Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
Navegar
7 resultados
Resultados da Pesquisa
Item Identification of acetates in Elasmopalpulus lignosellus pheromone glands using a newly created mass spectral database and kóvats retention indices(Química Nova, 2007-07) Jham, Gulab N.; Silva, Alexsandro A. da; Lima, Eraldo R.; Viana, Paulo A.Based on a specially created mass spectral database utilizing 23 tetradecenyl and 22 hexadecenyl acetate standards along with Kóvats retention indices obtained on a very polar stationary phase [poly (biscyanopropyl siloxane)] (SP 2340), (Z)-9-hexadecenyl acetate, (Z)-11-hexadecenyl acetate and (E)-8-hexadecenyl acetate were identified in active pheromone extracts of Elasmopalpus lignosellus. This identification was more efficient than our previous study using gas chromatography/mass spectrometry with a dimethyl disulfide derivative where we could only identify the first two acetates. The acetate composition of the pheromone gland differed from region to region in Brazil and from that from the Tifton (GA, USA) population, suggesting polymorphism or a different sub-species.Item Comparison of GC and HPLC for quantification of organic acids in two jaboticaba (Myrciaria) fruit varieties(Química Nova, 2007) Jham, Gulab N.; Fernandes, Sergio A.; Garcia, Clerverson F.; Palmquist, DebraGas chromatography (GC) with trimethylsilyl derivative formation was compared to high-performance liquid chromatography (HPLC) for quantification of organic acids (OAs) in two jaboticaba (Myrciaria) fruit (pulp and pericarp) varieties (Sabará and Açu Paulista). Succinic and citric acids were the major OAs found in all the samples analyzed. Besides being much more tedious, the results obtained with GC were significantly lower than HPLC (p<0.05) when the data (acids, variety, two parts and flowering days) were considered together. The presence of both acids was confirmed by gas chromatography-mass spectrometry (GC-MS).Item Triacylglycerol molecular species variation in stored coffee beans determined by reverse-high-performance liquid chromatography/refractive index detector(Journal of Stored Products Research, 2008) Jham, Gulab N.; Muller, Helcio Vidigal; Cecon, PauloSamples of three types of coffee beans (immature, random mixture and cherry) were each divided into roughly two halves and dried by two widely known procedures (conventional dryer and open air cement floor patio) to attain about 14% moisture. All samples were stored on wood shelves without temperature or moisture control. After 4, 7, 10, 13, 16 and 19 months, portions of all samples were withdrawn and the relative percentages of the nine triacylglycerol (TAG) molecular species determined by reverse-high-performance liquid chromatography with a refractive index detector. The experiment consisted of 36 treatments (combinations of bean types, drying procedures and storage times) in a randomized block design with three repetitions. Nine TAG molecular species were identified in all the coffee samples. While apparently random variation was observed in TAG composition in a few cases, no significant effects of storage time, storage type or coffee type on TAG composition were observed.Item Purification of the seven tetranortriterpenoids in neem (Azadirachta indica) seed by counter-current chromatography sequentially followed by isocratic preparative reversed-phase high-performance liquid chromatography(Journal of Chromatography A, 2007-03-30) Silva, Júlio César T.; Jham, Gulab N.; Oliveira, Rosângela D’arc L.; Brown, LeslieCounter-current chromatography (CCC) sequentially followed by isocratic preparative reversed-phase high-performance liquid chromatography was used to isolate the seven bio-actives (azadirachtin A, azadirachtin B, azadirachtin H, desacetylnimbin, desacetylsalannin, nimbin and salannin) from the seed concentrate (NSC) of the neem tree (Azadirachta indica A. Juss). Reproducible, narrow polarity range, high purity fractions were obtained from repeated injections of the NSC (700 mg loadings/injection), on to a relatively small volume CCC coil (116 mL). The CCC biphasic solvent system chosen was hexane:butanol:methanol:water (1:0.9:1:0.9, v/v). A mass balance of injected material showed that 95+% were recovered.Item Identification (GC and GC-MS) of unsaturated acetates in Elasmopalpus lignosellus and their biological activity (GC-EAD and EAG)(Journal of Separation Science, 2004-12-15) Jham, Gulab N.; Silva, Alexsandro A. da; Lima, Eraldo R.; Viana, PauloTwo insect colonies of Elasmopalpus lignosellus were reared in our laboratory, the first being initiated from pupae obtained from a cornfield in the region of Sete Lagoas, Minas Gerais and the second from a cornfield in the region of Goiânia, Goiás. From the two colonies, two extracts were prepared from the pheromone glands of virgin E. lignosellus females. The extract obtained from the first colony was designated as extract 1 while the extract obtained from the second colony was designated as extract 2. Extract 1 was analyzed by gas chromatography-mass spectrometry (GC-MS) with (Z)-9-hexadecenyl acetate [(Z)-9-HDA] and (Z)-11-hexadecenyl acetate [(Z)-11-HDA] being identified and confirmed by the formation of DMDS derivatives. In addition, a third acetate, which could be either (E)-8-hexadecenyl acetate [(E)-8-HDA] or (E)-9-hexadecenyl acetate [(E)-9-HDA] was detected by GC-MS. Extract 2 was analyzed by gas chromatography (GC) and gas chromatography-electroannetography (GC-EAD) revealing the presence of (Z)-11-HDA and (Z)-9-TDA. In addition, the same compounds elicited a response with the E. lignosellus male antenna obtained from the second insect colony. Electroantennography (EAG) screening with the male E. lignosellus antenna (obtained from the second insect colony) was conducted with the 23 possible tetradecenyl acetates (TDA) and 22 hexadecenyl acetates (HDA) as standards. Out of the 23 TDA isomers evaluated, only (Z)-9-TDA elicited a response and out of the 22 HDA [(Z) and (E) isomers gamma2 to delta13] evaluated only (Z)-11-HDA elicited a response. The acetate compositions of two extracts obtained from insects originating from the two states (Minas Gerais and Goiás) of Brazil were different from one another as well as from that obtained from insects in Tifton, GA, USA. The bioactivity data (GC-EAD) of the extract 2 differed from those reported for the Tifton, GA, USA population. These data suggest polymorphism in relation to the insect populations found in Brazil and in the USA. The possibility of the existence of an E. lignosellus sub-species cannot be ruled out.Item Determination of the triacylglycerol composition of coffee beans by reverse-phase high-performance liquid chromatography(Phytochemical Analysis, 2003-09-08) Jham, Gulab N.; Nikolova-Damyavova, Boryana; Viera, Mirtes; Natalino, Ricardo; Rodrigues, Augusto CezarReverse-phase HPLC with refractive index and light scattering detectors in isocratic and gradient elution modes, respectively, was applied for the separation of the major triacylglycerols (TAG) in coffee lipids. Twelve TAG species could be identified and determined using a linear gradient of acetonitrile in dichloromethane: dichloroethane. The quantitative evaluation was based on the relative area percentages derived directly from a data-station. The procedure was applied to determine the TAG composition of three types of coffee beans harvested in two coffee producing areas in Brazil and dried by two commonly used procedures. No significant differences in the TAG compositions due to the type, origin and drying procedure were found.Item Comparison of GC and HPLC for the quantification of organic acids in coffee(Phytochemical Analysis, 2001-05-16) Jham, Gulab N.; Fernande, Sergio A.; Garcia, Cleverson Fernando; Silva, Alexsandro Araujo daA GC and an HPLC method for the quantification of organic acids OAs in coffee have been compared. The GC procedure, employing trimethylsilyl derivatives, was found to be very tedious. The HPLC method, which employed an ion exchange column using a flow gradient of water containing 1% phosphoric acid and UV detection (210 nm), was found to be much simpler for the quantification of eight organic acids (oxalic, succinic, fumaric, malic, tartaric, citric, quinic and fumaric acids) in four representative coffee samples. The HPLC procedure was more convenient than that described in the literature since no pre-purification was required for quantification of the OAs.