Tea (Camellia sinensis): A Review of Nutritional Composition, Potential Applications, and Omics Research

A method for mining condition-specific co-expressed genes in Camellia sinensis based on k-means clustering

BACKGROUND

As one of the world's most important beverage crops, tea plants (Camellia sinensis) are renowned for their unique flavors and numerous beneficial secondary metabolites, attracting researchers to investigate the formation of tea quality. With the increasing availability of transcriptome data on tea plants in public databases, conducting large-scale co-expression analyses has become feasible to meet the demand for functional characterization of tea plant genes. However, as the multidimensional noise increases, larger-scale co-expression analyses are not always effective. Analyzing a subset of samples generated by effectively downsampling and reorganizing the global sample set often leads to more accurate results in co-expression analysis. Meanwhile, global-based co-expression analyses are more likely to overlook condition-specific gene interactions, which may be more important and worthy of exploration and research.

RESULTS

Here, we employed the k-means clustering method to organize and classify the global samples of tea plants, resulting in clustered samples. Metadata annotations were then performed on these clustered samples to determine the "conditions" represented by each cluster. Subsequently, we conducted gene co-expression network analysis (WGCNA) separately on the global samples and the clustered samples, resulting in global modules and cluster-specific modules. Comparative analyses of global modules and cluster-specific modules have demonstrated that cluster-specific modules exhibit higher accuracy in co-expression analysis. To measure the degree of condition specificity of genes within condition-specific clusters, we introduced the correlation difference value (CDV). By incorporating the CDV into co-expression analyses, we can assess the condition specificity of genes. This approach proved instrumental in identifying a series of high CDV transcription factor encoding genes upregulated during sustained cold treatment in Camellia sinensis leaves and buds, and pinpointing a pair of genes that participate in the antioxidant defense system of tea plants under sustained cold stress.

CONCLUSIONS

To summarize, downsampling and reorganizing the sample set improved the accuracy of co-expression analysis. Cluster-specific modules were more accurate in capturing condition-specific gene interactions. The introduction of CDV allowed for the assessment of condition specificity in gene co-expression analyses. Using this approach, we identified a series of high CDV transcription factor encoding genes related to sustained cold stress in Camellia sinensis. This study highlights the importance of considering condition specificity in co-expression analysis and provides insights into the regulation of the cold stress in Camellia sinensis.

Using QuEChERS and HPLC Method to Monitor the Background Concentration of Polycyclic Aromatic Hydrocarbons in Commercial Black Tea Leaves and Infusions in Taiwan

Tea is an integral part of Taiwanese culture and is a popular drink as it contains many beneficial compounds. However, during the processing of tea, polycyclic aromatic hydrocarbons (PAHs) may form. This study investigated the concentrations of PAH4 in different black tea leaves and tea infusions based on the origin of the tea. The samples were extracted using QuEChERS, while the content of PAH4 was analyzed by high performance liquid chromatography coupled to a fluorescence detector (HPLC-FLD). The content of PAH4 in the tea leaves ranged from 2.88 µg/kg to 218.2 µg/kg (dry weight), with the highest concentration being found in teas from Vietnam. The concentration of BaP ranged from ND to 47.92 µg/kg. The release of PAH4 from tea leaves to tea infusions was significantly low, with the highest transfer being 25.8%. In this study, all PAH4 compounds in commercial black tea leaves can be detected by QuEChERS extraction with a simple HPLC method.

Dietary Exposure and Health Risk Assessment of Polycyclic Aromatic Hydrocarbons in Black Tea Consumed in Taiwan

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds found in many foods and drinks, and there have been some concerns over these compounds due to their carcinogenic nature. This study evaluated the concentrations of PAH4 (BaP, BaA, BbF, and CHR) in different black tea infusions and drinks based on the origin of the tea. The release of PAH4 from tea leaves to tea infusions was significantly low, with the highest transfer being 25.81%. The mean concentrations of BaP and PAH4 in tea infusions were used to conduct a risk assessment for the Taiwanese population, which showed that the 19-65 age group had the highest estimated intake of PAH4 and BaP among all age groups. These results, however, also showed margin of exposure (MOE) values well above the benchmark of 10,000. This indicated that PAH exposure from black tea consumption for the Taiwanese population constitutes a low-level health concern.

Therapeutic potentialities of green tea (Camellia sinensis) in ischemic stroke: biochemical and molecular evidence

Ischemic stroke is a leading cause of disability and death in patients. Despite considerable recent advances in the treatment of ischemic stroke, only a limited number of effective neuroprotective agents are available for stroke. Green tea (Camellia sinensis) is a popular herbal plant, and numerous studies have indicated its health benefits for several diseases. Green tea is of interest due to its high content of catechin derivatives, including epicatechin, gallocatechin, epicatechin gallate, epigallocatechin, and epigallocatechin-3-gallate. This review tried to develop a feasible background for the potential effects of green tea and its bioactive derivatives concerning protection against ischemic stroke. Green tea's antioxidants, anti-inflammatory, anti-apoptotic, and neuroprotective effects are believed to be efficacious in stroke treatment. Evidence supports the idea that green tea can be used to assist in treating ischemic stroke.

Comparative Phylogenetic Analysis of Ancient Korean Tea "Hadong Cheon-Nyeon Cha (Camellia sinensis var. sinensis)" Using Complete Chloroplast Genome Sequences

Wild teas are valuable genetic resources for studying evolution and breeding. Here, we report the complete chloroplast genome of the ancient Korean tea 'Hadong Cheon-nyeon Cha' (C. sinensis var. sinensis), which is known as the oldest tea tree in Korea. This study determined seven Camellia sinensis var. sinenesis, including Hadong Cheon-nyeon Cha (HCNC) chloroplast genome sequences, using Illumina sequencing technology via de novo assembly. The chloroplast genome sizes ranged from 157,019 to 157,114 bp and were organized into quadripartite regions with the typical chloroplast genomes. Further, differences in SNPs and InDels were detected across the seven chloroplast genomes through variance analysis. Principal component and phylogenetic analysis suggested that regional constraints, rather than functional constraints, strongly affected the sequence evolution of the cp genomes in this study. These genomic resources provide evolutionary insight into Korean tea plant cultivars and lay the foundation for a better understanding of the ancient Korean tea plant HCNC.

Seasonal variations in the phenolic profile, antioxidant activity, and mineral content of south Indian black tea (Camellia sinensis (L.) O. Kuntze)

In the Anamallais region of south India, crop shoots from the UPASI-3, UPASI-9, UPASI-17, Assam seedlings, and TRI-2043 cultivars were examined for seasonal variations in total phenolics, antioxidant activity, and minerals during four harvest seasons: summer (January to March), premonsoon (April and May), monsoon (June to September), and winter (October to December) of two consecutive years. The total phenolics of all cultivars were lower in monsoon period and grew over rest of the seasons and it was greater during summer. Crop shoot antioxidant activity as measured by the DPPH radical scavenging experiment exhibited a similar pattern to total phenolics. Summer was the season with the highest antioxidant activity across all cultivars, followed by premonsoon, winter, and monsoon. On the other hand, the employed cultivars differed noticeably in terms of seasonal change of minerals. These results appear to indicate that the harvest period is hypercritical in deciding the antioxidant potency of tea crop shoots.

Evaluation of the antibacterial activity of selected Kenyan medicinal plant extract combinations against clinically important bacteria

BACKGROUND

Infectious diseases are a major global public health concern as antimicrobial resistance (AMR) currently accounts for more than 700,000 deaths per year worldwide. The emergence and spread of resistant bacterial pathogens remain a key challenge in antibacterial chemotherapy. This study aims to investigate the antibacterial activity of combined extracts of various Kenyan medicinal plants against selected microorganisms of medical significance.

METHODS

The antibacterial activity of various extract combinations of Aloe secundiflora, Toddalia asiatica, Senna didymobotrya and Camelia sinensis against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Methicillin Resistant Staphylococcus aureus was assessed using the agar well diffusion and the minimum inhibitory concentration in-vitro assays. The checkerboard method was used to evaluate the interactions between the various extract combinations. ANOVA test followed by Tukey's post hoc multiple comparison test was used to determine statistically significant differences in activity (P < 0.05).

RESULTS

At concentrations of 100 mg/ml (10,000 µg/well), the different combinations of the aqueous, methanol, dichloromethane and petroleum ether extracts of the selected Kenyan medicinal plants revealed diverse activity against all the test bacteria. The combination of methanolic C. sinensis and A. secundiflora was the most active against E. coli (14.17 ± 0.22 mm, diameter of zones of inhibition (DZI); MIC 2500 µg/well). The combination of methanolic C. sinensis and S. didymobotrya was the most active against S. aureus (16.43 ± 0.10 mm; MIC 1250 µg/well), K. pneumonia (14.93 ± 0.35 mm, DZI; MIC 1250 µg/well), P. aeruginosa (17.22 ± 0.41 mm, DZI; MIC 156.25 µg/well) and MRSA (19.91 ± 0.31 mm, DZI; MIC 1250 µg/well). The Minimum Inhibitory Concentration of the different plant extract combinations ranged from 10,000 µg/ well to 156.25 µg/well. The ANOVA test indicated statistically significant differences (P < 0.05) between single extracts and their combinations. The fractional inhibitory concentration indices (FICI) showed that the interactions were either synergistic (10.5%), additive (31.6%), indifferent (52.6%), or antagonistic (5.3%) for the selected combinations.

CONCLUSION

This study findings validate the ethnopractice of selectively combining medicinal plants in the management of some bacterial infections in traditional medicine.

Ultrasonic-assisted enzymatic improvement of polyphenol content, antioxidant potential, and in vitro inhibitory effect on digestive enzymes of Miang extracts

The aims of this research were to optimize the ultrasonic-assisted enzymatic extraction of polyphenols under Miang and tannase treatment conditions for the improvement of antioxidant activity of Miang extracts via response surface methodology. Miang extracts treated with and without tannase were investigated for their inhibitory effects on digestive enzymes. The optimal conditions for ultrasonic-assisted enzymatic extraction of the highest total polyphenol (TP) (136.91 mg GAE/g dw) and total flavonoid (TF) (5.38 mg QE/g dw) contents were as follows: 1 U/g cellulase, 1 U/g xylanase, 1 U/g pectinase, temperature (74 °C), and time (45 min). The antioxidant activity of this extract was enhanced by the addition of tannase obtained from Sporidiobolus ruineniae A45.2 undergoing ultrasonic treatment and under optimal conditions (360 mU/g dw, 51 °C for 25 min). The ultrasonic-assisted enzymatic extraction selectively promoted the extraction of gallated catechins from Miang. Tannase treatment improved the ABTS and DPPH radical scavenging activities of untreated Miang extracts by 1.3 times. The treated Miang extracts possessed higher IC₅₀ values for porcine pancreatic α-amylase inhibitory activity than those that were untreated. However, it expressed approximately 3 times lower IC₅₀ values for porcine pancreatic lipase (PPL) inhibitory activity indicating a marked improvement in inhibitory activity. The molecular docking results support the contention that epigallocatechin, epicatechin, and catechin obtained via the biotransformation of the Miang extracts played a crucial role in the inhibitory activity of PPL. Overall, the tannase treated Miang extract could serve as a functional food and beneficial ingredient in medicinal products developed for obesity prevention.