Lipolytic effects of citrus peel oils and their components

This study was conducted to determine the lipolytic effects of eight kinds of citrus peel oils and their components. All of the citrus peel oils revealed lipolytic effects on olive oil model solution ranging from 10.9 to 73.8%. Hakyul (Citrus natsudaidai Hayata) showed the highest lipolytic effect (73.8%), followed by yuza (Citrus junos Sieb. ex Tanaka, 68.1%) and lemon (Citrus limonium, 63.4%), and their effects were comparable with or stronger than that of 5 mM raspberry ketone (p < 0.05). Among 17 authentic compounds relating to citrus peel oils, octanal (78.6%) showed the highest lipolytic effect, followed by gamma-terpinene (76.3%), limonene (75%), terpinen-4-ol (70.7%), nerol (69.9%), p-cymene (67.7%), and geranyl acetate (67.2%), and their effects were stronger than that of 5 mM raspberry ketone (p < 0.05). Ethyl acetate, alpha-pinene, myrcene, citronellal, linallyl acetate, and citronellol exhibited poor lipolytic effect in the model solution. Lipolytic effect was found to be high when the oils included a higher content of gamma-terpinene and p-cymene. Limonene showed potential lipolytic effect, and its effect is likely to be enhanced by the presence of gamma-terpinene and p-cymene. It is considered that monoterpene hydrocarbons consisting of one or two double bonds would have stronger lipolytic effect than those having three double bonds.     

Inhibitory effect of yuzu essential oil on the formation of N-nitrosodimethylamine in vegetables

The inhibitory effect of yuzu (Citrus junos Tanaka) essential oil on the formation of N-nitrosodimethylamine (NDMA) in the presence of vegetables (31 species) or saliva was investigated by HPLC. Most vegetable extracts enhanced the formation of NDMA. However, the formation ratio of NDMA in vegetable extracts was decreased by yuzu oil in the range of 59 to 22%. In the presence of yuzu oil and saliva, its ratio ranged between 62 and 24%. These results indicated that yuzu oil inhibited the formation of NDMA even in vegetables and saliva. The contents of ascorbic acid, nitrate, and nitrite in the 31 vegetable species were 0.3-65 mg/100 g, 3-581 mg/100 g, and 10-750 microg/100 g, respectively. Ascorbic acid and nitrite had little effect on the inhibition or formation of NDMA at their intact levels. Nitrate accelerated the formation of NDMA, and the addition of saliva further enhanced it. The mechanism of inhibition of NDMA formation by alpha-terpinene was studied. It was assumed from the results of LC-MS that a new compound formed by the reaction of alpha-terpinene with nitrite would be a derivative of alpha-terpinene with dinitroso groups. The molecular weight of this compound was 194. It is suggested that terpene hydrocarbons in citrus essential oils would contribute to the decrease of NDMA formation.     

Inhibitory effects of Orostachys japonicus extracts on the formation of N-nitrosodimethylamine

In Korea, Orostachys japonicus has been used traditionally as a drug and health food. The aim of this study was to investigate possible inhibitory effects of O. japonicus extracts on the formation of N-nitrosodimethylamines (NDMA). Chloroform extraction was the most effective method for recovering the highest number of phenolic compounds and flavonoids; in these extracts the greatest nitrite-scavenging activity and inhibition of NDMA formation occurred at pH 2.5. The chloroform extract was separated into 10 fractions (J1-J10); fraction J4 inhibited NDMA formation by 90.1 +/- 0.4%. This fraction was then separated into five subfractions (J4-1-J4-5) using a silica gel column. Subfractions J4-2 [(+)-catechin] and J4-4 (3,4-dihdroxybenzoic acid) inhibited NDMA formation by 89.5 +/- 0.9 and 77.6 +/- 0.8%, respectively.     

Radical-scavenging activities of citrus essential oils and their components: detection using 1,1-diphenyl-2-picrylhydrazyl

Thirty-four kinds of citrus essential oils and their components were investigated for radical-scavenging activities by the HPLC method using 1,1-diphenyl-2-picrylhydrazyl (DPPH). To examine the oils' relative radical-scavenging activities compared with that of a standard antioxidant, Trolox was employed. All of the essential oils were found to have scavenging effects on DPPH in the range of 17. 7-64.0%. The radical-scavenging activities of 31 kinds of citrus essential oils were comparable with or stronger than that of Trolox (p < 0.05). The oils of Ichang lemon (64.0%, 172.2 mg of Trolox equiv/mL), Tahiti lime (63.2%, 170.2 mg of Trolox equiv/mL), and Eureka lemon (61.8%, 166.2 mg of Trolox equiv/mL) were stronger radical scavengers than other citrus oils. Citrus volatile components such as geraniol (87.7%, 235.9 mg of Trolox equiv/mL), terpinolene (87.4%, 235.2 mg of Trolox equiv/mL), and gamma-terpinene (84.7%, 227.9 mg of Trolox equiv/mL) showed marked scavenging activities on DPPH (p < 0.05).     

Tyrosinase inhibitory activity of citrus essential oils

Thirteen kinds of citrus essential oils and their volatile flavor constituents were investigated for tyrosinase inhibitory activity. Eureka lemon, Lisbon lemon, Keraji, and Kiyookadaidai significantly inhibited the oxidation of L-dihydroxy phenylalanine (L-DOPA) by mushroom tyrosinase. Citral and myrcene among volatile flavor constituents of citrus essential oils exhibited tyrosinase inhibitory activities with Ki values of 0.318 and 2.38 mM, respectively. The inhibition kinetics analyzed by a Lineweaver-Burk plot indicated that citral is a noncompetitive inhibitor and myrcene is a competitive inhibitor. These results indicated that citral and myrcene are responsible for the tyrosinase inhibitory activity of citrus essential oils.     

植物精油与环糊精包合物的制备及对柑橘绿霉病的抑制作用

植物精油及其活性组分能降低柑橘采后病害且不影响果实品质,是一种潜在的生物杀菌剂,但存在易挥发和不稳定等问题,限制了其实际应用。将植物精油与环糊精包合能有效克服上述缺陷,提高植物精油的应用效果。为了提升植物精油组分反式-2-己烯醛对柑橘绿霉病菌的控制效果,该研究拟采用饱和水溶液法制备反式-2-己烯醛与α-环糊精（α-CD）、β-环糊精（β-CD）、γ-环糊精（γ-CD）和羟丙基-β-环糊精（HP-β-CD）包合物,并考察包合物对指状青霉的离体和活体控制效果,在此基础上解析效果较优包合物的结构特点和包合模式。结果显示,通过饱和水溶液法成功制备了反式-2-己烯醛与α-CD、β-CD、γ-CD和HP-β-CD的4种包合物（α-CDTH、β-CDTH、γ-CDTH和HP-β-CDTH）。外观形态结果显示,α-CDTH、β-CDTH和γ-CDTH粉末细腻绵密,HP-β-CDTH粉末粗糙,颗粒分明。4种环糊精包合物均能有效抑制P.digitatum菌丝体的生长且具有浓度依赖性,β-CDTH和γ-CDTH抑制P.digitatum菌丝体生长的最小杀菌浓度（Minimum Fugicide Concen...     

Contamination of Italian citrus essential oils: presence of chloroparaffin

In this study, the contamination by chloroparaffin of Sicilian and Calabrian citrus essential oils, produced in the crop years 1994-1996, was investigated. The analyses were carried out on 102 lemon oils, 98 orange oils, and 96 mandarin oils, using a dual-channel GC-ECD. It was found that 53% of lemon oil, 33% of orange oil, and 38% of mandarin oil samples were contaminated. The mean contamination levels were 7.1 ppm (lemon), 2.5 ppm (orange), and 5.3 ppm (mandarin). The highest concentration of chloroparaffin found was 60 ppm in a lemon oil sample.     

Comparison of fast and conventional GC analysis for citrus essential oils

This investigation concerns the application of fast GC in the analysis of essential oils. These are complex matrixes that usually undergo GC separation with conventional methods involving long columns, slow programmed temperature rates, and consequently, a high cost in terms of time. Fast GC techniques are based on the use of narrow bore capillary columns that allow the achievement of high-speed separations on complex samples while maintaining excellent resolution. This work saw the application of two methods on five different citrus essential oils and the comparison of all the results obtained.     

Production process contamination of citrus essential oils by plastic materials

Twelve samples of plastic materials employed in the industrial extraction of citrus essential oils were analyzed for the presence of phosphorated plasticizers, chloroparaffins, and phthalate esters. The samples tested were found to release these contaminants into the essential oils during the production process. Contamination tests were carried out using dichloromethane and uncontaminated samples of citrus essential oils as extractants. The extracts were analyzed by HRGC/FPD, ECD, and MS. Only one sample of plastic material was found to release triaryl phosphates, 5 samples released chloroparaffins, 6 released diisobutyl phthalate, and 8 released bis(2-ethylhexyl) phthalate. Significantly larger quantities of contaminants were released by new plastic parts than by used plastic parts.     

Contamination of Italian citrus essential oils: presence of phthalate esters.

Contamination by phthalate esters of Sicilian and Calabrian citrus essential oils, produced in the crop years 1994-1996, was investigated using a GC-MS system with direct injection of the samples. A total of 35 lemon oils, 31 orange oils, and 21 mandarin oils were analyzed. Diisobutyl phthalate and/or bis(2-ethylhexyl) phthalate were found in almost all samples, while di-n-butyl phthalate was present in 8. Concentrations up to a maximum of 62 ppm were found for diisobutyl phthalate and up to a maximum of 29.9 ppm for bis(2-ethylhexyl) phthalate.     

Fast HPLC for the analysis of oxygen heterocyclic compounds of citrus essential oils.

A fast HPLC method for the determination of the oxygen heterocyclic compounds of citrus essential oils was developed. Five different oils were analyzed under identical conditions, by reversed-phase HPLC with photodiode array detector, for a direct comparison of the composition of their oxygen heterocyclic fraction. Analysis time was 7 min. The oils analyzed were lemon, bergamot, mandarin, sweet orange, and bitter orange. The method developed is good for rapid screening or fingerprinting of these essential oils; a slightly slower method is recommended for higher resolution and better quantitative results.     

Allelopathic effect of some essential oils and components on germination of weed species

Abstract

In this study, allelopathic effects of some essential oil plants (Carum carvi L., Coriandrum sativum L., Foeniculum vulgare Mill., Lavandula stoechas L., Mentha spicata L.,Origanum onites L., Pimpinella anisum L., Rosmarinus officinalis L., Salvia officinalis L. and Thymbra spicata L.) were investigated against some common weed species (Alcea pallida Waldst. & Kit., Amaranthus retroflexus L., Centaurea salsotitialis L., Raphanus raphanistrum L., Rumex nepalensis Spreng., Sinapis arvensis L. and Sonchus oleraceus L.) that grow in field and horticultural crops. Different concentrations (3, 6, 10 and 20 µl) of the essential oils were tested against weed seeds in vitro and their effect on germination was determined. Inhibitory effects of essential oils and concentrations were analysed with Freadman's test and they were found significant. Essential oils from Carum carvi, Mentha spicata, Origanum onites and Thymbra spicata showed high inhibitory effect against weed seeds at lower concentrations. The main components (carvacrol, thymol, carvone, limonene) of these four essential oils were tested for seed germination at four different concentrations (500, 250, 125 and 62.5 µg/ml) against the same weeds.Thymol, carvacrol and carvone showed high inhibition even at low concentrations against weed seeds. Only Alcea pallida seeds showed resistance against all essential oils and components.     

Organochlorine pesticide residues in Italian citrus essential oils, 1991-1996

Organochlorine pesticide contamination in 148 lemon essential oils, 123 sweet orange oils, 121 mandarin oils, and 147 bergamot oils produced in Italy in the years 1991-1996 was studied by HRGC-ECD. Confirmation analyses were carried out by GC-MS. Tetradifon, dicofol and its decomposition product 4,4'-dichlorobenzophenone were found. Over the course of the study dicofol and tetradifon residues steadily decreased; the percentage of contaminated samples reflects this course and decreases considerably from 1991 to 1996.     

Antitermitic activity of leaf essential oils and components from Cinnamomum osmophleum

The antitermitic activities of the essential oils from the leaves of two Cinnamomum osmophloeumclones (A and B) and their chemical ingredients against Coptotermes formosanus Shiraki were investigated according to direct contact application. Results from this experiment have demonstrated that the indigenous cinnamon B leaf essential oil has a more effective antitermitic activity than indigenous cinnamon A leaf essential oil. Furthermore, when cinnamaldehyde, eugenol, and alpha-terpineol are extracted from indigenous cinnamon leaf essential oil and used at the strength of 1 mg/g, their antitermitic effectiveness is much higher than that using indigenous cinnamon leaf essential oil. Among the congeners of cinnamaldehyde examined, cinnamaldehyde has exhibited the strongest termiticidal property.     

Acaricidal activity of pine essential oils and their main components against Tyrophagus putrescentiae,a stored food mite

Some essential oils obtained from the branches of four Pinus species (P. pinea L., P. halepensis Mill., P. pinaster Soil in Ait., and P. nigra Arnold) have been evaluated for their acaricidal activity by aerial diffusion against the stored food mite Tyrophagus putrescentiae (L.). All the essential oils showed a good efficacy, but P. pinea oil and its two constituents 1,8-cineole and limonene were the most effective compounds, showing 100% acaricidal activity at 8 microL; 1,8-cineole showed the same activity at 6 microL.     

Survey of polychlorinated dibenzo-p-dioxins (PCDDs), Polychlorinated Dibenzo-p-furans (PCDFs), polychlorinated biphenyls (PCBs), and mineral components in Italian citrus cold-pressed essential oils

Investigation of PCDDs, PCDFs, PCBs, Al, As, Pb, Ba, Co, Cu, Cr, Fe, Mn, Cd, Ag, Sn, Zn, and Hg contents in 60 samples of cold-pressed essential oils produced in Calabria and Sicily in 2003-2005 was carried out. PCDDs, PCDFs, and PCBs were analyzed by HRGC-HRMS techniques using U.S. EPA 1613/94 and U.S. EPA 1668/A (1999) analytical methods. Mineral components were determined through GFAAS techniques; Hg content was determined by FI-M/H-AAS. The results of this study showed that essential oil contamination was due to a widespread pollution, typical background of rural areas, with relatively higher concentrations of PCDDs compared to PCDFs and little presence of PeCDF. Congeners OCDD, HpCDF, and OCDF were found at high concentrations. Regarding mineral components, mean values of Cr, Fe, and Ni were in agreement with data reported in the literature. Concentrations of As and Pb were below the maximum limits accepted by the current legislation. Finally, none of the samples analyzed were contaminated with Hg.     

Determination of some heavy metals and selenium in Sicilian and Calabrian citrus essential oils using derivative stripping chronopotentiometry

This paper aims to bring some novelty about the concentration of some heavy metals and selenium in biological citrus essential oils (CEO) produced in Sicily and Calabria in different crop years. Derivative stripping chronopotentiometry has been used as an accurate, sensitive, and rapid technique for the determination of Cd, Cu, Mn, Ni, Pb, Zn, and Se in hydrochloric acid extracts of CEO; in the optimized electrochemical conditions, detection limits of <1 microg kg(-1) were obtained for all of the studied metals. In particular, the concentrations of metals were determined in biological bergamot essential oils produced in Calabria in 1999 and 2000 and in biological CEO produced in Sicily in 2003 and 2004. The obtained results provided evidence that Mn was the most abundant metal in all of the studied CEO followed by Zn, Ni, Cu, Pb, and Se; Cd concentrations were always lower than the limit of detection (0.6 microg kg(-1)).     

Structure-activity relationship of citrus polymethoxylated flavones and their inhibitory effects on Aspergillus niger

Citrus peels are rich in polymethoxylated flavones (PMFs) and are potential sources of natural preservatives. Six PMFs extracts, isolated and purified from the peels of three mandarins (Citrus reticulata) and three sweet oranges (Citrus sinensis), were identified and quantitated. Their inhibitory effects on Aspergillus niger were evaluated using a microbroth dilution assay. The Red tangerine variety exhibited the greatest antifungal activity (MIC = 0.2 mg/mL), while Jincheng showed the lowest activity (MIC = 1.8 mg/mL). An analysis of principal components was applied to the results in order to elucidate the structure-activity relationships of the citrus PMFs. The structure-activity relationship analysis revealed that, for good inhibitory effect, the 5-OH, 3-OCH?, and 8-OCH? functionalities were essential, while the presence of 3-OH and 3'-OCH? greatly reduced inhibition. The findings of this study provide important information for the exploitation and utilization of citrus PMFs as natural biopreservatives.     

Oxidative stability of algal oils as affected by their minor components

Algal oils, namely, arachidonic acid single-cell oil (ARASCO), docosahexaenoic acid single-cell oil (DHASCO), and a single-cell oil rich in both docosahexaenoic acid and docosapentaenoic acid (OMEGA-GOLD oil), were evaluated for their oxidative stability, as such and after stripping of their minor components, in the dark at 60 degrees C and under fluorescent light at 27 degrees C. Several analytical methods were used to assess the oxidative stability of these oils. Oil extracts were also investigated for their scavenging of 1,1-diphenyl-2-picrylhydrazyl radical by a spectrophotometric method and by measuring their total phenolic contents. The results indicated that minor oil constituents play a major role in their oxidative stability in the dark as well as under fluorescent light. The stability of the oils was dictated by their fatty acid composition, total tocopherols, and the type of pigment present. DHASCO contained a significant level of natural radical scavengers and phenolic compounds that contributed to its higher stability compared to the ARASCO and OMEGA-GOLD oils. Thus, the importance of minor components in the stability of the oils examined was demonstrated.     

Antibacterial activities of plant essential oils and their components against Escherichia coli O157:H7 and Salmonella enterica in apple juice

We evaluated 17 plant essential oils and nine oil compounds for antibacterial activity against the foodborne pathogens Escherichia coli O157:H7 and Salmonella enterica in apple juices in a bactericidal assay in terms of % of the sample that resulted in a 50% decrease in the number of bacteria (BA(50)). The 10 compounds most active against E. coli (60 min BA(50) range in clear juice, 0.018-0.093%) were carvacrol, oregano oil, geraniol, eugenol, cinnamon leaf oil, citral, clove bud oil, lemongrass oil, cinnamon bark oil, and lemon oil. The corresponding compounds against S. enterica (BA(50) range, 0.0044-0.011%) were Melissa oil, carvacrol, oregano oil, terpeineol, geraniol, lemon oil, citral, lemongrass oil, cinnamon leaf oil, and linalool. The activity (i) was greater for S. enterica than for E. coli, (ii) increased with incubation temperature and storage time, and (iii) was not affected by the acidity of the juices. The antibacterial agents could be divided into two classes: fast-acting and slow-acting. High-performance liquid chromatography analysis showed that the bactericidal results are related to the composition of the oils. These studies provide information about new ways to protect apple juice and other foods against human pathogens.