Antimicrobial Activity and Prebiotic Effects of Senna alata Leaf Extracts

Abstract

Medicinal plants are a great source of antibacterial and prebiotic properties that can treat a wide range of human diseases. Senna alata, also known as "candle bush," has many health benefits. It has antimicrobial properties and has been used for centuries to treat skin infections [1] and digestion-related problems such as constipation, stomach discomfort, and liver diseases [2]. This study aimed to screen the phytoconstituents of S. alata leaf extracts, study their antimicrobial activity against several intestinal pathogens, and investigate their potential prebiotic effects against a few probiotic strains.
 
 Aqueous and ethanolic S. alata leaf extracts were obtained by the maceration method, then dried and stored until used. A qualitative phytochemical analysis of S. alata leaf extracts was performed to determine the presence of biomolecules such as anthraquinones, carbohydrates, flavonoids, phenols, saponins, tannins, and alkaloids. For the antimicrobial study, serial two-fold dilutions of leaf extracts in concentrations ranging from 10 mg/mL to 0.02 mg/mL were performed in a 96-well microplate to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). For the prebiotic study, serial two-fold dilutions of leaf extracts in concentrations ranging from 10 mg/mL to 1.25 mg/mL were conducted in a 96-well microplate to study the growth rate of probiotics by measuring its optical density (OD) at 0 and 24 hours of incubation at 600 nm.
 
 Aqueous and ethanolic leaf extracts showed the presence of tannin, saponins, alkaloids, carbohydrates, and flavonoids. Anthraquinones were not detected in any of the extracts, and phenols could only be detected in the ethanolic leaf extract. At the tested concentrations, both leaf extracts showed antimicrobial activity against Escherichia coli, Staphylococcus aureus, Salmonella Typhi, and Klebsiella pneumoniae based on the MIC values (Table 1). The growth rate of Lactobacillus helveticus and Bifidobacterium longum were significantly increased (p <0.05) after being treated with aqueous leaf extract at 24 hours of incubation (Figure 1). A similar growth pattern was obtained with L. helveticus and B. longum treated with ethanolic leaf extracts (Figure 2).
 In conclusion, aqueous and ethanolic S. alata leaf extracts displayed antimicrobial activities to certain intestinal pathogenic bacteria at the preliminary extract concentrations employed in the present study. Besides, the extracts have a stimulative effect on the growth of probiotic microorganisms which are typical members of intestinal microbiota. This study provides further evidence that suggests S. alata is one of the prebiotics which could potentially be used to ease the related digestive problems.