Evaluation of the Antioxidant, Antibacterial, and In Vivo Wound- Healing Activities of 9-Isopropyl-3,6-Dimethoxy-9-Methyl-9H- Fluorene, a Bioactive Compound Isolated from the Marine Bacterium Shewanella algae

Abstract

Background: Marine bacteria are valuable sources of structurally diverse secondary metabolites with potential pharmaceutical applications. The present study evaluated the antioxidant, antibacterial, antifungal, and wound-healing properties of 9-isopropyl-3,6-dimethoxy-9-methyl-9H-fluorene isolated from the marine bacterium Shewanella algae. Methods: Antioxidant activity was assessed using the DPPH radical-scavenging assay at concentrations ranging from 1.56 to 100 µg/mL, with ascorbic acid as the reference standard. Antibacterial activity was evaluated against Staphylococcus aureus and Escherichia coli by agar well diffusion, followed by determination of the minimum inhibitory concentration (MIC). Morphological changes in MIC-treated S. aureus were examined using high-resolution transmission electron microscopy (HR-TEM). Antifungal activity was assessed against Candida albicans. Wound-healing activity was investigated in Wistar albino rats treated with 50 and 100 mg of the compound, using simple ointment and silver sulfadiazine as controls. Results: The compound demonstrated concentration-dependent DPPH scavenging, increasing from 10.63% at 1.56 µg/mL to 73.13% at 100 µg/mL. A 16 mm inhibition zone was observed against S. aureus, with an MIC of 100 µg/mL, whereas no inhibition was detected against E. coli or C. albicans. HR-TEM revealed substantial morphological and structural alterations in treated S. aureus cells. In the wound model, the 100 mg treatment produced 93.86 ± 2.45% wound closure on day 21, significantly exceeding the simple ointment group (88.02 ± 3.12%) and approaching silver sulfadiazine treatment (99.21 ± 0.42%). Histopathological findings supported improved tissue regeneration. Conclusion: 9-Isopropyl-3,6-dimethoxy-9-methyl-9H-fluorene exhibited promising antioxidant, selective antibacterial, and wound-healing activities, particularly at the 100 mg dose. These findings support further investigation of this marine-derived compound as a potential bioactive agent for wound management.