Tomáš Bajer

Comparison of various techniques for the extraction and determination of antioxidants in plants.

The following extraction techniques have been used for extracting antioxidants (apigenin, coumarin, esculetin, umbelliferone, bergapten, quercetin, rutin, scopoletin and xanthotoxin) from plant material: supercritical fluid extraction, pressurized liquid extraction, extraction by means of Soxhlet apparatus, ultrasonic extraction in ultrasonic bath, and by means of ultrasonic probe. The analytical method based on HPLC-UV detection for the determination of selected antioxidants was developed. For all extracts the antioxidant capacity based on the reduction of free 2,2-diphenyl-1-picrylhydrazyl radical was also determined. Comparing all results the ultrasonic probe method using 0.75 g of sample extracted by 50 mL of acetonitrile in water (30%, v/v) for 25 min at room temperature and with amplitude at 60% (equal to 90 W) without pulsation was evaluated as the best tool. The most significant indicator demonstrating this statement is the antioxidant capacity expressed as gallic acid equivalent where the ultrasonic probe method showed the best results in 10 of 16 samples. Also the operability of ultrasonic probe extraction method compared to other tested methods is more favorable.

Unremitting problems with chlorogenic acid Nomenclature: A review

Tento clanek shrnuje problematiku nazvoslovi isomerů patřicich do skupiny chlorogenových kyselin od jejich prvniho výskytu až dosud. Během desetileti bylo publikovano mnoho clanků zabývajicich se touto skupinou. Bohužel výzkumnici, kteři chtěli ziskat informace o tomto tematu, mohli být po přecteni několika clanků silně znechuceni. Kvůli postupným objevům a izolacim jednotlivých isomerů z nejrůznějsich matric a měnici se terminologii po těchto objevech jsou běžne nesrovnalosti mezi jednotlivými clanky. Přicinou těchto nesrovnalosti je hlavni sloucenina teto skupiny, a to 5-kafeoylchinova kyselina (znama jako kyselina chlorogenova) byla jako kyselina 3-kafeoylchinova opravdu nazývana před rokem 1976, kdy byla publikovana nova pravidla pro nazvoslovi. Nicmeně mnoho výzkumniků a take dodavatelů chemikalii zůstalo u použivani „pre UIPAC“ nazvoslovi a chybně nazývaji 3-kafeoylchinovou kyselinu jako kyselinu chlorogenovou, tj. hlavni substituent teto skupiny. Přestože několik praci s touto nesrovnalosti zapasi, tento problem stale přetrvava. Proto byla sepsana tato prace.

Design of the extraction process for terpenes and other volatiles from allspice by solid‐phase microextraction and hydrodistillation

Methods for the separation and determination of terpenes (mono- and sesqui-) and phenylpropanoids such as eugenol and methyleugenol from samples of allspice berries have been developed. Chromatographic analyses of isolated groups of compounds were carried out by means of gas chromatography coupled with mass spectrometry. A comparison of various types of solid-phase microextraction fibers was performed. The highest yields of terpenes were extracted by polydimethylsiloxane and divinylbenzene/Carboxen/polydimethylsiloxane fibers (almost the same for these two fibers), approximately twice as much as by Carbowax/divinylbenzene fiber. The highest amounts of monoterpenes were extracted by divinylbenzene/Carboxen/polydimethylsiloxane fiber, and the highest amounts of sesquiterpenes were extracted by polydimethylsiloxane fiber. Moreover, the effect of water addition on extraction yields as well as time and temperature of extraction were tested. Aroma profiles of extracts obtained by solid-phase microextraction and essential oil obtained by hydrodistillation of allspice berries were compared. The aroma profile of the divinylbenzene/Carboxen/polydimethylsiloxane fiber extract was similar to the aroma profile of essential oil. Particular characteristics of volatile allspice matters were presented. The linear retention indices for each compound were calculated.

Comparison of Two Ultrasonic Systems with Different Settings for Extraction of Capsaicinoids from Chili Peppers

Abstract Two ultrasonic systems were compared with different settings for extraction of capsaicinoids (capsaicin, dihydrocapsaicin and nordihydrocapsaicin) from chili peppers. The first system was ultrasonic homogenizer using an ultrasonic probe operating at a working frequency of 20 kHz, with variable setting of power output. The second one was ultrasonic cleaner operating at a working frequency of 35 kHz, with fixed power output of 50 W. Determination of the optimum extraction procedures was performed by comparison of the extraction yields. Content of capsaicinoids was determined by high-performance liquid chromatography-mass spectrometry (HPLC-MS). Optimization studies of extractions by both ultrasonic systems were performed. Ten various real samples of chili underwent optimum extraction conditions in both ultrasonic systems. The results were compared with each other and to a conventional Soxhlet extraction. The ultrasonic methods provide the higher extraction efficiency and simple and straightforward operation. System working at higher power of ultrasound resulted in higher extraction yields. An application of ultrasonic system working at lower frequency of ultrasonic waves is slightly advantageous.