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

Exploring the Antimicrobial, Anticancer, and Apoptosis Inducing Ability of Biofabricated Silver Nanoparticles Using Lagerstroemia speciosa Flower Buds against the Human Osteosarcoma (MG-63) Cell Line via Flow Cytometry

Biosynthesized nano-composites, such as silver nanoparticles (AgNPs), can be engineered to function as smart nano-biomedicine platforms for the detection and management of diverse ailments, such as infectious diseases and cancer. This study determined the eco-friendly fabrication of silver nanoparticles using Lagerstroemia speciosa (L.) Pers. flower buds and their efficacy against antimicrobial and anticancer activities. The UV-Visible spectrum was found at 413 nm showing a typical resonance spectrum for L. speciosa flower bud extract-assisted silver nanoparticles (Ls-AgNPs). Fourier transform infrared analysis revealed the presence of amines, halides, and halogen compounds, which were involved in the reduction and capping agent of AgNP formation. X-ray diffraction analysis revealed the face-centered cubic crystals of NPs. Energy dispersive X-ray verified the weight of 39.80% of silver (Ag), TEM analysis revealed the particles were spherical with a 10.27 to 62.5 nm range, and dynamic light scattering recorded the average particle size around 58.5 nm. Zeta potential showed a significant value at -39.4 mV, and finally, thermo-gravimetric analysis reported higher thermal stability of Ls-AgNPs. Further, the obtained Ls-AgNPs displayed good antimicrobial activity against clinical pathogens. In addition, a dose-dependent decrease in the anticancer activity by MTT assay on the osteosarcoma (MG-63) cell line showed a decrease in the cell viability with increasing in the concentration of Ls-AgNPs with an IC₅₀ value of 37.57 µg/mL. Subsequently, an apoptotic/necrosis study was conducted with the help of Annexin-V/PI assay, and the results indicated a significant rise in early and late apoptosis cell populations. Therefore, green synthesized Ls-AgNPs were found to have potent antimicrobial and anticancer properties making them fascinating choices for future bio-medical implementations.

Synthesis and Characterization of ZnO Nanoparticles Derived from Biomass (Sisymbrium Irio) and Assessment of Potential Anticancer Activity

Cancer treatment development is hampered by chemotherapy side effects, drug resistance, and tumor metastasis, giving cancer patients a gloomy prognosis. Nanoparticles (NPs) have developed as a promising medicinal delivery technique in the last 10 years. The zinc oxide (ZnO) NPs can precisely and captivatingly promote the apoptosis of cancer cells in cancer treatment. There is also an urgent need to discover novel anti-cancer therapies, and current research suggests that ZnO NPs hold significant promise. ZnO NPs have been tested for phytochemical screening and in vitro chemical efficiency. The green synthesis method was employed for the preparation of ZnO NPs from Sisymbrium irio (L.) (Khakshi). An alcoholic and aqueous extract of S. irio was prepared using the Soxhlet method. Various chemical compounds were revealed in the methanolic extract through qualitative analysis. The results of quantitative analysis showed that the total phenolic content has the highest amount (42.7861 mgGAE/g), while the resultant amounts of (5.72175 mgAAE/g) and (15.20725 mgAAE/g) were obtained in total flavonoid content and antioxidant property, respectively. ZnO NPs were prepared using a 1:1 ratio. The synthesized ZnO NPs were identified to have a hexagonal wurtzite crystal arrangement. The nanomaterial was characterized by scanning electron microscopy, transmission electron microscopy, and UV-visible spectroscopy. The ZnO-NPs' morphology exhibited an absorbance at 350-380 nm. Furthermore, different fractions were prepared and assessed for anticancer activity. As a result of this anticancer activity, all fractions exhibited cytotoxic activity against both BHK and HepG2 human cancer cell lines. The methanol fraction showed the highest activity of 90% (IC50 = 0.4769 mg/mL), followed by the hexane fraction that showed 86.72%, ethyl acetate showed 85%, and chloroform fraction showed 84% against BHK and HepG2 cell lines. These findings suggested that synthesized ZnO-NPs have anticancer potential.

Bio-Fabrication of Silver Nanoparticles Using Citrus aurantifolia Fruit Peel Extract (CAFPE) and the Role of Plant Extract in the Synthesis

The green synthesis of silver nanoparticles has been proposed as an eco-friendly and cost-effective substitute for chemical and physical methods. The aim of this study was to synthesize and characterize silver nanoparticles using the peel extract of Citrus aurantifolia fruit, and to determine the possible phytochemical constituents' presence in the plant extracts that might be responsible for the synthesis. Citrus aurantifolia fruit peel extraction was followed by phytochemical studies of secondary metabolites, FTIR analysis confirmation of functional groups, and GC-MS analysis. Silver nanoparticles were synthesized through bio-reduction of silver ions (Ag⁺) to silver nanoparticles using CAFPE and characterized using UV-Vis spectroscopy, HR-TEM, FESEM, EDX, XRD, DLS, and FTIR. The presence of plant secondary metabolites such as alkaloids, flavonoids, tannins, saponins, phenols, terpenoids, and steroids was detected. The FTIR analysis of the extract revealed the presence of functional groups like hydroxyl, carboxyl, carbonyl, amine, and phenyl, whereas the GC-MS analysis indicated presence of chemical compounds such as 1,2,4-Benzenetricarboxylic acid, Fumaric acid, nonyl pentadecyl, and 4-Methyl-2-trimethylsilyloxy-acetophenone, etc., with similar functional groups. The synthesized silver nanoparticle (AgNP) has displayed the characteristics of a surface plasmon resonance (SPR) band peak from 360-405 nm. High resolution transmission electron microscope (HR-TEM) and field emission scan electron microscope (FESEM) confirm polydisperse, spherical shaped, and smooth surface nanoparticles with an average size of 24.023 nm. Energy dispersive X-ray (EDX) analysis further revealed that silver is the most abundant element found in the micrograph of the nanoparticles, and FTIR analysis further confirmed the presence of different functional groups in the surface of the nanoparticle. The XRD analysis also confirmed that the nanoparticles synthesized are crystalline in nature. Based on the findings of this study, it is understood that the variety of natural compounds that are present in plant extracts of Citrus aurantifolia fruit peel can act as both reducing and stabilizing agents for the synthesis of silver nanoparticles. It is, therefore, concluded that Citrus aurantifolia peel extract can be potentially used for the large production of silver nanoparticles for several applications.

Synthesis of Tungsten Oxide Nanoflakes and Their Antibacterial and Photocatalytic Properties

This current work revealed a single-step fabrication of tungsten oxide nanoflakes (WO3 NFs) with the help of Terminalia arjuna bark extract. Bioactive phytoconstituents of T. arjuna bark extract were involved in the nucleation process and promoted the material crystalline growth in a particular direction. The as-prepared sample thermal decomposition was analyzed by TG/DTG. The as-prepared sample was annealed at 300 °C for 2 h, and the annealed sample was characterized by UV-Vis-DRS, FTIR, Raman, XRD, SEM, EDX, and TEM. Synthesized WO3 samples showed a monoclinic phase of the flake-like structure with lengths of 25~230 nm and diameters of 25~120 nm. The WO3 NFs were evaluated against S. aureus and E. coli. Over 3 mg concentrations of WO3 NFs outperform the positive control in antibacterial activity. The pseudo-first-order kinetics of the WO3 NFs enhanced the photocatalytic performance of methylene blue (MB). These results prove that WO3 NFs have sustainable performance in antibacterial and MB degradation applications.

Larvicidal Activity of Two Rutaceae Plant Essential Oils and Their Constituents Against Aedes albopictus (Diptera: Culicidae) in Multiple Formulations

Aedes albopictus (Skuse) is a vector of several arboviruses, such as dengue, chikungunya, West Nile, and Zika viruses. At present, the use of synthetic insecticides is the main vector control strategy. However, the widespread and long-term use of insecticides has aroused several problems, including insecticide resistance, environmental pollution, and non-target species effects, thereby encouraging researchers to search for new alternatives derived from natural products. In recent decades, essential oils (EOs) as natural alternatives to control mosquitoes have received increasing attention. In the initial larvicidal activity screen, two Rutaceae plants (Citrus aurantium and Citrus paradisi) EOs were selected and evaluated for killing Ae. albopictus larvae. The LC50 values of C. aurantium and C. paradisi EOs against Ae. albopictus were 91.7 and 100.9 ppm, respectively. The main components of C. aurantium EO include diethyl o-phthalate (37.32%), limonene (10.04%), and methyl dihydrojasmonate (6.48%). The main components of C. paradisi EO include limonene (60.51%), diethyl o-phthalate (11.75%), linalool (7.90%), and styralyl acetate (6.28%). Among these main components of the two EOs, limonene showed potent larvicidal activity, with the LC50 value of 39.7 ppm. The nanoemulsions of limonene were prepared and characterized. The duration of larvicidal activity was greater in the limonene nanoemulsions than when limonene was applied in solvent. This study demonstrates that EOs of plants in family Rutaceae are a potential resource to develop new larvicides, and nanoemulsification is an effective method for improving the physicochemical properties and efficacy of natural products as larvicides.

Green synthesis of silver nanoparticles using Rhodiola imbricata and Withania somnifera root extract and their potential catalytic, antioxidant, cytotoxic and growth-promoting activities

This study presents the development of a sustainable production process of environmentally benign silver nanoparticles (AgNPs) from aqueous root extract of Rhodiola imbricata (RI) and Withania somnifera (WS) for mitigating environmental pollution and investigating their potential applications in agriculture and biomedical industry. RIWS-AgNPs were characterized using several analytical techniques (UV-Vis, DLS, HR-TEM, SAED, EDX and FTIR). The antioxidant and anticancer activity of RIWS-AgNPs were estimated by DPPH and MTT assay, respectively. UV-Vis and DLS analysis indicated that equal ratio of RIWS-extract and silver nitrate (1:1) is optimum for green synthesis of well-dispersed AgNPs (λ_max: 430 nm, polydispersity index: 0.179, zeta potential: - 17.9 ± 4.14). HR-TEM and SAED analysis confirmed the formation of spherical and crystalline RIWS-AgNPs (37-42 nm). FTIR analysis demonstrated that the phenolic compounds are probably involved in stabilization of RIWS-AgNPs. RIWS-AgNPs showed effective catalytic degradation of hazardous environmental pollutant (4-nitrophenol). RIWS-AgNPs treatment significantly increased the growth and photosynthetic pigments of Hordeum vulgare in a size- and dose-dependent manner (germination (77%), chlorophyll a (12.62 ± 0.07 μg/ml) and total carotenoids (7.05 ± 0.04 μg/ml)). The DPPH assay demonstrated that RIWS-AgNPs exert concentration-dependent potent antioxidant activity (IC₅₀: 12.30 μg/ml, EC₅₀: 0.104 mg/ml, ARP: 959.45). Moreover, RIWS-AgNPs also confer strong cytotoxic activity against HepG2 cancer cell line in dose-dependent manner (cell viability: 9.51 ± 1.55%). Overall, the present study for the first time demonstrated a green technology for the synthesis of stable RIWS-AgNPs and their potential applications in biomedical and agriculture industry as phytostimulatory, antioxidant and anticancer agent. Moreover, RIWS-AgNPs could potentially be used as a green alternative for environmental remediation.

Botanical insecticide-based nanosystems for the control of Aedes (Stegomyia) aegypti larvae

Aedes (Stegomyia) aegypti is a cosmopolitan species that transmits arbovirus of medical importance as dengue, Zika, and chikungunya. The main strategy employed for the control of this mosquito is the use of larvicidal agents. However, the overuse of synthetic chemical larvicides has led to an increase in resistant insects, making management difficult. Therefore, the use of botanical insecticide-based nanosystems as an alternative to the use of synthetic agents for the control of Ae. aegypti has gained more considerable attention in the last years, mainly due to the advantages of nanostructured delivery systems, such as (a) controlled release; (b) greater surface area; (c) improvement of biological activity; (d) protection of natural bioactive agents from the environment and thus achieving stability; and (e) lipophilic drugs are easier dispersed even in aqueous vehicles. This review summarizes the current knowledge about botanical insecticide-based nanosystems as larvicidal against Ae. aegypti larvae. The majority of papers used metallic nanoparticles (NPs) as larvicidal agents, mainly silver nanoparticles (AgNPs), showing potential for their use as an alternative, followed by nanoemulsions containing vegetable oils, most essential oils, nanosystems that allow the dispersion of this high hydrophobic product in water, the environment of larval development. The final section describes scientific findings about the mode of action of these NPs, showing the gap about this subject in literature.

Biocontrol of mosquito vectors through herbal-derived silver nanoparticles: prospects and challenges

Mosquitoes spread several life-threatening diseases such as malaria, filaria, dengue, Japanese encephalitis, West Nile fever, chikungunya, and yellow fever and are associated with millions of deaths every year across the world. However, insecticides of synthetic origin are conventionally used for controlling various vector-borne diseases but they have various associated drawbacks like impact on non-targeted species, negative effects on the environment, and development of resistance in vector species by alteration of the target site. Plant extracts, phytochemicals, and their nanoformulations can serve as ovipositional attractants, insect growth regulators, larvicides, and repellents with least effects on the environment. Such plant-derived products exhibit broad-spectrum resistance against various mosquito species and are relatively cheaper, environmentally safer, biodegradable, easily accessible, and are non-toxic to non-targeted organisms. Therefore, in this review article, the current knowledge of phytochemical sources exhibiting larvicidal activity and their variations in response to solvents used for their extraction is underlined. Also, different methods such as physical, chemical, and biological for silver nanoparticle (AgNPs) synthesis, their mechanism of synthesis using plant extract, their potent larvicidal activity, and the possible mechanism by which these particles kill mosquito larvae are discussed. In addition, constraints related to commercialization of nanoherbal products at government and academic or research level and barriers from laboratory experiments to field trial have also been discussed. This comprehensive information can be gainfully employed for the development of herbal larvicidal formulations and nanopesticides against insecticide-resistant vector species in the near future. Graphical abstract.

Recent Developments in Nanotechnology for Detection and Control of Aedes aegypti-Borne Diseases

Arboviruses such as yellow fever, dengue, chikungunya and zika are transmitted mainly by the mosquito vector Aedes aegypti. Especially in the tropics, inefficacy of mosquito control causes arboviruses outbreaks every year, affecting the general population with debilitating effects in infected individuals. Several strategies have been tried to control the proliferation of A. aegypti using physical, biological, and chemical control measures. Other methods are currently under research and development, amongst which the use of nanotechnology has attracted a lot of attention of the researchers in relation to the production of more effective repellents and larvicides with less toxicity, and development of rapid sensors for the detection of virus infections. In this review, the utilization of nano-based formulations on control and diagnosis of mosquito-borne diseases were discussed. We also emphasizes the need for future research for broad commercialization of nano-based formulations in world market aiming a positive impact on public health.

Screening for bioactive secondary metabolites in Sri Lankan medicinal plants by microfractionation and targeted isolation of antimicrobial flavonoids from Derris scandens

ETHNOPHARMACOLOGICAL RELEVANCE

Sri Lanka is known to have very diverse flora. Many of these species are used for plant-based remedies, which form the integral part of two Sri Lankan systems of traditional medicine, Ayurveda and Deshiya Chikitsa. Despite their widespread use, only a limited number of studies have probed into the scientific evidence for bioactivity of these medicinal plants. Such studies rarely progress to the identification of bioactive natural products.

AIM OF THE STUDY

The primary aim was to develop a bioactivity screening method and apply it to 50 Sri Lankan medicinal plants where antimicrobial properties could be relevant for its traditional use. The subsequent aim was the progression into defining and characterising potent isolates within targeted compound classes from such plants, i.e. Derris scandens and its antimicrobial flavonoids.

MATERIAL AND METHODS

The plant collection comprised 24 species of Fabaceae, 15 Rubiaceae, 7 Solanaceae and 4 Cucurbitaceae plants. These 50 species were collected based on their ethnopharmacological importance and use in Sri Lankan traditional medicine. Crude extracts from each species were initially subjected to radial disc diffusion and microdilution assays. Subsequently, aqueous extracts of all plants were microfractionated in deep well plates using reversed-phase HPLC. Fractions were tested for antibacterial and cytotoxic activities and masses of target bioactive compounds were identified using mass spectrometry. Bioactive compounds with the masses identified through microfractions were isolated from Derris scandens using reversed-phase HPLC. The isolated pure compounds were characterised using LC-MS and NMR.

RESULTS

Crude aqueous extracts from 19 species showed activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) in the radial disc diffusion assay. Crude aqueous extracts from 34 plant species and organic extracts from 46 plant species were active against S. aureus (≤4 mg mL^-1) in the microdilution assay. Microfractionation demonstrated antibacterial activity for 19 plants and cytotoxicity for 6 plants. Furthermore, target bioactive compounds and their molecular ions were identified during microfractionation. Dalpanitin and vicenin-3, two of the flavonoids isolated from Derris scandens gave MICs of 23 μg mL^-1 against S. aureus. Dalpanitin also exhibited relevant MICs on Gram-negative bacteria (94 μg mL^-1 against Escherichia coli and Pseudomonas aeruginosa).

CONCLUSION

The microfractionation protocol developed in this study enabled time-efficient screening of many plants species, using a small quantity of sample material. In addition, microfractionation served as a guiding tool for identifying individual antimicrobial compounds. Through this process, flavonoids were isolated from Derris scandens, out of which dalpanitin and vicenin-3 showed activity in the low micromolar range. The high hit rate for in vitro antibacterial properties from this ethnopharmacologically guided sample collection gives credence to Sri Lankan traditional herbal medicine as a source for drug discovery.

One-step Synthesis of Silver Nanoparticles Using Saudi Arabian Desert Seasonal Plant Sisymbrium irio and Antibacterial Activity Against Multidrug-Resistant Bacterial Strains

Globally, antimicrobial resistance has grown at an alarming rate. To combat the multidrug-resistant (MDR) superbugs, silver nanoparticles (Ag NPs) were synthesized using an aqueous leaf extract of seasonal desert plant Sisymbrium irio obtained from the central region of Saudi Arabia by a simple one-step procedure. The physical and chemical properties of the Ag NPs were investigated through ultraviolet visisble analysis (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) analysis. The UV-vis spectrum showed an absorption band at 426 nm. The XRD results showed a highly crystalline face-centered cubic structure. The surface morphology analyzed using SEM and TEM analyses showed the particle size to be in the range 24 nm to 50 nm. Various concentrations of Ag NPs were tested against MDR Pseudomonas aeruginosa and Acinetobacter baumanii that cause ventilator-associated pneumonia (VAP). American Type Culture Collection (ATCC) Escherichia coli-25922 was used as the reference control strain. The Ag NPs effectively inhibited tested pathogens, even at the lowest concentration (6.25 µg) used. The bacterial inhibitory zone ranged from 11–21 mm. In conclusion, the newly synthesized Ag NPs could be a potential alternative candidate in biomedical applications in controlling the spread of MDR pathogens.

Plant-based larvicidal agents: An overview from 2000 to 2018

Current review aims to systematically segregate, analyze and arrange the key findings of the scientific reports published on larvicidal plants including larvicidal formulations. The investigation was carried out by analyzing the published literature in various scientific databases, subsequently, the key findings of the selective scientific reports having larvicidal potency (LC₅₀) of extract or isolated oil<100 μg/mL were tabulated to provide the concise and crucial information. Special emphasis was given on reports in which LC₅₀ of extract or isolated oil was reported to be < 10 μg/mL, genus or species documented in multiple independent studies, advancement in larvicidal formulations and activity of isolated phytoconstituents. Extensive analysis of published literature revealed that the larvicidal potency of herbal resources varied from sub-microgram/ml to practically insignificant. Overall, this unprecedented summarized and arranged information can be utilized for design, development and optimization of herbal based formulation having potential larvicidal activity.