The effects of clove oil on coral: An experimental evaluation using Pocillopora damicornis (Linnaeus)

Clove oil solution (10% clove oil, 90% ethanol) is an anaesthetic that is widely used to catch demersal fish on coral reefs. This study assessed the effects of clove oil solution on colonies of Pocillopora damicornis, a cosmopolitan reef coral. In the laboratory, low concentrations (0.5 ppt) of clove oil solution had no effect on coral colour or photosynthetic efficiency, irrespective of exposure time (1-60 min). Corals treated with high concentrations (50 ppt) of clove oil solution died immediately, including those that were exposed briefly (1 min). Intermediate concentrations (5 ppt) of clove oil solution produced variable results: a 1 min exposure had no effect, a 10 min exposure caused bleaching and reduced photosynthetic efficiency, and a 60 min exposure caused total mortality. To validate these observations, clove oil solution was applied to corals in situ. Sixty-three days after application, corals treated with 10 ml of clove oil solution appeared to be unaffected. It was concluded that (1) limited amounts of clove oil solution are unlikely to harm this coral, and (2) clove oil solution may represent an ‘eco-friendly’ alternative to cyanide for use in the live reef-fish trade.     

Comparative bioactivity of selected extracts from Meliaceae and some commercial botanical insecticides against two noctuid caterpillars, <Emphasis Type="Italic">Trichoplusia ni</Emphasis> and <Emphasis Type="Italic">Pseudaletia unipuncta</Emphasis>

Plant-derived extracts and phytochemicals have long been a subject of research in an effort to develop alternatives to conventional insecticides but with reduced health and environmental impacts. In this review we compare the bioactivities of some plant extracts with those of commercially available botanical insecticides against two important agricultural pests, the cabbage looper, Trichoplusia ni and the armyworm, Pseudaletia unipuncta. Test materials included extracts of Azadirachta indica (neem), A. excelsa (sentang), Melia volkensii, M. azedarach (Chinaberry) and Trichilia americana, (all belonging to the family Meliaceae) along with commercial botanical insecticides ryania, pyrethrum, rotenone and essential oils of rosemary and clove leaf. Most of the extracts and botanicals tested proved to be strong growth inhibitors, contact toxins and significant feeding deterrents to both lepidopteran species. However, there were interspecific differences with T. ni generally more susceptible to the botanicals than the armyworm, P. unipuncta. All botanicals were more inhibitory to growth and toxic (through feeding) to T. ni than to P. unipuncta, except for M. azedarach which was more toxic to P. unipuncta than to T. ni. Athough, pyrethrum was the most toxic botanical to both noctuids, A. indica, A. excelsa, and M. volkensii were more toxic than ryania, rotenone, clove oil and rosemary oil for T. ni. As feeding deterrents, pyrethrum was the most potent against T. ni, whereas A. indica was the most potent against the armyworm. Based upon growth inhibition, chronic toxicity, and antifeedant activity, some of these plant extracts have levels of activity that compare favorably to botanical products currently in commercial use and have potential for development as commercial insecticides.     

不同麻醉方法对降低草鱼捕捉应激的作用

正应激(Stress)指生物受到外源或内源刺激后内稳态改变而产生的一系列反应~[1]。在鱼类养殖中,各种操作对鱼产生的惊扰及环境变化均会导致鱼类应激~[2,3]。应激使鱼类代谢强度增加,免疫和生长性能下降~[4,5]。有关人类和哺乳动物的应激研究已积累了大量的资料,相比之下,鱼类应激方面     

Antioxidant effects of clove bud (Syzygium aromaticum) extract used with different extenders on ram spermatozoa during cryopreservation

Clove bud (Syzygium aromaticum) extract was added at concentrations of 0, 35, 75, and 115 μg/ml to ovine semen extenders in order to investigate the antioxidant activities of clove bud extract and its effects on semen quality parameters after cryopreservation of ram spermatozoa. The basic extender was composed of Tris, egg yolk, and glycerol. Two other extenders were prepared by substitution of egg yolk with either LDL or egg yolk + SDS. The DPPH inhibition test was employed to assess the antioxidant activity of clove bud extract. Results showed that, compared to vitamin E, clove bud extract had a higher antioxidant activity. Better sperm motility and movement characteristics (P < 0.05) were observed in the semen diluted with medium containing egg yolk + SDS than in that containing egg yolk and LDL. Progressive motility and movement characteristics of the sperm were significantly improved (P < 0.05) by adding 35 and/or 75 μg/ml of clove bud extract to semen extenders. Sperm viability and plasma membrane integrity were also higher (P < 0.05) in the semen exposed to medium containing egg yolk + SDS and 75 μg of clove buds extract after cryopreservation processes. Higher levels of clove bud extract, however, had adverse effects on all the sperm quality parameters and significantly reduced (P < 0.05) the motility, movement parameters, viability, and plasma membrane integrity of ovine sperm. It was concluded that the clove bud extract had an antioxidant potential that makes it useful for addition to semen extenders and that the best results are obtained with a maximum clove bud extract of 75 μg/ml. Moreover, the combination of egg yolk and a detergent was found to improve sperm quality after the cooling and freeze–thawing processes.     

Bioactivity of selected essential oils and some components on Listeria monocytogenes biofilms

Listeria monocytogenes is a Gram-positive bacterium, able to survive and grow in water, soil, agricultural products, various foods and the food-processing environment. The ubiquitous nature of the organism, coupled with its ability to colonise food-processing surfaces by forming biofilms, causes it to be of a major concern to the industry. Increased foodborne pathogen resistance and negative consumer perceptions regarding the use of synthetic bacteriocides, has resulted in natural antimicrobials being sourced from the plant kingdom. The listerial antibiofilm activities of Syzygium aromaticum (clove), Mentha spicata (spearmint), Lippia rehmannii and Cymbopogon citratus (lemongrass) essential oils and their major components were evaluated using the crystal violet assay and confocal scanning laser microscopy. Listerial biofilms treated with S. aromaticum or M. spicata essential oils, or the pure compounds nerol and citral, exhibited a similar biofilm biomass to the positive control. However, the essential oils of lemongrass, L. rehmannii, eugenol and R-carvone caused biofilm enhancement, rather than inhibition. L. rehmannii and lemongrass essential oils did not display any antibiofilm properties. Results obtained were confirmed by microscopic observations indicating either a reduction (inhibition) or an increase (enhancement) in biofilm biomass when exposed to the essential oils or pure compounds. The present study revealed that M. spicata and S. aromaticum essential oils as well as pure citral and nerol are good candidates for further development of ecofriendly disinfectants.     

Antifungal activities of essential oils applied by dip-treatment on areca palm (Areca catechu) leaf sheath and persistence of their potency upon storage

The antifungal activities of cinnamon oil, clove oil, anise oil, and peppermint oil, and their main components (cinnamaldehyde, eugenol, trans-anethole, and menthol, respectively) against molds identified from areca palm leaf sheath (Mucor dimorphosporus, Penicillium sp., Aspergillus niger, and Rhizopus sp.) were investigated. An agar dilution method was employed to determine the minimum inhibitory concentration (MIC) of essential oils and their main components. Zone inhibition tests and the inhibitory effect of the leaf sheath dip-treated with essential oils against those molds were examined. Major components of essential oils on the leaf sheath during storage were quantified by gas chromatography analysis. The MIC values of essential oils on agar and on the leaf sheath were identical. With an MIC of 50 ??g ml⁻¹, cinnamon oil had the strongest inhibitory effect. At their MICs the oils were capable of providing protection against mold growth on the leaf sheath for at least 12 weeks during storage at 25 °C and 100% RH. Scanning electron microscope examination showed that essential oils prevented spore germination. Except for menthol in peppermint oil, the main components of the essential oils, which were fairly stable over the storage period, largely contributed to the antifungal activity.     

The effects of clove oil on the enzyme activity of Varroa destructor Anderson and Trueman (Arachnida: Acari: Varroidae)

Varroa destructor, a key biotic threat to the Western honey bee, has played a major role in colony losses over the past few years worldwide. Overuse of traditional acaricides, such as tau-fluvalinate and flumethrin, on V. destructor has only increased its tolerance to them. Therefore, the application of essential oils in place of traditional pesticides is an attractive alternative, as demonstrated by its high efficiency, lack of residue and tolerance resistance. To study the acaricidal activity of essential oils, we used clove oil (Syzygium aromaticum L.), a typical essential oil with a wide range of field applications, and examined its effects on the enzyme activities of Ca²⁺-Mg²⁺-ATPase, glutathione-S-transferase (GST) and superoxide dismutase (SOD) and its effects on the water-soluble protein content of V. destructor body extracts after exposure to 0.1 μl and 1.0 μl of clove oil for 30 min. Our results showed that the water-soluble protein content significantly decreased after the treatments, indicating that the metabolism of the mites was adversely affected. The bioactivity of GSTs increased significantly after a low dosage (0.1 μl) exposure but decreased at a higher dosage (1.0 μl), while the activities of SOD and Ca²⁺-Mg²⁺-ATPase were significantly elevated after treatments. These results suggest that the protective enzyme SOD and detoxifying enzymes Ca²⁺-Mg²⁺-ATPase and GST contributed to the stress reaction of V. destructor to the essential oils and that the detoxification ability of V. destructor via GST was inhibited at higher dosages. Our findings are conducive to understanding the physiological reactions of V. destructor to treatment with essential oils and the underlying mechanisms behind the acaricidal activities of these natural products.     

The larvicidal effect of neemazal T/S,clove oil and ginger oil on tomato leafminer,Tuta absoluta compared to coragen

The present study aimed to evaluate the toxicity and biochemical changes of Tuta absoluta 3^rd instar larvae affected by neemazal T/S, clove oil and ginger oil. These compounds were evaluated compared to the recommended pesticide, Coragen 20% SC. by means of sublethal concentrations, LC₂₅ and LC₅₀ under constant laboratory conditions. Results showed that neemazal T/S is more toxic than detected oils compared with higher toxicity of coragen with LC₅₀ values of 57.52, 159.94, 633.38 and 930.71 μg mL^?1 for coragen, neemazal, ginger oil and clove oil, respectively. There were highly significant differences between all treatments and untreated larvae. Neemazal possessed the greatest effect on activity level of most physiological parameters than selected oils. Larval content of digestive enzymes was decreased significantly 48 h after all treatments except for lipase, α-esterase and β-esterase (in case of coragen and clove oil). Also, total proteins, total carbohydrates, total lipids and total free amino acids take the same trend. Based on this study, these sublethal doses caused a significantly dose-dependent perturbation in determined components.     

Preparation of vanillin by bioconversion in a silicon rubber membrane bioreactor

In this study, the bioconversion of clove oil into vanillin using soybean lipoxygenase (SBLOX) as biocatalyst was investigated in a silicon rubber membrane bioreactor (SRMBR) and shaking flasks. High performance liquid chromatography (HPLC) analysis indicated that the vanillin concentration was 8.14 mg/L after 36 h of conversion in a shaking flask. It reached up to 121.53 mg/L in the receiving solution after 36 h of conversion in the SRMBR. The conversion rate of clove oil was 0.033% in the shaking flask. It was 1.01% in the SRMBR. The peak area ratio of vanillin in the receiving solution of the SRMBR was 70.08%. By adding activated carbon into the conversion broth of the SRMBR, the vanillin concentration in the receiving solution reached 140.27 mg/L, the conversion rate of clove oil increased to 1.14%, and the peak area ratio of vanillin in the receiving solution reached 93.53%.     

Bioactivity of semisynthetic eugenol derivatives against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae infesting maize in Colombia

The anti-acetylcholinesterase, larvicidal, antifeedant activities and general toxicity of 15 semisynthetic eugenol derivatives based on clove oil (including the own oil), were evaluated against the maize armyworm, Spodoptera frugiperda (J.E. Smith). Therefore, promising eugenol molecules were classified with larvicidal, anti-acetylcholinesterase and antifeedant activities for controlling this pest. During structure–activity relationship studies and physicochemical profile analysis, it was found that among tested molecules 1–15, eugenol 1, prenyl eugenol 4, isoeugenol 8 and isoeugenol acetate 11 exhibited lethal effects LD₅₀ at concentrations <1 mg/g of insect. On the other hand, eugenol 1, metallyl eugenol 3, isoeugenol 8 and isoeugenol acetate 11 showed a good antifeedant activity (CE₅₀ = 158–209 µg/mL) with a high antifeedant index (70–78%) at concentration 1000 µg/mL, possessing a weak anti-acetylcholinesterase activity (IC₅₀ = 21–31 μg/mL). According to their ecotoxicological profiles (LC₅₀ = 2033.1–6303.8 µg/mL on Artemia salina larvae), isoeugenol 8 and its acetate derivative 11 could be potential used in control of the growth, feeding, or reproduction of S. frugiperda larvae, acting as moderate insecticidal acetylcholinesterase inhibitors and/or antifeedant molecules. Such structure–activity relationship studies could stimulate the identification of lead structures from natural sources for the development of larvicidal and deterrent products against S. frugiperda and related insect pests.