## 1 Introduction  
Digestion and nutrient intake are fundamental requirements for health, with oral health considered to be an integral part of overall health [1]. Common oral diseases include dental caries and periodontal disease, characterized by their chronic nature that continuously worsens once developed, making prevention crucial [2]. According to the 2023 Korean Dental Medical Yearbook report, among the top one-hundred common diseases in 2022, nine were dental diseases, and, among them, gingivitis and periodontal disease ranked second with 18.12 million patients, and the prevalence of periodontal disease, which is the proportion of people who require periodontal disease treatment beyond periodontal tissue disease treatment in adults, temporarily decreased from 35.5% in 2007 to 22.7% in 2012 but increased after 2013 to 30.5% in 2016-2018 [3]. Periodontal disease is a prevalent disease that affects approximately 20-50% of the world's population, with a high prevalence in adolescents, adults, and the elderly, and it causes destruction of periodontal tissues such as gingival bleeding, gingival recession, periodontal pocket formation, and alveolar bone destruction, as well as tooth loss [4]. Periodontal disease is closely linked with various systemic diseases, altering normal host responses and being reported to affect conditions such as coronary artery disease, stroke, diabetes, preterm birth, low-birth-weight infants, and respiratory diseases [5]. Periodontal disease is defined as an inflammation of the supporting tissues of the teeth, caused by specific bacteria or groups of bacteria, and characterized by the progressive destruction of periodontal ligaments and the formation and recession of periodontal pockets in the alveolar bone [6]. Since periodontal disease progresses from gingivitis, preventing gingivitis may prevent severe periodontitis [7]. In recent years, numerous studies have focused on the equilibrium between the immune system and dental plaque as a foundational mechanism for periodontal disease. _Porphylomonas gingivalis (P. gingivalis)_, a Gram-negative anaerobic bacterium in dental plaque, is involved in the onset of periodontitis, an inflammatory disease that damages the supporting tissues of teeth, eventually leading to tooth loss [8]. Among the over 500 bacterial species in the oral cavity, _P. gingivalis_, which belongs to the \"red complex\" that classifies bacteria that cause severe forms of periodontal disease, is known to be the most important causative agent of periodontal disease. _P. gingivalis_ inherently carries resistance to certain antibiotics while tending to acquire resistance to many others, making it one of the strongest and most virulent bacteria in the oral microbiome. When periodontal disease occurs, the number of _P. gingivalis_ in periodontal lesions increases, and, as the disease progresses, _P. gingivalis_ is frequently found infiltrating the sulcus epithelium [9; 10; 11; 12]. Given the complex interplay between microbial pathogens like _P. gingivalis_ and periodontal disease and the limitations of the current antimicrobial treatments, exploring natural substances such as _Lespedeza cuneata_, which may offer targeted antimicrobial activity with fewer side effects, becomes particularly relevant. In the treatment of periodontal disease, root surface scaling and root planing are commonly performed. However, there is a risk of recurrence if bacteria that cause periodontal disease, such as _P. gingivalis_, are present or regrow in the treated area. Therefore, topical or systemic administration of antimicrobial agents is sometimes added to enhance the effectiveness of mechanical periodontal therapy [13]. However, the misuse and overuse of antibiotics have led to changes in bacterial resistance genes, resulting in the emergence of super bacteria that cannot be treated with the existing antibiotics, posing a major challenge in public health [14].