Evaluation of in-vitro antibacterial and antifungal activities of crude extracts and solvent fractions of methanol extract of leaves of Ricinus communis Linn (Euphorbiaceae) against selected pathogens.
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Date
2020-06
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Addis Abeba University
Abstract
Infectious disease impacts are reduced due to development of antimicrobial agents. However, the
effectiveness of the antimicrobial agent is reduced over time because of the emergence of
antimicrobial resistance. To overcome these problems scholars have been searching for alternative
medicines, particularly focusing on traditionally used medicinal plants. Ricinus communis Linn is
used as a traditional treatment for bovine mastitis, wound infection, and other medicinal purposes.
Moreover, the antimicrobial activity of Ricinus communis Linn leaf at crude extract level has been
confirmed against human originated pathogens in the previous studies. The objective of the present
study was to further evaluate the antimicrobial activities of Ricinus communis Linn leaf extracts
and fractions. Ricinus communis Linn leaves were macerated in absolute methanol and acetone
solvents. The methanol crude extract was shown best antimicrobial activity and subjected to
further fractionation via increasing polarity of solvents (n-hexane, chloroform, ethyl acetate, and
aqueous). Test microorganisms included in the study were six laboratory reference bacteria (E.
coli, S. aureus, S. agalactiae, K. pneumoniae, P. aeruginosa, and S. Pyogenes), two clinical isolate
bacteria (E. coli and S. aureus), and one fungus (Candida albicans). The agar well diffusion
method was employed to determine antimicrobial activity. The minimum inhibitory concentrations
(MIC) and minimum bactericidal/fungicidal concentrations (MBC/MFC) were determined
through broth microdilution. The results indicated that the best antimicrobial activity for
ethylacetate fraction ranging from 14.67 mm (clinical E. coli) to 20.33 mm (S. aureus) at
400mg/ml however, n-hexane exhibited lowest antimicrobial activity. Among tested fractions,
ethyl acetate fraction was produced lowest MIC values ranging from 1.5625mg/ml (S. aureus) to
16.67 mg/ml (Candida albicans). The ethyl acetate fraction showed bactericidal activity against
all tested microorganisms. In conclusion, ethyl acetate fraction of crude methanol extract of
Ricinus communis Linn leaf exhibited the best antimicrobial activity.
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Keywords
Antibacterial activity, Antifungal activity, Ricinus communis Linn, MIC, MBC