Evaluation of Cocoa Bean Shell Antimicrobial Activity: A Tentative Assay Using a Metabolomic Approach for Active Compound Identification

Abstract

Cocoa bean shell is one of the main by-products of chocolate manufacturing and possesses several compounds with biofunctionalities. It can function as an antibacterial agent, and its action is mostly reported against Streptococcus mutans. However, only a few studies have investigated the cocoa bean shell compounds responsible for this activity. This study aimed to evaluate several extracts of cocoa bean shells from different geographical origins and cocoa varieties and estimate their antimicrobial properties against different fungal and bacterial strains by determining their minimal inhibitory concentration. The results demonstrated antimicrobial activity of cocoa bean shell against one of the tested strains, S. mutans. Cocoa bean shell extracts were further analysed via LC-HRMS for untargeted metabolomic analysis. LC-HRMS data were analysed (preprocessing and statistical analyses) using the Workflow4Metabolomics platform. The latter enabled us to identify possible compounds responsible for the detected antimicrobial activity by comparing the more and less active extracts. Active extracts were not the most abundant in polyphenols but contained higher concentrations of two metabolites. After tentative annotation of these metabolites, one of them was identified and confirmed to be 7-methylxanthine. When tested alone, 7-methylxanthine did not display antibacterial activity. However, a possible cocktail effect due to the synergistic activity of this molecule along with other compounds in the cocoa bean shell extracts cannot be neglected. In conclusion, cocoa bean shell could be a functional ingredient with benefits for human health as it exhibited antibacterial activity against S. mutans. However, the antimicrobial mechanisms still need to be confirmed.

Optimizing vacuum drying process of polyphenols, flavanols and DPPH radical scavenging assay in pod husk and bean shell cocoa

“…These compounds present in cocoa by-products have shown various biological effects 2 . Among the bio-functionalities of the cocoa shell, it is postulated as an antibacterial agent, inhibiting the activity against Streptococcus mutans 11 . Rossin et al 12 have reported a preventive effect against damage associated with intestinal integrity from oxidative/inflammatory reactions.…”

Cocoa Bean Shell: A By-Product with High Potential for Nutritional and Biotechnological Applications

“…Tamrin et al, 2020 [89] reported similar antibacterial activities related to CBS extracts (aqueous, ethanolic, methanolic and acetone) against E. coli, B. cereus and S. aureus (approximately 7 mm inhibition zone). Moreover, Rojo-Poveda et al, 2021 [90] tested the antimicrobial capacity of CBS extracts at different concentrations (0.004 to 0.5 mg of dry extract per ml) in eight bacterial and fungal strains. These authors found that inhibition was only detected at the maximum concentration (0.5 mg/mL) against E. coli, Pseudomonas aeruginosa, Saccharomyces cerevisiae, Candida albicans, methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA).…”

Biological Properties and Antimicrobial Potential of Cocoa and Its Effects on Systemic and Oral Health

“…In both experiments, reductions in plaque index and caries scores were obtained by using cocoa bean husk extract at concentrations higher than 0.5 mg/mL and 1.0 mg/mL, respectively [ 44 ]. In addition, a recent study that investigated the antimicrobial effect of several extracts obtained from a variety of cocoa beans from different origins reported that almost all of the tested extracts showed activity against S. mutans [ 50 ].…”