Phytochemical profiling and biofilm inhibitory potential of Sphaerostephanos unitus (L.) Holttum

Purpose The aim of this study was to investigate the phytochemical composition and antioxidant, cytotoxic, antimicrobial, and antibiofilm activities of Sphaerostephanos unitus (L.) Holttum, a fern traditionally used in Northeast India. Methods Sequential solvent extraction was performed using methanol, ethanol, acetone, and ethyl acetate as solvents. Qualitative and quantitative phytochemical screening was followed by antioxidant assays, such as DPPH and nitric oxide scavenging, and cytotoxicity testing using brine shrimp lethality test. Antimicrobial and antibiofilm activities were studied against multidrug-resistant clinical isolates including Pseudomonas aeruginosa , Klebsiella pneumoniae , and Candida spp. The fatty acid-rich fraction was further analyzed using GC-MS. Results Ethanol extract had the highest phenolic and flavonoid content, exhibiting the most potent antioxidant activity with an IC₅₀ of 35.74 µg/mL. In addition, the fatty acid fraction exhibited the lowest minimum inhibitory concentration at 0.25 mg/mL and the strongest antibiofilm inhibition activity (94.8%). GC-MS analysis identified major fatty acids such as dodecanoic, tetradecanoic, and oleic acids, which are well known for their antimicrobial and anti-quorum sensing activities. Conclusion S. unitus demonstrates considerable antioxidant and antimicrobial potential, supporting its ethnomedicinal relevance and emphasizing its importance for future drug discovery.