Ren-You Gan

Impacts of Gut Bacteria on Human Health and Diseases

Gut bacteria are an important component of the microbiota ecosystem in the human gut, which is colonized by 1014 microbes, ten times more than the human cells. Gut bacteria play an important role in human health, such as supplying essential nutrients, synthesizing vitamin K, aiding in the digestion of cellulose, and promoting angiogenesis and enteric nerve function. However, they can also be potentially harmful due to the change of their composition when the gut ecosystem undergoes abnormal changes in the light of the use of antibiotics, illness, stress, aging, bad dietary habits, and lifestyle. Dysbiosis of the gut bacteria communities can cause many chronic diseases, such as inflammatory bowel disease, obesity, cancer, and autism. This review summarizes and discusses the roles and potential mechanisms of gut bacteria in human health and diseases.

Antioxidant Phytochemicals for the Prevention and Treatment of Chronic Diseases

Overproduction of oxidants (reactive oxygen species and reactive nitrogen species) in the human body is responsible for the pathogenesis of some diseases. The scavenging of these oxidants is thought to be an effective measure to depress the level of oxidative stress of organisms. It has been reported that intake of vegetables and fruits is inversely associated with the risk of many chronic diseases, and antioxidant phytochemicals in vegetables and fruits are considered to be responsible for these health benefits. Antioxidant phytochemicals can be found in many foods and medicinal plants, and play an important role in the prevention and treatment of chronic diseases caused by oxidative stress. They often possess strong antioxidant and free radical scavenging abilities, as well as anti-inflammatory action, which are also the basis of other bioactivities and health benefits, such as anticancer, anti-aging, and protective action for cardiovascular diseases, diabetes mellitus, obesity and neurodegenerative diseases. This review summarizes recent progress on the health benefits of antioxidant phytochemicals, and discusses their potential mechanisms in the prevention and treatment of chronic diseases.

Dietary Sources and Bioactivities of Melatonin

Insomnia is a serious worldwide health threat, affecting nearly one third of the general population. Melatonin has been reported to improve sleep efficiency and it was found that eating melatonin-rich foods could assist sleep. During the last decades, melatonin has been widely identified and qualified in various foods from fungi to animals and plants. Eggs and fish are higher melatonin-containing food groups in animal foods, whereas in plant foods, nuts are with the highest content of melatonin. Some kinds of mushrooms, cereals and germinated legumes or seeds are also good dietary sources of melatonin. It has been proved that the melatonin concentration in human serum could significantly increase after the consumption of melatonin containing food. Furthermore, studies show that melatonin exhibits many bioactivities, such as antioxidant activity, anti-inflammatory characteristics, boosting immunity, anticancer activity, cardiovascular protection, anti-diabetic, anti-obese, neuroprotective and anti-aging activity. This review summaries the dietary sources and bioactivities of melatonin, with special attention paid to the mechanisms of action.

Optimization of Ultrasound-Assisted Extraction of Antioxidants from the Mung Bean Coat

Mung bean (Vigna radiata) sprout is commonly consumed as a vegetable, while the coat of the germinated mung bean is a waste. In this paper, an ultrasound-assisted extraction method has been developed to extract natural antioxidants from the seed coat of mung bean. Several experimental parameters—which included ethanol concentration, solvent/material ratio, ultrasound extraction time, temperature, and power—were studied in single-factor experiments. The interaction of three key experimental parameters (ethanol concentration, solvent/material ratio, and ultrasonic extraction time) was further investigated by response surface method. Besides, traditional extracting methods, including maceration and Soxhlet extraction methods, were also carried out for comparison. The results suggested that the best extracting condition was 37.6% (v/v) of ethanol concentration, 35.1:1 mL/g of solvent/material ratio and ultrasonic extraction of 46.1 min at 70 °C under 500 W ultrasonic irradiation. The antioxidant capacity (178.28 ± 7.39 µmol Trolox/g DW) was much stronger than those obtained by the maceration extraction process (158.66 ± 4.73 µmol Trolox/g DW) and the Soxhlet extraction process (138.42 ± 3.63 µmol Trolox/g DW). In addition, several antioxidant components in the extract were identified and quantified. This study is helpful for value-added utilization of the waste from germinated mung bean.

Bioactivity, Health Benefits, and Related Molecular Mechanisms of Curcumin: Current Progress, Challenges, and Perspectives

Curcumin is a principal curcuminoid of turmeric (Curcuma longa), which is commonly used as a spice in cooking and a yellow pigment in the food processing industry. Recent studies have demonstrated that curcumin has a variety of biological activities and pharmacological performances, providing protection and promotion of human health. In addition to presenting an overview of the gut metabolism of curcumin, this paper reviews the current research progress on its versatile bioactivity, such as antioxidant, anti-inflammatory, and immune-regulatory activities, and also intensively discusses its health benefits, including the protective or preventive effects on cancers and diabetes, as well as the liver, nervous system, and cardiovascular systems, highlighting the potential molecular mechanisms. Besides, the beneficial effects of curcumin on human are further stated based on clinical trials. Considering that there is still a debate on the beneficial effects of curcumin, we also discuss related challenges and prospects. Overall, curcumin is a promising ingredient of novel functional foods, with protective efficacy in preventing certain diseases. We hope this comprehensive and updated review will be helpful for promoting human-based studies to facilitate its use in human health and diseases in the future.

Gut Microbiota’s Relationship with Liver Disease and Role in Hepatoprotection by Dietary Natural Products and Probiotics

A variety of dietary natural products have shown hepatoprotective effects. Increasing evidence has also demonstrated that gut microorganisms play an important role in the hepatoprotection contributed by natural products. Gut dysbiosis could increase permeability of the gut barrier, resulting in translocated bacteria and leaked gut-derived products, which can reach the liver through the portal vein and might lead to increased oxidative stress and inflammation, thereby threatening liver health. Targeting gut microbiota modulation represents a promising strategy for hepatoprotection. Many natural products could protect the liver from various injuries or mitigate hepatic disorders by reverting gut dysbiosis, improving intestinal permeability, altering the primary bile acid, and inhibiting hepatic fatty acid accumulation. The mechanisms underlying their beneficial effects also include reducing oxidative stress, suppressing inflammation, attenuating fibrosis, and decreasing apoptosis. This review discusses the hepatoprotective effects of dietary natural products via modulating the gut microbiota, mainly focusing on the mechanisms of action.

Five-Golden-Flowers Tea: Green Extraction and Hepatoprotective Effect against Oxidative Damage

The consumption of herbal teas has become popular in recent years due to their attractive flavors and outstanding antioxidant properties. The Five-Golden-Flowers tea is a herbal tea consisting of five famous edible flowers. The effects of microwave-assisted extraction parameters on the antioxidant activity of Five-Golden-Flowers tea were studied by single-factor experiments, and further investigated using response surface methodology. Under the optimal parameters (53.04 mL/g of solvent/material ratio, 65.52 °C, 30.89 min, and 500 W), the ferric-reducing antioxidant power, Trolox equivalent antioxidant capacity, and total phenolic content of the herbal tea were 862.90 ± 2.44 µmol Fe2+/g dry weight (DW), 474.37 ± 1.92 µmol Trolox/g DW, and 65.50 ± 1.26 mg gallic acid equivalent (GAE)/g DW, respectively. The in vivo antioxidant activity of the herbal tea was evaluated on alcohol-induced acute liver injury in mice. The herbal tea significantly decreased the levels of aspartate aminotransferase, total bilirubin, and malonaldehyde at different doses (200, 400, and 800 mg/kg); improved the levels of liver index, serum triacylglycerol, and catalase at dose of 800 mg/kg. These results indicated its role in alleviating hepatic oxidative injury. Besides, rutin, chlorogenic acid, epicatechin, gallic acid, and p-coumaric acid were identified and quantified by high performance liquid chromatography (HPLC), which could contribute to the antioxidant activity of the herbal tea.

Potential of Grape Wastes as a Natural Source of Bioactive Compounds

Grapes are widely used in the wine and juice industries, which can lead to massive amounts of waste, mostly grape peels and seeds. The antioxidant capacities, total phenolic and flavonoid contents and phenolic profiles of peels and seeds from 30 grape varieties were systemically assessed. The antioxidant activities of fat-soluble, water-soluble and insoluble-bound fractions of grape peels and seeds were evaluated using ferric-reducing antioxidant power and Trolox equivalent antioxidant capacity assays, and their total phenolic contents and total flavonoid contents were determined by the Folin-Ciocalteu method and AlCl3 colorimetry, respectively. It was found that the antioxidant capacities were diverse among different grape peels and seeds. Moreover, several phenolic compounds were identified and quantified, including gallic acid, cyanidin-3-glucoside, epicatechin, catechin gallate, ferulaic acid, rutin and resveratrol, which could contribute to the antioxidant capacities of these grape peels and seeds. Several grape wastes with strong antioxidant activity could be abundant sources of natural bioactive compounds, and have the potential for development into functional foods, food additives and pharmaceuticals.

Comparison of Antioxidant Activities of Different Grape Varieties

Grapes are widely consumed in the world, and different grape varieties could exhibit distinctly different antioxidant activities. In this study, the free radical-scavenging and antioxidant activities of lipophilic, hydrophilic, and insoluble-bound fractions from 30 grape varieties were evaluated by ferric-reducing antioxidant powers (FRAP), Trolox equivalent antioxidant capacities (TEAC), total phenolic contents (TPC), and total flavonoid contents (TFC). The results indicated that the 30 grape varieties exhibited diverse FRAP values (1.289–11.767 μmol Fe(II)/g FW), TEAC values (0.339–4.839 μmol Trolox/g FW), TPC values (0.294–1.407 mg GAE/g FW) and TFC values (0.082–0.132 mg QE/g FW). Several grapes, such as Pearl Black Grape (Xinjiang), Summer Black Grape (Shaanxi), Pearl Green Grape (Xinjiang), Seedless Green Grape (Xinjiang), and Seedless Red Grape (Yunnan), exhibited strong free radical-scavenging and antioxidant activities, which could be consumed as good sources of natural antioxidants to prevent several diseases induced by oxidative stress, such as cardiovascular disease and cancer. Furthermore, several antioxidants were identified and quantified, including caffeic acid, catechin gallate, epicatechin, gallic acid, protocatechuic acid and rutin, which could contribute to the antioxidant activities of grapes.