Test Method of Red Yeast Rice Extract (monacolin-K)
Due to the lipid-lowering activity, monacolin K is used as a quality control indicator of RED YEAST RICE EXTRACT(RYR). The detection methods for monacolin K in RED YEAST RICE EXTRACT(RYR) are mainly including HPLC, HPLC-MS/MS, GC-MS, and so on.
In HPLC analysis, the separation and detection of species of several elements in a single analytical run can be accomplished. In order to make HPLC analysis simpler and more efficient, it is often coupled with UV and DAD detectors. For research into RED YEAST RICE EXTRACT(RYR) products, HPLC is a common detection method and most laboratories and manufacturers can satisfy this condition . As can be seen from the data in Table 2, the detection method of monacolins in RED YEAST RICE EXTRACT(RYR) is mostly HPLC and the detection index of RED YEAST RICE EXTRACT(RYR) is mostly monacolin K lactone. For monacolin K acid and other monacolins, acetonitrile: 0.1% trifluoroacetic acid, acetonitrile: 50 mM potassium hydrogen phosphate and methanol: 0.1% aqueous phosphoric acid were used as the mobile phase. Tsukahara  used methanol: 0.1% aqueous phosphoric acid (72:28, v/v) as the mobile phase, isocratic elution for 25 min, and linear elution with 100% methanol until 30 min, respectively. The contents of monacolin K (lactone) and citrinin were detected; Monascus sp. with a deep red color, high monacolin K production, and no citrinin was screened. Although there are many HPLC methods, the measurement conditions such as a mobile phase, separation column, and detector are different for each research purpose, resulting in different detectable components. Zhang et al. [48,49] developed a new SSF process using agar as a carrier and then optimized the grain for the highest yield of monacolin K by SSF with determination of monacolin K by HPLC, and the effects of fermentation substrate, fermentation temperature, and time on the yield of monacolin K were investigated. Liu et al.  used HPLC-UV to optimize the extraction conditions of monacolin K in functional RED YEAST RICE EXTRACT(RYR).
MISPE is a solid-phase extraction technique based on molecular imprinting which is often combined with HPLC and HPLC-MS/MS. It can significantly improve the extraction rate and purity of monacolin K in RED YEAST RICE EXTRACT(RYR), and reduce the impurity of the components to be tested. The matrix effects on the analysis results can be removed, and the subsequent analysis of monacolin K was more efficient and faster. Eren et al.  developed a sensitive molecular imprinted quartz crystal microbalance (QCM) sensor for the selective determination of monacolin K lactone in RED YEAST RICE EXTRACT(RYR).
GC-MS/MS and HPLC-MS/MS are joint detection techniques. In the actual analysis, HPLC-MS/MS is more commonly used. The tandem mass spectrometry technology has higher resolution and a faster analysis speed. It offers good detection of monacolin analogs in RED YEAST RICE EXTRACT(RYR). Donna et al.  uses the multiple reaction monitoring (MRM) mode and HPLC-MS/MS as the analytical method: simvastatin and pravastatin were used as indicators to determine the acid and lactone monacolin K content in RED YEAST RICE EXTRACT(RYR). Different detectors have different detection ranges. Svoboda et al.  connected solid-phase extraction of molecularly imprinted polymers, developing a UHPLC-MS method without a matrix effect. Mornar et al.  connected diode arrays, fluorescence, and mass spectrometry detectors to simultaneously measure monacolin K, L, M, monacolin K hydroxy acid, dehydromonacolin K, and citrinin in RED YEAST RICE EXTRACT(RYR) products.
In addition, Nigovic et al.  developed a simple and fast voltammetric method to detect the content of lactone monacolin K in RED YEAST RICE EXTRACT(RYR), and used micellar electrokinetic capillary chromatography to detect the two configurations of monacolin K in red yeast preparations .
Standards of of Red Yeast Rice Extract (monacolin-K)
Due to the lack of scientific data, RED YEAST RICE EXTRACT(RYR) has not been officially registered by the FDA . Therefore, RED YEAST RICE EXTRACT(RYR) is often used as a food or as a dietary supplement abroad. Taiwan promulgated the Hongqu Health Food Standard in 2007 (Taiwan Guardian Food No. 0960406448). Regarding the red blood safety index, the national standard for the detection of citrinin is “Determination of citrinin in RED YEAST RICE EXTRACT(RYR) products (GB T5009. 222-2008).” The European Food Safety Authority is currently reassessing the safety of a 10-mg dose of monacolin K as a food supplement .
In addition, according to a literature search, only the British Pharmacopoeia provides the functional RED YEAST RICE EXTRACT(RYR) standard abroad. Most of the standards are the laws of various provinces and cities in China. In China, monacolin K is the lipid-lowering component in functional RED YEAST RICE EXTRACT(RYR), so the pharmacopoeia, ministerial standards, and regional standards evaluate the quality of functional RED YEAST RICE EXTRACT(RYR) based on the content of monacolin K lactone.
most standards have no clear requirement for inspection of the content of monacolin K of RED YEAST RICE EXTRACT(RYR); some of the above criteria clarify the required content of monacolin K lactone in RED YEAST RICE EXTRACT(RYR) (generally not less than 0.40%), while just a few standards mentioned the content requirements of monacolin K lactone and acid. Only five standards have been specified for the determination of monacolin K in functional RED YEAST RICE EXTRACT(RYR). In the Chinese Pharmacopoeia (2015), monacolin K lactone is the only index of quality control of functional RED YEAST RICE EXTRACT(RYR) and the limit of minimum content of monacolin K lactone is 0.22%. “The standard of Chinese herbal medicine of Yunnan Province (2005)” and “Standard for Chinese Medicine Yinpian Processing of Sichuan Province (2015)” also required that monacolin K lactone should serve as the quality control of functional RED YEAST RICE EXTRACT(RYR) and the lowest content is 0.40%. However, there are two standards that indicate requirements for the acid structure. In the industrial standard “Functional red yeast rice QB/T 2847-2007,” it is regulated that the sum of monacolin K lactone and acid in functional RED YEAST RICE EXTRACT(RYR) should be not less than 0.40%. The “Standard for Chinese Medicine Yinpian Processing of Zhejiang Province (2015)” required that in functional RED YEAST RICE EXTRACT(RYR), the sum of monacolin K lactone and acid must be more than 0.30% and the peak area of acid monacolin K must not be less than 5% of the lactone monacolin K peak area. In addition to the above criteria, the other standards listed in Table 3 do not mention the quality control components and content limits of functional RED YEAST RICE EXTRACT(RYR).
Monascus can produce harmful secondary metabolites during the fermentation process, such as citrinin, which is a highly toxic, mutagenic, and carcinogenic metabolite and has been implicated as a causative agent in human hepatic and extrahepatic carcinogenesis . It causes serious health problems such as liver and kidney disease, nervous system damage, and carcinogenicity. In addition, aflatoxin may be generated, caused by bacterial contamination in the fermentation process, for a variety of reasons. Aflatoxins are potent carcinogens that affect all organ systems, particularly the liver and kidneys, and are also genotoxic and may cause birth defects in children. They can cause immunosuppression and may reduce resistance to infectious agents such as HIV and tuberculosis. The ingestion of citrinin and aflatoxins is harmful to humans and animals. Therefore, it is necessary to carry out a safety check on the RED YEAST RICE EXTRACT(RYR). There are three standards that require security checks. For the determination of citrinin, “Standard for Chinese Medicine Yinpian Processing of Sichuan Province (2015)” and “Functional red yeast rice QB/T 2847-2007” use the HPLC method; detection is by a fluorescence detector with excitation wavelength λex = 331 nm, emission wavelength λem = 500 nm. The two standards decree that the content of citrinin should not exceed 50 μg/kg. The ‘’Food additives Red yeast rice GB1886.19-2015′’ and “Standard for Chinese Medicine Yinpian Processing of Sichuan Province (2015)” utilize two methods to detect the content of aflatoxins. One is HPLC with a fluorescence detector (λex = 360 or 365 nm, λem = 450 nm). The other is HPLC-MS with ESI, in positive ion mode, with triple quadrupole tandem mass spectrometry as the detector. The two standards require that the content of aflatoxin B1 not exceed 5 μg/kg.
Molecules. 2019 May; 24(10): 1944.
Published online 2019 May 20. doi: 10.3390/molecules24101944
Quality and Authenticity Control of Functional Red Yeast Rice—A Review
Jiawen Song,† Jia Luo,† Zubing Ma, Qiang Sun, Chunjie Wu,* and Xiaofang Li*