## 4 Discussion  
In this study, we investigated whether antibiotic-induced changes in intestinal microflora could be readjusted using herbal medicines [23]. We reviewed 25 experimental studies related to intestinal microbes in Eastern medicine in terms of the effects of intestinal microbe-related diseases, research subjects used in experiments, methods of establishing experimental models for each disease, drugs used in the experiments, and herbal medicines [24]. Among the studies on the gut microbiome, [PERSON] et al. [25] reported the role and function of gut microbes from a pediatric point of view, with a focus on gut microbes and oriental medicine research. Experimental studies have analyzed the role of intestinal microbes in metabolic diseases, related to the intestine, such as diabetes [26; 27; 28; 29], obesity [30; 31; 32; 33], irritable bowel syndrome [34; 35], and intestinal inflammatory diseases [36; 37]. Several studies have also analyzed the effect of herbal medicines on the imbalance of intestinal microflora caused by antibiotics [16; 17; 18; 19], but they are limited to some prescriptions and individual drugs and have not been reported in Korea. Therefore, in this study, before examining the effects of herbal medicines on antibiotic-induced changes, we selected 10 herbal medicinal extracts with anti-inflammatory effects through an in vitro experiment. Since it is difficult to experimentally test diarrhea in vitro, we wanted to find a drug that can improve diarrhea from various herbal medicines with anti-inflammatory effects. Further experiments were performed to investigate their mechanism of action. In the in vivo experiment, we selected an herbal extract with an anti-inflammatory effect, and elucidated its anti-diarrheal effect on the AAD mouse model and analyzed its effect on the intestinal microflora. Three prescriptions (_Lizhong-tang, Osuyu-tang,_ and  
Figure 8: Comparison of operational taxonomic units (OTUs) 133, 147, 485, 548, and 558 between the normal, control, and _Lizhong-tang_-administered groups. After the in vivo experiment (to assess the anti-diarrheal effect of _Lizhong-tang_ on mice in an antibiotic-associated diarrhea (AAD) model induced by means of limomycin oral administration), DNA was isolated from the feces-containing intestinal tissues of each mouse. Microbiome analysis was carried out using the T-RFLP method. N1–N5: normal groups (groups not given any treatment). E1–E5: sample groups (in these groups, _Lizhong-tang_ was orally administered to the animals, post-AAD establishment), C1–C5: control groups (AAD groups). Oryeong-san_) and seven herbal medicines (_Attractylodes japonica Koidz_, _Coix lacryma-jobi_, _Angelica dahurica_, _Cinamomum cassia_, _Aucklandiae radix_, _and Machilus thunbergii_) were selected because they displayed anti-inflammatory, -digestive, and -diarrheal effects [20,21]. Antibiotics not only kill pathogenic bacteria, but also eliminate normal gut microbes, which allows harmful bacteria to multiply. In particular, _Clostridium difficile_ proliferates excessively in the intestine, damages the intestinal wall, and produces chemicals that cause enteritis, abdominal pain, and diarrhea [38,39]. Diarrhea can be alleviated by inhibiting inflammation; thus, the inhibitory effect of 10 herbal medicines on NO production was first evaluated by means of an in vitro experiment. The results showed that _M. thunbergii_ and _Lizhong-tang_ exhibited no cytotoxicity and the best activity at 100 \(\mathrm{\SIUnitSymbolMicro mL}\) concentration (Figure 2). Immune response occurs in macrophages and produces free radicals (such as NO) and cytokines (such as IL-6 and TNF-\(\alpha\)). NO is a highly reactive oxygen species that mediates vasodilation and signal transduction in the human body [40,41]. Therefore, inhibition of NO production decreases the anti-inflammatory response.