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.

A series of biosafe mixed-ligand complexes of silver with heterocyclic thioamides have been studied for their antimicrobial/anticancer activity.

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Zinc(ii)-thiosemicarbazone complexes have high antimicrobial activity against MRSA,S. aureus,K. pneumoniae,Sh. flexneri,S. typhimuriumandC. albicans.

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Berberis aristata is an important part of traditional healing system from more than 2500 years. The aqueous extract of Berberis aristata root bark displayed broad spectrum activity against 13 test pathogens, ranging from 12 to 25 mm. In classical optimization, 15% concentration prepared at 40 °C for 40 min was optimal and thermostable. Statistical optimization enhanced the activity by 1.13–1.30-folds. Ethyl acetate was the best organic solvent to elute out the potential compound responsible for antimicrobial activity. Diterpenes were the most abundant phytoconstituent (15.3%) and showed broad spectrum antimicrobial activity ranging from 16.66 to 42.66 mm. Ethyl acetate extract displayed the lowest minimum inhibitory concentration (0.05–1 mg/mL), followed by diterpenes (0.05–5 mg/mL) and flavonoids (0.05–10 mg/mL). The test extracts were microbicidal in nature and showed a prolonged post antibiotic effect ranging from 2 to 8 h. They were found to be biosafe as per Ames and MTT assay. The in vitro cytotoxicity evaluation of diterpenes against L20B, RD and Hep 2 cell lines revealed its IC50 ranging from 245 to 473 µg/mL. Acute oral toxicity of diterpenes on Swiss albino mice did not show any changes in behavioral pattern, body weight, biochemical parameters as well as organs’ architecture. The study thus indicates B. aristata could be a potential candidate for development of potent drug owing to its antimicrobial potential and biosafe profile.

Background Plants provide a ray of hope to combat the ever increasing antibiotic resistance and Symplocos racemosa is a valuable medicinal plant. The study focused on highlighting the importance of this plant’s phytoconstituents as potential source of novel antimicrobials against planktonic as well as biofilm forming microorganisms, along with their antiproliferative activity. The biosafety of the phytoconstituents was also established, followed by detection of probable antimicrobial components. Methods The best organic extractant and major groups of phytoconstituents were tested for their antimicrobial activity against reference microbial strains and drug-resistant clinical isolates. The anti-proliferative potential of the most active group of phytoconstituents was evaluated against cancerous cell lines. The in vitro biosafety of phytoconstituents was evaluated by Ames and MTT assay, while in vivo biosafety of the most active phytoconstituents, i.e., flavonoids was determined by acute oral toxicity. Further, the probable antimicrobial components in the flavonoids were detected by TLC and GC-MS. Results Ethyl acetate extract was the most effective among various organic extracts, whereas phytoconstituents such as flavonoids, cardiac glycosides, saponins, tannins, triterpenes and phytosterols were the major groups present, with flavonoids being the most potent antimicrobials. The phytoconstituents displayed a significant antibiofilm potential, as exhibited by inhibition of initial cell attachment, disruption of the pre-formed biofilms and reduced metabolic activity of biofilms. The phytoconstituents were significantly active against the drug-resistant strains of E.coli, MRSA and Salmonella spp. Further, flavonoids showed significant cytotoxic effect against the cancerous cell lines but were non-cytotoxic against Vero (normal) cell line. All the test preparations were biosafe, as depicted by the Ames test and MTT assay. Also, flavonoids did not induce any abnormality in body weight, clinical signs, biochemical parameters and organs’ histopathology of the Swiss albino mice during in vivo acute oral toxicity studies. The flavonoids were resolved into 4 bands (S1-S4), where S3 was the most active and its GC-MS analysis revealed the presence of a number of compounds, where Bicyclo [2.2.1]heptan-2-one,1,7,7-trimethyl-, (1S)- was the most abundant. Conclusions These findings suggest that the phytoconstituents from Symplocos racemosa bark could act as potential source of antimicrobial as well as antiproliferative metabolites.

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