• Journal of the Korean Wood Science and Technology
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• v.50 no.4
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• pp.272-282
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• 2022

The essential oil extracted from Citrus × natsudaidai (Yu. Tanaka) Hayata peels is known to have various biological properties. However, the chemical composition of essential oil is influenced by the ripening stages of fruits, which then affects related biological activities. This study investigates the antioxidant activities of essential oils extracted from Citrus × natsudaidai peels at different ripening stages (immature, mature, and overripe). The essential oils were extracted using the hydro-distillation method. As a result of gas chromatography-mass spectrometry (GC-MS) analysis, d-limonene was dominant and was increased as matured. However, 𝛄-terpinene was decreased. The antioxidant properties and their total phenolic content (TPC) were influenced by the ripening stages. The TPC was highest in the immature stage of essential oil (1,011.25 ± 57.15 mg GAE/100 g). 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was excellent in the immature stage (EC₅₀ = 15.91 ± 0.38 mg/mL). 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity was superior in overripe stage (EC₅₀ = 20.43 ± 0.37 mg/mL). The antioxidant activity measured using ferric reducing antioxidant power (FRAP) assay showed higher values for the essential oils in immaturity (1,342.37 ± 71.07 mg Fe²⁺/100 g). Comprehensively, the essential oil in the immature stage showed the best antioxidant activity. Finally, knowing the chemical composition and antioxidant activity at different ripening stages will provide data for selecting the right fruit.

• Journal of Microbiology and Biotechnology
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• v.18 no.3
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• pp.497-502
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• 2008

The essential oil from the cones of Pinus koraiensis was prepared after removing the seeds, and its chemical composition analyzed using gas chromatography-mass spectrometry (GC-MS). Hydrodistillation of the P. koraiensis cones yielded 1.07% (v/w) of essential oil, which was almost three times the amount of essential oil extracted from the needles of the same plant. Moreover, the antimicrobial activities of the oil against the growth of Gram-positive bacteria, Gram-negative bacteria, and fungi were evaluated using the agar disc diffusion method and broth microdilution method. Eighty-seven components, comprising about 96.8% of the total oil, were identified. The most abundant oil components were limonene (27.90%), ${\alpha}$-pinene (23.89%), ${\beta}$-pinene (12.02%), 3-carene(4.95%), ${\beta}$-myrcene (4.53%), isolongifolene (3.35%), (-)-bornyl acetate (2.02%), caryophyllene (1.71%), and camphene (1.54%). The essential oil was confirmed to have significant antimicrobial activities, especially against pathogenic fungal strains such as Candida glabrata YFCC 062 and Cryptococcus neoformans B 42419. Therefore, the present results indicate that the essential oil from the cones of Pinus koraiensis can be used in various ways as a nontoxic and environmentally friendly disinfectant.

• The Journal of Korean Association of Computer Education
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• v.20 no.3
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• pp.1-11
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• 2017

In this research, we applied the problem-based learning (PBL) on a college computer system programming course and analyzed how it affected students' academic achievement and job essential skills. After course contents analysis, we divided the course into three subsections and provided three problems for each subsection. For measuring the effect on academic achievement, we compared with scores of the previous year's students. For job essential skills, we used Korea collegiate essential skills assessment (K-CESA) operated by Korea Research Institute for Vocational Education & Training. Students took the test twice before and after the course. Results showed that PBL has positive effects on both academic achievement and job essential skills.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.2
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• pp.128-133
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• 2000

This study was carried out to investigate the effect of forms and levels of nitrogen fertilizer on plant growth and essential oil production of Agastache rugosa. Calcium nitrate had more influenced on length and width of leaves and lateral branch length than did urea. When nitrogen fertilizer level was increased from 12 kgN/I0a to 24kgN/I0a, plant growth was stimulated and dry matter of leaf and inflorescence were increased. Top dry matter of plant with calcium nitrate treatment (38.4 g) was heavier than that of urea treatment (32.8 g). Interactions among accession and nitrogen form and nitrogen rate were not significantly different for top dry matter. The forms and rate of nitrogen fertilizer did not affect estragole content. The estragole contents was higher in leaf (91.8%) than that of inflorescence (81.3%). While the essential oil content was not affected by different nitrogen forms, nitrogen level affected the essential oil contents positively by increasing dry matter. Essential oil yield was not affected by accession or nitrogen form, but by nitrogen rate. With increasing N application from 12kgN/I0a to 24 kgN/I0a, essential oil yield was increased by 95.8 %.

• The Plant Pathology Journal
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• v.23 no.2
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• pp.97-102
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• 2007

A total of 39 essential oils were tested for antifungal activities as volatile compounds against five phytopathogenic fungi at a dose of 1 ${\mu}l$ per plate. Five essential oils showed inhibitory activities against mycelial growth of at least one phytopathogenic fungus. Origanum vulgare essential oil inhibited mycelial growth of all of the five fungi tested. Both Cuminum cyminum and Eucalyptus citriodora oils displayed in vitro antifungal activities against four phytopathogenic fungi except for Colletotrichum gloeosporioides. The essential oil of Thymus vulgaris suppressed the mycelial growth of C. gloeosporioides, Fusarium oxysporum and Rhizoctonia solani and that of Cymbopogon citratus was active to only F. oxysporum. The chemical compositions of the five active essential oils were determined by gas chromatography-mass spectrometry. This study suggests that both E. citriodora and C. cyminum oils have a potential as antifungal preservatives for the control of storage diseases of various crops.

• The Journal of Pediatrics of Korean Medicine
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• v.12 no.1
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• pp.1-39
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• 1998

Recently, Many people begin to be interested in aromatherapy and as the effects of aromatherapy(or essential oils) are being known widely. as aromatherapy is regarded as a new effective method of natural therapy in treatment of human Aromatherapy is defined, 'therapy that methods of inhalation, massage, drink is used, to medical effects, physical effects, psychologic effects.' In this paper, By investigating differences and commons between useful essential oils that are used frequently in children's aroma care and herb medicine, digesting several aromathrapy books and 'Boncho(Herbs)'books, I can obtain such conclusions. 1. Most essential oils mainly can cure skin trobles, psychological troubles. 2. Systemic curing ability of essential oils in human body are urination in reproductive system, sediation in psychological system, sweating in circulation system, anti-inflammation in respiratory system, tonic in digestive system, pain-killing in musclular system, stimulating-immunity in immune system, menstruation in OB & GY3. Herb medicine correspond to essential oils are Chamomile(母:菊: Moguk), Ginger(生畺: Saengang), Frankinsense(乳香: Yuhyang), Eucalyptus(按葉: Anyup), Rosemary(迷迭: Mizil), Rose(薔薇: Jangmi), Sandalwood(檀香: Danhyang), Thyme(麝香草: Sahyangcho) Ylang Ylang(依蘭: Eulan), Lemon(??皮: Ryungmongpi), Madarin(陣皮: Zinpi), Orange(枳殼: Zigak). 4. There are differences of curing ability in human between herb medicine and essential oils because of curing mechanism, but effect on human body are so simular.

• Interdisciplinary Bio Central
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• v.4 no.4
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• pp.11.1-11.8
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• 2012

Genes that are indispensable for survival are referred to as essential gene. Due to the momentous significance of these genes for cellular activity they can be selected potentially as drug targets. Here in this study, an essential gene for Streptococcus suis was predicted using coherent statistical analysis and powerful genome comparison computational method. At first the whole genome protein scatter plot was generated and subsequently, on the basis of statistical significance, a reference genome was chosen. The parameters set forth for selecting the reference genome was that the genome of the query (Streptococcus suis) and subject must fall in the same genus and yet they must vary to a good degree. Streptococcus pneumoniae was found to be suitable as the reference genome. A whole genome comparison was performed for the reference (Streptococcus pneumoniae) and the query genome (Streptococcus suis) and 14 conserved proteins from them were subjected to a screen for potential essential gene property. Among those 14 only one essential gene was found to be with impressive similarity score between reference and query. The essential gene encodes for a type of 'Clp protease'. Clp proteases play major roles in degrading misfolded proteins. Results found here should help formulating a drug against Strptococcus suis which is responsible for mild to severe clinical conditions in human. However, like many other computational studies, the study has to be validated furthermore through in vitro assays for concrete proof.

• Microbiology and Biotechnology Letters
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• v.29 no.4
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• pp.253-257
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• 2001

Essential oil of Chamaecyparis obtusa showed antimicrobial on relatively broad spectrum of bacterial and fungal species. Staphylococcus epidermidis was highly sensitive to the essential oil but Streptococcus aureus and Streptococcus mutans were not. Vibro parahemolyticus, Pseudomoas aeruginosa and Pseudomoas putida showed sensitivity at the concentration higher that 400 ppm, Thegrowth of a pathogenic yeast Candida albicans was inhibited by the essential oil above 200ppm. The radialgrowth of several filamentous fungi was also inhibited The antifungal activity of the essential oil was effective on two plant pathogens Fusarium oxysporum and Altenaria mali. These results sug-gest that essential oil of Chamaecyparis obtusa has an antimicrobial activity by inhibiting bacterial and fungal species.

• Natural Product Sciences
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• v.23 no.4
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• pp.235-238
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• 2017

Colorado potato beetle is a most destructive insect pest of potato throughout the world. Although utilization of chemical insecticides is a main method for management of this pest, their negative side-effects such as threat to humans and the environmental pollution prompted researchers to search for natural alternatives. Recently plant essential oils with low or without side-effects against noun-targeted organisms and with high availability were considered as safe bio-pesticides. In the present study, toxicity of essential oil of Iranian lemongrass, Cymbopogon citratus Stapf, was evaluated against 3th instar larvae and adults of Colorado potato beetle by a leaf dipping method. Results displayed essential oil had notable toxicity against both larvae and adults after 24 and 48 h exposure times. Probit analysis revealed $LC_{50}$ values (lethal concentration to kill 50% of population) with 95% confidence limits were 10.32 (9.17 - 11.72) and 7.76 (6.80 - 8.74) ${\mu}l/ml$ for larvae and 6.27 (4.82 - 8.15) and 4.35 (3.24 - 5.62) ${\mu}l/ml$ for adults after 24 and 48 h, respectively. Based on regression analysis, a positive correlation between log concentration of essential oil and insect mortality was achieved. Results indicated C. citratus essential oil can be candidate as a natural alternative to the harmful chemical insecticides in the management of Colorado potato beetle.

• The Korean Journal of Food And Nutrition
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• v.25 no.2
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• pp.274-283
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• 2012

The volatile flavor compounds of the essential oils from Ixeris dentate (Thunb.) Nakai and I. stolonifera A. Gray were investigated. The essential oils were extracted by hydro distillation extraction method. Ninety-three volatile flavor components were identified from I. dentate (Thunb.) Nakai essential oil. Hexadecanoic acid(33.73%) was the most abundant compound, followed by (Z,Z,Z,)-9,12,15-octadecatrienoic acid(18.59%), 6,10,14-trimethyl-2-pentadecanonel(10.39%) and phytol(5.21%). Ninety-seven volatile flavor components were identified from the essential oil of I. stolonifera A. Gray. Hexadecanoic acid was the most abundant component(39.7%), followed by (Z,Z,Z)-9,12,15-octadecatrienoic acid(12.63%), 9,12-octadecadienoic acid, ethyl ester(12.36%), pentacosane(5.2%) and 6,10,14-trimethyl-2-pentadecanone(3.18%). The volatile composition of I. dentate (Thunb.) Nakai was characterized by higher contents of phytol and phthalides than those of I. stolonifera A. Gray. The volatile flavor composition of I. stolonifera A. Gray can easily be distinguished by the percentage of sesquiterpene compounds against I. dentate (Thunb.) Nakai essential oil.