Preliminary study of phytochemical constituents and antimicrobial activity of two varieties of cashew apple grown in Nigeria

ABSTRACT

Aims@#The specific aim of this study was to investigate the phytochemical constituents and antimicrobial activities of cashew apple (Anacardium occidentale) grown in Nigeria. @*Methodology and results@#The cashew apples (red and yellow) were plucked directly from parent tree, sliced and drained in a press. Thereafter, it was dried, grounded and extracted using solvent percolation. The extracts were screened for the presence of phytochemicals and antimicrobial activities against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, Aspergillus fumigatus and Candida albicans using agar well diffusion method while the minimum inhibitory concentration was done using tube dilution technique. Alkaloids, tannins, flavonoids, steroids, glycosides, terpenoids, phenols and anthraquinones were found in the two varieties at varying degree. However, saponin was not detected in either of the variety. The antimicrobial activities of the red and yellow cashew apples were comparable at all the concentrations used. Also, these activities were concentration dependent in all the samples as increased zones of inhibition were observed as the concentrations increased. There was a significant (p ≤ 0.05) difference between the antimicrobial activities of the different extracts. The largest inhibition zones were recorded against E. coli (22.33±0.15 mm) and K. pneumoniae (24.33±0.01 mm) for red cashew apple ethanol extracts at 30mg/mL while A. fumigatus (5.33±0.00 mm) showed the least zone of inhibition against the same extract. Ethanol extracts recorded the highest inhibitory activities against all the test organisms, followed by aqueous extract while n-hexane extract had the least inhibitory activity on the organisms. The least MIC recorded was 2.5 mg/mL and it was obtained against S. aureus (Red aqueous extract, red and yellow ethanol extracts), E. coli and K. pneumoniae (red and yellow ethanol extracts) while the highest MIC was 30 mg/mL recorded against B. subtilis (yellow n-hexane extract). In all, the ethanol extracts of the cashew apples showed comparable antimicrobial activities with the controls at 30 mg/mL. @*Conclusion, significance and impact of study@#The result of this investigation confirms the presence of bioactive substances in cashew apple which may be responsible for its antimicrobial activities against selected microorganisms, consequently, supporting the folkloric use of the apple in the treatment of various diseases.