Evaluation of Phenolic Content and Antibacterial Activity of Coconut (Cocos nucifera L.) Shell and Coir Powder in Different Extraction Solvents

Abstract

The issue of microbial resistance to synthetic antibiotics is receiving more serious attention. There are many
studies on the search for new sources of antibiotics or antimicrobials from natural sources. Coconut is one
of the most important crops in tropical countries with various uses. Every part of the tree and coconut fruit
is very useful with different purposes such as being processed into drinks, food, fibre, building materials,
chemicals and medical agents. Studies have showed that coconut shell and coir have phenolic content that
gives antioxidant and antimicrobial properties. However, studies like this for Malaysian coconut are very
limited. This research activity was conducted to determine the antibacterial activity of coconut shell and
coir. Coconut shells and coirs randomly obtained from MARDI Station Bagan Datuk, were dried and
ground into powder, and extracted using different solvents namely ethanol, methanol and acetone. The
antibacterial activity of shell and coir extracts was determined using disc diffusion method against five
pathogenic strains which were Bacillus cereus ATCC 10876, Cronobacter sakazakii ATCC 29544,
Enterobacter aerugenes ATCC 13048, Listeria innocua ATCC 33090 and Staphylococcus aureus ATCC
25923. The analysis results obtained showed that coconut shell and coir extracts have potential antibacterial
activity against all pathogenic strains tested with a wide range of inhibition zone sizes starting from 7.75 to
11.25 mm for the shell extract and 9.25 to 17.00 mm for the coir extract. The usage of different solvents in
extraction affected the phenolic content and antibacterial activity of coir and shell extracts. The coir showed
higher (p<0.05) total phenolic content in all solvents compared to the shell. The highest antibacterial activity
was observed in the ethanolic coir extract against S. aureus, while the lowest activity was against C.
sakazakii in the ethanolic shell extract. Methanolic and acetone extracts for both shell and coir exhibited
lower minimum inhibitory and minimum bactericidal concentrations compared to ethanolic extract. With
the results of this study, it is hoped that coconut coir and shell can be studied further and processed into
promising antimicrobial agents.