The aim of the present study was to compare the in vitro inhibitory effects on the salivary and pancreatic α-amylases and the in vivo hypoglycemic actions of the hydrolysable tannin from Chinese natural gall and the condensed tannin from Acacia mearnsii. The human salivary α-amylase was more strongly inhibited by the hydrolysable than by the condensed tannin, with the concentrations for 50% inhibition (IC50) being 47.0 and 285.4 μM, respectively. The inhibitory capacities of both tannins on the pancreatic α-amylase were also different, with IC50 values being 141.1 μM for the hydrolysable tannin and 248.1 μM for the condensed tannin. The kinetics of the inhibition presented complex patterns in that for both inhibitors more than one molecule can bind simultaneously to either the free enzyme of the substrate-complexed enzyme (parabolic mixed inhibition). Both tannins were able to inhibit the intestinal starch absorption. Inhibition by the hydrolysable tannin was concentration-dependent, with 53% inhibition at the dose of 58.8 μmol/kg and 88% inhibition at the dose of 294 μmol/kg. For the condensed tannin, inhibition was not substantially different for doses between 124.4 μmol/kg (49%) and 620 μmol/kg (57%). It can be concluded that both tannins, but especially the hydrolysable one, could be useful in controlling the postprandial glycemic levels in diabetes.

A practical approach to control glycemia in diabetes is to use plant natural products that delay hydrolysis of complex sugars and promote the diminution of the release of glucosyl units into the blood plasma. Polyphenolics have been described as being effective in inhibiting amylases and α-glucosidases. Grape pomace is an important sub product of the wine industry, still rich in many compounds such as polyphenolics. In this context, the purpose of this study was to search for possible effects of a grape pomace extract on salivary and pancreatic αamylases and α-glucosidase, as well as on intestinal glucose absorption. The Merlot grape pomace extract (MGPE) was prepared using a hydroalcoholic mixture (40% ethanol + 60% water). In vitro inhibition was quantified using potato starch (for amylases) and maltose (for α-glucosidase) as substrates. In vivo inhibition was evaluated by running starch and maltose tolerance tests in rats with or without administration of MGPE. Ranking of the extract compounds for its affinity to the α-amylases was accomplished by computer simulations using three different programs. Both α-amylases, pancreatic and salivary, were inhibited by the MGPE. No inhibition on α-glucosidase, however, was detected. The IC 50 values were 90 ± 10 μg/mL and 143 ± 15 μg/mL for salivary and pancreatic amylases, respectively. Kinetically this inhibition showed a complex pattern, with multiple binding of the extract constituents to the enzymes. Furthermore, the in silico docking simulations indicated that several phenolic substances, e.g., peonidin-3-O-acetylglucoside, quercetin-3-O-glucuronide and isorhamnetin-3-O-glucoside, besides catechin, were the most likely polyphenols responsible for the α-amylase inhibition caused by MGPE. The hyperglycemic burst, an usual phenomenon that follows starch administration, was substantially inhibited by the MGPE. Our results suggest that the MGPE can be adequate for maintaining normal blood levels after food ingestion.

The purpose of the study was to evaluate the possible effects of the administration of a green tea extract on the oxidative state of the liver and brain of adjuvant-induced arthritic rats, a model for human rheumatoid arthritis. Daily doses of 250 mg kg(-1) (59.8 mg catechins per kg) for 23 days were administered. This treatment produced significant diminutions in protein and lipid damage in liver, brain and plasma. It also diminished the tissue ROS contents and increased the antioxidant capacity of the plasma. The antioxidant defenses, which are diminished by arthritis, were improved by the green tea treatment, as revealed by the restoration of the GSH and protein thiol levels and by the strong tendency for normalizing the activities of the antioxidant enzymes. The activity of glucose 6-phosphate dehydrogenase, which is increased by arthritis in the liver, was also almost normalized by the treatment. In conclusion, it can be said that green tea consumption is possibly beneficial for the liver and brain of patients suffering from rheumatoid arthritis because it attenuates the pronounced oxidative stress that accompanies the disease and, thus, diminishes the injury to lipids and proteins in both liver and brain. There are also indications that, in the liver, the green tea can contribute to normalize the metabolic functions that are substantially modified by arthritis. For example, the green tea normalized the activity of glucose 6-phosphate dehydrogenase, a key enzyme of an important metabolic route (pentose monophosphate pathway). It is expected that the green tea treatment is equally able to normalize the activity of other enzymes (e.g., glucokinase and glucose 6-phosphatase), a hypothesis to be tested by future work.

The amount and quality of the evidence that has been accumulating during the last decade strongly speaks in favor of the health benefits of the ingestion of A.blazei or derived products. However, there are many uncertainties and limitations when attempts are made to extrapolate or to demonstrate their biological effects in the human organism in health or disease. Clearly, more clinical trials, using reliable statistical methods and standardized preparations are needed to establish the efficacy of A. blazei as a therapeutic agent.

Anti-inflammatory and antioxidant properties have been attributed to constituents of Rosmarinus officinalis. Considering the inflammatory nature of arthritis and the oxidative stress induced by the disease, this work aimed to investigate if R. officinalis is able to attenuate oxidative and inflammatory injuries caused by the disease. Rats with complete Freund's adjuvant induced arthritis were used. An aqueous extract of the rosemary leaves was administered orally. The parameters related to oxidative stress were measured in the liver, brain and plasma. The administration of the rosemary extract (RE) to arthritic rats diminished oxidative damage (e.g., less carbonylated proteins), improved the oxidative state (e.g., less reactive oxygen species) and also increased the antioxidant capacity by increasing the GSH level and the GSH/GSSG ratio and by almost normalizing the activity of several antioxidant enzymes. The treatment of arthritic rats with the extract also diminished paw edema, the number of leukocytes recruited in the femoro-tibial joint cavities and the weight of the lymph nodes and delayed the appearance of secondary lesions. Twelve phenolic compounds were identified and quantified in the aqueous RE, rosmarinic acid being the most abundant one. In addition, the extract also contains polysaccharides and proteins. The anti-inflammatory and antioxidant activities of the RE can be attributed, partly at least, to its content of polyphenolics with the strong possibility of synergistic interactions as well as metabolic activations. The results corroborate and amplify the general notion that rosemary aqueous extracts possess efficient anti-inflammatory agents and suggest that they are able to attenuate the oxidative stress inherent to arthritis.