Comparative physicochemical and microbial evaluation of six herbal bitters distributed within southwestern Nigeria

Abstract

Background: Medicinal herbal bitters sold as dietary supplement, digestive  stimulant and detoxifier are widely distributed and consumed in Nigeria with similar claims but wide variations in prices.
Objective: Comparative evaluation of the physicochemical properties of six brands of bitters with the aim of proposing possible justification for their interchangeability.
Materials and Methods: The herbal bitters were subjected to physicochemical and phytochemical evaluation; organoleptic test, phytochemical screening, thin layer chromatography (TLC), heavy metal content, total phenolic acid and antioxidant activities as well as microbiological assessment to determine microbial load and antimicrobial properties.
Results: All the bitters were acidic (pH 2.35 - 5.63), of varying colours (orange to  brown), characteristic odour and bitter taste with different types and amount of  phytochemicals. The TLC profile varied from three to eight spots. The Fe, Zn and Cu content were within acceptable limit. Total phenolic acid content varied from  528.33±33.71 to 1589±11.92mgGAE/ml, while antioxidant properties gave IC₅₀ of 4.28±0.01 to 9.54±1.24μg/ml. No direct correlation between the total phenolic  contents and antioxidant activity was observed. Microbial evaluation showed  absence of bacteria with fungi level within official specifications. Four brands were active on six bacterial clinical isolates, while one brand was totally inactive.  Variations in physicochemical parameters does not have any direct correlation with antioxidant and antimicrobial activities, and does not reflect in the variation in the constituent plants, but may be due to possibly processing methods.
Conclusions: The samples were highly distinct from each other, and could not be substituted for each other.

Keywords: Herbal bitters, Total phenolic acid, Antioxidant properties, Heavy metals, Antimicrobial properties