Chemical composition and insecticidal activity of the essential oil from Helichrysum faradifani endemic to Madagascar

Research progress on pharmacological properties and application of probiotics in the fermentation of Scutellaria baicalensis Georgi

Scutellaria baicalensis Georgi is a medicinal herb with a rich history of use in traditional Chinese medicine. This review concentrates on the chemical constituents of Scutellaria baicalensis Georgi, with a particular emphasis on flavonoids such as baicalin, baicalein, and wogonin. Additionally, it examines the effects of probiotic fermentation on the plant's chemical profile and pharmacological actions. Evidence suggests that probiotic fermentation markedly modifies the bioactive components of Scutellaria baicalensis Georgi, thereby augmenting its medicinal potency. The paper delves into the mechanisms by which the primary active constituents of Scutellaria baicalensis Georgi are altered during fermentation and how these changes influence its pharmacological properties. This review aims to lay a theoretical groundwork for the clinical utilization of Scutellaria baicalensis Georgi and the formulation of innovative therapeutic approaches.

Volatiloma analyses of four South African Helichrysum spp. grown in Italy

The volatiloma of four Helichrysum species (H. anomalum, H reflexum, H. retortum and H. rugulosum) was analysed here for the first time by GC-MS for a chemotaxonomic contribution to this genus. Sesquiterpene hydrocarbons (SHs) prevailed in the aroma profile (VOCs) of H. reflexum, H. rugulosum and H. anomalum (74.7%, 93.6% and 41.6%, respectively), even though the main compounds were different (β-caryophyllene, α-humulene and α-copaene, respectively). The VOCs of H. retortum showed a high percentage of aliphatic hydrocarbons (NTs, 77.7%) mainly represented by octyl ether. The essential oil composition of each of H. rugulosum and H. retortum followed the same trend as VOCs related to the main class (SHs and NTs, respectively). In H. reflexum EO, the SHs were replaced by oxygenated sesquiterpenes (OS, 49.0%) with caryophyllene oxide as the main compound, while in H. anomalum the SHs were swapped in NTs (37.3%).

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.

Evaluation of Drimys winteri (Canelo) Essential Oil as Insecticide against Acanthoscelides obtectus (Coleoptera: Bruchidae) and Aegorhinus superciliosus (Coleoptera: Curculionidae)

Adverse effects caused by synthetic pesticides have increased interest in plant-derived insecticidal compounds, in particular essential oils, as a more compatible and ecofriendly alternative for pest control of economic importance. For this reason, the essential oil isolated from leaves and shoots of Drimys winteri (J.R. Forster & G. Forster)-also named canelo (CEO)-was investigated for its chemical profile and insecticidal action against Acanthoscelides obtectus (Say)-one of the most important post-harvest pests of dry beans in the world-and Aegorhinus superciliosus (Guérin)-a significant pest of fruit trees in Chile. The analysis by gas chromatography, paired with mass spectrometry (GC/MS) determined 56 compounds, corresponding to 92.28% of the detected compounds. Elemol (13.54%), γ-eudesmol (11.42%), β-eudesmol (8.49%), α-eudesmol (6.39%), α-pinene (7.92%) and β-pinene (5.17%) were the most abundant. Regarding the bioactivity of the CEO, the results demonstrated toxicological effects against A. obtectus. A concentration of 158.3 µL L^-1 had a mortality rate of 94% after 24 h exposure. The LC₅₀ and LC₉₀ values at 24 h were 60.1 and 163.0 µL L^-1. Moreover, behavioral bioassays showed a repellent effect against A. superciliosus with a dose of one microliter of CEO. Both sexes of the raspberry weevil stayed for very short times in the treated area with the oil (<0.8 min), showing a homogeneous repellency in the species. The overall data suggest that canelo leaves and shoots essential oil has an insecticide effect and is worth exploring to better understand the synergistic relationship between the compounds present in the essential oil.

Chemical Composition of Aerial Parts Essential Oils from Six Endemic Malagasy Helichrysum Species

The essential oils of six endemic Malagasy Helichrysum species were investigated by GC (RI), GC–MS and ¹³C NMR spectrometry. In total, 153 compounds were identified accounting for 90.8% to 99.9% of the total composition. The main constituents were α-pinene for H. benthamii, 1,8-cineole for H. dubardii, (E)-β-caryophyllene for H. indutum, and H. bojerianum. H. diotoides essential oil was characterized by the presence of two lilac alcohols and four lilac acetates whereas H. hirtum essential oil exhibited an atypical composition with 7β-H-silphiperfol-5-ene, 7-epi-subergorgiol, and 7-epi-silphiperfol-5-en-13-oic acid as major components.

Insecticidal and mosquito repellent efficacy of the essential oils from stem bark and wood of Hazomalania voyronii

ETHNOPHARMACOLOGICAL RELEVANCE

The use of Hazomalania voyronii, popularly known as hazomalana, to repel mosquitoes and resist against insect attacks is handed down from generation to generation in Madagascar. In the present study, we investigated the ability of the essential oils (EOs) obtained from the stem wood, fresh and dry bark of H. voyronii to keep important mosquito vectors (Aedes aegypti and Culex quinquefasciatus) away, as well as their toxicity on three insect species of agricultural and public health importance (Cx. quinquefasciatus, Musca domestica and Spodoptera littoralis).

MATERIALS AND METHODS

Hydrodistillation was used to obtain EOs from stem wood, fresh and dry bark. The chemical compositions were achieved by gas chromatography-mass spectrometry (GC-MS). Toxicity assays using stem wood and bark EOs were performed on larvae of Cx. quinquefasciatus and S. littoralis, and adults of M. domestica by WHO and topical application methods, respectively. Mosquito repellent activity of the most effective EO, i.e. the bark one, was determined on human volunteers by arm-in-cage tests, and results were compared with that of the commercial repellent N,N-ddiethyl-m-toluamide (DEET).

RESULTS

The H. voyronii EOs were characterized by oxygenated monoterpenes with perilla aldehyde (30.9-47.9%) and 1,8-cineole (19.7-33.2%) as the main constituents. The fresh and dry bark EOs were the most active on Cx. quinquefasciatus and S. littoralis larvae, respectively, with LC₅₀/LD₅₀ of 65.5  mg L^-1, and 50.5  μg larva^-1; the EOs from wood and fresh bark displayed the highest toxicity on M. domestica (LD₅₀ values 60.8 and 65.8 μg adult^-1, respectively). Repellence assay revealed an almost complete protection (>80%) from both mosquito species for 30 min when pure fresh bark EO was applied on the volunteers' arm, while DEET 10% repelled >80% of the mosquitoes up to 120 min from application.

CONCLUSION

The traditional use of the bark EO to repel insects has been demonstrated although an extended-release formulation based on H. voyronii EOs is needed to increase the repellent effect over time. A wide spectrum of insecticidal activity has been provided as well, suggesting a possible use of H. voyronii EOs in the fabrication of green repellents and insecticides useful to control mosquito vectors and agricultural pests.

New solutions using natural products

Most antibiotics are derived from natural products, like penicillin, as well as recent insecticides, like pyrethroids. Secondary metabolites are produced by plants as ecological chemical mediators, and can therefore possess intrinsic physiological properties against other organisms. These benefits are far from being fully explored. In particular, attention is here focused on the multipurpose neem tree (Azadirachta indica), reporting several experiments of applications in the field of seed oil and neem cake. The latter product seems to be promising because of the low cost, the possible production on a large scale, and the selection of effects in favor of beneficial organisms. Neem cake is able to act on different sites, as required by integrated pest management. Several utilizations of neem products are reported and their potentiality evidenced. Some considerations in this chapter may appear distant from the title of the book, but only by applying the general natural rules can the reason of the single phenomenon be understood. Other studies on resistance mechanisms of Plasmodium are enabling new possible methods of control always based on natural products activity.

The desert wormwood (Artemisia herba-alba) - From Arabian folk medicine to a source of green and effective nanoinsecticides against mosquito vectors

The development of eco-friendly and effective insecticides is crucial for public health worldwide. Herein, we focused on the desert wormwood (Artemisia herba-alba), a plant widely used in Arabian traditional medicine, as a source of green nanoinsecticides against mosquito vectors, as well as growth inhibitors to be employed against microbial pathogens. Ag nanoparticles (AgNPs) fabricated with the A. herba-alba extract were tested on Indian and Saudi Arabian strains of Anopheles, Aedes and Culex mosquitoes. The chemical profile of the A. herba-alba extract was determined by LC-DAD-MS and ¹H NMR studies. Then, AgNPs were studied using UV-vis spectroscopy, XRD, FTIR spectroscopy, TEM, and EDX analyses. Artemisia herba-alba-synthesized AgNPs showed high larvicidal toxicity against mosquitoes from both Indian and Saudi Arabian strains. LC₅₀ of AgNPs against Indian strains was 9.76 μg/ml for An. stephensi, 10.70 μg/ml for Ae. aegypti and 11.43 μg/ml for Cx. quinquefasciatus, whereas against Saudi Arabian strains it was 33.58 μg/ml for Ae. aegypti and 38.06 μg/ml for Cx. pipiens. In adulticidal experiments, A. herba-alba extract showed LC₅₀ ranging from 293.02 to 450 μg/ml, while AgNP LC₅₀ ranged from 8.22 to 27.39 μg/ml. Further, low doses of the AgNPs inhibited the growth of selected microbial pathogens. Overall, A. herba-alba can be further considered as a source of phytochemicals, with special reference to saponins, for effective and prompt fabrication of AgNPs with relevant insecticidal and bactericidal activity against species of high public health importance.