Physicochemical Properties and Antimicrobial Activities of Cashew By-products in Côte d’Ivoire

Antimicrobial resistance has increased interest in plant-derived materials that may contain biologically active compounds. This study evaluated the physicochemical properties and antimicrobial activity of cashew nut shell liquid (CNSL) obtained from cashew shells collected in northern Côte d’Ivoire. CNSL was obtained using thermal extraction, ethanolic maceration and aqueous decoction. Extraction yield, pH, titratable acidity, dry matter and total polyphenol content were assessed. Antimicrobial activity was evaluated against Staphylococcus aureus and Candida albicans using agar diffusion assays, whilst minimum inhibitory concentrations were determined by broth microdilution. Thermal extraction produced the highest extraction yield (28.4%), followed by ethanolic maceration (24.1%) and aqueous decoction (19.6%). The extracts were slightly acidic, with pH values ranging from 5.0 to 5.4. Ethanolic extraction produced the highest total polyphenol value (291.66 ± 2.88), compared with aqueous (209.30 ± 8.32) and thermal (178.33 ± 2.88) extraction. The ethanolic extract also produced the greatest inhibition zones against both tested microorganisms. At 100 mg/mL, inhibition zones reached 24 ± 0.7 mm against S. aureus and 21 ± 0.6 mm against C. albicans. Its minimum inhibitory concentration against S. aureus was 12.5 mg/mL. These findings indicate that extraction method influences the physicochemical characteristics and in vitro antimicrobial activity of CNSL, with ethanolic maceration providing the most active extract among the methods evaluated.