Study on the conversion law and antioxidant activity changes of 6-gingerol during the processing of turmeric
Dried ginger is the dried rhizome of Zingiber officinale Rose, a plant in the ginger family. It has a pungent taste, a warm nature, and has the effects of warming the middle and dispelling cold, returning yang and promoting blood circulation, and warming the lungs and promoting diuresis. Pao Jiang is a commonly used medicinal product in clinical practice. After being processed by sand steaming, it can alleviate the spiciness of dried ginger and increase its warming and hemostatic effects. Research has shown that gingerol compounds are the main spicy and active ingredients in ginger, including dozens of compounds such as 6-gingerol, 8-gingerol, 10 gingerol, and 12 gingerol, which have various pharmacological activities such as antioxidant, anti-inflammatory, antipyretic, neuroprotective, and anti-tumor. The content of 6-gingerol in ginger is the highest, and it is also an indicator component for determining the content of ginger, dried ginger, and turmeric in the 2020 edition of the Chinese Pharmacopoeia. Antioxidant activity is one of the main pharmacological activities of 6-gingerol. The molecular structure of 6-gingerol contains β – hydroxyketone and phenolic hydroxyl groups, making it effective in clearing hydroxyl radicals, superoxide radicals, and lipid peroxides. It can also effectively protect against DNA damage caused by hydrogen peroxide and is a natural antioxidant with excellent properties. The qualitative and quantitative analysis of the chemical composition of dried ginger before and after processing by the research group in the early stage showed that the content of gingerol components in dried ginger decreased significantly after processing into turmeric, with the content of 6-gingerol decreasing between 15% and 42%; The content of components such as 6-gingerol, 8-gingerol, and 10 gingerol significantly increased, and new components such as gingerone were produced during the processing. However, the rules and effects of processing on the transformation of turmeric phenolic compounds and their activity are not fully understood, and further research is warranted.
After processing dried ginger into turmeric, the medicinal effects undergo corresponding changes due to the changes in the “quality” and “quantity” of the gingerol components it contains. In order to investigate the transformation law of gingerol components during the processing of turmeric and the effect of component transformation on its activity, this experiment measured the changes in the content of 6-gingerol, 6-gingerol, and gingerone in turmeric samples with different sand blanching processes. Combined with the simulated processing method of 6-gingerol monomer, the variation law of 6-gingerol and its transformation products 6-gingerol and gingerone with processing time and processing temperature was explored; At the same time, using in vitro antioxidant methods, the correlation between component transformation and antioxidant activity was preliminarily verified, in order to provide a basis for revealing the processing mechanism of turmeric.

 

In the early stage of the research group, the processing temperature was 180-200 ℃ and the processing time was 6, 7, and 8 minutes. Based on this, this experiment selected the processing technology of ginger for 6, 7, and 8 minutes at 170 ± 2 ℃, 190 ± 2 ℃, and 210 ± 2 ℃, respectively, to prepare ginger samples with different sand blanching processes. Pre experiments were conducted to investigate the temperature and time of simulated processing of 6-gingerol. It was found that when the oil bath temperature was below 170 ℃, no gingerone was detected in the simulated processing product of 6-gingerol. When the oil bath temperature was 250 ℃ and the oil bath time was 15 minutes, carbonization appeared in the simulated processing product of 6-gingerol. Therefore, we selected oil bath temperatures of 170 ℃, 190 ℃, 210 ℃, and 230 ℃, and times of 4, 6, 8, 10, and 12 minutes as the conditions for simulated processing of 6-gingerol.
Through the analysis of the content and antioxidant activity of 6-gingerol in ginger samples using different sand blanching processes, it can be seen that when the sand blanching temperature is within (190 ± 2) ℃ and the time is within 7 minutes, the appearance of the ginger samples meets the quality requirements of the processed products, and the content of 6-gingerol also meets the quality control requirements of ginger, with little effect on antioxidant activity. Therefore, when determining the processing technology of turmeric, the sand blanching temperature should be chosen at around 190 ℃ and the sand blanching time should be 7 minutes, which is similar to the previously selected processing technology of turmeric by the research group, which is 195 ℃ and 7 minutes. The results of simulated processing of 6-gingerol combined with in vitro antioxidant experiments showed a significant positive correlation between its content and antioxidant activity. That is, with the prolongation of processing time and the increase of processing temperature, 6-gingerol was partially converted into 6-gingerol and gingerone, which gradually reduced the antioxidant activity of turmeric. This indicates that processing will weaken the antioxidant activity of turmeric samples to a certain extent.
This article conducted a preliminary study on the quantitative changes and antioxidant activity of 6-gingerol and its transformed products 6-gingerol and gingerone in the simulated processing products of 6-gingerol. As 6-gingerol contains phenolic hydroxyl groups and β – hydroxyketones, it has a clear antioxidant activity. Therefore, the in vitro antioxidant index was selected to preliminarily reflect its activity changes. Due to the processing of dried ginger into turmeric, its warming and hemostatic effects are mainly enhanced. In the future, we will select more targeted indicators related to the efficacy of turmeric, such as coagulation and hemostasis, and comprehensively evaluate the impact of gingerol conversion on the efficacy of turmeric through cell experiments and overall animal experiments during the processing.