria has a distinctive turmeric scent and slightly bitter.Meanwhile Curcuma amada Roxb.has a fresh aroma like a mango fruit and a bit astringent [2].Therefore, in this study Curcuma amada Roxb.was chosen as an object for this research.Many people call Curcuma amada Roxb.as Curcuma mangga or mango ginger.This is because it has a fresh scent like a mango fruit [3].
Curcuma mangga has several active compounds which are volatile, terpenoid, phenolic and curcuminoid compounds.Because these active compounds, Curcuma mangga can be used as an antioxidant, anti-inflammatory, antifungal, anticancer, antiallergic, antibacterial, analgesic, and cytotoxicity [2].Volatile and terpenoid compounds have non-polar properties, so they can dissolve in non-polar organic solvents such as chloroform and n-hexane.Meanwhile phenolic and curcuminoid compounds have polar properties, so they can dissolve in polar solvents such as water and ethanol [4].Previous studies in the field of analysing Curcuma herbal extracts for antioxidant, anti-inflammatory, antibacterial, anti-cancer, and so on, using organic solvents (ethanol, n-hexane, diethyl ether, and chloroform).Because the application of the results of this research is for herbal drinks, the novelty of this research is using drinkable solvent (aqueous solvent / aquadest).
The antioxidant analysis of Curcuma mangga herb using DPPH method.DPPH (1,1-diphenyl-2picrylhydrazyl) is a type of free radical with a dark purple colour [5].Antioxidants from Curcuma mangga extracts will donate their hydrogen atoms to DPPH radicals (change to DPPH-H), so DPPH loses its reactivity which causes the purple colour being degraded [6].Analysis antioxidant of Curcuma mangga was carried out using variations of drying method.It is suspected that differences temperature in drying methods can affected toward antioxidant activity of Curcuma mangga.Base on previous research, red chilies were dried at different temperature (50, 60, 70, 80 and 90 ℃) have the difference antioxidant activity.The higher drying temperature, decrease the antioxidant activity of red chili extracts, because the active compounds were degraded [7].

Preparation of curcuma mangga powders
Eight kg of Curcuma mangga rhizomes were washed and sliced to small pieces, and divided into eight parts.Each part is dried using a different drying method, they are sun drying (constant in five days), room temperature drying (constant in six days), vacuum freeze drying (constant in three days), oven drying at 50℃ (constant in six hours), 60℃ (constant in five hours), 70℃ (constant in five hours), 80℃ (constant in four hours), and 90°C (constant in four hours).After the pieces of Curcuma mangga have a constant weight, they were grinded and sieved to obtained uniform powder grains.

Analysis stability of curcuma mangga aqueous extracts
Curuma mangga powders in every drying method were extracted using aqueous solvent until six hours in room temperature with maceration process.After six hours, the mixture was filtered, and the filtrate was collected in a glass vial.The filtrate was analysed for its stability in over time (6th, 7th, 8th, 9th, 12th, 15th, 18th, 30th, 54th and 78th hours).Each filtrate in every time variation was analysed for absorbance using Genesys 10S UV-Vis at a wavelength of 218 nm [8].

Analysis FTIR to determine of polar functional groups
Curcuma mangga powders was extracted using aquadest solvent, therefore the active compounds were extracted also polar compounds.Curcuma mangga extracts each drying variation was analysed using Shimadzu-FTIR-8400S to determine polar functional groups.

Analysis antioxidant activity of curcuma mangga aqueous extract at various temperatures
Curuma mangga extracts in every drying method was analysed antioxidant activity with 0,002% (20 ppm) DPPH in 98% ethanol, using Genesys 10S UV-Vis at 517 nm [4].The results of the antioxidant activity analysis were used to calculate the IC 50 value using a linear regression equation.The entire process in this research was replicated three times and average results were obtained.

Preparation of curcuma mangga powders
Bellow in Figure 1 is a picture of the leaves, flowers and rhizome of Curcuma mangga.Curcuma mangga has yellowish white rhizomes, green leaves and pink flower petals.Then in Figure 2 is a picture of Curcuma mangga dried powders in variation drying method.Curcuma mangga powders were dried using an oven at temperatures of 50, 60, 70, 80, 90°C and sun drying have the same yellow color.Curcuma mangga powders were dried using a vacuum freeze dryer has a paler yellow colour.
And Curcuma mangga powders in room temperature drying method has a darker yellow colour.

Analysis stability of curcuma mangga aqueous extracts
Analysis stabilization of Curcuma mangga extracts is aims to determine stability of extracts to store in room temperature during varoius of time.Three samples were taken from eight drying variations to analysis their stability in over time.The results of the stabilization of the Curcuma mangga aqueous extracts can be seen in Figure 3. Based on this graph, Curcuma mangga extracts decrease in absorbance in over time.Curcuma mangga aqueous extracts can be safed at room temperature for a maximum time is 6 hours.From the 7th hour onwards, the liquid extract must be stored in a refrigerator or stored as powders by removing the solvent using vacuum freeze dryer instrument.Extracts as powders form, will last longer to safe in room temperature than aqueous extracts.
Removing solvent using vacuum freeze dryer, keep the quality of Curcuma mangga herb, because solvent removal is carried out under vacuum conditions and a low temperature at -57℃.This method is better if compared with removing solvent using an evaporator or other instruments with high temperatures, but it has a expensive cost.Based on previous research curcumin content in Curcuma zanthorrhiza has been analysed by spectrophotometer UV-Vis in 0, 1, 2, 3, 4, 5, 6 and 7 days in room temperature.The result is, curcumin content decreases day by day.Even from the first day there was a reduction in curcumin of 14.94 ppm.There has been no analysis of the stability of liquid extracts in hours, therefore this research carried out analysis of liquid extracts at hourly intervals [10].

Analysis FTIR to determine of polar functional groups
Analysis FTIR of Curcuma mangga extracts is determined of polar functional groups.Because the extraction process uses distilled water, so active compounds were extracted are polar.The results of FTIR analysis of Curcuma mangga extracts can be seen in  The results of FTIR analysis in eight variation drying method have the same functional groups, except for drying using oven at 90°C.There are missing functional groups, namely free O-H and C=C bonds.This missing is thought to be caused by degradation of active compounds due to heating at the high temperature.According to the previous research, the use of high temperatures in turmeric extraction process using aqueous solvent for a longer time causes degradation of curcuminoids compounds and reduce antioxidant activity [11].In this research we don't determine active compounds in Curcuma mangga extracts, so we use study literature to knowing the active compounds.Based on the literature, we knows that Curcuma mangga extracts in polar solvents contains several active compounds, including curcumin, bismethoxy-curcumin, bisdhemethoxycurcumin, cinamic acid, P-coumaric acid, syringic acid, gallic acid, protocatechuic acid, gentistic acid, ferulic acid, and caffeic acid [3].FTIR analysis cannot determine the structure of active compounds, but it can be support that the active compounds have some polar functional groups according to the structure have been found in a previous research.The structure of polar active compounds in Curcuma mangga extracts can be seen in Figure 5.

Analysis antioxidant activity of curcuma mangga aqueous extract at various temperatures
Based on this research, drying variation method are affected on antioxidant activity.Each drying variation method has a different antioxidant activity.The sequence of antioxidant activity Curcuma mangga extracts from highest to lowest is freeze drying > room temperature drying > oven drying at 50℃ > 60℃ > 70℃ > 80℃ > sun drying > oven drying at 90°C.Higher temperature in drying methods on antioxidant activity are decreased active compounds of Curcuma mangga extracts.In previous research, variation times and boiled temperatures of Turmeric-Tamarind herb are affected on antioxidant activity [12].According to Lodh at.al. curcumin level content was increase at shorter heating duration, but it's decrease when heated for a longer period of time [13].
In this research, best variation drying method is vacuum freeze drying, with the highest antioxidant activity, because it is carried out under vacuum conditions and low temperatures up to -57°C.So, the active compounds in Curcuma mangga extracts are safed and high quality.The second result of antioxidant activity test is room temperature drying.The active compounds in Curcuma mangga extracts is still safed at room temperature, but being in open air for a long time causes the contaminated with bacteria and fungi, therefore this antioxidant activity is lower than vacuum freeze drying method.Drying method using oven in Figure 6, we can see that higher the temperature drying causes lower antioxidant activity.Increasing temperatures will causes the active content of Curcuma mangga are degraded [14].Meanwhile, drying method by the sun is not recommended, because the active compounds in Curcuma mangga can be degraded by UV light.Based on previous research, UV light can degrade organic compounds.Sujatha at.al. says heterogeneous photocatalysis (UV lightirradiated) can degrade organic compounds [15].The antioxidant activity graph of Curcuma mangga extracts in various drying method can be seen in Figure 6.
The best results for drying method of Curcuma mangga herb is vacuum freeze drying.We can using linear regression equation form Figure 6, to determine IC 50 value.And IC 50 value of Curcuma mangga exctracts using vacuum freeze drying is 106.95 ppm.The IC 50 value of 100-150 ppm was classified as a moderate antioxidant [16].The drying technology has positive and negative impacts.With drying technology, Curuma mangga powders can be stored for longer time at room temperature.However, the best drying results is using vacuum freeze drying, it require relatively high costs.Therefore, the functional herbal drink of Curcuma mangga herb can also consumed in fresh extracts but it must be drunk immediately before 6 hours at room temperature.

Conclusion
Drying method of Curcuma mangga has impact toward antioxidant activity test.The higher temperature has lower antioxidant activity.The best results for drying method of Curcuma mangga herb is vacuum freeze drying (IC 50 value is 106.95 ppm) it was classified as a moderate antioxidant.
Oven drying at 50'C

Figure 4 .
Figure 4. FTIR Spectra of Curcuma mangga extracts in eight drying variations

Figure 6 .
Figure 6.Antioxidant activity graph of Curcuma mangga extracts in drying variations