Polyphenol-rich extract and fractions of Terminalia phaeocarpa Eichler possess hypoglycemic effect, reduce the release of cytokines, and inhibit lipase, α-glucosidase, and α-amilase enzymes

New Therapeutic Strategies for Obesity and Its Metabolic Sequelae: Brazilian Cerrado as a Unique Biome

Brazil has several important biomes holding impressive fauna and flora biodiversity. Cerrado being one of the richest ones and a significant area in the search for new plant-based products, such as foods, cosmetics, and medicines. The therapeutic potential of Cerrado plants has been described by several studies associating ethnopharmacological knowledge with phytochemical compounds and therapeutic effects. Based on this wide range of options, the Brazilian population has been using these medicinal plants (MP) for centuries for the treatment of various health conditions. Among these, we highlight metabolic diseases, namely obesity and its metabolic alterations from metabolic syndrome to later stages such as type 2 diabetes (T2D). Several studies have shown that adipose tissue (AT) dysfunction leads to proinflammatory cytokine secretion and impaired free fatty acid (FFA) oxidation and oxidative status, creating the basis for insulin resistance and glucose dysmetabolism. In this scenario, the great Brazilian biodiversity and a wide variety of phytochemical compounds make it an important candidate for the identification of pharmacological strategies for the treatment of these conditions. This review aimed to analyze and summarize the current literature on plants from the Brazilian Cerrado that have therapeutic activity against obesity and its metabolic conditions, reducing inflammation and oxidative stress.

Adansonia digitata L. (Baobab) Bioactive Compounds, Biological Activities, and the Potential Effect on Glycemia: A Narrative Review

Adansonia digitata L. fruit, also known as baobab, has been used traditionally throughout the world for its medicinal properties. Ethnopharmacological uses of various plant parts have been reported for hydration, antipyretic, antiparasitic, antitussive, and sudorific properties and also in the treatment of diarrhea and dysentery in many African countries. Several studies have revealed that in addition to these applications, baobab has antioxidant, anti-inflammatory, analgesic, and antimicrobial activities. The health benefits of baobab have been attributed to its bioactive compounds, namely phenols, flavonoids, proanthocyanins, tannins, catechins, and carotenoids. Baobab fruit is also an important source of vitamin C and micronutrients, including zinc, potassium, magnesium, iron, calcium, and protein, which may reduce nutritional deficiencies. Despite scientific studies revealing that this fruit has a wide diversity of bioactive compounds with beneficial effects on health, there is a gap in the review of information about their mechanisms of action and critical analysis of clinical trials exploring, in particular, their effect on glycemia regulation. This work aims to present a current overview of the bioactive compounds, biological activities, and effects of A. digitata fruit on blood glucose, highlighting their potential mechanisms of action and effects on glycemia regulation, evaluated in recent animal and human trials.

Oral sub-chronic treatment with Terminalia phaeocarpa Eichler (Combretaceae) reduces liver PTP1B activity in a murine model of diabetes

ETHNOPHARMACOLOGICAL RELEVANCE

The endemic Brazilian medicinal plants of the genus Terminalia (Combretaceae), popularly known as capitão, comprising the similar species Terminalia phaeocarpa Eichler and Terminalia argentea, are traditionally and indistinguishably used in the country to treat diabetes.

AIM OF THE STUDY

The present work investigated the effect of 28 days of treatment with the crude ethanolic extract (CEE) and its derived ethyl acetate fraction (EAF) from T. phaeocarpa leaves in a mice model of diabetes.

MATERIALS AND METHODS

Streptozotocin-nicotinamide-fructose diabetic model was used to evaluate the antidiabetic activity of 28 days of treatment with the CEE and EAF from the leaves of T. phaeocarpa and metformin as a positive control. Serum levels of total cholesterol, triglycerides, uric acid, ALP, AST, and ALT were measured with specific commercial kits and glucose with a strip glucometer. The thiobarbituric acid method measured the liver MDA level, while a colorimetric assay measured the GSH level and PTP1B activity. A UPLC-DAD profile was obtained to identify the main polyphenolic compound in the EAF.

RESULTS

Treatment with CEE and EAF reduced plasma glucose in diabetic mice. At the end of the treatment, the plasma glucose level was significantly lower in EAF-treated (100 mg/kg) diabetic mice (106.1 ± 13.7 mg/dL) than those treated with 100 mg/kg CEE (175.2 ± 20.9 mg/dL), both significantly lower than untreated diabetic mice (350.4 ± 28.1 mg/dL). The serum levels of total cholesterol, triglycerides, uric acid, ALP, AST, and ALT were significantly reduced in diabetic mice treated with CEE and EAF. In the livers of diabetic mice, the treatment with CEE and EAF reduced MDA levels and the activity of the enzyme PTP1B (96.9 ± 3.7%, 113.8 ± 2.8%, and 134.8 ± 4.6% for CEE-, EAF-treated, and untreated diabetic mice, respectively). Galloylpunicalagin was the main polyphenol observed in the EAF of T. phaeocarpa.

CONCLUSION

The present results demonstrate the significant antidiabetic effect of CEE and EAF of T. phaeocarpa and their reduction on the markers of liver dysfunction in diabetic mice. Moreover, the antidiabetic activity of T. phaeocarpa might be associated with lowering the augmented activity of the PTP1B enzyme in the liver of diabetic mice.

Screening and identification of lipase inhibitors extracted from Dioscorea nipponica Makino by UV-vis and HPLC coupled to UPLC-Q-TOF-MS/MS

Dioscoreae nipponica Makino (D. nipponica) as the rhizome of dioscoreaceae rich in steroidal saponins, has been reported to have the hypolipidemic effects etc. However, it is still unclear which exact active components are primary responsible for the beneficial effects. This study was conducted to fish out the lipase inhibitors from D. nipponica, and evaluate the inhibitory activity on porcine pancreatic lipase (PPL) through in vitro kinetic assay using p-nitrophenyl palmitate as substrate. Accordingly, the ethanolic extract was subjected to D101 macroporous resin purification for spectrophotometric screening, high performance liquid chromatography (HPLC) separation and structural characterization by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Through orlistat validation, the PPL inhibitory activity and IC₅₀ value of the extract were respectively 68.34 ± 1.47 % and 107.05 μg/mL under the optimized inhibition conditions. From 6 steroidal saponins identified, the inhibitory components named the protodioscin, protogracillin, dioscin and gracillin were fished out by grouping separation and HPLC analysis. Furthermore, dioscin and gracillin with the parent structure of diogenin were confirmed as the major inhibitors by virtue of stability tests based on transformation of protodioscin and protogracillin. Finally, the inhibitory mechanism of the major inhibitors toward PPL was further clarified by kinetic analysis and molecular docking analysis. The proposed method not only revealed the PPL inhibitory components in D. nipponica, but also provided an effective approach to hierarchical screening of PPL inhibitors from natural plants.

Bioaccessibility of phenolic compounds using the standardized INFOGEST protocol: A narrative review

The INFOGEST protocol creation was a watershed for phenolic bioaccessibility studies. Because of this important initiative to standardize bioaccessibility studies, data comparisons between different laboratories are now expedited. It has been eight years since the INFOGEST protocol creation, and three from the latest update. However, the current status in terms of phenolic bioaccessibility and how far different laboratories are from reaching a consensus are still unrevealed. In this sense, this narrative review considered an evaluation of different studies that applied the INFOGEST protocol to investigate the bioaccessibility of phenolic compounds. The central objective was to compile the main findings and consensus and to identify possible gaps and future opportunities. This approach intends to further facilitate the use of this protocol by professionals in the field of food science and technology and related areas, generating a reflection on the actual level of standardization of the method. Despite the differences in phenolic compounds from diverse food matrices, and their peculiar behavior, some trends could be elucidated, in terms of phenolic release, stability, and/or transformation upon in vivo digestion. In contrast, there was no general consensus regarding sample preparation, how to report results and the form to calculate bioaccessibility, making it difficult to compare different studies. There is still a long road to effectively standardize the results obtained for phenolic bioaccessibility using the INFOGEST protocol, which is also an opportunity in terms of food analysis that can impact the food industry, especially for the development of nutraceuticals and functional foods.

Definition of chemical markers for Hancornia speciosa Gomes by chemometric analysis based on the chemical composition of extracts, their vasorelaxant effect and α-glucosidase inhibition

ETHNOPHARMACOLOGICAL RELEVANCE

Hancornia speciosa Gomes (Apocynaceae) is a tree found in the Brazilian savannah, traditionally used to treat several diseases, including diabetes and hypertension. The anti-hypertensive activity of H. speciosa leaves (HSL) has been demonstrated in different models and is credited to the vasodilator effect and ACE (angiotensin-converting enzyme) inhibition. The hypoglycemic effect of HSL has been also reported.

AIM OF THE STUDY

To establish correlations between the biological activities elicited by H. speciosa extracts and the contents of their major compounds, aiming to define chemical markers related to the potential antihypertensive and antidiabetic effects of the species. Additionally, it aimed to isolate and characterize the chemical structure of a marker related to the α-glucosidase inhibitory effect.

MATERIALS AND METHODS

Extracts of a single batch of H. speciosa leaves were prepared by extraction with distinct solvents (ethanol/water in different proportions; methanol/ethyl acetate), employing percolation or static maceration as extraction techniques, at different time intervals. The contents of chlorogenic acid, rutin and FlavHS (a tri-O-glycoside of quercetin) were quantified by a developed and validated HPLC-PDA method. Bornesitol was determined by HPLC-PDA after derivatization with tosyl chloride, whereas total flavonoids were measured spectrophotometrically. Identification of other constituents in the extracts was performed by UPLC-DAD-ESI-MS/MS analysis. The vasorelaxant activity was assayed in rat aortic rings precontracted with phenylephrine, and α-glucosidase inhibition was tested in vitro. Principal component analysis (PCA) was employed to evaluate the contribution of each marker to the biological responses. Isolation of compound 1 was carried out by column chromatography and structure characterization was accomplished by NMR and UPLC-DAD-ESI-MS/MS analyses.

RESULTS

The contents of the chemical markers (mean ± s.d. % w/w) varied significantly among the extracts, including total flavonoids (2.68 ± 0.14 to 5.28 ± 0.29), bornesitol (5.11 ± 0.26 to 7.75 ± 0.78), rutin (1.46 ± 0.06 to 1.97 ± 0.02), FlavHS (0.72 ± 0.05 to 0.94 ± 0.14) and chlorogenic acid (0.67 ± 0.09 to 0.91 ± 0.02). All extracts elicited vasorelaxant effect (pIC₅₀ between 4.97 ± 0.22 to 6.48 ± 0.10) and α-glucosidase inhibition (pIC₅₀ between 3.49 ± 0.21 to 4.03 ± 0.10). PCA disclosed positive correlations between the vasorelaxant effect and the contents of chlorogenic acid, rutin, total flavonoids, and FlavHS, whereas a negative correlation was found with bornesitol concentration. No significant correlation between α-glucosidase inhibition and the contents of the above-mentioned compounds was found. On the other hand, PCA carried out with the areas of the ten major peaks from the chromatograms disclosed positive correlations between a peak ascribed to co-eluted triterpenes and α-glucosidase inhibition. A triterpene was isolated and identified as 3-O-β-(3'-R-hydroxy)-hexadecanoil-lupeol.

CONCLUSION

According to PCA results, the vasorelaxant activity of H. speciosa extracts is related to flavonoids and chlorogenic acid, whereas the α-glucosidase inhibition is associated with lipophilic compounds, including esters of lupeol like 3-O-β-(3'-R-hydroxy)-hexadecanoil-lupeol, described for the first time for the species. These compounds can be selected as chemical markers for the quality control of H. speciosa plant drug and derived extracts.

Hydrolysable tannins, physicochemical properties, and antioxidant property of wild-harvested Terminalia ferdinandiana (exell) fruit at different maturity stages

Terminalia ferdinandiana Exell., also known as Kakadu plum, is a wild-harvested native Australian fruit with limited information on how maturity is affecting the phytonutritional properties and bioactivities of the fruit. Thus, this study investigated changes in hydrolysable tannins, phenolic acids, sugar profile, standard physicochemical parameters, and antioxidant-scavenging capacity of wild-harvested Kakadu plum fruits at four different maturity stages, from immature to fully mature. Fruits harvested <25, 25-50, 50-75, and 75-100% degree of fullness were classified as highly immature (stage 1), immature (stage 2), semi-mature (stage 3), and fully mature (stage 4), respectively. Results showed that chebulagic acid, geraniin, chebulinic acid, castalagin, punicalagin, and gallic acid continuously decreased during fruit maturity, while elaeocarpusin, helioscopin B, corilagin, 3,4,6-tri-O-galloyl-S-glucose, and ellagic acid increased at the beginning of fruit growth (from stage 1 to 2), but decreased when the fruits reached their full maturity (stage 4). The levels of hydrolysable tannins and phenolic acids in fully mature fruits (stage 4) were significantly (p ≤ 0.05) lower than that in their immature counterparts (stages 1 and 2). Total phenolic content (TPC) and DPPH antioxidant radical-scavenging activity did not vary significantly between different maturity stages. Pearson's correlation coefficient test indicated that TPC and DPPH positively (p ≤ 0.05) correlate with most of the studied tannin compounds. Sugars (glucose, fructose, and sucrose), total soluble solid content, and titratable acidity increased during the fruit development. Furthermore, principal component analysis (PCA) revealed the difference between the immature and mature samples, based on their nutritional profile and bioactive compounds. The PCA results also suggested a considerable variability between the individual trees, highlighting the challenges of wild-harvest practice.

Antidiabetic potential of Catechu via assays for α-glucosidase, α-amylase, and glucose uptake in adipocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Catechu is the dry water extract of barked branches or stems from Senegalia catechu(L. F.)P. J. H. Hurter & Mabb, which is used as a hypoglycemic regulator in recent researches. Potential anti-hyperglycemic components and the putative mechanisms were evaluated in this investigation.

AIM OF THE STUDY

Evaluated the hypoglycemic activity of Catechu via α-glucosidase, α-amylase inhibition assays, and glucose uptake in 3T3-L1 adipocytes.

MATERIALS AND METHODS

The effects of Catechu on α-glucosidase, α-amylase inhibition assays and glucose uptake experiment were tested after the ethanol extract of Catechu (EE) was sequentially partitioned with petroleum ether (PEE), ethyl acetate (EAE), and n-butanol fractions (NBE). Next, HPLC-MS and traditional Chinese medicine (TCM) database were used to detect and analyze the primary active ingredients presented in hypoglycemic fraction. In addition, in silico molecular docking study was used to evaluate the candidates' inhibitory activity against α-glucosidase and α-amylase.

RESULTS

The results of α-glucosidase and α-amylase inhibition assays indicated that all fractions, with the exception of PEE, presented significant inhibitory effects on α-glucosidase and α-amylase. The inhibitory effect of NBE on α-glucosidase was similar to the positive control (NBE IC₅₀ = 0.3353 ± 0.1215 μg/mL; Acarbose IC₅₀ = 0.1123 ± 0.0023 μg/mL). Furthermore, the inhibitory kinetics of α-glucosidase revealed that all fractions except for PEE belong to uncompetitive type. In silico molecular docking analysis showed that the main compositions of NBE ((-)-epicatechin, cyanidin, and delphinidin) possessed superior binding capacities with α-glucosidase (3WY1 AutoDock score: 4.82 kcal/mol; -5.59 kcal/mol; -5.63 kcal/mol) and α-amylase (4GQR AutoDock score: 4.80 kcal/mol; -5.89 kcal/mol; -4.26 kcal/mol), respectively. The results of glucose uptake experiment indicated that EE, PEE, EAE, and NBE without significant promotion effect on glucose uptake rate of 3T3-L1 adipocytes (P > 0.05).

CONCLUSION

This study revealed that the hypoglycemic effect of Catechu might be related to the inhibitory effects of phenols on digestive enzymes (α-glucosidase and α-amylase), and the possible active phenols were (-)-epicatechin, cyanidin, delphinidin and their derivatives, which provided scientific evidences for Catechu's traditional use to treat T2DM.

Anti-Zika Virus Activity of Plant Extracts Containing Polyphenols and Triterpenes on Vero CCL-81 and Human Neuroblastoma SH-SY5Y Cells

Zika virus (ZIKV) infection is a global threat associated to neurological disorders in adults and microcephaly in children born to infected mothers. No vaccine or drug is available against ZIKV. We herein report the anti-ZIKV activity of 36 plant extracts containing polyphenols and/or triterpenes. ZIKV-infected Vero CCL-81 cells were treated with samples at non-cytotoxic concentrations, determined by MTT and LDH assays. One third of the extracts elicited concentration-dependent anti-ZIKV effect, with viral loads reduction from 0.4 to 3.8 log units. The 12 active extracts were tested on ZIKV-infected SH-SY5Y cells and significant reductions of viral loads (in log units) were induced by Maytenus ilicifolia (4.5 log), Terminalia phaeocarpa (3.7 log), Maytenus rigida (1.7 log) and Echinodorus grandiflorus (1.7 log) extracts. Median cytotoxic concentration (CC₅₀ ) of these extracts in Vero cells were higher than in SH-SY5Y lineage. M. ilicifolia (IC₅₀ =16.8±10.3 μg/mL, SI=3.4) and T. phaeocarpa (IC₅₀ =22.0±6.8 μg/mL, SI=4.8) were the most active extracts. UPLC-ESI-MS/MS analysis of M. ilicifolia extract led to the identification of 7 triterpenes, of which lupeol and a mixture of friedelin/friedelinol showed no activity against ZIKV. The composition of T. phaeocarpa extract comprises phenolic acids, ellagitannins and flavonoids, as recently reported by us. In conclusion, the anti-ZIKV activity of 12 plant extracts is here described for the first time and polyphenols and triterpenes were identified as the probable bioactive constituents of T. phaeocarpa and M. ilicifolia, respectively.

Hypoglycemic Effect of Two Mexican Medicinal Plants

Type 2 diabetes is a worldwide prevalent disease that is due to a progressive loss of adequate β-cell insulin secretion, frequently against a background of insulin resistance. In Mexican traditional medicine, the therapeutic use of hypoglycemic plants to control the disease is a common practice among type 2 diabetic patients. In the present work, we examined the traditional use of the aerial parts of Eryngium longifolium and the rhizome of Alsophila firma, consumed by people use over the day (in fasting state) to control their blood glucose levels, therefore, we aimed to assess the acute hypoglycemic effect of both plants. First, basic phytochemical profiles of both plants were determined and, subsequently, acute toxicity tests were carried out. Then, in vivo hypoglycemic tests were performed in streptozotocin-nicotinamide (STZ-NA) induced hyperglycemic Wistar rats and finally the effect of the plants on three enzymes involved in glucose metabolism was assayed in vitro. Through HPLC-DAD chromatography, caffeic acid, chlorogenic acid, rosmarinic acid, isoflavones, and glycosylated flavonoids were identified in E. longifolium, while the possible presence of flavanones or dihydroflavonols was reported in A. firma. Both plants exhibited a statistically significant hypoglycemic effect, without a dose-dependent effect. Furthermore, they inhibited glucose 6-phosphatase and fructose 1,6-bisphosphatase in in vitro assays, which could be associated with the hypoglycemic effect in vivo. Thus, this study confirmed for the first time the traditional use of the aerial part of E. longifolium and the rhizome of A. firma as hypoglycemic agents in a hyperglycemic animal model. In addition, it was concluded that their ability to regulate hyperglycemia could involve the inhibition of hepatic glucose output, which mainly controls glucose levels in the fasting state.

Pharmacological Properties of Polyphenols: Bioavailability, Mechanisms of Action, and Biological Effects in In Vitro Studies, Animal Models, and Humans

Drugs are bioactive compounds originally discovered from chemical structures present in both the plant and animal kingdoms. These have the ability to interact with molecules found in our body, blocking them, activating them, or increasing or decreasing their levels. Their actions have allowed us to cure diseases and improve our state of health, which has led us to increase the longevity of our species. Among the molecules with pharmacological activity produced by plants are the polyphenols. These, due to their molecular structure, as drugs, also have the ability to interact with molecules in our body, presenting various pharmacological properties. In addition, these compounds are found in multiple foods in our diet. In this review, we focused on discussing the bioavailability of these compounds when we ingested them through diet and the specific mechanisms of action of polyphenols, focusing on studies carried out in vitro, in animals and in humans over the last five years. Knowing which foods have these pharmacological activities could allow us to prevent and aid as concomitant treatment against various pathologies.