Abstract
Clinacanthus nutans (Burm. f.) Lindau has been extensively utilized in Thai folk medicine. However, there has been no prior exploration of its genetic diversity or its correlation with biological activity and phytochemical profiles. Herein, a total of 10 samples of C. nutans were collected from different geographic locations in different environments of Thailand, encompassing Northern, Northeastern, and Central regions. The genetic diversity study using sequence-related amplified polymorphism (SRAP) markers showed that all C. nutans samples were closely related, as indicated by UPGMA cluster analysis. When comparing the biological activities of C. nutans extracts, our findings demonstrated that those sourced from Northern Thailand exhibited the most potent activity in reducing lipopolysaccharide-inducing cell death, as accessed by cell viability assay. Furthermore, they showed remarkable antioxidant and antibacterial activities against Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. High-performance liquid chromatography (HPLC) analysis of phytochemical profiles revealed consistent chromatography peak patterns across all C. nutans extracts. However, they exhibited varying levels of phenolic contents, as judged by the Folin-Ciocalteu assay, which positively correlated with their observed activities. In conclusion, this study highlights the limited genetic variation within C. nutans population in Thailand. Furthermore, it underscores the association between the biological activity and the total phenolic contents which might be mainly impacted by environmental conditions.