Nanosilver crystals capped with Bauhinia acuminata phytochemicals as new antimicrobials and mosquito larvicides.

To develop novel nanoformulated insecticides and antimicrobials, herein we produced Ag nanoparticles (AgNPs) using the Bauhinia acuminata leaf extract. This unexpensive aqueous extract acted as a capping and reducing agent for the formation of AgNPs. We characterized B. acuminata-synthesized AgNPs by UV-vis and FTIR spectroscopy, XRD and TEM analyses. UV-vis spectroscopy analysis of B. acuminata-synthesized AgNPs showed a peak at 441.5 nm. FTIR shed light on functional groups from the phytoconstituents involved in nanosynthesis. XRD of B. acuminata-synthesized AgNPs suggested a face-centered cubic structure, with a highly crystalline nature. TEM of B. acuminata-synthesized AgNPs revealed mean size of 25 nm, with round shape. AgNPs tested at 60 µg/mL inhibited the growth of 5 bacteria and 3 fungal pathogens. In the insecticidal assays on important mosquito species, LC50 of the aqueous extract of B. acuminata leaves on the larvae of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus were 204.07, 226.02, and 249.24 µg/mL, respectively. The B. acuminata-synthesized AgNPs exhibited higher larvicidal efficacy, with LC50 values of 24.59, 27.19, and 30.19 µg/mL, respectively. Therefore, herein we developed a single-step, reliable, inexpensive, and environmentally non-toxic synthesis process to obtain AgNPs with high bioactivity against pathogens and vectors. Given the effective antimicrobial and larvicidal activity, nanoparticles fabricated using plant extracts and extremely low concentrations of trace elements, such as silver, can be exploited for multipurpose activities. Our results pointed out that B. acuminata-synthesized AgNPs have a promising potential in antimicrobial food packaging, as well as a foliar spray to control plant pathogens in the field, and to synergize the efficacy of fungicidal and larvicidal formulations.

In vitro, fluorescence-quenching and computational studies on the interaction between lipoxygenase and 5-hydroxy-3',4',7-trimethoxyflavone from Lippia nodiflora L.

Lippia nodiflora L. is extensively used in traditional medicine for several medicinal purposes, including their use in inflammatory disorders. In this study, the folk use of L. nodiflora was validated using the isolated natural compound, 5-hydroxy-3',4',7-trimethoxyflavone (HTMF) by in vitro, fluorescence spectroscopic and molecular modeling studies with lipoxygenase (LOX), because LOX plays an essential role in inflammatory responses. In this perspective, the methanol extract and HTMF are shown to demonstrate prominent inhibitory activity against soybean lipoxygenase, with an IC50 value of 21.12 and 23.97 µg/ml, respectively. The data obtained from the spectroscopic method revealed that the quenching of intrinsic fluorescence of LOX is produced as a result of the complex formation of LOX-HTMF. The binding mode analysis of HTMF within the LOX enzyme suggested that hydrogen bond formation, hydrophobic interaction and π-π stacking could account for the binding of HTMF. Molecular dynamics results indicated the interaction of HTMF with LOX and the stability of ligand-enzyme complex was maintained throughout the simulation. The computational results are reliable with experimental facts and provided a good representation for understanding the binding mode of HTMF inside the active site of lipoxygenase enzyme.