Fast Inspection of Quality of Indigo Naturalis by Multiple Light Scattering

Summary

Here, we present a quality evaluation method based on a multiple light scattering technique to evaluate the quality of Indigo Naturalis.

Abstract

Quality control of Chinese herbal medicine is a crucial component of Chinese herbal medicine research and development. Faced with the challenges of modernization and internationalization of Chinese herbal medicine, it is urgent to establish thorough and effective procedures for quality identification of Chinese herbal medicine, and there is an urgent need for new analytical and testing techniques that are efficient, accurate, and environmentally friendly.

Multiple light scattering is a cutting-edge and analytical method that can accurately and rapidly assess the quality of Chinese herbal medicine without altering the nature or state of the sample or using organic reagents. Indigo Naturalis is considered a good remedy for pediatric hyperthermia, psoriasis, leukemia, and ulcerative colitis. In this study, the process of addition of Indigo Naturalis powder in water was recorded precisely using a multiple light scattering instrument.

The qualitative and quantitative measurements of the instrument can be used to accurately capture the overall trajectory and sinking behavior of Indigo Naturalis powder into water and to establish a rapid evaluation method for the quality of Indigo Naturalis with the transmission and backscattering spectrograms of the sample as qualitative indicators and stability index as a quantitative indicator. The analytical technique based on multiple light scattering provides a fast, accurate, green, and environmentally friendly method for the quality evaluation of Indigo Naturalis and supports the development and transformation of high-quality Indigo Naturalis.

Introduction

In traditional Chinese medicine, during the course of disease treatment, the clinical effectiveness of medications and the safety of the course of treatment are directly impacted by the quality of Chinese herbal medicine. Utilizing cutting-edge identification technology, one can assess the efficacy of Chinese herbal medicine and guarantee user safety. The Chinese herbal medicine water test method refers to immersing the herbs in water or solvent, then quickly and precisely determining the medicine's authenticity by observing the changes in color, size, and shape¹.

It was originally a good choice for the identification of Chinese medicine. However, the disadvantage of the traditional water test method is that the accuracy and sensitivity of distinguishing the authenticity of Chinese medicine are low because of the subjectivity of observation by the naked eye². One of the key medicinal materials used in the water test method is Indigo Naturalis, considered an effective remedy for pediatric hyperthermia, psoriasis, leukemia, and ulcerative colitis³. The genuine Indigo Naturalis floats on the surface of water, and the water does not turn dark blue after shaking. However, the fake Indigo Naturalis has particles that sink, and the water will turn dark blue after shaking⁴. Its principle is due to hydrophobic and easily floatable indigo, indirubin, and other organic components of high-quality Indigo Naturalis. On the contrary, due to low organic matter, a large amount of lime, and heavy texture, some particles doped with fake Indigo Naturalis will sink quickly⁵. However, this method is only a simple qualitative identification, and it limits the rapid identification of the authenticity of Chinese herbal medicine and fails to reveal the changes of Indigo Naturalis in water.

Multiple light scattering technology is a technology that can measure multi-angle light signal scanning based on a laser passing through the sample. The incident light will be scattered when it penetrates the sample or encounters particles. If the scattered light penetrates through the sample, a transmission light signal is formed; If the sample concentration is high, the light will be reflected by the particles, forming a backscattering light signal. The changes in light intensity reflect the changes in particle concentration and particle size in liquid preparation⁶. The multiple light scattering instruments can quickly and accurately analyze phenomena such as emulsification, flocculation, precipitation, and rupture of suspension, emulsion, and foam liquid by multiple light scattering technology, as well as quantitatively analyze characteristics such as the rate of occurrence of the above phenomena.

Multiple light scattering technology has demonstrated significant benefits in particle stability monitoring⁷, red wine clarification⁸, and milk fermentation quality control⁹. Using this technology, the traditional water test method of Indigo Naturalis may be intuitive, quantitative, and scientific. Therefore, based on the principle of multiple light scattering technology, this study established a rapid evaluation method for the quality of Indigo Naturalis, taking the Turbiscan stability index (TSI) of the sample as the index of quality control (Figure 1).

Protocol

1. Preparation of test sample Set up four different batches of Indigo Naturalis herbal powder for the test. Pass each sample through the seventh sieve and ninth sieve in turn and collect the sample between the seventh and ninth sieve5. NOTE: The average aperture size of the seventh sieve is 125 µm ± 5.8 µm. The average aperture size of the ninth sieve is 75 µm ± 4.1 µm. Accurately weigh 0.2 g of the sample (Indigo Naturali…

Representative Results

Figure 2A-D correspond to S1, S2, S3, and S4 of Indigo Naturalis, respectively. A is of high-quality Indigo Naturalis, showing the same light transmittance at any height within 0-10 min, which is very stable. B is the common Indigo Naturalis, and its light transmittance fluctuates slightly with the change of time and is generally stable. C and D are fake and inferior products. There may be two conditions in the transmission spectrograms of fake Indigo Natura…

Discussion

According to traditional Chinese medicine, Indigo Naturalis has the power to clear heat and detoxification, cool blood, eliminate spots, purge fire, and arrest convulsion. Based on randomized double-blind controlled clinical trials^11,12,13, Indigo Naturalis is effective in the treatment of psoriasis, ulcerative colitis, and acute promyelocytic leukemia in addition to its traditional treatment of cough and phlegm, hemorrhagic sym…

Materials

Analytical balance (1/10,000)	Sartorious, Germany	BSA224S	www.sartorius.com.cn
Funnel	Chengdu Kelong Chemical Co. LTD	Diameter 5 cm	www.cdkelongchem.com
Indigo Naturalis S1	Xianyou, Fujian	20210501
Indigo Naturalis S2	Yaan, Sichuan	20201102
Indigo Naturalis S3	Xianyou, Fujian	20161012
Indigo Naturalis S4	Xianyou, Fujian	20180305
Iron ring	Chengdu Kelong Chemical Co. LTD	/	www.cdkelongchem.com
Iron stand	Chengdu Kelong Chemical Co. LTD	/	www.cdkelongchem.com
Mili-Q ultra-pure water meter	Milipore, USA	Mili-Q	www.merckmillipore.com
Ninth sieve	Chengdu Kelong Chemical Co. LTD	Average aperture size 75 µm	www.cdkelongchem.com
Sample bottle	French Formulaction Company	Bottom diameter 2.6 cm, height 6 cm	www.formulaction.com
Seventh sieve	Chengdu Kelong Chemical Co. LTD	Average aperture size 125 µm	www.cdkelongchem.com
Turbisoft Lab multiple light scattering instrument	French Formulaction Company	Turbisoft Lab 2.3.1.125 Fanalyser 1.3.5	www.formulaction.com
Weighing paper	Chengdu Kelong Chemical Co. LTD	/	www.cdkelongchem.com