Analysis of the key aroma components of Pu'er tea by synergistic fermentation with three beneficial microorganisms

Aroma is a key indicator of the quality and value of Pu'er tea. A total of 36 aroma components were detected,which Saccharomyces, Rhizopus, and Aspergillus niger, were in the ratios of 2:1:2, 2:2:2, and 2:3:2 inoculated to ferment Pu'er tea, comparing with natural fermentation. In addition, 12 key aroma compounds were identified by analysing ROAVs. Methoxyphenyl compounds and β-ionone were the primary contributors to the formation of aged and woody aroma when fermenting Pu'er tea naturally or using Rhizopus, while linalool and its oxides, benzyl alcohol, hexanal, and limonene were the primary contributors to the formation of floral and fruity aroma when fermenting Pu'er tea using synergistic fermentation with Saccharomyces, Rhizopus, and Aspergillus niger. This study identified the key aroma components of the Pu'er tea fermented using five methods, which revealed and demonstrated the potential application of synergistic effects of different microorganisms in the changes of aroma of Pu'er tea.

assamica) to climate conditions and change in China

Crop cultivation suitability plays a vital role in determining the distribution, quality, and production of crop and can be greatly affected by climate change. Therefore, evaluating crop cultivation suitability under climate change and identifying the factors influencing it can optimize crop cultivation layout and improve production and quality. Based on comprehensive datasets including geographical distribution points, climate data, soil characteristics, and topography, our study employed the MaxEnt model to simulate the potential distribution of Pu'er tea (Camellia sinensis var. assamica) cultivation suitability in Yunnan Province from 1961 to 2020. Furthermore, we assessed the consistency between the simulated suitable areas and the actual production of Pu'er tea. The results showed that precipitation of the warmest quarter, precipitation of the driest month, and average temperature in January were the three dominant environmental variables affecting the cultivation distribution of Pu'er tea. The high suitable areas for Pu'er tea cultivation in Yunnan Province were mainly distributed in the western and southern regions, accounting for 13.89% of the total area of Yunnan Province. The medium suitable areas are mainly distributed in the central and western regions of Yunnan Province, accounting for 20.07% of the total area of Yunnan Province. Over the past 60 years, the unsuitable area for Pu'er tea has increased, while the suitable area has shown a trend of migration to the southwest. Changes in precipitation and temperature were found to be the main drivers of the changes in the distribution of suitable areas for Pu'er tea. We also found a mismatch between the cultivation suitability and the actual production of Pu'er tea. Our study provides an accurate assessment and zoning analysis of the suitability of Pu'er tea cultivation in Yunnan Province, which can help optimize the layout of Pu'er tea cultivation and reduce potential climate risks.

Pu'er tea rich in strictinin and catechins prevents biofilm formation of two cariogenic bacteria, Streptococcus mutans and Streptococcus sobrinus

Cariogenic bacteria, such as Streptococcus mutans and Streptococcus sobrinus, are main pathogens responsible for human dental caries. Pu'er tea is empirically observed to prevent tooth decay. Besides caffeine and catechins commonly found in oolong tea, strictinin is also found as an abundant phenolic compound in Pu'er tea. Infusion of Pu'er tea as well as single compound, strictinin, caffeine or (−)-epigallocatechin gallate (EGCG) was examined for its inhibitory effects on S. mutans and S. sobrinus. Relatively weak inhibition of bacterial growth was observed for these Pu'er tea constituents. However, biofilm formation of S. mutans or S. sobrinus was strongly prevented by the infusion of Pu'er tea as well as by strictinin or EGCG, but not caffeine. Relatively, strictinin showed a higher potency than EGCG to prevent biofilm formation. Anti-caries effect of Pu'er tea seems to be resulted from the prevention of biofilm formation of cariogenic bacteria mainly by strictinin and catechins.

Pu'er tea water extract protects against cognitive impairment in a mouse model of lipopolysaccharide-induced neuroinflammation

BACKGROUND

Pu'er tea, a type of post-fermented tea made from Camellia sinensis leaves, has long been widely used in East Asian countries. It is mainly produced in southern China and is effective in preventing obesity due to its ability to break down fat. However, the effects of Pu'er tea on cognitive impairment or neuroinflammation by endotoxin have not yet been studied.

PURPOSE

Here, we assessed the inhibitory activity of Pu'er tea hot water extract (PTW) on neuroinflammation and cognitive impairment and explored its mechanism.

STUDY DESIGN

The ability of PTW to inhibit cognitive impairment was investigated in a mouse model of lipopolysaccharide (LPS)-induced neuroinflammation and murine microglia BV2 cells.

METHODS

We examined whether oral administration of PTW prevented cognitive impairment and LPS-induced neuroinflammation using behavioral tests, Nissl staining, immunohistochemistry, western blotting, real-time reverse transcription-polymerase chain reaction (real-time RT-PCR), Griess assay, and enzyme-linked immunosorbent assay (ELISA).

RESULTS

First, Morris water maze (MWM) and passive avoidance (PA) tests demonstrated that oral administration of PTW effectively attenuated LPS-induced spatial memory loss and inhibited neuronal damage of mouse brains. Histopathological analysis showed that PTW repressed LPS-induced expression of the activation markers ionized calcium-binding adaptor molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP). Furthermore, PTW inhibited the expression of amyloidogenesis proteins such as amyloid-β precursor protein (APP), C99, and β-secretase-1 (BACE-1); production of inflammatory proteins such as Iba-1, GFAP, inducible nitric oxide synthase (iNOS), and cyclooxygenase (COX)-2; activation of inflammatory pathways; and expression of inflammatory mediator mRNAs in hippocampal tissue. In cultured microglia, PTW treatment inhibited the generation of various inflammatory factors activated by LPS.

CONCLUSION

Our results in vivo and in vitro demonstrate that PTW effectively prevents cognitive impairment caused by neuroinflammation and is, therefore, a potential candidate for the development of a therapeutic agent for neurodegenerative diseases.

Monitoring the authenticity of pu'er tea via chemometric analysis of multielements and stable isotopes

Mineral elements and stable isotopes combined with stoichiometric methods were used as a potential tool for first authenticating Chinese tea according to it's production year. A total of 86 mineral elements and stable isotope compositions were determined from the Xiangzhujing Pu'er tea in five different production years using ICP-MS and ICP-OES. On the basis of 78 statistically significant mineral elements and stable isotopes, HCA, PCA, PLS-DA, BP-ANN, and LDA were employed to build authentication models for predicting the Pu'er tea with different production years. The clustering results of the HCA and PCA were worse than that of PLS-DA, BP-ANN, and LDA. The PLS-DA model displayed a perfect model performance (R²X = 0.86, R²Y = 0.974, and Q² = 0.922). The authentication performance of LDA and BP-ANN revealed their 100% recognition sensitivity and prediction ability and was thus better than that of PLS-DA. Mn, ⁶⁸Zn, and ²⁰³Tl were the markers for enabling the successful authentication of Pu'er tea with different production years. This study contributes toward generalizing the use of mineral element and stable isotope fingerprinting combined with LDA and BP-ANN as a promising tool for authentication of tea worldwide.

nov., isolated from Pu'er tea

A novel bacterial strain, designated T8^T, isolated from ripened Pu'er tea, was investigated by using a polyphasic taxonomic approach. Cells stained Gram-positive and were aerobic, sporogenous and rod-shaped with flagella. Phylogenetic analysis of 16S rRNA gene sequences revealed the strain belonged to the family Bacillaceae in the class Bacilli and represented an independent taxon separated from other genera. Strain T8^T shared low levels of 16S rRNA gene sequence similarity (<94 %) to members of other genera in the family Bacillaceae and was most closely related to Bacillus composti SgZ-9^T (93.3 % sequence similarity). The DNA G+C content of strain T8^T was 40 mol%. The major fatty acids (>10 %) of strain T8^T were iso-C15 : 0 and iso-C16 : 0. The strain had a cell-wall type A1γ peptidoglycan with meso-diaminopimelic acid as the diagnostic diamino acid. MK-7 (62 %), MK-6 (31 %) and MK-8 (7 %) were detected as the isoprenoid quinones. The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine and six unidentified phospholipids. On the basis of the polyphasic evidence presented, strain T8^T is considered to represent a novel genus and species in the family Bacillaceae, for which we propose the name Pueribacillus theae gen. nov., sp. nov. The type strain is T8^T (=CGMCC 1.15924^T=KCTC 333888^T).

nov., isolated from Pu'er tea

A novel aerobic, Gram-stain-positive, sporogenous, rod-shaped bacterial strain, 7578-1^T, was isolated from ripened Pu'er tea. Based on 16S rRNA gene sequence similarity comparisons, strain 7578-1^T was grouped into the genus Bacillus and appeared to be closely related to the type strains Bacillus shackletoniiLMG 18435^T (98.4 %), Bacillus acidicolaDSM 14745^T (97.6 %), Bacillus paralicheniformis KACC 18426^T (97.2 %) and Bacillus ginsengihumi KCTC 13944^T (96.7 %). The fatty acid profile containing the major fatty acids, iso-C15 : 0, anteiso-C15 : 0 and anteiso-C17 : 0 supported the allocation of strain 7578-1^T to the genus Bacillus. The strain had a cell-wall type A1γ peptidoglycan with meso-diaminopimelic acid as the diagnostic diamino acid. The major menaquinone was MK-7 (95 %). The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, one unidentified phospholipid and one unidentified lipid. The average nucleotide identity values between strain 7578-1^T and its most closely related species were 67.8-82.4 % by OrthoANIu analysis. The DNA-DNA relatedness value between strain 7578-1^T and the type strains of closely related species were 17-39 %, again indicating that strain 7578-1^T represented a novel species in the genus Bacillus. The DNA G+C content of strain 7578-1^T was 36.0 mol%. On the basis of the presented polyphasic evidence, strain 7578-1^T is considered to represent a novel species of the genus Bacillus, for which we propose the name Bacillus camelliae sp. nov. The type strain is 7578-1^T (=CGMCC 1.15374^T=KCTC 33845^T).

Antibacterial and laxative activities of strictinin isolated from Pu'er tea (Camellia sinensis)

Strictinin, the major phenolic compound in Pu'er teas produced from young leaves and buds of wild trees, was isolated to evaluate its antibacterial and laxative activities. The minimum inhibitory concentrations of strictinin against Propionibacterium acnes and Staphylococcus epidermidis were determined as 250 μM and 2000 μM, respectively, apparently higher than those of several antibiotics commonly used for bacterial infections. The additive and synergistic effects on the inhibitory activities of strictinin combined with other commercial antibiotics were observed in two bacteria tested in this study via the analysis of fractional inhibitory concentrations. Laxative activity was observed on defecation of the rats fed with strictinin. Further analysis showed that the laxative effect of strictinin was presumably caused by accelerating small intestinal transit, instead of enhancing gastric emptying, increasing food intake, or inducing diarrhea in the rats. Taken together with the antiviral activities demonstrated previously, it is suggested that strictinin is one of the active ingredients responsible for the antiviral, antibacterial, and laxative effects of wild Pu'er tea, and has the potential to be developed as a mild natural substitute for antibiotics and laxatives.

Significant elevation of antiviral activity of strictinin from Pu'er tea after thermal degradation to ellagic acid and gallic acid

Compared with abundant catechins, strictinin is a minor constituent in teas and has been demonstrated to possess inhibitory potency on influenza virus. In this study, strictinin was found as the major phenolic compound in Pu’er teas produced from leaves and buds of wild trees. Due to its thermal instability, strictinin, in tea infusion or in an isolated form, was completely decomposed to ellagic acid and gallic acid after being autoclaved for 7 minutes. A plaque reduction assay was employed to compare the relative inhibitory potency between strictinin and its thermally degraded products against human influenza virus A/ Puerto Rico/8/34. The results showed that the antiviral activity of ellagic acid regardless of the presence or absence of gallic acid was significantly higher than that of strictinin. Thermal degradation of strictinin to ellagic acid and gallic acid seems to be beneficial for the preparation of Pu’er teas in terms of enhancing antiviral activity.