Determination of the chemical composition of tea by chromatographic methods: a review

Despite the fact that mankind has been drinking tea for more than 5000 years, its chemical composition has been studied only in recent decades. These studies are primarily carried out using chromatographic methods. This review summarizes the latest information regarding the chemical composition of different tea grades by different chromatographic methods, which has not previously been reviewed in the same scope. Over the last 40 years, the qualitative and quantitative analyses of high volatile compounds were determined by GC and GC/MS. The main components responsible for aroma of green and black tea were revealed, and the low volatile compounds basically were determined by HPLC and LC/MS methods. Most studies focusing on the determination of catechins and caffeine in various teas (green, oolong, black and pu-erh) involved HPLC analysis. Knowledge of tea chemical composition helps in assessing its quality on the one hand, and helps to monitor and manage its growing, processing, and storage conditions on the other. In particular, this knowledge has enabled to establish the relationships between the chemical composition of tea and its properties by identifying the tea constituents which determine its aroma and taste. Therefore, assessment of tea quality does not only rely on subjective organoleptic evaluation, but also on objective physical and chemical methods, with extra determination of tea components most beneficial to human health. With this knowledge, the nutritional value of tea may be increased, and tea quality improved by providing via optimization of the growing, processing, and storage conditions.</p

An Age-Structured Extension to the Vectorial Capacity Model

Vectorial capacity and the basic reproductive number (R(0)) have been instrumental in structuring thinking about vector-borne pathogen transmission and how best to prevent the diseases they cause. One of the more important simplifying assumptions of these models is age-independent vector mortality. A growing body of evidence indicates that insect vectors exhibit age-dependent mortality, which can have strong and varied affects on pathogen transmission dynamics and strategies for disease prevention.Based on survival analysis we derived new equations for vectorial capacity and R(0) that are valid for any pattern of age-dependent (or age-independent) vector mortality and explore the behavior of the models across various mortality patterns. The framework we present (1) lays the groundwork for an extension and refinement of the vectorial capacity paradigm by introducing an age-structured extension to the model, (2) encourages further research on the actuarial dynamics of vectors in particular and the relationship of vector mortality to pathogen transmission in general, and (3) provides a detailed quantitative basis for understanding the relative impact of reductions in vector longevity compared to other vector-borne disease prevention strategies.Accounting for age-dependent vector mortality in estimates of vectorial capacity and R(0) was most important when (1) vector densities are relatively low and the pattern of mortality can determine whether pathogen transmission will persist; i.e., determines whether R(0) is above or below 1, (2) vector population growth rate is relatively low and there are complex interactions between birth and death that differ fundamentally from birth-death relationships with age-independent mortality, and (3) the vector exhibits complex patterns of age-dependent mortality and R(0) ∼ 1. A limiting factor in the construction and evaluation of new age-dependent mortality models is the paucity of data characterizing vector mortality patterns, particularly for free ranging vectors in the field

Creation of a Databank for Content of Antioxidants in Food Products by an Amperometric Method

Oxidative stress, i.e. excessive content of reactionary, oxygen, and nitrogen compounds (ROAC), including free radicals, is one of the causes of various dangerous diseases as well as premature aging. The adverse effect of free radicals can be neutralized by antioxidants. In order to carry out antioxidant therapy, one needs to know the contents of antioxidants in food products. We have created the databank for the contents of antioxidants in 1,140 food products, beverages, etc. Apart from water-soluble antioxidants, fat-soluble antioxidants in dairy and fish products, cacao, chocolate, nuts etc. were determined for the first time using an amperometric method

Method for optimizing of reproductive function in postpartum cows

According to the official veterinary reports cattle in the Nizhny Novgorod region in 2014-2016 showed a decreased level of carotene in 50.2.57.9%, a total serum protein - in 20.0.24.5%, total calcium - in 33.0.35.7%, inorganic phosphorus - in 29.0.32.5%, alkaline reserve - in 12.0.13.8% of the samples studied; in the structure of non-contagious pathology, the leading place was occupied by diseases of the reproductive organs, registered in 34.0% of diseased сattle. Our own studies revealed a decreased level of inorganic phosphorus and phagocytic activity of neutrophils in dry cows in a base economy. We developed a method for optimizing the reproductive function of cows comprising daily peroral application of remedy Bio-PHAYAL at a dose of 15.20 mg/kg body weight for 5 days starting at onset of the lactation period and 10 days prior to calving, in combination with the two-fold subcutaneous injection of the preparation Bio-TEK at a dose of 10 ml/head 60 and 30 days prior to calving, two-fold intramuscular injection of tetrahydrovit at a dose of 10 ml/head 60 and 30 days prior to calving and a single intramuscular injection of sedimin at a dose of 10 ml/head 45 days prior to calving. The developed method contributed to the optimization of the reproductive function of postpartum cows, which was characterized by a decrease in the level of obstetric morbidity by 19.0.49.3%, less time required for the uterine involution by 2.8.6.1 days, a reduction in the infertility by 7.7.21.6 days and an increase of their fertility by 5.7.13.0% in comparison with analogues

Impact of composition of organic acids on indicators characterizing endogenous intoxication in cows

In modern conditions of livestock-keeping and animal husbandry obstetric pathology is an important problem on many dairy operations that can have substantial effects on cow reproductive performance and productivity which emphasizes the need for working out of new means and schemes for prevention and studies to clarify their impacts on immune and biochemical homeostasis of animals. The objective of the present researches was to found out whether organic acid composition can influence blood indices characterizing the endogenous intoxication (EI) intensity and postpartum morbidity in cows. Study was conducted in conditions of a dairy farm typical of the Nizhny Novgorod region on two groups of Black-and-white Holstein dairy cows (body weight (BW) 500-550 kg, average milk yield 5300 kg). As a result of conducted researches it is established that the composition preparation BioFAYAL containing fumaric, ascorbic, succinic and citric acids when administrated to cows orally daily 65 days before and 10 days after calving in dose 10 mg per kg BW led to more physiological dynamics and stabilization of markers characterizing the EI intensity resulted in statistically significant reduction of high incidence of pre- and postpartum diseases by 44,1% (placental retention by 22,5%, endometritis by 31,2%). 10-14 days after calving decrease of the level of substances of low and medium molecular mass (SLMMM) on erythrocytes by 8,8% (р≤0,01), beta-hydroxybutirat by 38,6% (р≤0,05) and sorption capacity of erythrocytes by 5,1% was estimated in cows treated with the composition of organic acids when compared with intact animals