Abstract:
Introduction: Plant-based antimicrobials have been proven to be a promising treatment
option with several advantages, including fewer side effects and highly diverse
pharmacological activities due to secondary metabolites. Erythrina variegata, known as
the Coral tree, possesses many therapeutic activities, including antibacterial, antioxidant,
anthelminthic, anti-inflammatory, and cytotoxic activities, and is frequently used in Siddha
medicine. Erythrina variegata is widely distributed in Malaysia, Sri Lanka, and India.
Objective: To evaluate the antibacterial and antioxidant properties of different solvent
extractions of leaves and bark of Erythrina variegata.
Methodology: Dried leaves and bark powder were macerated separately with water,
ethanol, and ethyl acetate. The antibacterial activity of extracts was tested against
Staphylococcus aureus and Pseudomonas aeruginosa using the agar well diffusion
method, and the zone of inhibition for each extract was measured. Gentamycin and
Ciprofloxacin were used as positive controls. The antioxidant activity of the extracts was
determined by the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assay method, and
ascorbic acid was used as standard. IC50 values of plant extracts and standard were
measured. All the tests were triplicated. Independent samples t-test was used to compare
the anti-bacterial activity with positive control at a 95% confidence level, and a p-value
less than 0.05 was considered statistically significant. All the results were analysed using
SPSS version 26.
Results: The highest antioxidant activity was observed with ethanol bark extract
(IC50=420.18 g/ml), and leaf aqueous plant extract had IC50 of 528.74 g/ml. Anti-
bacterial activity of all extracts showed significant differences with positive controls
(p<0.05). Ethyl acetate extract of leaves and bark showed the highest inhibitory activity
against Staphylococcus aureus (18±1.00 cm), while ethanolic leaf extract showed the
highest inhibitory activity against Pseudomonas aeruginosa (29.5 cm).
Conclusion: The plant leaves of Erythrina variegata had more anti-bacterial activity, while
the bark of Erythrina variegata showed more antioxidant activity. Further studies are
needed to identify the compounds responsible for the antioxidant and antibacterial
activities of the plant.
