Abstract
Andrographis paniculata (Kalmegh) has been considered as a medicinal shrub and used as a medicinal plant in the remote areas of Bangladesh. A. paniculata leaf and stem extracts were prepared using the polar (i.e., water, and 70% ethanol) and nonpolar (i.e., hexane) solvents. The phytochemical contents, total phenol contents (TPC), antioxidant activity, and antibacterial activity of all the extracts of A. paniculata leaf and stem were investigated. Both the gram-positive (i.e., Bacillus subtillis) and gram-negative (i.e., E. coli, and Salmonella typhi) strains of bacteria were used for the antibacterial activity assay of the sample extracts. The ethanolic stem extracts contained the maximum amount of TPC when compared to that of the leaf extracts. However, the aqueous stem extracts had the highest free radical scavenging activity in vitro. The extracts prepared from A. paniculata stem showed better antibacterial activity against all the strains of bacteria (i.e., E. coli, S. typhi, and B. subtillis) when compared to that of the leaf extracts. More specifically, the aqueous stem extract showed superior antibacterial effect against E. coli, and B. subtillis, and the zones of inhibition were 21 mm, and 29 mm in diameter, respectively. On the other hand, the ethanolic stem extract showed the maximum antibacterial activity against S. typhi and the zone of inhibition was 8.15 mm. The minimum inhibitory concentration (MIC) value and IC50 value for all the A. paniculata extracts were ~0.05 μg/μL, and ~1 μg/μL, respectively.
Highlights
Free radicals and other reactive oxygen species are being constantly produced in the human body and they are known to be responsible for various deadly diseases such as cancer, aging, atherosclerosis, immunodeficiency, and infections
The total phenol content (TPC) of the A. paniculata extracts was determined by Folin Ciocalteu method and the results were expressed in μg CAE/mL
The minimum amount of total phenol contents (TPC) in the hexane extract of leaf and stem is due to the use of nonpolar hexane as the solvent of extraction as because most of the phenolic compounds are soluble in polar solvents [16]
Summary
Free radicals and other reactive oxygen species are being constantly produced in the human body and they are known to be responsible for various deadly diseases such as cancer, aging, atherosclerosis, immunodeficiency, and infections. Due to the toxicity and side effects of modern therapeutic drugs, people across the world are looking for the alternative medicines from natural sources and herbal plants are the most sought after [2]. Because A. paniculata extracts have antihypertensive effects and decreases plasma angiotensin converting enzyme (ACE) activity, and lipid peroxidation in kidneys [4]. They have antimicrobial, antioxidant and anti-inflammatory activities, antihyperglycemic and hypoglycemic activities [5]. It has been reported that the crude aqueous as well as the ethanolic extracts of A. paniculata do not show any antibacterial effect against gram-negative E. coli [6] [7]. To perform the antibacterial activity of the extracts, both the gram-positive (i.e., B. subtillis), and gram-negative (i.e., E. coli, and S. typhi) bacterial strains were used
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