Cardio-protective effects of phytosterol-enriched functional black tea in mild hypercholesterolemia subjects

Effects of phytosterols on cardiovascular risk factors: A systematic review and meta-analysis of randomized controlled trials

Cardiovascular diseases are the major cause of death globally. The primary risk factors are high blood lipid levels, hypertension, diabetes, and obesity. Phytosterols are naturally occurring plant bioactive substances. Short-term clinical trials have demonstrated phytosterols' cholesterol-lowering potential, but their effects on cardiovascular risk factors remain controversial, and relevant meta-analyses are limited and incomplete. We conducted a systematic and comprehensive search of PubMed, Web of Science, Embase and Cochrane Library up to December 22, 2023. A total of 109 randomized controlled trials (RCTS) of phytosterols (PS) intervention on cardiovascular risk factor outcomes were included in a preliminary screening of the retrieved literature by Endnote 20. We assessed the quality of all included randomized controlled trials using the Cochrane Collaboration's Risk of Bias tool. Cochrane data conversion tool was used for data conversion, and finally Stata was used for meta-analysis, egger test and sensitivity analysis of the included studies. The results indicated that dietary phytosterols intake could significantly decrease total cholesterol (TC) level (mean difference = -13.41; 95% confidence interval [CI]: -15.19, -11.63, p < 0.001), low density lipoprotein cholesterol (LDL-C) level (mean difference = -12.57; 95% CI: -13.87, -11.26, p < 0.001), triglycerides (TG) level (mean difference = -6.34; 95% CI: -9.43, -3.25, p < 0.001), C-reactive protein (CRP) level (mean difference = -0.05; 95% CI: -0.08, -0.01, p = 0.671), systolic blood pressure (SBP) level (mean difference = -2.10; 95% CI: -3.27, -0.9, p < 0.001), diastolic blood pressure (DBP) level (mean difference = -0.83; 95% CI: -0.58, -0.07, p = 0.032), increased high-density lipoprotein cholesterol (HDL-C) level (mean difference = 0.46; 95% CI: 0.13, 0.78, p = 0.005), but did not alter the levels of blood glucose (GLU) (mean difference = -0.44; 95% CI: -1.64, 0.76, p = 0.471), glycosylated hemoglobin, Type A1C (HbA1c) (mean difference = -0.28; 95% CI: -0.75, 0.20, p = 0.251), interleukin-6 (IL-6) (mean difference = 0.00; 95% CI: -0.02, 0.02, p = 0.980), tumor necrosis factor (TNF-α) (mean difference = 0.08; 95% CI: -0.08, 0.24, p = 0.335), oxidized low-density lipoprotein cholesterol (OXLDL-C) (standard mean difference = 0.16; 95% CI: -0.38, 0.06, p = 0.154), body mass index (BMI) (mean difference = 0.01; 95% CI: -0.07, 0.09, p = 0.886), waist circumference (WC) (mean difference = -0.10; 95% CI: -0.50, 0.30, p = 0.625) and body weight (mean difference = 0.03; 95% CI: -0.18, 0.24, p = 0.787). Our results suggest that phytosterols may be beneficial in reducing the levels of TC, LDL-C, TG, CRP, SBP, and DBP, but have no significant effect on GLU, HbA1c, TNF-α, IL-6, OXLDL-C, BMI, WC, and Weight. However, there were a small number of RCTS included in this study and their small population size may have reduced the quality of the study. And most of the included studies were short-term intervention trials. Therefore, higher quality studies need to be designed in future studies to establish more accurate conclusions.

Hypolipidemic activity of phytochemical combinations: A mechanistic review of preclinical and clinical studies

Hyperlipidemia, a condition characterized by elevated levels of lipids in the blood, poses a significant risk factor for various health disorders, notably cardiovascular diseases. Phytochemical compounds are promising alternatives to the current lipid-lowering drugs, which cause many undesirable effects. Based on in vivo and clinical studies, combining phytochemicals with other phytochemicals, prebiotics, and probiotics and their encapsulation in nanoparticles is more safe and effective for managing hyperlipidemia than monotherapy. To this end, the results obtained and the mechanisms of action of these combinations were examined in detail in this review.

Effect of Phytosterols on Serum Levels of C-Reactive Protein: A Time- and Dose-Response Meta-analysis of Randomized Controlled Trial

INTRODUCTION

Phytosterols are recognized for their cholesterol-reducing effects and are commonly used as dietary supplements or added to foods due to their potential cardiovascular benefits. However, evidence regarding the impact of phytosterol supplementation on inflammatory markers remains inconclusive.

AIM

This systematic review and meta-analysis aim to evaluate the effect of phytosterols in reducing levels of C-reactive protein (CRP) and high-sensitivity CRP (hs-CRP).

METHODS

A systematic literature search of the primary databases was conducted up to May 2024 to identify eligible studies. The measurement of effect sizes was determined using WMD (weighted mean difference) and 95% CI.

RESULTS

For the meta-analysis, 14 publications (19 study arms) for hs-CRP and 10 publications (16 study arms) for CRP were included. The pooled analysis showed that the administration of phytosterol did not significantly reduce CRP compared to control with WMD= -0.04 mg/l (95% CI: -0.28 to 0.20, P = 0.74). However, phytosterol supplementation significantly decreased the hs-CRP level compared to the control group with WMD of -0.25 mg/l (95% CI: -0.42 to -0.07, P = 0.006). The WMD for hs-CRP reduction was - 0.36 mg/l (95% CI: -0.53 to -0.18, P < 0.001) for supplementation with a phytosterol dose ≥ 2000 mg/day compared to the control group.

CONCLUSIONS

Phytosterol supplementation may be effective in reducing hs-CRP levels.

Advances in the Utilization of Tea Polysaccharides: Preparation, Physicochemical Properties, and Health Benefits

Tea polysaccharide (TPS) is the second most abundant ingredient in tea following tea polyphenols. As a complex polysaccharide, TPS has a complex chemical structure and a variety of bioactivities, such as anti-oxidation, hypoglycemia, hypolipidemic, immune regulation, and anti-tumor. Additionally, it shows excellent development and application prospects in food, cosmetics, and medical and health care products. However, numerous studies have shown that the bioactivity of TPS is closely related to its sources, processing methods, and extraction methods. Therefore, the authors of this paper reviewed the relevant recent research and conducted a comprehensive and systematic review of the extraction methods, physicochemical properties, and bioactivities of TPS to strengthen the understanding and exploration of the bioactivities of TPS. This review provides a reference for preparing and developing functional TPS products.

Comparison of the chemical composition and antioxidant, anti-inflammatory, α-amylase and α-glycosidase inhibitory activities of the supernatant and cream from black tea infusion

Tea cream is a kind of turbid substance commonly existing in tea infusion and tea beverage upon cooling. Herein, a comparative study was conducted on the supernatant and cream from black tea infusion in terms of antioxidant, anti-inflammatory and enzyme inhibitory activities, and chemical composition. Ultraviolet-visible (UV-vis) spectrometry and high-performance liquid chromatography (HPLC) analysis showed that the contents of protein, polyphenols, theaflavins, thearubigins, theabrownins, and caffeine in cream were significantly higher than those in the supernatant. The contents of Al, Ca, Cu, and Fe elements in cream were higher than those in the supernatant. However, higher levels of monosaccharides and free amino acids were detected in the supernatant compared with cream. The ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) based metabolomics analysis revealed that the main marker compounds between the supernatant and the cream were organic acids, phenolic acids, and flavan-3-ols and their oxidation products, flavonol glycosides and amino acids. The cream showed better antioxidant and anti-inflammatory, as well as α-amylase and α-glycosidase inhibitory activities than the supernatant, because it contained higher contents of polyphenols than the supernatant. The present study expanded the new vision towards the cream of black tea infusion.

Targeted and nontargeted metabolomics analysis for determining the effect of storage time on the metabolites and taste quality of keemun black tea

The black tea could be stored for a long time, and subsequently affects the flavor characteristics. In the present study, the effects of storage years (1, 2, 3, 4, 5, 10, 17 and 20 years) on the chemical profiling and taste quality of keemun black tea (KBT) were compared by metabolomics and quantitative sensory evaluation. The main polyphenols were degraded during the storing, especially 10-year storage, but caffeine and theobromine were stable. The intensity of bitterness, astringency, umami was negatively correlated to storage years, with correlation coefficient at -0.95, -0.91 and -0.83 respectively, whereas sweetness had positive correlation coefficient at 0.74. Quinic acid, galloylated catechins, linolenic acid, linoleic acid, malic acid, palamitic acid, and theaflavin-3́-gallate were marker compounds which were responsible for distinguishing short and long time preserved KBT. The contents of fatty acids were positively correlated to storage time and sweet intensity.

Antioxidant Food Components for the Prevention and Treatment of Cardiovascular Diseases: Effects, Mechanisms, and Clinical Studies

Cardiovascular diseases (CVDs) have gained increasing attention because of their high prevalence and mortality worldwide. Epidemiological studies revealed that intake of fruits, vegetables, nuts, and cereals could reduce the risk of CVDs, and their antioxidants are considered as the main contributors. Moreover, experimental studies showed that some antioxidant natural products and their bioactive compounds exerted beneficial effects on the cardiovascular system, such as polyphenols, polysaccharides, anthocyanins, epigallocatechin gallate, quercetin, rutin, and puerarin. The mechanisms of action mainly included reducing blood pressure, improving lipid profile, ameliorating oxidative stress, mitigating inflammation, and regulating gut microbiota. Furthermore, clinical trials confirmed the cardiovascular-protective effect of some antioxidant natural products, such as soursop, beetroot, garlic, almond, and green tea. In this review, we summarized the effects of some antioxidant natural products and their bioactive compounds on CVDs based on the epidemiological, experimental, and clinical studies, with special attention paid to the relevant mechanisms and clinical trials.

Short-Term Tea Consumption Is Not Associated with a Reduction in Blood Lipids or Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

A recent systematic review of epidemiological evidence suggests that higher amounts of tea intake are associated with lower risks of cardiovascular disease (CVD) incidence and mortality.

OBJECTIVES

Our study objective was to assess mechanisms by which tea consumption may influence CVD risks.

METHODS

A systematic review and meta-analysis was conducted to investigate the effects of green and/or black tea consumption (≥4 wk) on systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol, LDL cholesterol, HDL cholesterol, and triglyceride (TG) in healthy populations and among at-risk adults (analyzed separately) with metabolic syndrome, prediabetes, and hypercholesterolemia. The Grading of Recommendations Assessment, Development and Evaluation approach was used to rate the strength of evidence (SoE).

RESULTS

A total of 14 unique RCTs which randomly assigned 798 participants to either green tea, black tea, or placebo controls were included in our analyses. Intervention durations ranged from 4 to 24 wk (mean: 7.4 wk). Individual studies were judged as moderate to high quality based on risk of bias assessments. SoE was low to moderate owing to low sample sizes and insufficient power for most included studies to observe changes in the measured CVD biomarkers. Meta-analyses showed no significant effects of tea consumption on SBP, DBP, total cholesterol, LDL cholesterol, HDL cholesterol, and TG in healthy and at-risk adults (i.e., adults with obesity, prediabetes, borderline hypercholesterolemia, and metabolic syndrome).

CONCLUSIONS

Short-term (4-24 wk) tea consumption does not appear to significantly affect blood pressure or lipids in healthy or at-risk adults, although the evidence is limited by insufficient power to detect changes in these CVD biomarkers. High-quality RCTs with longer durations and sufficient sample sizes are needed to fully elucidate the effects of tea. This systematic review was registered at www.crd.york.ac.uk/prospero/ as CRD42020134513.

The Pharmacological Activity of Camellia sinensis (‎L.‎) ‎Kuntze‎ on Metabolic and Endocrine Disorders: A Systematic Review

Tea made from Camellia sinensis leaves is one of the most consumed beverages worldwide. This systematic review aims to update Camellia sinensis pharmacological activity on metabolic and endocrine disorders. Inclusion criteria were preclinical and clinical studies of tea extracts and isolated compounds on osteoporosis, hypertension, diabetes, metabolic syndrome, hypercholesterolemia, and obesity written in English between 2014 and 2019 and published in Pubmed, Science Direct, and Scopus. From a total of 1384 studies, 80 reports met inclusion criteria. Most papers were published in 2015 (29.3%) and 2017 (20.6%), conducted in China (28.75%), US (12.5%), and South Korea (10%) and carried out with extracts (67.5%, especially green tea) and isolated compounds (41.25%, especially epigallocatechin gallate). Most pharmacological studies were in vitro and in vivo studies focused on diabetes and obesity. Clinical trials, although they have demonstrated promising results, are very limited. Future research should be aimed at providing more clinical evidence on less studied pathologies such as osteoporosis, hypertension, and metabolic syndrome. Given the close relationship among all endocrine disorders, it would be of interest to find a standard dose of tea or their bioactive constituents that would be beneficial for all of them.

Modulation of Glucose Metabolism by Leaf Tea Constituents: A Systematic Review of Recent Clinical and Pre-clinical Findings

Leaf teas are widely used as a purported treatment for dysregulated glucose homeostasis. The objective of this study was to systematically evaluate the clinical and cellular-metabolic evidence, published between January 2013 and May 2019, and indexed on PubMed, ScienceDirect, and Web of Science, supporting the use of leaf teas for this purpose. Fourteen randomized controlled trials (RCTs) (13 on Camellia sinensis teas) were included, with mixed results, and providing scant mechanistic information. In contrast, 74 animal and cell culture studies focusing on the pancreas, liver, muscle, and adipose tissue yielded mostly positive results and highlighted enhanced insulin signaling as a recurring target associated with the effects of teas on glucose metabolism. We conclude that more studies, including RCTs and pre-clinical studies examining teas from a wider variety of species beyond C. sinensis, are required to establish a stronger evidence base on the use of leaf teas to normalize glucose metabolism.

Health Functions and Related Molecular Mechanisms of Tea Components: An Update Review

Tea is widely consumed all over the world. Generally, tea is divided into six categories: White, green, yellow, oolong, black, and dark teas, based on the fermentation degree. Tea contains abundant phytochemicals, such as polyphenols, pigments, polysaccharides, alkaloids, free amino acids, and saponins. However, the bioavailability of tea phytochemicals is relatively low. Thus, some novel technologies like nanotechnology have been developed to improve the bioavailability of tea bioactive components and consequently enhance the bioactivity. So far, many studies have demonstrated that tea shows various health functions, such as antioxidant, anti-inflammatory, immuno-regulatory, anticancer, cardiovascular-protective, anti-diabetic, anti-obesity, and hepato-protective effects. Moreover, it is also considered that drinking tea is safe to humans, since reports about the severe adverse effects of tea consumption are rare. In order to provide a better understanding of tea and its health potential, this review summarizes and discusses recent literature on the bioactive components, bioavailability, health functions, and safety issues of tea, with special attention paid to the related molecular mechanisms of tea health functions.

Effects and Mechanisms of Tea and Its Bioactive Compounds for the Prevention and Treatment of Cardiovascular Diseases: An Updated Review

Cardiovascular diseases (CVDs) are critical global public health issues with high morbidity and mortality. Epidemiological studies have revealed that regular tea drinking is inversely associated with the risk of CVDs. Additionally, substantial in vitro and in vivo experimental studies have shown that tea and its bioactive compounds are effective in protecting against CVDs. The relevant mechanisms include reducing blood lipid, alleviating ischemia/reperfusion injury, inhibiting oxidative stress, enhancing endothelial function, attenuating inflammation, and protecting cardiomyocyte function. Moreover, some clinical trials also proved the protective role of tea against CVDs. In order to provide a better understanding of the relationship between tea and CVDs, this review summarizes the effects of tea and its bioactive compounds against CVDs and discusses potential mechanisms of action based on evidence from epidemiological, experimental, and clinical studies.

Effectiveness of black tea versus placebo in subjects with hypercholesterolemia: A PRISMA systematic review and meta-analysis

AIM

To determine if the black tea is more effective in serum lipid profile that placebo in subjects with hypercholesterolemia.

DESIGN

Systematic review with meta-analysis of randomized clinical trials (RCTs).

DATA SOURCES

The databases Medline, Central, Embase, Lilacs, Cinahl, SPORTDiscus, and Web of Science were searched from inception up to January 2019.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

RCTs that compared black tea versus placebo, that included serum lipid profile outcomes in subjects older than 18 years of age with hypercholesterolemia.

RESULTS

Seven RCTs met the eligibility criteria, and for the quantitative synthesis, six studies were included. Mean difference for total cholesterol was 1.67 mg/dl 95% CI = -5.47 to 8.80 (p = 0.65), mean difference 0.28 mg/dl, 95% CI = -3.89 to 4.45 (p = 0.90) for triglycerides, mean difference 3.21 mg/dl, 95% CI = -11.02 to 4.60 (p = 0.42) for low density lipoprotein-cholesterol, mean difference 0.38 mg/dl, 95% CI = -1.12 to 1.87 (p = 0.62) for high density lipoprotein-cholesterol.

CONCLUSION

In the short term, no significant differences were found in lipid serum profile comparing black tea consumption with placebo.

Enhancement of Galloylation Efficacy of Stigmasterol and β-Sitosterol Followed by Evaluation of Cholesterol-Reducing Activity

In this study, incorporation of gallic acid into typical phytosterols (β-sitosterol and stigmasterol) through Steglich esterification was optimized employing the protection and deprotection strategy. A novel mechanism leading to side esterification was discovered. Complication of the phenolic hydroxyl groups and side reactions were successfully reduced under the optimized conditions. The structural identity and purity of galloyl stigmasterol and galloyl β-sitosterol were confirmed by NMR, FT-IR, and HPLC-MS. Evaluation of galloyl β-sitosterol and galloyl stigmasterol revealed their excellent antioxidant and cholesterol-reducing activities. Significant enhancement of cholesterol-reducing activity by galloylation was unveiled especially for β-sitosterol. Galloyl β-sitosterol had slightly better antioxidant activity at ambient temperature and better cholesterol-reducing activity. Molecular modeling suggested that a subtle difference of galloyl β-sitosterol and galloyl stigmasterol in activities could be attributed to variation of molecular rigidity and conformation. The excellent properties of galloyl β-sitosterol and galloyl stigmasterol suggested their great potential application in the food industry.

Mild and Efficient Preparation of Phytosteryl Amino Acid Ester Hydrochlorides and Their Emulsifying Properties

The aim of this work was to produce a series of phytosteryl amino acid ester hydrochlorides by a two-step method, which involved esterification of phytosterols with N- tert-butoxycarbonyl (BOC) amino acid and deprotection of the BOC group. The highest yield of over 95.0% was obtained when the catalysts were the mixtures of 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochlide, 4-dimethylaminopyridine, and triethylamine. It was found that batch charging of the reactants and catalysts was conducive to improving the yield. In addition, over 99.0% of the BOC group deprotection degree was achieved using the HCl/ethyl acetate deprotection method. All of the compounds were characterized by fourier transform infrared spectroscopy, mass spectroscopy, and nuclear magnetic resonance spectroscopy. The emulsifying properties of phytosterols and phytosteryl amino acid ester hydrochlorides were also investigated. The results showed higher emulsifying properties of phytosteryl amino acid ester hydrochlorides, which could favor its wide application in food systems.

Highly efficient synthesis of phytosterol linolenate in the presence of Bronsted acidic ionic liquid

Phytosterols are effective in reducing plasma cholesterol. However, phytosterols in a free form have some disadvantages because they have a high melting point and a poor oil solubility, thereby limiting their practical application in foods. The present study was to establish a green and highly efficient method to synthesize phytosterol linolenate for the first time by employing Bronsted acidic ionic liquid (IL) as a catalyst in order to improve its oil solubility. The product was separated, analyzed and subsequently characterized using thin layer chromatography, fourier transform infrared spectroscopy and mass spectroscopy. The conversion of phytosterols could reach above 96% in a very short time (30 min) under the following optimum conditions: 3% 1-butylsulfonate-3-methylimidazolium trifluoromethanesulfonate ([BSO₃HMim]OTf) as a catalyst, 110 °C and 1:1.75 M ratio of phytosterols to ethyl linolenate. The present method demonstrated that [BSO₃HMim]OTf would be a potential catalyst for phytosterol ester synthesis. Most importantly was that the oil solubility of phytosterol linolenate was much greater than its corresponding free phytosterols.

Defatted Kenaf (Hibiscus cannabinus L.) Seed Meal and Its Phenolic-Saponin-Rich Extract Protect Hypercholesterolemic Rats against Oxidative Stress and Systemic Inflammation via Transcriptional Modulation of Hepatic Antioxidant Genes

The present study aimed to investigate the antioxidant and anti-inflammatory properties of defatted kenaf seed meal (DKSM) and its phenolic-saponin-rich extract (PSRE) in hypercholesterolemic rats. Hypercholesterolemia was induced using atherogenic diet feeding, and dietary interventions were conducted by incorporating DKSM (15% and 30%) or PSRE (at 2.3% and 4.6%, resp., equivalent to the total content of DKSM-phenolics and saponins in the DKSM groups) into the atherogenic diets. After ten weeks of intervention, serum total antioxidant capacities of hypercholesterolemic rats were significantly enhanced by DKSM and PSRE supplementation (p < 0.05). Similarly, DKSM and PSRE supplementation upregulated the hepatic mRNA expression of antioxidant genes (Nrf2, Sod1, Sod2, Gsr, and Gpx1) of hypercholesterolemic rats (p < 0.05), except for Gpx1 in the DKSM groups. The levels of circulating oxidized LDL and proinflammatory biomarkers were also markedly suppressed by DKSM and PSRE supplementation (p < 0.05). In aggregate, DKSM and PSRE attenuated the hypercholesterolemia-associated oxidative stress and systemic inflammation in rats, potentially by enhancement of hepatic endogenous antioxidant defense via activation of the Nrf2-ARE pathway, which may be contributed by the rich content of phenolics and saponins in DKSM and PSRE. Hence, DKSM and PSRE are prospective functional food ingredients for the potential mitigation of atherogenic risks in hypercholesterolemic individuals.