Hypotriglyceridemic potential of fermented mixed tea made with third-crop green tea leaves and camellia (Camellia japonica) leaves in Sprague-Dawley rats

Antiobesity effect of healthy food crops and functional foods: A systematic review of their mechanisms

Diet is a modifiable risk factor in the prevention and management of obesity, and various foods have the potential to aid in obesity management by modulating different pathways involved in the disease's pathology. We performed a systematic review of literature, using CINAHL, PubMed, and Google Scholar, focusing on the antiobesity potential of foods crops and functional food products, and their mechanisms of action and clinical evidence. Sixty-four articles were identified, of which 41 investigated food crops, while 23 investigated functional products. Food crops, such as cereals, vegetables, fruits, mushrooms, seaweeds, legumes, herbs, spices, and cocoa seeds, have antiobesity effects through mechanisms such as altering the metabolism of glucolipids by inhibiting enzymes like α-amylase and α-glucosidase, stimulating the bioenergetics of thermogenic fat, modulating gut microbiota, and inhibiting lipogenesis and storage. In addition, developed functional teas, beverages, and yoghurt have antiobesity effects through similar or different mechanisms, such as enhancing energy expenditure and satiety, suppressing adipogenesis and lipolysis, improving glucose and lipid metabolism, and altering hormonal secretion. This review reemphasized the significance of food in the control of obesity, and highlights the distinct methods these explored foods exert their antiobesity effects. In conclusion, foods are safe and effective means of combating obesity without the side effects of conventional drugs, which can help inform dietary choices, assist professionals in providing more accurate advice, and also lead to better understanding of food and its effect on overall health of the public. This approach will eradicate global diseases, especially if more underutilized and indigenous food crops are extensively researched.

[Dynamic Chemistry of Tannins]

Tannins are a group of polyphenols that possess the ability to precipitate proteins, causing an undesirable astringent taste by interacting with salivary peptides. This interaction deactivates the digestive enzymes; therefore, tannins are considered as plant defense substances. The health benefits of tannins and related polyphenols in foods and beverages have been demonstrated by biological and epidemiological studies; however, their metabolism in living plants and the chemical changes observed during processing of foods and medicinal herbs raises some questions. This review summarizes our studies concerning dynamic changes observed in tannins. Ellagitannins present in the young leaves of Camellia japonica and Quercus glauca undergo oxidative degradation as the leaves mature. Similar oxidative degradation is also observed in whiskey when it is kept for aging in oak barrels, and in decaying wood caused by fungi in natural forests. In contrast, ellagitannins have been observed to undergo reduction in the leaves of Carpinus, Castanopsis, and Triadica species as the leaves mature. This phenomenon of reductive metabolism in leaves enabled us to propose a new biosynthetic pathway for the most fundamental ellagitannin acyl groups, which was also supported by biomimetic synthetic studies. Polyphenols undergo dynamic changes during the process of food processing. Catechin in tea leaves undergo oxidation upon mechanical crushing to generate black tea polyphenols. Though detailed production mechanisms of catechin dimers have been elucidated, structures of thearubigins (TRs), which are complex mixtures of oligomers, remain ambiguous. Our recent studies suggested that catechin B-ring quinones couple with catechin A-rings during the process of oligomerization.

A Comprehensive Review on Anti-obesity Potential of Medicinal Plants and their Bioactive Compounds

Background:

Obesity is a complex health and global epidemic issue. It is an increasing global health challenge covering significant social and economic costs. Abnormal accumulation of fat in the body may increase the health risks including diabetes, hypertension, osteoarthritis, sleep apnea, cardiovascular diseases, stroke and cancer. Synthetic drugs available on the market reported to have several side effects. Therefore, the management of obesity got to involve the traditional use of medicinal plants which helps to search the new therapeutic targets and supports the research and development of anti-obesity drugs.

Objective:

This review aim to update the data and provide a comprehensive report of currently available knowledge of medicinal plants and phyto-chemical constituents reported for their anti-obesity activity.

Methodology:

An electronic search of the periodical databases like Web of Science, Scopus, PubMed, Scielo, Niscair, ScienceDirect, Springerlink, Wiley, SciFinder and Google Scholar with information reported the period 1991-2019, was used to retrieve published data.

Results:

A comprehensive report of the present review manuscript is an attempt to list the medicinal plants with anti-obesity activity. The review focused on plant extracts, isolated chemical compounds with their mechanism of action and their preclinical experimental model, clinical studies for further scientific research.

Conclusion:

This review is the compilation of the medicinal plants and their constituents reported for the managements of obesity. The data will fascinate the researcher to initiate further research that may lead to the drug for the management of obesity and their associated secondary complications. Several herbal plants and their respective lead constituents were also screened by preclinical In-vitro and In-vivo, clinical trials and are effective in the treatment of obesity. Therefore, there is a need to develop and screen large number of plant extracts and this approach can surely be a driving force for the discovery of anti-obesity drugs from medicinal plants.

Effect of Active Groups and Oxidative Dimerization on the Antimelanogenic Activity of Catechins and Their Dimeric Oxidation Products

Some catechins and their dimeric oxidation products are well known to possess antimelanogenic activity, which could be influenced by their structures and oxidative dimerization. This study compared the antimelanogenic activity of different catechins and dimeric oxidation products and clarified the mechanism using an α-MSH-stimulated B16F10 cell model. It was found that 100 μg/mL (-)-gallocatechin gallate, (-)-epigallocatechin gallate, theasinensin A, and theaflavine-3,3'-digallate could significantly inhibit melanin synthesis without cytotoxicity. The tyrosinase (TYR) activities were 26.24 ± 4.97, 31.57 ± 5.37, 66.10 ± 9.62, and 78.19 ± 5.14%, respectively, and the melanin contents were 38.29 ± 3.50, 41.21 ± 7.62, 62.13 ± 9.80, and 68.82 ± 11.62%, respectively. These compounds inhibit melanin production by attenuating the mRNA levels of TYR, TRP1, and TRP2 gene. The structure-activity relationship showed that geometrical isomerism was not the key factor affecting catechins' antimelanogenic activity. Compared with the catechol, catechins with B-ring pyrogallol inhibited melanin synthesis more effectively. The number of galloyl groups was positively correlated with antimelanogenic activity. Compared with 3-galloyl, 3'-galloyl was a stronger active group in antimelanogenesis. Interestingly, the contribution of B-ring pyrogallol to the antimelanogenic activity was significantly stronger than that of 3-galloyl in catechins. Additionally, the antimelanogenic activity of the dimeric oxidation product at 100 μM was more than or equal to that of individual substrate-catechin, while being significantly less than that of the substrate-catechin mixture. Results indicated that pyrogallol and galloyl were the active groups inhibiting melanin synthesis. The oxidative dimerization weakened the antimelanogenic activity of the substrate-catechin mixture.

Natural Products as Potential Lead Compounds for Drug Discovery Against SARS-CoV-2

For the past 2 years, the coronavirus responsible for the COVID-19 infection has become a world pandemic, ruining the lives and economies of several nations in the world. This has scaled up research on the virus and the resulting infection with the goal of developing new vaccines and therapies. Natural products are known to be a rich source of lead compounds for drug discovery, including against infectious diseases caused by microbes (viruses, bacteria and fungi). In this review article, we conducted a literature survey aimed at identifying natural products with inhibitory concentrations against the coronaviruses or their target proteins, which lie below 10 µM. This led to the identification of 42 compounds belonging to the alkaloid, flavonoid, terpenoid, phenolic, xanthone and saponin classes. The cut off concentration of 10 µM was to limit the study to the most potent chemical entities, which could be developed into therapies against the viral infection to make a contribution towards limiting the spread of the disease.

Evaluating the appropriate oral lipid tolerance test model for investigating plasma triglyceride elevation in mice

The oral lipid tolerance test (OLTT) has been known to assess intestinal fat metabolism and whole-body lipid metabolism, but rodent models for OLTT are not yet established. Differences in OLTT methodology preclude the generation of definitive results, which may cause some confusion about the anti-hypertriglyceridemia effects of the test materials. To standardize and generate more appropriate methodology for the OLTT, we examined the effects of mice strain, dietary lipid sources, fasting period, and gender on lipid-induced hypertriglyceridemia in mice. First, lipid-induced hypertriglyceridemia was more strongly observed in male ddY mice than in C57BL/6N or ICR mice. Second, the administration of olive and soybean oils remarkably represented lipid-induced hypertriglyceridemia. Third, fasting period before the OLTT largely affected the plasma triglyceride elevation. Fasting for 12 h, but less than 48 h, provoked lipid-induced hypertriglyceridemia. Fourth, we explored the suppressive effects of epigallocatechin gallate (EGCG), a green tea polyphenol, on lipid-induced hypertriglyceridemia. The administration of 100 mg/kg of EGCG suppressed lipid-induced hypertriglyceridemia and intestinal lipase activity. Fifth, EGCG-induced suppressive effects were observed after lipid-induced hypertriglyceridemia was observed in male mice, but not in female mice. Lastly, lipid-induced hypertriglyceridemia could be more effectively induced in mice fed a high-fat diet for 1 week before the OLTT. These findings indicate that male ddY mice after 12 h fasting displayed marked lipid-induced hypertriglyceridemia in response to soybean oil. Hence, the defined experiment condition may be a more appropriate OLTT model for evaluating lipid-induced hypertriglyceridemia.

A fermented mixed tea made with camellia (Camellia japonica) and third-crop green tea leaves prevents nonalcoholic steatohepatitis in Sprague-Dawley rats fed a high-fat and high-cholesterol diet

Background

Established treatments for non-alcoholic steatohepatitis (NASH) are few, thus it is imperative to develop novel dietary strategies that can prevent NASH. A fermented mixed tea (FMT) made with Camellia japonica (Japanese camellia) and third- crop green tea leaves by tea-rolling processing was reported to reduce body weight and adipose tissue weight in Sprague-Dawley (SD) rats. Because visceral fat is one of the most important factors for the development of hepatic steatosis, this FMT supplementation can be a candidate dietary strategy for the prevention of NASH.

Methods

Nine-week-old male SD rats were fed a high-fat and high-cholesterol (HFC) diets with or without FMT (camellia and third-crop green tea leaves at ratios of 1:5, 1:2 and 1:1) for 9 weeks (n=6-7/group). Histopathology, serology and expressions of fibrogenetic, proinflammatory, oxidative stress and lipid metabolism-related genes in the liver were evaluated.

Results

Histologically, HFC diet with FMT at a ratio of 1:5 dramatically reduced NASH progression (14%) compared to the HFC diet without FMT (100%). FMT at a ratio of 1:5 reduced hepatic steatosis due to the activation of microsomal triglyceride transfer protein, and FMT at a ratio of 1:2 reduced mRNA levels of some proinflammatory, lipid metabolism-related, fibrogenic and oxidative stress marker genes.

Conclusions

Our data suggest that FMT at a ratio of 1:5 or 1:2 likely possesses a preventive effect on NASH progression.

Plumbagin exerts antiobesity effects through inhibition of pancreatic lipase and adipocyte differentiation

Plumbagin is a naphthoquinone found in the roots of Plumbago zeylanica. Here, we report an investigation to evaluate its antiobesity activity. The preliminary binding affinity of plumbagin to human pancreatic lipase (PL) was determined using molecular docking simulation. The in vitro PL inhibitory potential and the kinetics of inhibition were studied to validate and confirm the results obtained from molecular docking. The IC₅₀ for PL was found to be 82.08 ± 9.47 μM, and the kinetics of inhibition was found to be of the mixed type. Further, the in vivo evaluation revealed that rats treated with plumbagin 1 mg/kg showed significant decrease in serum triglycerides (TG) and area under the curve of serum TG when compared with vehicle-treated rats. It was also seen that plumbagin possessed significant antiadipogenic effect as demonstrated by reduced oil red O staining and decreased TG contents. Thus, we conclude that plumbagin is a promising molecule to combat obesity and further optimization of plumbagin to yield plumbagin analogues will result in its improved activity profile.

Antiatherogenic Effect of Camellia japonica Fruit Extract in High Fat Diet-Fed Rats

Hypercholesterolemia is a well-known etiological factor for cardiovascular disease and a common symptom of most types of metabolic disorders. Camellia japonica is a traditional garden plant, and its flower and seed have been used as a base oil of traditional cosmetics in East Asia. The present study was carried out to evaluate the effect of C. japonica fruit extracts (CJF) in a high fat diet- (HFD-) induced hypercholesterolemic rat model. CJF was administered orally at three different doses: 100, 400, and 800 mg·kg⁻¹·day⁻¹ (CJF 100, 400, and 800, resp.). Our results showed that CJF possessed strong cholesterol-lowering potency as indicated by the decrease in serum total cholesterol (TC), triglyceride (TG), and low-density lipoprotein (LDL), accompanied by an increase in serum high-density lipoprotein (HDL). Furthermore, CJF reduced serum lipid peroxidation by suppressing the formation of thiobarbituric acid reactive substance. In addition, oil red O (ORO) staining of rat arteries showed decreased lipid-positive staining in the CJF-treated groups compared to the control HFD group. Taken together, these results suggest that CJF could be a potent herbal therapeutic option and source of a functional food for the prevention and treatment of atherosclerosis and other diseases associated with hypercholesterolemia.

Identification of a novel hedycaryol synthase gene isolated from Camellia brevistyla flowers and floral scent of Camellia cultivars

A novel terpene synthase (Tps) gene isolated from Camellia brevistyla was identified as hedycaryol synthase, which was shown to be expressed specifically in flowers. Camellia plants are very popular because they bloom in winter when other plants seldom flower. Many ornamental cultivars of Camellia have been bred mainly in Japan, although the fragrance of their flowers has not been studied extensively. We analyzed floral scents of several Camellia cultivars by gas chromatography-mass spectrometry (GC-MS) and found that Camellia brevistyla produced various sesquiterpenes in addition to monoterpenes, whereas Camellia japonica and its cross-lines produced only monoterpenes, including linalool as the main product. From a flower of C. brevistyla, we isolated one cDNA encoding a terpene synthase (TPS) comprised of 554 amino acids, which was phylogenetically positioned to a sole gene clade. The cDNA, designated CbTps1, was expressed in mevalonate-pathway-engineered Escherichia coli, which carried the Streptomyces mevalonate-pathway gene cluster in addition to the acetoacetate-CoA ligase gene. A terpene product was purified from recombinant E. coli cultured with lithium acetoacetate, and analyzed by (1)H-nulcear magnetic resonance spectroscopy ((1)H-NMR) and GC-MS. It was shown that a sesquiterpene hedycaryol was produced, because (1)H-NMR signals of the purified product were very broad, and elemol, a thermal rearrangement product from hedycaryol, was identified by GC-MS analysis. Spectroscopic data of elemol were also determined. These results indicated that the CbTps1 gene encodes hedycaryol synthase. Expression analysis of CbTps1 showed that it was expressed specifically in flowers, and hedycaryol is likely to be one of the terpenes that attract insects for pollination of C. brevistyla. A linalool synthase gene, which was isolated from a flower of Camellia saluenensis, is also described.

A Single Oral Administration of Theaflavins Increases Energy Expenditure and the Expression of Metabolic Genes

Theaflavins are polyphenols found in black tea, whose physiological activities are not well understood. This study on mice evaluated the influence of a single oral administration of theaflavins on energy metabolism by monitoring the initial metabolic changess in skeletal muscle and brown adipose tissue (BAT). Oxygen consumption (VO2) and energy expenditure (EE) were increased significantly in mice treated with theaflavin rich fraction (TF) compared with the group administered vehicle alone. There was no difference in locomotor activity. Fasting mice were euthanized under anesthesia before and 2 and 5, 20-hr after treatment with TF or vehicle. The mRNA levels of uncoupling protein-1 (UCP-1) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) in BAT were increased significantly 2-hr after administration ofTF. The levels of UCP-3 and PGC-1α in the gastrocnemius muscle were increased significantly 2 and 5-hr after administration of TF. The concentration of phosphorylated AMP-activated protein kinase (AMPK) 1α was also increased significantly in the gastrocnemius 2 and 5-hr after treatment with TF. These results indicate that TF significantly enhances systemic energy expenditure, as evidenced by an increase in expression of metabolic genes.

Oleanane triterpenes from the flowers of Camellia japonica inhibit porcine epidemic diarrhea virus (PEDV) replication

Porcine epidemic diarrhea virus (PEDV) infections have resulted in a severe economic loss in the swine industry in many countries due to no effective treatment approach. Fifteen oleanane triterpenes (1-15), including nine new ones (1-4 and 10-14), were isolated from the flowers of Camellia japonica, and their molecular structures were determined by extensive spectroscopic methods. These compounds were evaluated for their antiviral activity against PEDV replication, and the structure-activity relationships (SARs) were discussed. Compounds 6, 9, 11, and 13 showed most potent inhibitory effects on PEDV replication. They were found to inhibit PEDV genes encoding GP6 nucleocapsid, GP2 spike, and GP5 membrane protein synthesis based on RT-PCR data. Western blot analysis also demonstrated their inhibitory effects on PEDV GP6 nucleocapsid and GP2 spike protein synthesis during viral replication. The present study suggested the potential of compounds 6, 9, 11, and 13 as promising scaffolds for treating PEDV infection via inhibiting viral replication.