Chemical composition and mosquito repellency of essential oil of Conyza newii propagated in different geographical locations of Kenya

Molecular pharmacology and therapeutic advances of monoterpene perillyl alcohol

BACKGROUND

Perillyl alcohol (POH) is a aroma monoterpene commonly obtained from various plants' essential oil. Recently, increasing researches have demonstrated that POH may be useful, not only as flavor compound, but also as bioactive molecule because of a variety of biological activities.

PURPOSE

The aim of this review is to summarize the production, pharmacological activities and molecular mechanism, active derivatives, toxicity and parmacokinetics, and industrial application of POH.

METHODS

A systematic search of published articles up to January 2024 in Web of Science, China Knowledge Network, and PubMed databases is conducted using the following keywords: POH, POH derivatives, biological or pharmacological, production or synthesis, pharmacokinetics, toxicity and application.

RESULTS

Biotechnological production is considered to be a potential alternative approach to generate POH. POH provides diverse pharmacological benefits, including anticancer, antimicrobial, insecticidal, antioxidant, anti-inflammatory, hypotensive, vasorelaxant, antinociceptive, antiasthmatic, hepatoprotective effects, etc. The underlying mechanisms of action include modulation of NF-κB, JNK/c-Jun, Notch, Akt/mTOR, PI3K/Akt/eNOS, STAT3, Nrf2 and ERS response pathways, mitigation of mitochondrial dysfunction and membrane integrity damage, and inhibition of ROS accumulation, pro-inflammatory cytokines release and NLRP3 activation. What's more, the proteins or genes influenced by POH against diseases refer to Bax, Bcl-2, cyclin D1, CDK, p21, p53, HIF-1α, AP-1, caspase-3, M6P/IGF2R, PARP, VEGF, etc. Some clinical studies report that intranasal delivery of POH is a safe and effective treatment for cancer, but further clinical investigations are needed to confirm other health benefits of POH in human healthy. Depending on these health-promoting properties together with desirable flavor and safety, POH can be employed as dietary supplement, preservative and flavor additive in food and cosmetic fields, as building block in synthesis fields, as anticancer drug in medicinal fields, and as pesticides and herbicides in agricultural fields.

CONCLUSION

This review systematically summarizes the recent advances in POH and highlights its therapeutic effects and potential mechanisms as well as the clinical settings, which is helpful to develop POH into functional food and new candidate drug for prevention and management of diseases. Future studies are needed to conduct more biological activity studies of POH and its derivatives, and check their clinical efficacy and potential side effects.

Effect of nanostructure lipid carrier of methylene blue and monoterpenes as enzymes inhibitor for Culex pipiens

Solid lipid nanoparticles second generation, nanostructure lipid carrier (NLC), is one of the most important biodegradable nanoparticles. Nanostructure Lipid carrier (NLC) was used to encapsulate methylene blue (MB) dye, carvacrol and citronellal and their efficacy as insecticidal against Culex pipiens (Cx. pipiens) were distinguished. The prepared nanoformulation revealed very good physicochemical properties, especially the homogeneity of the particle size. Transmission electron microscope showed spherical shaped nanoparticles within range less than 200 nm. The prepared NLC-MB-MT system showed a very competitive insecticidal activity and high virulence against the mosquito larvae with higher mortality rate of LC50 of 0.141 µl/mL, in addition to high level of Oxidative stress parameters obtained through all the tested enzymes including hydrogen peroxide (4.8 ppm), protein carbonyl amount (0.12 OD/mg protein), ascorbic acid (0.15 mg) and Superoxide dismutase (SOD) showed strong increasing (0.09 OD/mg protein/min) at 6 µg/mL, respectively. Whereas paradoxical results of the oxidative stress enzymes were obtained from different concentration of nanoformulation that introduce a convenient reason for their potential insecticidal effect. The cytotoxic effect of NLC-MB-MT was evaluated using WI38 human lung cell lines, the LC50 was 6.4 mg/mL. The low cytotoxic reactivity towards the tested cell line makes the NLC-MB-MT nanoformulation has its promising insecticidal efficacy. Molecular docking study for each component were done against acetylcholine esterase protein and accepted binding modes achieved by the three compounds.

Engineering microbes to synthesize functionalized biopolymers

Engineering metabolism of microbes has allowed simultaneous co-production of functional small molecules and biopolymers. This Perspective briefly introduced its working principles and summarized my views on how this approach could...

Monoterpenoid biosynthesis by engineered microbes

Monoterpenoids are C10 isoprenoids and constitute a large family of natural products. They have been used as ingredients in food, cosmetics and therapeutic products. Many monoterpenoids such as linalool, geraniol, limonene and pinene are volatile and can be found in plant essential oils. Conventionally, these bioactive compounds are obtained from plant extracts by using organic solvents or by distillation method, which are costly and laborious if high purity product is desired. In recent years, microbial biosynthesis has emerged as alternative source of monoterpenoids with great promise for meeting the increasing global demand for these compounds. However, current methods of production are not yet at levels required for commercialization. Production efficiency of monoterpenoids in microbial hosts is often restricted by high volatility of the monoterpenoids, a lack of enzymatic activity and selectivity, and/or product cytotoxicity to the microbial hosts. In this review, we summarize advances in microbial production of monoterpenoids over the past three years with particular focus on the key metabolic engineering strategies for different monoterpenoid products. We also provide our perspective on the promise of future endeavors to improve monoterpenoid productivity.

Effectiveness of plant-based repellents against different Anopheles species: a systematic review

Plant-based repellents have been applied for generations in traditional practice as a personal protection approach against different species of Anopheles. Knowledge of traditional repellent plants is a significant resource for the development of new natural products as an alternative to chemical repellents. Many studies have reported evidence of repellant activities of plant extracts or essential oils against malaria vectors worldwide. This systematic review aimed to assess the effectiveness of plant-based repellents against Anopheles mosquitoes. All eligible studies on the repellency effects of plants against Anopheles mosquitoes published up to July 2018 were systematically searched through PubMed/Medline, Scopus and Google scholar databases. Outcomes measures were percentage repellency and protection time. A total of 62 trials met the inclusion criteria. The highest repellency effect was identified from Ligusticum sinense extract, followed by citronella, pine, Dalbergia sissoo, peppermint and Rhizophora mucronata oils with complete protection time ranging from 9.1 to 11.5 h. Furthermore, essential oils from plants such as lavender, camphor, catnip, geranium, jasmine, broad-leaved eucalyptus, lemongrass, lemon-scented eucalyptus, amyris, narrow-leaved eucalyptus, carotin, cedarwood, chamomile, cinnamon oil, juniper, cajeput, soya bean, rosemary, niaouli, olive, tagetes, violet, sandalwood, litsea, galbanum, and Curcuma longa also showed good repellency with 8 h complete repellency against different species of Anopheles. Essential oils and extracts of some plants could be formulated for the development of eco-friendly repellents against Anopheles species. Plant oils may serve as suitable alternatives to synthetic repellents in the future as they are relatively safe, inexpensive, and are readily available in many parts of the world.

Hemi-Synthesis of Chiral Imine, Benzimidazole and Benzodiazepines from Essential Oil of Ammodaucus leucotrichus subsp. leucotrichus

The hemi-synthesis of chiral imine, benzimidazole and benzodiazepine structures is reported by the condensation of (S)-(-)-perillaldehyde, the major phytochemical of Ammodaucus leucotrichus subsp. leucotrichus essential oil, with different amine derivatives of 2,3-diaminomaleonitrile, o-phenylenediamine and 3-[(2-aminoaryl)amino]dimedone. The reaction proceeds in situ at ambient temperature without prior isolation of the natural (S)-(-)-perillaldehyde. Final products precipitate in the ethanolic reaction medium. 2D NMR and single-crystal X-ray diffraction studies were used to unequivocally characterize the structures in solution and in the solid state, respectively. Chiral HPLC analysis confirms the formation of unique enantiomers and diastereomeric mixtures.

Growth-disrupting Murraya koenigii leaf extracts on Anopheles gambiae larvae and identification of associated candidate bioactive constituents

Plant-based constituents have been proposed as eco-friendly alternatives to synthetic insecticides for control of mosquito vectors of malaria. In this study, we first screened the effects of methanolic leaf extracts of curry tree (Murraya koenigii) growing in tropical (Mombasa, Malindi) and semi-arid (Kibwezi, and Makindu) ecological zones of Kenya on third instar An. gambiae s.s. larvae. Extracts of the plant from the semi-arid region, and particularly from Kibwezi, led to high mortality of the larvae. Bioassay-guided fractionation of the methanolic extract of the leaves of the plants from Kibwezi was then undertaken and the most active fraction (20 fold more potent than the crude extract) was then analyzed by Liquid chromatography quadruple time of flight coupled with mass spectrometry (LC-QtoF-MS) and a number of constituents were identified, including a major alkaloid constituent, Neplanocin A (5). Exposure of the third instar larvae to a sub-lethal dose (4.43 ppm) of this fraction over 7-day periods induced gross morphogenetic abnormalities in the larvae, with reduced locomotion, and delayed pupation. Moreover, the few adults that emerged from some pupae failed to fly from the water surface, unlike in the untreated control group. These results demonstrate subtle growth-disrupting effects of the phytochemical blend from M. koenigii leaves on aquatic stages An. gambiae mosquito. The study lays down some useful groundwork for the downstream development of phytochemical blends that can be evaluated for integration into eco-friendly control of An. gambiae vector population targeting the often overlooked but important immature stages of the malaria vector.

Preparation of Ecofriendly Formulations Containing Biologically Active Monoterpenes with Their Fumigant and Residual Toxicities against Adults of Culex pipiens

Different mixtures of monoterpenes (ketone, alcohol, and alkene) were loaded on paper discs and wax and their knockdown activities were evaluated against Culex pipiens adults. Some individual monoterpenes were also evaluated by residual toxicity technique. Citronella oil as a reference was also loaded separately or in combination with monoterpenes on paper discs and wax. The ketone monoterpenes mixture (camphor, menthone, carvone, and fenchone) on paper discs was the most active (KT₅₀ = 17.20 min) followed by ketone monoterpenes with citronella oil (KT₅₀ = 20.79 min) and citronella oil alone (KT₅₀ = 28.72 min). Wax formulations proved that the ketone and alcohol (geraniol, thymol, and menthol) monoterpenes gave the most activity as knockdown (KT₅₀ = 31.79 and 43.39 min, resp.). Alcohol monoterpenes formulation recorded KT₅₀ = 43.39 min. Residual activity of tested individual monoterpenes reported that the menthol was more toxic than camphor and camphene. Generally, this study suggests that the monoterpenes have the properties, which make them used as eco-friendly compounds in the control programs of Cx. pipiens adult. The use of paper discs is more applicable than wax in the adulticidal formulations.

Repellency of Plant Extracts against the Legume Flower Thrips Megalurothrips sjostedti (Thysanoptera: Thripidae)

Megalurothrips sjostedti Trybom is an important pest of cowpea (Vigna unguiculata L.) in Africa. To propose an alternative to chemical control, the repellency of 24 plant extracts was evaluated against adult female thrips of M. sjostedti in the laboratory. Plant extracts in ethanol were separately applied on a filter paper disk in a still air visual cue olfactometer. The results showed highly significant differences in repellency among extract type, concentration and their interactions. We classified the level of repellency into four categories as strong, good, moderate and weak or non- repellent based on hierarchical ascendant classification. We identified Piper nigrum, Cinnamomum zeylanicum, Cinnamomum cassia as strong repellents. Five extracts were classified as good, eight as moderate and the remaining eight extracts were weak or non-repellent. Repellency of the extracts increased with the concentration suggesting that the behavioral response of M. sjostedti was dose-dependent. Mono- and sesquiterpene hydrocarbon compounds from seven highly repellent extracts were identified by gas chromatography-mass spectrometry (GC/MS). The use of repellent extracts could be useful in developing integrated pest management strategies for thrips on legume crops. In this regard, the specific modes of action of the identified compounds need to be investigated to incorporate them into the existing crop protection strategies.