Piper betle L. (betel quid) shows bacteriostatic, additive, and synergistic antimicrobial action when combined with conventional antibiotics

In this work, we report a completely green chemistry approach to synthesize silver nanoparticles (AgNPs) using the compound β-sitosterol-D-glucopyranoside (BS) isolated from the Indian sacred grass Desmostachya bipinnata, using natural sunlight as the initiator. BS synthesizes the AgNPs, in a free radical exchange process involving reactive oxygen species. The possible mechanism of the influence of BS on the reduction and stabilization of AgNPs is also discussed. The optical properties and morphology of the AgNPs were characterized by absorption spectroscopy and transmission electron microscopy. These bio-inspired AgNPs exhibited good catalytic activity during the catalytic degradation of environmentally hazardous organic dyes like methylene blue, methyl red, Congo red and acridine orange, in aqueous media.

β-Sitosterol-D-glucopyranoside isolated from Desmostachya bipinnata mediates photoinduced rapid green synthesis of silver nanoparticles

Biogenic silver nanoparticles synthesis using the extract of the medicinal plant Clerodendron serratum and its in-vitro antiproliferative activity

Antimicrobial flavonoids isolated from Indian medicinal plant Scutellaria oblonga inhibit biofilms formed by common food pathogens.

Increasing prevalence of antibiotic resistance has led research to focus on discovering new antimicrobial agents derived from the marine biome. Although ample studies have investigated sponges for their bioactive metabolites with promising prospects in drug discovery, the potentiating effects of sponge extracts on antibiotics still remains to be expounded. The present study aimed to investigate the antibacterial capacity of seven tropical sponges collected from Mauritian waters and their modulatory effect in association with three conventional antibiotics namely chloramphenicol, ampicillin and tetracycline. Disc diffusion assay was used to determine the inhibition zone diameter (IZD) of the sponge total crude extracts (CE), hexane (HF), ethyl acetate (EAF) and aqueous (AF) fractions against nine standard bacterial isolates whereas broth microdilution method was used to determine their minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs) and antibiotic potentiating activity of the most active sponge extract. MIC values of the sponge extracts ranged from 0.039 to 1.25mg/mL. Extracts from Neopetrosia exigua rich in beta-sitosterol and cholesterol displayed the widest activity spectrum against the 9 tested bacterial isolates whilst the best antibacterial profile was observed by its EAF particularly against Staphylococcus aureus and Bacillus cereus with MIC and MBC values of 0.039mg/mL and 0.078mg/mL, respectively. The greatest antibiotic potentiating effect was obtained with the EAF of N. exigua (MIC/2) and ampicillin combination against S. aureus. These findings suggest that the antibacterial properties of the tested marine sponge extracts may provide an alternative and complementary strategy to manage bacterial infections.

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Antibacterial and antibiotic potentiating activities of tropical marine sponge extracts

Desmostachya bipinnata (L.) Stapf, Poaceae, or Kusha in Sanskrit, is a sacred grass used extensively in Indian Vedic practices. It is well known for its medicinal value and is used in traditional Indian medicine to treat microbial infection in combination with other herbs. An effort has been made to isolate and characterize the bioactive compounds from the hydroalcoholic extract of D. bipinnata through bioassay guided fractionation, column chromatography. Their individual or combined antimicrobial properties were determined by the Resazurin Microtitre Assay, the checkerboard assay in combination with antibiotics, and by time kill curve analysis. β-Sitosterol-D-glucopyranoside was the bioactive compound identified to have the best antimicrobial activity (MIC 6-50 µg/ml) and it works synergistically with most antibiotics, especially with ciprofloxacin. Time kill curves showed that BS kills most of the pathogens within 5-10 h. To our knowledge at its best, this is the first time report of antibacterial synergy of β-sitosterol-D-glucopyranoside from D. bipinnata.

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Synergistic antibacterial action of β-sitosterol-D-glucopyranoside isolated from Desmostachya bipinnata leaves with antibiotics against common human pathogens

Manikandaraja Keerthiraja

Papers

Synergistic antibacterial action of β-sitosterol-D-glucopyranoside isolated from Desmostachya bipinnata leaves with antibiotics against common human pathogens