Chemical profiling and evaluation of in vitro antibacterial and antibiotic synergistic activities of Cleistanthus bracteosus Jabl. from Malaysian rainforests

Dassanayake, MK, Khoo, T-J, Chong, CH, Wiart, C, Elfar, OA, Symonds, R ORCID: 0000-0001-6838-2904 and Ansari, MT (2026) Chemical profiling and evaluation of in vitro antibacterial and antibiotic synergistic activities of Cleistanthus bracteosus Jabl. from Malaysian rainforests. BMC complementary medicine and therapies. ISSN 2662-7671

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Abstract

Background
Plants are rich and valuable sources of phytochemical constituents that can contribute to a variety of biological activities. The research in discovering novel antimicrobial compounds from plants has been of increased interest due to the global rise of antibiotic resistance. The present study aims to evaluate the in vitro antibacterial, antibiotic synergistic potential and the chemical profile of plant extracts associated with Cleistanthus bracteosus Jabl. found in Malaysian rainforests for the first time.

Methods
The antibacterial activity and synergistic antibacterial activity of chloroform, methanol and n-hexane crude extracts of C. bracteosus were determined against bacterial pathogens of Escherichia coli, Bacillus subtilis, Staphylococcus aureus, B. cereus, Pseudomonas aeruginosa, Salmonella typhi and Acinetobacter baumannii. The chloroform extracts were subjected to fractionation, chemical profiling, and field emission scanning electron microscopic (FE-SEM) analysis.

Results
The chloroform stem extract exhibited the highest antibacterial activity which indicated a mean inhibition zone diameter (IZD) of 10 ± 0.26 mm against the Gram-positive bacterium B. cereus. The best synergistic activity was shown for chloroform wood extract when combined with ampicillin against A. baumannii, with a growth inhibitory index (GIIs) of 1.33. Potassium clavulanate actively synergised with chloroform stem extract against E. coli ATCC 10536 (IZD = 27 ± 0.56 mm) and chloroform bark extract against S. typhi (IZD = 28 ± 0.54 mm). C. bracteosus extracts showed the presence of secondary metabolites like flavonoids, phenols, tannins, alkaloids, coumarins, saponins and traces of terpenoids, with chloroform extracts of bark, stem and wood consisting of 20 bioactive phytochemical compounds according to gas chromatography–mass spectrometry analysis (GC–MS). Further analysis with high-performance liquid chromatography (HPLC) implied the presence of digoxigenin and lauric acid. The FE-SEM observations further elucidated the effects of C. bracteosus chloroform extracts on the morphology of susceptible organisms.

Conclusion
The findings of this investigation justify that chloroform extracts of C. bracteosus can function as a novel antibacterial agent with synergistic potential.

Item Type:	Article
Uncontrolled Keywords:	Antibacterial activity; Cleistanthus bracteosus; FE-SEM; GC–MS; GIIs; HPLC; Synergistic activity; 42 Health Sciences; 4208 Traditional, Complementary and Integrative Medicine; Emerging Infectious Diseases; Infectious Diseases; Dietary Supplements; Biodefense; Complementary and Integrative Health; Antimicrobial Resistance; 5.1 Pharmaceuticals
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences Q Science > QH Natural history > QH301 Biology S Agriculture > SB Plant culture
Divisions:	Biological and Environmental Sciences (from Sep 19)
Publisher:	Springer
Date of acceptance:	11 June 2026
Date of first compliant Open Access:	2 September 2026
Date Deposited:	02 Sep 2026 08:56
Last Modified:	02 Sep 2026 08:56
DOI or ID number:	10.1186/s12906-026-05439-7
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29284

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