Phytochemical and Antibacterial Action of Taro (Colocasia esculenta, Araceaea) Aqueous-Ethanolic Leaf Extract against Selected Bacterial Strains

Abstract

Taro (Colocasia esculenta) plant is commonly available and popularly used as food and alternative medicine. To prove its medicinal value, the study explored its secondary metabolites from aqueous-ethanolic leaf extract. Specifically, this investigation aimed to classify its acute dermal toxicity and antibacterial activity, determine its Minimum Inhibitory Concentration (MIC), and identify the equipotency with the standard drug and mutagenic activity. Phytochemical screening of tannins, alkaloids, saponins, cardenolides and bufadienolides, flavonoids, polyphenol compounds and anthraquinones was performed. Five healthy female rabbits were used for toxicity test based on OECD guidelines 404. Kirby-Bauer method was employed for antibacterial activity (susceptibility and potency tests) using Methicillin-Resistant Staphylococcus aureus ATCC 43300, Clinical Isolate Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. A two-fold agar dilution was applied for Minimum Inhibitory Concentration and Ames test was employed for direct mutagenicity assay using Salmonella typhimurium TA98. Results showed that leaf extract has no anthraquinone and it is categorized as non toxic up to allowable dose of 5000 mg/kg. The findings showed a significant difference on the mean zones of inhibition between Vancomycin and plant extract against S. aureus and between tetracycline and the extract towards E.coli. The MRSA and P. aeruginosa showed no significant differences. The MIC of extract is effective to MRSA and S. aureus at 105.26 and 50 mg/mL respectively. However, E. coli and P. aeruginosa are resistant up to the 105.26 mg/mL. Potency test revealed a non-comparability in strength between the extract and Azithromycin using Gram-negative bacteria. However, the extract showed comparable strength with the standard drug using MRSA and S. aureus. Ames test revealed a mutagenic activity using Salmonella typhimurium TA98.