What is the aquatic toxicity of saponin-rich plant extracts used as biopesticides?

Hydrolysis, Photolysis, and Biotoxicity Assessment of a Novel Biopesticide, Guvermectin

Guvermectin is a biopesticide isolated from the secondary metabolites of Streptomyces sp. NEAU6, an endogenous actinomyces of a Chinese medicine named Paris polyphylla. However, the environmental degradation behavior and biotoxicity of guvermectin are still unclear, which may affect its rational application. Therefore, the degradation of guvermectin in water at different pH values (pH 4, pH 6, pH 7, and pH 9) and with or without light was investigated in the laboratory. The results showed that guvermectin could be degraded in pH 4 solution, and the presence of light irradiation enhanced the degradation process with a DT₅₀ of 2.95 and 12 days for photolysis and hydrolysis, respectively. However, guvermectin was fairly stable in other conditions. Three products transformed from guvermectin degradation were identified by UPLC-QTOF/MS. Biotoxicity assessment was performed on Danio rerio and Daphnia magna Straus by ECOSAR prediction and in vivo biological tests. The test data showed that guvermectin and its transformation products exhibited low toxicities to D. rerio and D. magna Straus (LC₅₀/EC₅₀ > 100 mg a.i./L), and the transformation products had lower toxicity than their parent substance. The results provided a reference for elucidating the potential risk of guvermectin to nontarget organisms and promoting its rational use.

Biological functions of active ingredients in quinoa bran: Advance and prospective

Quinoa is known to be a rich source of nutrients and bioactive components. Quinoa bran, used mainly as animal feed in processing by-products, is also a potential source of bioactive ingredients being conducive to human health. The importance of nutrition and function of quinoa seed has been discussed in many studies, but the bioactive properties of quinoa bran often are overlooked. This review systemically summarized the progress in bioactive components, extraction, and functional investigations of quinoa bran. It suggests that chemically assisted electronic fractionation could be used to extract albumin from quinoa bran. Ultrasound-assisted extraction method is a very useful method for extracting phenolic acids, triterpene saponins, and flavonoids from quinoa bran. Based on in vitro and in vivo studies for biological activities, quinoa bran extract exhibits a wide range of beneficial properties, including anti-oxidant, anti-diabetes, anti-inflammation, anti-bacterial and anti-cancer functions. However, human experiments and action mechanisms need to investigate. Further exploring quinoa bran will promote its applications in functional foods, pharmaceuticals, and poultry feed in the future.

Nanotechnology-Based Bioactive Antifeedant for Plant Protection

The productivity of vegetable crops is constrained by insect pests. The search for alternative insect pest control is becoming increasingly important and is including the use of plant-derived pesticides. Plant-derived pesticides are reported as effective in controlling various insect pests through natural mechanisms, with biodegradable organic materials, diverse bioactivity, and low toxicity to non-target organisms. An antifeedant approach for insect control in crop management has been comprehensively studied by many researchers, though it has only been restricted to plant-based compounds and to the laboratory level at least. Nano-delivery formulations of biopesticides offer a wide variety of benefits, including increased effectiveness and efficiency (well-dispersion, wettability, and target delivery) with the improved properties of the antifeedant. This review paper evaluates the role of the nano-delivery system in antifeedant obtained from various plant extracts. The evaluation includes the research progress of antifeedant-based nano-delivery systems and the bioactivity performances of different types of nano-carrier formulations against various insect pests. An antifeedant nano-delivery system can increase their bioactivities, such as increasing sublethal bioactivity or reducing toxicity levels in both crude extracts/essential oils (EOs) and pure compounds. However, the plant-based antifeedant requires nanotechnological development to improve the nano-delivery systems regarding properties related to the bioactive functionality and the target site of insect pests. It is highlighted that the formulation of plant extracts creates a forthcoming insight for a field-scale application of this nano-delivery antifeedant due to the possible economic production process.

Ecotoxicity of plant extracts and essential oils: A review

Plant-based products such as essential oils and other extracts have been used for centuries due to their beneficial properties. Currently, their use is widely disseminated through a variety of industries and new applications are continuously emerging. For these reasons, they are produced industrially in large quantities and consequently they have the potential to reach the environment. However, the potential effects that these products have on the ecosystems' health are mostly unknown. In recent years, the scientific community started to focus on the possible toxic effects of essential oils and plant extracts towards non-target organisms. As a result, an increasing body of knowledge has emerged. This review describes the current state of the art on the toxic effects that essential oils and plant extracts have towards organisms from different trophic levels, including producers, primary consumers, and secondary consumers. The majority of the studies (76.5%) focuses on the aquatic environment, particularly in aquatic invertebrates (45.1%) with only 23.5% of the studies focusing on the potential toxicity of plant-derived products on terrestrial ecosystems. While some essential oils and extracts have been described to have no toxic effects to the selected organisms or the toxic effects were only observable at high concentrations, others were reported to be toxic at concentrations below the limit set by international regulations, some of them at very low concentrations. In fact, L(E)C₅₀ values as low as 0.0336 mg.L^-1, 0.0005 mg.L^-1 and 0.0053 mg.L^-1 were described for microalgae, crustaceans and fish, respectively. Generally, essential oils exhibit higher toxicity than extracts. However, when the extracts are obtained from plants that are known to produce toxic metabolites, the extracts can be more toxic than essential oils. Overall, and despite being generally considered "eco-friendly" products and safer than they synthetic counterparts, some essential oils and plant extracts are toxic towards non-target organisms. Given the increasing interest from industry on these plant-based products further research using international standardized protocols is mandatory.

Ecotoxicological evaluation of fruit extracts from yerba mate progenies (Ilex paraguariensis a St-Hil.): a natural biopesticide

This study evaluated the biocidal activity of aqueous fruit extracts from Ilex paraguariensis progenies at different ripening stages in two ecotoxicity assays using Pomacea canaliculata juveniles and Danio rerio larvae. Mutagenicity was verified by the Salmonella/microsome assay (TA 98 and TA 100) in the presence and absence of hepatic metabolism in vitro. The results showed that the snails were more sensitive than the larvae to the P.1 progeny extracts in all three evaluated ripening stages. P.3 progeny extracts were the most toxic to Danio rerio larvae after 96 hours of exposure. The toxicity results indicate that the progenies' selection influenced the metabolic contents present in the fruits in all ripening stages over time, indicating high molluscicidal activity for the P.1 progeny. In the Salmonella/microsome assays, the semi-ripe and ripe extracts from progenies P.1 and P.3 showed mainly base pair substitution mutation in assays with metabolism, but at higher doses than the toxic concentrations detected for Danio rerio or Pomacea canaliculata. Therefore, the toxicological investigation of the progenies' extracts can be interesting, given the selection of plant materials influenced the response of the bioassays.

Environmental risks to freshwater organisms from the mycotoxins deoxynivalenol and zearalenone using Species Sensitivity Distributions

In this study, laboratory experiments have addressed the acute toxicity of two common mycotoxins, deoxynivalenol (DON) and zearalenone (ZON), in a range of freshwater organisms (including rotifers Brachionus calyciflorus, insects Chironomus riparius (larvae), crustaceans Daphnia pulex and Thamnocephalus platyurus, cnidarians Hydra vulgaris, molluscs Lymnaea stagnalis (embryos) and Protozoa Tetrahymena thermophila). Acute EC₅₀ values highlight crustaceans as the most sensitive organisms to DON, with T. platyurus having a 24 h EC₅₀ of 0.14 and D. magna having a 48 h EC₅₀ of 0.13 mg DON/L. During exposures to ZON, H. vulgaris and L. stagnalis embryos showed the highest sensitivity; mortality EC₅₀ values were 1.1 (96 h) and 0.42 mg ZON/L (7 d), respectively. Combining these novel invertebrate toxicity results, along with recent published data for freshwater plant and fish toxicity for analysis of Species Sensitivity Distributions, provides freshwater HC₅ values of 5.2 μg DON/L and 43 μg ZON/L, respectively. Using highest reported environmental concentrations and following REACH guidelines, risk ratios calculated here show the risk of ZON to freshwater organisms is low. In contrast, DON may periodically because for concern in streams subject to high agricultural run-off, likely during certain times of year where cereal crops are susceptible to higher fungal infections rates and may pose increased risks due to climate change.

Effects of pollution on freshwater aquatic organisms

This paper presents the reviews of scientific papers published in 2018 issues on the effects of anthropogenic pollution on the aquatic organisms dwelling in freshwater ecosystem at global scale. The first part of the study provides the summary of relevant literature reviews followed by field and survey based studies. The second part is based on categories of different classes/sources of pollutants which affect freshwater organism. This is composed of several sections including metals and metalloids, wastewater and effluents, sediments, nutrients, pharmaceuticals, polycyclic aromatic hydrocarbons, flame retardants, persistent organic pollutants, pharmaceuticals and illicit drugs, emerging contaminants, pesticides, herbicides, and endocrine disruptors. The final part of the study highlights the reviews of published research work on new pollutants such as microplastics and engineered nanoparticles which affect the freshwater organisms. PRACTITIONER POINTS: Heavy metals concentrations should be assessed at nano-scale in aquatic environment. Air pollutants could have long-term effects on freshwater ecosystem. Future studies should focus on bioremediations of freshwater pollution.

Stability of saponin biopesticides: hydrolysis in aqueous solutions and lake waters

Saponins form a group of plant-produced glycosides with potential as biopesticide ingredients. The environmental fate of saponins has never been fully investigated. In the present study, we use QS-18, a specific saponin from Quillaja saponaria as an example, to quantify hydrolysis under different conditions of pH, temperature and water chemical composition. Saponin hydrolysis in buffer solutions was base-catalyzed and followed first-order kinetics. Thus, hydrolysis was slow at pH 5.1 with a half-life of 330 ± 220 d (26 °C), which increases to 0.06 ± 0.01 d at pH 10.0. Hydrolysis rates were highly sensitive to temperature with an activation energy of 56.9 ± 14.2 kJ mol-1 at pH 7.2. In strong contrast, hydrolysis in lake waters (pH 6.4-8.2) produced different patterns with a fast initial dissipation of 25 to 60% of the added saponin within the first five hours, followed by an extremely slow reaction with 25 to 75% unreacted saponin left after reaction times longer than 120 h. The fast dissipation followed by slow hydrolysis in lake water was hypothesized to be attributed to sorption and/or flocculation of saponins by inorganic nanoparticles and/or solutes in the lake water followed by inactivation of hydrolysis due to the sorption/flocculation. The present study demonstrates that saponins may hydrolyze slowly under acidic and cold conditions. In addition, it demonstrates that dissipation kinetics in natural waters may deviate substantially from the kinetics predicted based on laboratory experiments with "clean" buffered solutions. This emphasizes the need for a deeper understanding of the processes affecting the dissipation kinetics of potential toxins under natural conditions, as fate models based on laboratory derived kinetic data may be seriously flawed.

Quinoa Secondary Metabolites and Their Biological Activities or Functions

Quinoa (Chenopodium quinoa Willd.) was known as the "golden grain" by the native Andean people in South America, and has been a source of valuable food over thousands of years. It can produce a variety of secondary metabolites with broad spectra of bioactivities. At least 193 secondary metabolites from quinoa have been identified in the past 40 years. They mainly include phenolic acids, flavonoids, terpenoids, steroids, and nitrogen-containing compounds. These metabolites exhibit many physiological functions, such as insecticidal, molluscicidal and antimicrobial activities, as well as various kinds of biological activities such as antioxidant, cytotoxic, anti-diabetic and anti-inflammatory properties. This review focuses on our knowledge of the structures, biological activities and functions of quinoa secondary metabolites. Biosynthesis, development and utilization of the secondary metabolites especially from quinoa bran were prospected.

Potential of microalgae as biopesticides to contribute to sustainable agriculture and environmental development

The loss of yields from agricultural production due to the presence of pests has been treated over the years with synthetic pesticides, but the use of these substances negatively affects the environment and presents health risks for consumers and animals. The development of agroecological systems using biopesticides represents a safe alternative that contributes to the reduction of agrochemical use and sustainable agriculture. Microalgae are able to biosynthesize a number of metabolites with potential biopesticidal action and can be considered potential biological agents for the control of harmful organisms to soils and plants. The present work aims to provide a critical perspective on the consequences of using synthetic pesticides, offering as an alternative the biopesticides obtained from microalgal biomass, which can be used together with the implementation of environmentally friendly agricultural systems.

Environmental Aspects of the Use of Hedera helix Extract in Bioremediation Process

This paper analyzes the impact of saponins from English ivy leaves on the properties of environmental bacterial strains and hydrocarbon degradation ability. For this purpose, two bacterial strains, Raoultella ornitinolytica M03 and Acinetobacter calcoaceticus M1B, have been used in toluene, 4-chlorotoluene, and α,α,α-trifluorotoluene biodegradation supported by Hedera helix extract. Moreover, theeffects of ivy exposition on cell properties and extract toxicity were investigated. The extract was found to cause minor differences in cell surface hydrophobicity, membrane permeability, and Zeta potential, although it adhered to the cell surface. Acinetobacter calcoaceticus M1B was more affected by the ivy extract; thus, the cells were more metabolically active and degraded saponins at greater amounts. Although the extract influenced positively the cells' viability in the presence of hydrocarbons, it could have been used by the bacteria as a carbon source, thus slowing down hydrocarbon degradation. These results show that the use of ivy saponins for hydrocarbon remediation is environmentally acceptable but should be carefully analyzed to assess the efficiency of the selected saponins-rich extract in combination with selected bacterial strains.

Where does the toxicity come from in saponin extract?

Saponin-rich plant extracts contain bioactive natural compounds and have many applications, e.g. as biopesticides and biosurfactants. The composition of saponin-rich plant extracts is very diverse, making environmental monitoring difficult. In this study various ecotoxicity data as well as exposure data have been collected to explore which compounds in the plant extract are relevant as plant protection agents and furthermore to clarify which compounds may cause undesired side-effects due to their toxicity. Hence, we quantified the toxicity of different fractions (saponins/non-saponins) in the plant extracts on the aquatic crustacean Daphnia magna and zebrafish (Danio rerio) embryos. In addition, we tested the toxicity changes during saponin degradation as well. The results confirm that saponins are responsible for the majority of toxicity (85.1-93.6%) of Quillaja saponaria extract. We, therefore, suggest saponins to be the main target of saponin-rich plant extracts, for instance in the saponin-based biopesticide regulation. Furthermore, we suggest that an abundant saponin fraction, QS-18 from Q. saponaria, can be a key monitoring target to represent the environmental concentration of the saponins, as it contributes with 26% and 61% of the joint toxicity to D. magna and D. rerio, respectively out of the total saponins. The degradation products of saponins are 3-7 times less toxic than the parent compound; therefore the focus should be mainly on the parent compounds.