Astringent activity of folklore plant materials and selected formulations in relation to their antimicrobial activity

Purpose: The astringent activity of tannins is due to their ability to bind with proteins which in turn contributes to their antimicrobial properties. The study aimed at determining the correlation between the composite astringent power of folklore plant materials and selected herbal formulations in relation to their antimicrobial activity. Protein precipitating ability (Astringent Power) and Tannic Acid Astringent Equivalents of extracts of the materials were determined.

Method: A protein precipitation assay was designed to determine the Tannic Acid Astringent Equivalents of the samples. Antimicrobial activity was determined by agar disc diffusion assay with Escherichia coli and Staphylococcus aureus.

Results: Folklore materials and formulations showed strong negative correlation coefficients with Tannic Acid Astringent Equivalent values and antibacterial activities. Values observed for the folklore materials were, S. aureus (r = -0.937) and E. coli (r = -0.825) and for the formulations S.aureus (r = -0.9825) and E.coli (r = -0.8774). A new term ‘very tender coconut’ was introduced to describe Gobalu (Sinhala).

Conclusion: The folklore materials and marketed formulations have a strong correlation between composite astringent activities with their antimicrobial powers. High astringent activity corresponds with high antimicrobial activity justifying their ethnobotanical medicinal applications.