4.1. DNA Microarray Assays for Quality Control of Traditional Chinese Medicine
DMA has been used to detect and evaluate various activities of pure chemicals and mixtures of chemicals [13,188]. When DMA was applied for the study of TCM, gene sets specific to herbs were selected. For example, a set of 55 genes were screened by DMA in order to understand the effect of Qingfei Xiaoyan Wan formula on asthma by the regulation of gene/protein networks [80]. A set of 92 genes was found to be differentially regulated by Toki-shakuyaku-san, a formula effective for circulation problems [89]. A set of nine marker genes was initially screened by DMA and subsequently confirmed by RT-PCR to assess the batch-to-batch consistency of the biological effects of ISF-1, a formula used for the management of post-stroke disorders [6]. 
Once gene sets have been selected, they can be used for screening and/or quality control of the herbs. For example, DMA was used to screen TCM species with inhibitory effects on Cytochrome P450 (CYP450) intended to treat HIV infection [189]. High-throughput DMA were applied to screen for anti-mitotic effects (independent of toxicity) on the proliferation of MDA-MB-231 cells from 897 aqueous extracts of commonly used natural products, and less than 1.34% of the extracts tested showed growth inhibitory properties at a concentration of less than 0.0183 mg/mL [27]. The DMA based on the yeast transcriptome was used for quality control of the extracts of Equisetum arvense [30].
Specific activity was examined to evaluate the quality of materials in food and supplements. For example, estrogenic activity was examined by DMA using a customized DNA microarray containing 172 estrogen-responsive genes in order to evaluate food materials, such as phytoestrogens [127] and ginsenosides [148], and for the extracts of plants and mushrooms, such as soybeans [127], Glycyrrhiza glabra [150], and Agaricus blazei [138]. The estrogen-responsive genes were further classified into six functional groups (enzymes, signaling, proliferation, transcription, transport, and others) and some showed preferences for specific groups [183].