Influence of Geographical Area of Production on the Caffeine and Flavan-3-ol Profiles of Selected Clonal Green Tea Leaves from Smallholder Tea Farms in Kenya

Despite the use of similar cultivars in the smallholder tea sector in Kenya, resultant black tea quality varies. These variations could in part be arising from the formation of varying quantities and ratios of the black tea quality precursor compounds with agro-ecological zones of production. This study evaluated the variations in the caffeine and flavon-3-ol profiles of three cultivars (SFS 150, TRFK 31/8 and TRFK 303/577) of tea from smallholder tea farms in three agro-zones in Kenya. Overall, there were significant variations (p less than or equal to0.05) in the levels of caffeine and flavan-3-ols due to cultivars and agro-ecological zones of production. In the same cultivar, the components varied (p less than or equal to0.05) with an ecological area of production. The patterns in the changes were not systematically leading significant ecological zone x cultivar interactions effects in gallic acid, catechin, and epicatechin gallate. This demonstrated that it may not be predictable how the quality of clonal tea may vary when produced in different agro-ecological zone. Consequently, a high-quality clone in one agro-ecological zone may not replicate the same characteristics in the different agro-ecological zone. It is, therefore, necessary to test new clones in new environments before they are extensively exploited in these environments. The current findings suggest that flavon-3-ols may not be potential factors in the discrimination of tea quality within the ecological zones of Kenya.

Over 60% of tea in Kenya is produced by smallholder tea farmers distributed in the East and West of the Rift Valley. With all smallholder tea farmers using the same production technologies including planting materials, the quality of tea from different agro-ecological zones should be the same. However, black teas attract different prices. This study compared levels of leaf quality, catechins, and polyphenols in green leaf and quality parameters of black tea from twelve factories in three different agro-ecological zones in Kenya and assessed the relationships between the green leaf quality parameters and black tea quality parameters. The catechins contents, the black tea quality parameters, and sensory evaluations changed (p less than or equal to0.05) between the factories and with an agro-ecological zone of production. All black teas had high antioxidant activities, which differed (p less than or equal to0.05) across the factories and zones. Despite the use of same agronomic inputs in the smallholder tea growing zones in Kenya, the quality of resultant black teas was largely influenced by the environmental factors in the different regions. It is therefore not possible to produce black teas of the same quality across the country. Despite the variations, all regions exhibited high levels of black tea quality parameters and sensory evaluation, re-affirming the Kenyan smallholder black teas are of high quality. The high antioxidant activities suggest possible beneficial pharmacological activities from consumption the teas. The green leaf quality (leaf count) were significantly (p less than or equal to0.05) correlated with black tea brightness and all sensory evaluation parameters, demonstrating high benefits from good plucking standards. Green leaf gallic acid, epigallocatechin, epicatechin, epigallocatechin gallate, and total catechins levels were related (p less than or equal to0.05) to black tea total polyphenols and all sensory evaluation parameters. In addition, the green leaf caffeine, epicatechin, epigallocatechin gallate, and total catechins influenced (p less than or equal to0.05) theaflavins in black tea. These green leaf parameters are therefore key drivers of Kenyan plain black tea quality.

Extraction of catechins and caffeine from different tealeaves and comparison with micellar electrokinetic chromatography

The quality of Congou black tea fluctuates greatly with the changing seasons. However, variations in the taste quality of Congou black tea manufactured during a single spring season are far from clear. Here, we analyzed the taste quality of HuangJinCha (HJC) Congou black tea using sensory evaluation and found the taste quality of black tea manufactured in the early spring was better than that manufactured in the late spring. Principal component analysis (PCA) and cluster analysis for the data from the electronic tongue confirmed the variation and revealed that April 4 may be the critical time point at which variations in taste quality become apparent. The contents of tea polyphenols (TP), total catechins (TC), total flavones, (‐)‐epigallocatechin gallate (EGCG), (‐)‐epicatechin gallate (ECG), and gallic acid (GA) showed increasing trends, whereas total amino acids (TAA) declined over time. Moreover, the variations in total amino acids (r = 0.846) and total flavones (r = ‐ 0.858) were highly significantly correlated with the average taste quality score (p < .01), suggesting these compounds were the primary factors responsible for the fluctuation in taste quality of Congou black tea processed during a single spring season.

Final quality of black tea depends mainly on the chemical composition of the raw tea leaves. Various plucking methods have direct effect both on yield and quality in different cultivated variety and environments. Different literature reports indicated that polyphenols, caffeine, essential oils and amino acids are responsible for aroma and flavor of black tea. The oxidation process begins at rolling step and ends at initial stages of drying process until the heat denature the enzymes, which convert tea polyphenols (catechins) to theaflavins and thearubigins; both are responsible for brightness, color and taste of black tea. TR increased by increasing fermentation period. TF decreased by increasing fermentation period. The essential oils and the amino acids also contribute to characteristic tea taste and aroma. It was found that the essential oils content increased during the withering, rolling and fermentation steps; however this amount decreased during the drying step. But this reduction is compensated by the Millard reaction which is the reaction of amino acids with the sugars during drying, contributing positively to the tea flavor and color. Theaflavin, thearubigins and total color content of black tea stored in accelerated storage condition decreased slightly when compared with tea stored under normal conditions. It is concluded that plucking (interval, season and standard), processing steps and storage system plays major role in maintaining black tea quality. Key words: Tea processing, black tea, biochemical composition, sensory quality.

A reliable technique to identify superior quality clones from tea germplasm

The tea beverages processed from the young tender shoots of Camellia sinensis (L.) O. Kuntze, are claimed to be the most widely consumed fluids after water. The tea plant originates from the point of confluence of Northeast India, North Burma, Southwest China and Tibet. Its production has spread and economic production has been reported in between 49 ∘ N in Outer Carpathians to 33 ∘ S in Natal, South Africa, at altitudes ranging from sea level to 2,700 m above mean sea level. The adaptability of the plant to areas with large variations in geographical, climatic and environmental factors can cause changes in growth patterns in different genotypes leading to variations in yields and black tea quality. Tea producers usually import genotypes, management and production techniques suitable for optimal production in one region in the hope that beneficial attributes observed at source shall be maintained in the new areas. But the tea plant responses in new environments have not always yielded the desired results. Here we review the effects of genotypes, environment and management on the yields and quality of black tea. Previous investigations demonstrated that black tea yields and quality changes are due to environmental factors like soil type, altitude, seasons, weather factors, geographical areas of production, agronomic inputs, processing technologies and management. Black tea quality and yields of similar genotypes grown on different soils vary. The extent and patterns of the variations change with varieties. High altitude grown teas are more aromatic than low altitude grown black teas, implying that the low grown teas are plain in character. Thus producers at high altitudes should aim at producing aromatic black teas, although yields will be lower than same genotypes at lower altitudes. Producers growing teas at low altitudes should focus on high output and ensure optimal conditions for production of plain black teas. There are seasonal black tea quality and yield variations. Cold seasons lead to slow growth resulting in low yields, but high black tea quality. Provided soil moisture and temperatures are adequate, warm temperatures lead to fast growth, leading in turn to high yields, but low black tea quality. It is therefore not possible to have uniform production or to produce the same black tea quality throughout the year. The situation is adverse further away from the equator with no production in winter as the labour management can be critical during the long cold seasons, necessitating long labour layoffs. Many genotypes have been developed, some with very high yields and quality. As a result, producers continuously try to access the good varieties into new geographical areas in the hope the genotypes would retain their economic advantages. While some genotypes are stable to locational changes, most show wide variations due to planting in the new areas. Management policies induce yield and black tea quality differences. Imported management policies should be domesticated and modified to suit the new environments. Harvesting, by hand plucking, the young tender shoots is done when they are of the right size. Delayed harvesting leads to shoot overgrowth and crop loss. Whereas plucking two leaves and a bud is a compromise between yields and black tea quality, some growers practice coarser plucking standards. Black tea quality declines with coarse plucking standards. Short plucking rounds lead to high production and high quality black teas. When a plucking standard is preset, growers in a location need to establish the shortest harvesting interval for realization of good yields and quality. Fertilizers are essential for establishment and growth. Varying results have been recorded on yield and quality responses to NPK application. For potassium and phosphorus, evaluations are necessary in different regions because where there is no beneficial effects their application can be reduced to decrease costs. High rates of nitrogen reduce black tea quality and do not increase yields. Nitrogen fertilizers need to be applied at rates that are a compromise between yields and black tea quality. Such rates vary with regions and genotypes. To reach high production and quality, region- and genotype-specific fertilizer rates are needed. In regions producing relatively inferior black teas producers try to import processing technologies from other areas. These efforts may not improve quality due to variations of environmental conditions. Indeed, for the same genotype grown in different regions and processed under identical conditions, differences in quality and chemical composition have been reported. This was due to variations in the leaf biochemical constituents composition caused by the environment in which the plant was grown. Different regions must therefore optimize their processing conditions to realize high quality.

Part I: Development of a solid phase extraction coupled with high performance liquid chromatography method for the determination of aripiprazole and dehydroaripiprazole in biological fluid Aripiprazole is the first drug with dopamine partial agonist effect for schizophrenia. Dehydroaripiprazole is its major metabolite. The determination and validation of aripiprazole and dehydroaripiprazole in human serum and urine were performed by a combination of solid phase extraction (SPE) and high performance liquid chromatography (HPLC) in this study. The method includes the following steps: 1) pre-treatment of acid-base solutions for deproteination, 2) application of SPE using an Oasis HLB cartridge for cleaning-up and concentration of the samples, 3) HPLC analysis. The recovery of sample pretreatment step was relatively high with recovery rate of 88.20 - 99.83 %. The optimized HPLC conditions were using a C18 X Terra® column, with an isocratic elution consisted of dipotassium phosphate buffer, pH 8.35, and acetonitrile (40 : 60 v/v) at a flow rate of 1.0 mL/min. The concentration of aripiprazole and dehydroaripiprazole could be determined within 5 minutes. The relative standard deviation (RSD) of the peak area for method repeatability (n = 4) and intermediate precision (inter-day, n = 3) were lower than 0.11 % and 5.16 %, respectively. The calibration curves revealed the method that was linear with concentration range between 50 - 1000 ppb for aripiprazole and 50 - 800 ppb for dehydroaripiprazole. Finally, the validated method was successfully applied to analyze serum and urine samples collected from patients receiving the aripiprazole treatment. The developed method can be used to quantitative determination of aripiprazole and dehydroaripiprazole concentration in patients’ serum and urine for therapeutic monitoring and clinical research. Part II: Fingerprint analysis of rhubarb by capillary electrophoresis and ultra-high pressure liquid chromatography This study used capillary electrophoresis (CE) and ultra performance liquid chromatographic (UPLC) method for chromatographic fingerprint analysis of rhubarb. With the application of chemometric approach, chromatographic fingerprint could be used for species differentiation. Ten common constituents in rhubarb, including aloe-emodine, (+)catechin, chrysophanol, emodine, (-)epicatechin gallate, gallic acid, physcion, rhein, sennoside A and sennoside B, were selected for analytical method development. The optimum micellar electrokinetic chromatography (MEKC) conditions were as followed: 30 mM sodium tetraborate / sodium dihydrogen phosphate monohydrate, 30 mM sodium deoxycholate (SDC), pH 8.6 with 26 % acetonitrile (v/v) as background electrolyte. The optimum condition of UPLC method used a Waters Acquity UPLC BEH C18 column for the separation. The mobile phase was composed of 0.05 % phosphate solution (solution A) and acetonitrile (solution B). The gradient profile was ( solution A: solution B): 0 min, 90 : 10; 25 min, 79 : 21; 35 min, 67 : 33; 40 min, 35 : 65; 45, min 35 : 65. The detector wavelength was set at 254 nm for both methods, and the total analytical time was 21 min for CE and 45 min for UPLC. Sixteen samples of Rheum officinale and Rheum tanguticum collected from various sources were analyzed by optimum analytical conditions. Chromatographic fingerprints of CE were subjected to peak alignment and baseline correction for further similarity test. On the other side, analytical results of UPLC show high precision with flat baseline. Chromatographic fingerprints of UPLC were directly used for Principal component analysis (PCA) and similarity test. PCA shows the chromatographic fingerprints of the two species could be successfully classified. The sample showing the least correlation with the representative chromatographic fingerprint was studied for its DNA sequences. DNA analysis demonstrated the sample to be a hybrid rhizome. The developed CE and UPLC chromatographic fingerprint methods could be applied for the quality control of rhubarb.

Genotype and cultivar identification is essential for conserving tea genetic diversity within plantation ecosystems and ensuring the sustainability of high-quality tea production. This study represents the first large-scale genetic characterization of 200 elite varietal candidate tea (Camellia sinensis) clones, which were pre-selected from 2,034 genotypes originating from the Eastern and Western Black Sea regions of Türkiye. Eight polymorphic simple sequence repeat (SSR) markers located near loci associated with catechin content, including epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG), were employed. SSR profiles were generated for all 200 tea clones cultivated in control plots at the National Tea Gene Bank, and the resulting data were additionally used for DNA barcoding of 12 varietal candidate tea clones currently under registration. Among the evaluated markers, TM412 (EGC) exhibited the highest polymorphism information content (PIC = 0.8816), whereas TM376 (EC) showed the lowest (0.4321). Notably, TM412 (EGC) and TM399 (ECG) displayed high PIC values, indicating their strong discriminatory potential for Turkish tea genotypes. The findings indicate that Turkish tea germplasm possesses substantial genetic diversity, and some markers may be effectively utilized in variety registration and breeding efforts. This study presents the first comprehensive molecular characterization of tea genetic resources in Türkiye. It contributes to the long-term conservation of selected clones and supports the variety registration process through DNA barcoding and a QR code-based traceability system. The genetic dataset generated in this work contributed directly to the establishment of Türkiye’s first and the world’s fifth-largest tea gene pool in Rize Province, providing a valuable reference for strengthening tea genetic resource conservation and breeding programs at both national and global scales.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12870-025-07464-z.

Levels of essential elements with antioxidant activity, as well as catechins, gallic acid, and caffeine levels, in a total of 45 samples of different teas commercialized in Spain have been evaluated. Chromium, manganese, selenium, and zinc were determined in the samples mineralized with HNO(3) and V(2)O(5), using ETAAS as the analytical technique. The reliability of the procedure was checked by analysis of a certified reference material. Large variations in the trace element composition of teas were observed. The levels ranged from 50.6 to 371.4 ng/g for Cr, from 76.1 to 987.6 microg/g for Mn, from 48.5 to 114.6 ng/g for Se, and from 56.3 to 78.6 ng/g for Zn. The four major catechins [(-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC)], gallic acid (GA), and caffeine were simultaneously determined by a simple and fast HPLC method using a photodiode array detector. In all analyzed samples, EGCG ranged from 1.4 to 103.5 mg/g, EGC from 3.9 to 45.3 mg/g, ECG from 0.2 to 45.6 mg/g, and EC ranged from 0.6 to 21.2 mg/g. These results indicated that green tea has a higher content of catechins than both oolong and fermented teas (red and black teas); the fermentation process during tea manufacturing reduces the levels of catechins significantly. Gallic acid content ranged from 0.039 to 6.7 mg/g; the fermentation process also elevated remarkably gallic acid levels in black teas (mean level of 3.9 +/- 1.5 mg/g). The amount of caffeine in the analyzed samples ranged from 7.5 to 86.6 mg/g, and the lower values were detected in green and oolong teas. This study will be useful for the appraisal of trace elements and antioxidant components in various teas, and it will also be of interest for people who like drinking this beverage.

The preventive effects of (−)-epigallocatechin gallate (EGCg), (−)-epigallocatechin (EGC), gallic acid (GA), and a mixture of EGC and GA, and also of (−)-epicatechin gallate (ECg), (−)-epicatechin (EC), and a mixture of EC and GA against paraquat (PQ)-induced oxidative stress were compared in rats to determine whether the preventive effects of the EGCg and ECg against oxidative stress can be obtained by a mixture of their components or not. An increase in lung weight induced by PQ feeding was relieved by supplementing EGCg or ECg to the PQ diet, and the magnitude of relief was stronger than that achived by a mixture of EGC and GA, or EC and GA. An increase in liver TBARS, and decreases in the catalase activity in liver mitochondrial fraction and in liver triacylglycerol concentration, which were all induced by PQ feeding, were also relieved or tended to be relieved more effectively by EGCg or ECg than by either of the mixtures mentioned. These results demonstrated that the preventive effects of EGCg and ECg in vivo cannot be obtained by ingesting the mixtures of their components.

Tea catechins showed different trends in relative antioxidant activity in different lipid systems. In corn oil triglycerides oxidized at 50 °C, epigallocatechin (EGC), epigallocatechin gallate (EGCG), and epicatechin gallate (ECG) were better antioxidants than epicatechin (EC) and catechin at 140 μM. Used as reference compounds, gallic acid (GA) was more active than propyl gallate (PG), and both were more effective than EC and catechin. However, in the corresponding corn oil-in-water emulsions, all tea catechins, GA, and PG were prooxidants at 5 and 20 μM by accelerating hydroperoxide and hexanal formation. In contrast, in soy lecithin liposomes oxidized at 50 °C, EGCG and PG were the best antioxidants, followed by EC, EGC, ECG, catechin, and GA at 20 μM. In liposomes oxidized at 37 °C with 10 μM cupric acetate, catechin and EC were better antioxidants than ECG, but EGCG, EGC, PG, and GA promoted lipid oxidation. The improved antioxidant activity observed for tea catechins in liposomes compared to emulsio...

甘藷（Ipomoea batatas Lam.）之抗氧化研究

Caffeine (1, 3, 5-trimethylxanthine), a mild addicting drug though used for medicinal purposes is the active ingredient that makes tea and coffee valuable to humans. In this study, the levels of caffeine in certain coffee (nescafe, africafe, dormans) and tea (chai mara moja, kericho gold, sasini, finlays premium) brands found in the Kenyan market were determined using high performance liquid chromatography (hplc) and UV/ Vis spectrophotometric methods. The levels of caffeine in all the tea and coffee brands were found to be within the documented range. The order of caffeine concentration in tea samples was found as follows: chai mara moja > finlays premium > kericho gold > sasini. In coffee it was found that the caffeine content of africafe > nescafe > dormans. Generally, higher concentration of caffeine in all the samples were realized with the UV/ Vis spectrophotometric method compared to hplc method indicating that acidified water was a better caffeine extractor than pure water. Key words: Caffeine, tea, coffee, high performance liquid chromatography, UV/ Vis spectrophotometry, SPE chromatography.

Development of simple identification models for four main catechins and caffeine in fresh green tea leaf based on visible and near-infrared spectroscopy