Symplocos fasculata as a Source of Antimicrobial Compounds

Multidrug-resistant (MDR) bacteria are linked to numerous global medical challenges. Resistance commonly arises due to the acquisition of plasmids encoding multiple antibiotic resistance genes and/or the action of efflux pumps (e. g., NorA, TetK) with wide substrate specificities [1].

The bark of Symplocos fasculata Zoll (kindly provided by Dr Stephen Teo, Forest Department Sarawak, Malaysia) was investigated to identify compounds with antimicrobial activities, able to potentiate efflux-mediated resistance or inhibit bacterial conjugation [2]. Symplocos fasculata (Symplocaceae) is distributed in tropical and subtropical Asia, America and Malaysia

Minimum inhibitory concentrations (MICs) were determined on plant extracts, fractions and isolated compounds against Staphylococcus aureus (ATCC 259233, SA-1199B+NorA and XU212+TetK) and Escherichia coli NCTC10418. Ethyl acetate and acetone extracts had the lowest MIC values (4-8 µg/mL) against S. aureus. Two active compounds were isolated and identified using Nuclear magnetic resonance and Mass spectrometrytechniques (Figure 1).

Compounds isolated from an ethyl acetate extract of the bark from Symplocos fasculata.

The two compouds=Asiateic acid and Corsolic acid – are pentacylcic triterpenoids. They showed moderate activity against all strains of S. aureus used, the MIC value for both compounds was 16 µg/mL.

At sub-inhibitory concentrations, both compounds potentiated the activities of tetracycline and norfloxacin yielding a 2- or 4-fold reduction in MICs against S. aureus XU212+TetK and SA-1199B+NorA, respectively. Extracts and isolated compounds showed moderate activity (10-50% reduction) against the conjugal transfer of plasmids (R388, pKM101, R6K) to recipient E. coli JM109.

Overall, these findings indicate the potential of these compounds as drug leads in the management of bacterial MDR infections.

Statement on behalf of all authors. The abstract is original and not has been submitted to any other peer reviewed journal

• References

• 1 Cox G., Wright G.D. Intrinsic antibiotic resistance: Mechanisms, origins, challenges and solutions. International Journal of Medical Microbiology 2013; 303: 287-292
• 2 Rice L.B., Bonomo R.A. Genetic and biochemical mechanisms of bacterial resistance to antimicrobial agents In: Antibiotics in laboratory medicine. USA: Lippincott Williams & Wilkins; 2005

Publication History

Article published online:
13 December 2021