Antimicrobial activity of cashew nut testa extract (Anacardium occidentale L.)

The cashew nut (Anacardium occidentale L.) testa, commonly considered as a by-product of cashew processing, is rich in polyphenols. This research investigated the antimicrobial effects of the cashew nut testa extracts prepared using a mixture of 0.22% cellulase and pectinase (1:1, v/v) with a ratio of raw material to solvent of 1:55 (v/v), an extraction temperature of 49°C and pH 4.0 for 60 min. Phytochemical screening revealed the presence of various phenolic compounds in the testa extract, including saponins, coumarins, triterpenoids, tannins, flavonoids, and alkaloids. The extract’s antimicrobial efficacy was assessed against 4 bacterial strains associated with food poisoning: Bacillus cereus, Staphylococcus aureus, Shigella spp., and Salmonella typhimurium. Remarkably, the extract demonstrated inhibitory action against Staphylococcus aureus, producing an inhibition zone diameter of 1.00 mm at a concentration of 25 mg/mL and the largest diameter of 12.93 mm at 800 mg/mL. The Minimum Inhibitory Concentration (MIC) values were determined as follows: 200 mg/mL for Salmonella typhimurium, 100 mg/mL for both B. cereus and Shigella spp., and 25 mg/mL for Staphylococcus aureus.