A review of botanical phytochemicals with mosquitocidal potential.

The aim of this study was to investigate the larvicidal potential of the hexane, chloroform, ethyl acetate, acetone, methanol, and aqueous leaf extracts of Nelumbo nucifera Gaertn. (Nymphaeaceae) and synthesized silver nanoparticles using aqueous leaf extract against fourth instar larvae of Anopheles subpictus Grassi and Culex quinquefasciatus Say (Diptera: Culicidae). Nanoparticles are being used in many commercial applications. It was found that aqueous silver ions can be reduced by aqueous extract of plant parts to generate extremely stable silver nanoparticles in water. The results recorded from UV–vis spectrum, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared support the biosynthesis and characterization of silver nanoparticles. Larvae were exposed to varying concentrations of plant extracts and synthesized silver nanoparticles for 24 h. All extracts showed moderate larvicidal effects; however, the maximum efficacy was observed in crude methanol, aqueous, and synthesized silver nanoparticles against the larvae of A. subpictus (LC50 = 8.89, 11.82, and 0.69 ppm; LC90 = 28.65, 36.06, and 2.15 ppm) and against the larvae of C. quinquefasciatus (LC50 = 9.51, 13.65, and 1.10 ppm; LC90 = 28.13, 35.83, and 3.59 ppm), respectively. These results suggest that the leaf methanol, aqueous extracts of N. nucifera, and green synthesis of silver nanoparticles have the potential to be used as an ideal eco-friendly approach for the control of the A. subpictus and C. quinquefasciatus. This is the first report on the mosquito larvicidal activity of the plant extracts and synthesized nanoparticles.

Synthesis of silver nanoparticles using Nelumbo nucifera leaf extract and its larvicidal activity against malaria and filariasis vectors.

Tyrosinase is a copper-containing enzyme, which is widely distributed in microorganisms, animals and plants and is a key enzyme in melanin biosynthesis, involved in determining the color of mammalian skin and hair. In addition, unfavorable enzymatic browning of plant-derived foods by tyrosinase causes a decrease in nutritional quality and economic loss of food products. The inadequacy of current conventional methods to prevent tyrosinase action encourages researchers to seek new potent tyrosinase inhibitors for food and cosmetics. This article presents a study on the importance of tyrosinase, biochemical characteristics, type of inhibitions, activators from various natural sources with its clinical and industrial importance in recent prospects is discussed in this paper.

Naturally occurring tyrosinase inhibitors: mechanism and applications in skin health, cosmetics and agriculture industries

The type and amount of melanin synthesized by the melanocyte, and its distribution pattern in the surrounding keratinocytes, determines the actual color of the skin. Melanin forms through a series of oxidative reactions involving the amino acid tyrosine in the presence of the enzyme tyrosinase. Tyrosinase catalyses three different reactions in the biosynthetic pathway of melanin in melanocytes: the hydroxylation of tyrosine to l-DOPA and the oxidation of l-DOPA to dopaquinone; furthermore, in humans, dopaquinone is converted by a series of complex reactions to melanin. Among the skin-lightening and depigmenting agents, magnesium-l-ascorbyl-2-phosphate (MAP), hydroxyanisole, N-acetyl-4-S-cysteaminylphenol, arbutin (hydroquinone-beta-d-glucopyranoside) and hydroquinone (HQ) are the most widely prescribed worldwide. However, with reports of potential mutagenicity and epidemics of ochronosis, there has been an increasing impetus to find alternative herbal and pharmaceutical depigmenting agents. A review of the literature reveals that numerous other depigmenting or skin-lightening agents are either in use or in investigational stages. Some of these, such as kojic, glycolic and azelaic acids, are well known to most dermatologists. Others have been discovered and reported in the literature more recently. Several depigmentation and lightening agents are discussed, including their historical background, biochemical characteristics, type of inhibition and activators from various sources. In addition, the clinical importance of mushroom tyrosinase as a recent prospect is discussed in this paper.

Survey and mechanism of skin depigmenting and lightening agents.

Chemical compositions of leaf essential oils from eight provenances of indigenous cinnamon (Cinnamomum osmophloeum Kaneh.) were compared. According to GC-MS and cluster analyses, the leaf essential oils of the eight provenances and their relative contents were classified into five chemotypescinnamaldehyde type, linalool type, camphor type, cinnamaldehyde/cinnamyl acetate type, and mixed type. The larvicidal activities of leaf essential oils and their constituents from the five chemotypes of indigenous cinnamon trees were evaluated by mosquito larvicidal assay. Results of larvicidal tests demonstrated that the leaf essential oils of cinnamaldehyde type and cinnamaldehyde/cinnamyl acetate type had an excellent inhibitory effect against the fourth-instar larvae of Aedes aegypti. The LC50 values for cinnamaldehyde type and cinnamaldehyde/cinnamyl acetate type against A. aegypti larvae in 24 h were 36 ppm (LC90 = 79 ppm) and 44 ppm (LC90 = 85 ppm), respectively. Results of the 24-h mosquito larvicidal assays a...

Chemical Composition and Mosquito Larvicidal Activity of Essential Oils from Leaves of Different Cinnamomum osmophloeum Provenances

Mosquito larvicidal activity of Piper longum fruit-derived materials against the fourth-instar larvae of Aedes aegypti was examined. A crude methanol extract of P. longum fruits was found to be active against the larvae, and the hexane fraction of the methanol extract showed a strong larvicidal activity of 100% mortality. The biologically active component of P. longum fruits was characterized as pipernonaline by spectroscopic analyses. The LC(50) value of pipernonaline was 0.25 mg/L. The toxicity of pipernonaline is comparable to that of pirimiphos-methyl as a mosquito larvicide. In tests with available components derived from P. longum, no activity was observed with piperettine, piperine, or piperlongumine.

A piperidine amide extracted from Piper longum L. fruit shows activity against Aedes aegypti mosquito larvae.

Fungicidal activity of pipernonaline, a piperidine alkaloid derived from long pepper, Piper longum L., against phytopathogenic fungi

Toxicity of quinones against two-spotted spider mite and three species of aphids in laboratory and greenhouse conditions

This study examined the insecticidal effects of Sebastiania corniculata materials against Laodelphax striatellus, Nilaparvata lugens, and Sogatella furcifera. Based on the lethal dose50 (LD50) values, the chloroform fraction of S. corniculata showed the most potential activity against L. striatellus (1.09 μg/female), N. lugens (4.46 μg/female), and S. furcifera (2.32 μg/female). Therefore, we purified the active component of the chloroform fraction, using various chromatographies, and identified it as 8-hydroxyquinoline. To establish the structure-activity relationships, we tested 8-hydroxyquinoline and its derivatives against the 3 planthopper species. Based on 48 h LD50 values, isoquinoline and 6-methoxyquinoline were the most effective against the 3 species. 8-Hydroxyquinoline, 4-methylquinoline, 6-methylquinoline, and 8-hydroxy-2-methylquinoline showed high insecticidal effects. These results indicate that changing the nitrogen atom’s position in quinoline’s pyridine ring plays an important role in the insecticidal effects. We found a high correlation between the introduction of a functional group into the quinoline structure and toxicity against the 3 planthoppers. Our results indicate these insecticidal effects seem to require quinoline derivatives containing hydroxyl (R4 position), methyl (R2 and R3 position), and methoxy (R3 position) groups and a structural isomer of quinoline and suggest that these derivatives may be useful as new preventative agents against the damage caused by a wide range of pests in rice farming areas.

Insecticidal Properties of Euphorbiaceae: Sebastiania corniculata-derived 8-Hydroxyquinoline and Its Derivatives against Three Planthopper Species (Hemiptera: Delphacidae)

Acaricidal activities of Thymus vulgaris leaf-derived materials were examined using a fumigant and filter paper bioassay and compared to those of monoterpene alcohols and the synthetic acaricide, benzyl benzoate. In the fumigant bioassay, the LD50 value of the T. vulgaris oil was 3.1 and 3.7 μg/cm2 against Dermatophagoides farinae and D. pteronyssinus, respectively. Active constituent of T. vulgaris leaves was purified by various chromatographies and identified as carvacrol by various spectra. When the relative toxicity against Dermatophagoides spp. was measured using a fumigant and filter paper bioassay, carvacrol was 4.1 to 8.0-fold more toxic than benzyl benzoate, but less toxic than β-citronellol. Specifically, in case of acaricidal activity of β-citronellol was 32.2 to 63.1-fold higher than that of benzyl benzoate against Dermatophagoides spp. Taken as a whole, the filter paper bioassay with all tested compounds leading to more effective acaricidal activity than the fumigant bioassay. In addition, the results of this study revealed that carvacrol and the two monoterpene alcohols (β-citronellol and borneol) were generally higher than those of commercial acaricides such as benzyl benzoate against the two mite species. These results indicate that carvacrol, β-citronellol, and borneol could be useful as a new preventive agent against damage caused by arthropod pests.

Sang-Guei Lee

Papers

A piperidine amide extracted from Piper longum L. fruit shows activity against Aedes aegypti mosquito larvae.

Fungicidal activity of pipernonaline, a piperidine alkaloid derived from long pepper, Piper longum L., against phytopathogenic fungi

Toxicity of quinones against two-spotted spider mite and three species of aphids in laboratory and greenhouse conditions

Insecticidal Properties of Euphorbiaceae: Sebastiania corniculata-derived 8-Hydroxyquinoline and Its Derivatives against Three Planthopper Species (Hemiptera: Delphacidae)

Acaricidal effects of Thymus vulgaris leaf-derived materials and monoterpene alcohols against Dermatophagoides spp.