Sennosides A and B could contribute to the antimicrobial efficiency of Senna alexandrina Mill. against pathogenic bacteria in vitro and in vivo models

The search of new antimicrobial compounds is increasing in due with increasing bacterial infections. Discovering effective antibacterial medications is crucial for improving healthcare and combating bacterial infections. Senna alexandrina Mill. known as Tinnevelly senna, used as herbal extract in traditional medicine and found be rich in anthraquinone glycosides like sennoside A (SA) and sennoside B (SB), shows significant biological activity as a potential therapeutic agent. This study assessed the antibacterial effects of senna extracts on Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus bacteria, both in vitro and in vivo. HPLC analysis identified sennosides as the major compounds in senna extracts, with the highest concentration found in the leaves, followed by the pods, flowers, stems, and roots. The leaf extract showed the highest sennoside content (SA 27.21 mg/g and SB 29.1 mg/g) compared to other plant parts. FT-IR analysis confirmed the presence of sennosides through the detection of carboxylic acids and OH functional groups in S. alexandrina extracts. Extracts rich in sennosides displayed potent in vitro antibacterial activity (1000 µg/mL) by generating ROS, penetrating and becoming disruptive to bacterial functions. Similarly, in Caenorhabditis elegans model, they inhibited bacterial growth and colonization and enhanced physiological functions in the worms. Senna extract (1000 µg/mL) improved intestinal barrier's structural stability in C. elegans by outcompeting pathogenic bacteria and prolonged survival rates of those infected with P. aeruginosa and S. aureus to 56.6 % and 62.4 %, respectively, confirming the potent antibacterial efficacy of senna leaf methanolic extracts due to their high sennoside content in both in vitro and in vivo models.