In vitro antimicrobial potential of extracts and phytoconstituents from Gymnema sylvestre R.Br. leaves and their biosafety evaluation

Abstract

The in vitro antimicrobial screening of Gymnema sylvestre leaves against 13 test pathogens established its broad spectrum activity with average inhibition zone ranging from 14 to 23 mm. The antimicrobial activity of the classically- optimized aqueous extract was enhanced up to 1.45 folds, when subjected to statistical optimization using Response Surface Methodology (RSM) and was thermostable. Ethyl acetate was found to be the best organic extractant with Klebsiella pneumoniae 1 (31.5 mm) and Staphylococcus epidermidis (25.5 mm) being the most sensitive among Gram negative and Gram positive bacteria, respectively. Among the major group of phytoconstituents detected, tannins were the most abundant followed by flavonoids and phytosterols, while triterpenes were absent. Flavonoids and cardiac glycosides exhibited a broad range of antimicrobial potential, with inhibition zone ranging from 13 to 35 mm, where Candida albicans was the most sensitive organism. Ethyl acetate extract showed better potency with lowest Minimum inhibitory concentration (0.1–1 mg ml−1) than the aqueous extract (1–3 mg ml−1) and all partially purified phytoconstituents (0.1–10 mg ml−1). The ethyl acetate extract and flavonoids were highly potent, as they exhibited a total activity potency ranging from 41.4 to 1045 ml g−1. Time kill studies revealed their microbicidal action, where ethyl acetate extract had a kill time from 0 to 12 h. However, among phytoconstituents, flavonoids were the most effective (0–8 h). The MIC and time kill study was also compared to that of standard antibiotics. These findings indicate that Gymnema sylvestre can be a potential source for development of leading metabolites against pathogens of clinical importance like Pseudomonas aeruginosa, Candida albicans, Escherichia coli, Staphylococcus aureus etc. They were neither mutagenic nor cytotoxic, as revealed by Ames and MTT assay.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-017-0416-z) contains supplementary material, which is available to authorized users.

Scientific validation of the antimicrobial and antiproliferative potential of Berberis aristata DC root bark, its phytoconstituents and their biosafety

“…Thus, the alarming challenge for physicians and pharmacists is the need to develop alternative approaches and search for new antimicrobials from natural sources, which include microbial sources such as bacteria (Kos et al 2011) and fungi (Sondergaard et al 2016) as well as non-microbial sources such as animals (Burrowes et al 2004) and plants (Sibanda and Okoh 2007; Ayukekbong et al 2017). Among these, plants have provided a ray of hope for obtaining novel antimicrobial compounds (Zhao et al 2013; Farjana et al 2014; Ruma et al 2015; Arora and Sood 2017; Zheljazkov et al 2017; Oluwasina et al 2019).…”

Bioprospecting the antimicrobial, antibiofilm and antiproliferative activity of Symplocos racemosa Roxb. Bark phytoconstituents along with their biosafety evaluation and detection of antimicrobial components by GC-MS

“…The test preparations (ethyl acetate extract, flavonoids, cardiac glycosides) were studied for their MIC against the reference microbial strains (sensitive to the respective preparations in ADA) by Agar dilution method, as per the protocol followed in Arora and Sood [ 21 ] using various concentrations (Additional file 1 ) prepared from their respective stock solutions [i.e., Ethyl acetate extract: 30.5 mg/mL; Flavonoids: 54.75 mg/mL; Cardiac glycosides: 59.5 mg/mL]. Hundred microliters (100 μL) of the activated test organism (adjusted to 0.5 McFarland standards) was swabbed onto the solidified plates (containing different concentrations of a test preparation) and incubated at 37 °C (bacterial cultures) and 25 °C (yeast strains) for 18–24 h. The lowest concentration of the test preparations which inhibited the microbial growth were taken as their MIC.…”

“…The Ames test for different test preparations (Ethyl acetate extract: 30.5 mg/mL; Flavonoids: 54.75 mg/mL; Cardiac glycosides: 59.5 mg/mL) was carried out by plate incorporation method, as described earlier [ 21 ] (for details see Additional file 1 ). Sodium azide was taken as a standard mutagen, while 30% DMSO were used as a negative control.…”

Bioprospecting the antimicrobial, antibiofilm and antiproliferative activity of Symplocos racemosa Roxb. Bark phytoconstituents along with their biosafety evaluation and detection of antimicrobial components by GC-MS

“…The ethyl acetate extract and the active phytoconstituents were tested for their MIC against test organisms as per protocol followed in Arora and Sood [21]. The values were then compared with that of the standard antibiotics.…”

“…The test extracts were subjected to Ames test [21]. The overnight activated inoculum of Salmonella typhimurium (MTCC 1251, IMTECH, Chandigarh) was serially diluted and eventually mixed with equal volume of the extract (MIC concentration) and was then added to the top agar containing a histidinebiotin mixture (1:1 ratio).…”