4.2. Protocols of DNA Microarray Assays for Quality Control
Schemes of new DMA-based protocols for quality control of herbal extracts are summarized in Figure 2. A simplified protocol is based on gene expression profiles of different sources of herbal extracts (A1 to A5), which are compared with that of a standard (S) by correlation coefficients (R-values) based on linear regression (Figure 2A). Deviations (such as in A3, Figure 2A) can be detected by comparing R-values. While gene sets for expression profiling can be used without selection (Figure 2A), the genes having specific cell functions could be used to improve the level of quality control (Figure 2B,C), where the gene sets (G1 to G3) can be selected arbitrarily, such as those showing stable (G1), less stable (G2) or unstable (G3) reproducibility when various lots (A1 and A2) of the herbal extracts are compared with a standard (Figure 2B). Alternatively, gene sets can be selected according to gene functions (Figure 2C), where profiling can be performed with functionally grouped genes (F1 to F3) to give a protocol of efficacy-based quality control of herbal extracts. The advantages for using these protocols are that: (1) cell function-based gene expression profiling is good for efficacy-based quality control; (2) gene sets can be selected depending on the purpose; and (3) various activities can be monitored by different gene sets.