Development of Phytochemical-Enriched Leather Insoles with Antimicrobial Efficacy for Potential Use in Diabetic Foot Ulcer Management

Abstract

associated with microbial infection and require approaches that can support infection control alongside appropriate footwear protection. This study developed phytochemical-enriched leather insoles using ethanolic extracts of Bryophyllum pinnatum, Calendula officinalis, and Althaea officinalis and evaluated their phytochemical composition, antimicrobial activity, and chemical characteristics. Phytochemical screening detected nine metabolite classes, including alkaloids, cardiac glycosides, saponins, phenolics, tannins, steroids, carbohydrates, flavonoids, and terpenoids, while anthraquinones were absent. The crude extracts exhibited inhibition zones of 18–37 mm for B. pinnatum, 25–42 mm for C. officinalis, and 21–33 mm for A. officinalis against the tested microorganisms. C. officinalis produced the largest inhibition zone against S. aureus (42 mm), with MIC and MBC values of 0.10 and 0.20 mg/mL, respectively. B. pinnatum produced 37 mm inhibition zones against both E. coli and C. albicans, with corresponding MIC/MBC values of 0.20/0.40 mg/mL. Following incorporation into leather, inhibition zones ranged from 9–28 mm, with B. pinnatum-enriched leather producing 28 mm against E. coli and C. officinalis-enriched leather producing 27 mm against both S. aureus and E. coli. GC–MS analysis identified fatty acid derivatives as major constituents, including oleic acid methyl ester (42.32%) and methyl palmitate (27.80%) in C. officinalis, oleic acid methyl ester (20.80%) in B. pinnatum, and eicosane (8.11%) in A. officinalis. FTIR analysis revealed characteristic O–H, C–H, and C–O/N–H absorption regions and spectral differences between untreated and extract-containing leather. The findings demonstrate the feasibility of producing antimicrobial phytochemical-enriched leather insoles, although further studies are required to establish their safety, durability, release characteristics, pressure-offloading performance, and clinical applicability in DFU management.