Chemical Analysis and Antidiabetic Potential of a Decoction from Stevia serrata Roots

A decoction of the roots (31.6-316 mg/kg) from Stevia serrata Cav. (Asteraceae) as well as the main component (5-150 mg/kg) showed hypoglycemic and antihyperglycemic effects in mice. The fractionation of the active extract led to the isolation of dammaradiene acetate (1), stevisalioside A (2), and three new chemical entities characterized by spectroscopic methods and named stevisaliosides B-D (3-5). Glycoside 2 (5 and 50 mg/kg) decreased blood glucose levels and the postprandial peak during oral glucose and insulin tolerance tests in STZ-hyperglycemic mice. Compounds 1-5 were tested also against PTP1B1-400 and showed IC50 values of 1180.9 ± 0.33, 526.8 ± 0.02, 532.1 ± 0.03, 928.2 ± 0.39, and 31.8 ± 1.09 μM, respectively. Compound 5 showed an IC50 value comparable to that of ursolic acid (IC50 = 30.7 ± 0.00 μM). Docking studies revealed that 2-5 and their aglycones bind to PTP1B1-400 in a pocket formed by the C-terminal region. The volatilome of S. serrata was characterized by a high content of (E)-longipinene, spathulenol, guaiadiene, seychellene, and aromandendrene. Finally, a UHPLC-UV method was developed and validated to quantify the content of 2 in the decoction of the plant.

Antidiabetic Potential of a Trimeric Anthranilic Acid Peptide Isolated from Malbranchea flocciformis

Compound 3, a trimeric anthranilic acid peptide, and another three metabolites were isolated from an organic extract from the culture medium of Malbranchea flocciformis ATCC 34530. The chemical structure proposed previously for 3 was unequivocally assigned via synthesis and X-ray diffraction analysis. Tripeptide 3 showed insulinotropic properties by decreasing the postprandial peak in healthy and hyperglycemic mice. It also increased glucose-induced insulin secretion in INS-1E at 5 μM, specifically at higher glucose concentrations. These results revealed that 3 might act as an insulin sensitizer and a non-classical insulin secretagogue. Altogether, these findings are in harmony with the in vivo oral glucose tolerance test and acute oral hypoglycemic assay. Finally, the chemical composition of the extract was established by the Global Natural Products Social Molecular Network platform. Phylogenetic analysis using the internal transcribed spacer region revealed that M. flocciformis ATCC 34530 is related to the Malbrancheaceae.

Pharmacological disadvantages in the spasmolytic effects by using the mixture known as "three toronjiles" in folk medicine

ETHNOPHARMACOLOGY RELEVANCE

In Mexico, Agastache mexicana subsp. mexicana (PT) and subsp. xolocotziana (WT), and Dracocephalum moldavica (BT), are used together as the "three toronjiles" to treat gastrointestinal spasms.

AIM OF STUDY

To evaluate if the spasmolytic activity of these three medicinal species is better in combination or in an individual manner.

MATERIALS AND METHODS

Spasmolytic effect of PT, WT and BT alone or combinate were evaluated in rings of the guinea-pig ileum contracted with potassium chloride (KCl), electrical field stimulation (EFS), or acetylcholine (ACh). Chemical analysis by thin layer and ultra-high pressure liquid chromatography of the aqueous extracts of each species were done for their comparison, and their acute toxicity were determined in mice.

RESULTS

PT and WT diminished in a dose-dependent manner the contractions induced by KCl, EFS, and ACh. Whereas BT did not altered contractions in any experimental protocol. A combination of the PT (EC50) and WT (EC50) diminished the contractions induced by KCl or EFS. Interestingly, the addition of BT extract (10 μg/ml) to the combination (PT EC30 + WT EC30) blocked the inhibitory effect produced on the contracted tissue in the presence of KCl, EFS, or ACh. Moreover, addition of BT extract (100 μg/ml) to the same combination blocked the inhibitory effect on the pre-contracted tissue only in the presence of EFS. None of the aqueous extracts produced toxicity in its individual administration in mice. Chemical analysis demonstrated similarities between PT and WT, but differences with BT.

CONCLUSIONS

The results of this study confirmed that either combined or by themselves aqueous extracts of PT and WT produced a spasmolytic action on guinea pig ileum, suggesting that this combination of medicinal plants could relieve gastrointestinal diseases in human, but when BT aqueous extract is added to those obtained with PT and WT, the spasmolytic activity diminished or even was blocked. Our results give evidence that mixture of several plants might produce disadvantages in the medicinal properties of their individual activity.

Natural products from plants targeting key enzymes for the future development of antidiabetic agents

Covering: 2000 to January 2023Diabetes is a metabolic disease of serious concern nowadays, with a negative economic impact. In 2021, the International Diabetes Federation estimated that more than 537 million adults live with diabetes, causing over 6.7 million deaths in that year. Intensive scientific research on medicinal plants in the last 100 years reveals that herbal drugs have been an essential source of products for developing antidiabetic agents acting on different physiological targets. This review summarizes recent research from 2000 to 2022 on plant natural compounds affecting selected crucial enzymes (dipeptidyl peptidase IV, diacylglycerol acyltransferase, fructose 1,6-biphosphatase, glucokinase, and fructokinase) involved in glucose homeostasis. Enzyme-aimed treatments usually induce reversible inhibition, irreversible by covalent changes of the objective enzymes, or bind non-covalently but so tightly that their inhibition is irreversible. Depending on the binding site, these inhibitors could be orthosteric or allosteric; in any case, the desired pharmacological action is achieved. One crucial advantage of targeting enzymes in drug discovery is that the required assays are usually simple, using biochemical experiments capable of analyzing enzyme activity.

Antidiabetic Sterols from Peniocereus greggii Roots

The roots of the cactus Peniocereus greggii, which grows in Northern Mexico and in the south of Arizona, are highly valued by the Pima to treat diabetes and other illnesses, such as breast pain and common cold. As part of our chemical and pharmacological investigation on medicinal plants used for treating diabetes, herein we report the hypoglycemic and antihyperglycemic action of a decoction prepared from the roots of the plant. The active compounds were a series of cholestane steroids, namely, peniocerol (2), desoxyviperidone (3), viperidone (4), and viperidinone (5). Also, a new chemical entity was obtained from an alkalinized chloroform extract (CE1), which was characterized as 3,6-dihydroxycholesta-5,8(9),14-trien-7-one (6) by spectroscopic means. Desoxyviperidone (3) showed an antihyperglycemic action during an oral glucose tolerance test. Compound 3 was also able to decrease blood glucose levels during an intraperitoneal insulin tolerance test in hyperglycemic mice only in combination with insulin, thus behaving as an insulin sensitizer agent. Nevertheless, mitochondrial bioenergetic experiments revealed that compounds 3 and 6 increased basal respiration and proton leak, without affecting the respiration associated with ATP production in C2C12 myotubes. Finally, an ultraefficiency liquid chromatographic method for quantifying desoxyviperidone (3) and viperidone (4) in the crude drug was developed and validated. Altogether, our results demonstrate that Peniocereus greggii decoction possesses a hypoglycemic and antihyperglycemic action in vivo, that sterols 2 and 6 promotes insulin secretion in vitro, and that desoxyviperidone (3) physiologically behaves as an insulin sensitizer agent by a mechanism that may involve mitochondrial proton leak.

α-Glucosidase and PTP-1B Inhibitors from Malbranchea dendritica

An extract from a PDB static culture of Malbranchea dendritica exhibited α-glucosidase and PTP-1B inhibitory activities. Fractionation of the active extract led to the isolation of gymnoascolide A (1), a γ-butenolide, and xanthones sydowinin A (2), sydowinin B (3), and AGI-B4 (4), as well as orcinol (5). Compound 1 exhibited important inhibitory activity against yeast α-glucosidase (IC₅₀ = 0.556 ± 0.009 mM) in comparison to acarbose (IC₅₀ = 0.403 ± 0.010 mM). Kinetic analysis revealed that 1 is a mixed-type inhibitor. Furthermore, compound 1 significantly reduced the postprandial peak in mice during a sucrose tolerance test at the doses of 5.16 and 10 mg/kg. Compound 1 was reduced with Pd/C to yield a mixture of enantiomers 1a and 1b; the mixture showed similar activity against α-glucosidase (IC₅₀ = 0.396 ± 0.003 mM) and kinetic behavior as the parent compound but might possess better drug-likeness properties according to SwissADME and Osiris Property Explorer tools. Docking analysis with yeast α-glucosidase (pdb: 3A4A) and the C-terminal subunit of human maltase-glucoamylase (pdb: 3TOP) predicted that 1, 1a, and 1b bind to an allosteric site of the enzymes. Compounds 1-5 were evaluated against PTP-1B, but only xanthone 3 moderately inhibited in a noncompetitive fashion the enzyme with an IC₅₀ of 0.081 ± 0.004 mM. This result was consistent with that of docking analysis, which revealed that 3 might bind to an allosteric site of the enzyme. From the inactive barley-based semisolid culture of M. dendritica, the natural pigment erythroglaucin (6) and the nucleosides deoxyadenosine (7), adenosine (8), thymidine (9), and uridine (10) were also isolated and identified.

Multi-target antidiabetic mechanisms of mexicanolides from Swietenia humilis

BACKGROUND

Swietenia humilis seeds are consumed in Mexico to treat type 2 diabetes; the antihyperglycemic effect of this species was previously demonstrated and related to the presence of tetranortriterpenoids of the mexicanolide class.

PURPOSE AND STUDY DESIGN

The present investigation was conducted to determine the mechanism of action of selected mexicanolides, including 2-hydroxy-destigloyl-6-deoxyswietenine acetate (1), methyl-2-hydroxy-3-β-tigloyloxy-1-oxomeliac-8(30)-enate (2) and humilinolide H (3), using in vivo experiments with hyperglycemic mice, and cell-based models.

METHODS

Nicotinamide-streptozotocin hyperglycemic mice (50-130 mg/kg, i.p.) were used to build antihyperglycemic drug-response curves using an oral glucose tolerance test model. In vitro studies were carried out on INSE1, H4IIE and C2C12 cells to assess insulin secretion, glucose-6-phosphatase inhibition, glucose uptake and mitochondrial bioenergetics, respectively.

RESULTS

The combination of the decoction of S. humilis or 2-hydroxy-destigloyl-6-deoxyswietenine acetate (mexicanolide 1) with glibenclamide resulted in a reduction of the antihyperglycemic effect while a significant increase was observed when they were dosed with metformin. These effects were related to K_ATP SUR blockade, insulin secretion in INSE1 cells, and modulation of 5-HT₂ receptors. Furthermore, mexicanolides 1-3 inhibited glucose-phosphatase in H4IIE cells, and enhanced glucose uptake and spare respiratory capacity in C2C12 myotubes.

CONCLUSION

S. humilis mexicanolides interact with pharmacological targets at pancreas (K_ATP channels), liver (glucose-6-phosphatase), and skeletal muscle (mitochondria and possibly glucose transporters) to modulate glucose homeostasis, and could be a promising resource to treat type 2 diabetes.

Antidiabeticin vitroandin vivoevaluation of cyclodipeptides isolated fromPseudomonas fluorescensIB-MR-66e

Cyclodipeptides cyclo(l-Pro-l-Leu),1; cyclo(l-Pro-l-Val),2; and cyclo (l-Pro-l-Phe),3fromPseudomonas fluorescensIB-MR-66e showed α-glucosidase inhibitory activity.

Medicinal properties of mangosteen (Garcinia mangostana L.): A comprehensive update

Garcinia mangostana L. (Clusiaceae) is a tropical tree native to Southeast Asia known as mangosteen which fruits possess a distinctive and pleasant taste that has granted them the epithet of "queen of the fruits". The seeds and pericarps of the fruit have a long history of use in the traditional medicinal practices of the region, and beverages containing mangosteen pulp and pericarps are sold worldwide as nutritional supplements. The main phytochemicals present in the species are isoprenylated xanthones, a class of secondary metabolites with multiple reports of biological effects, such as antioxidant, pro-apoptotic, anti-proliferative, antinociceptive, anti-inflammatory, neuroprotective, hypoglycemic and anti-obesity. The diversity of actions displayed by mangosteen xanthones shows that these compounds target multiple signaling pathways involved in different pathologies, and place them as valuable sources for developing new drugs to treat chronic and degenerative diseases. This review article presents a comprehensive update of the toxicological findings on animal models, and the preclinical anticancer, analgesic, neuroprotective, antidiabetic and hypolipidemic effects of G. mangostana L. extracts and its main isolates. Pharmacokinetics, drug delivery systems and reports on dose-finding human trials are also examined.

Antinociceptive and hypoglycaemic evaluation of Conyza filaginoides (D.C.) Hieron Asteraceae

Objectives

This work was undertaken to assess the antinociceptive and hypoglycaemic properties of a quantified extract of Conyza filaginoides (CFOE), as well as the antinociceptive potential of rutin, the main active compound of the plant, in normoglycaemic and/or hyperglycaemic mice (nicotinamide-streptozotocin, NA-STZ).

Methods

The antinociceptive effect of CFOE was evaluated using the writhing, hotplate and formalin tests in mice. Rutin was also examined with the formalin test. In addition, the antihyperalgesic effect of CFOE was evaluated in hyperglycaemic mice. The hypoglycaemic effect of CFOE was tested using an acute hypoglycaemic assay, and oral glucose and sucrose tests in normoglycaemic and hyperglycaemic mice.

Key findings

CFOE showed antinociceptive effect when tested in normoglycaemic mice in the writhing and hotplate tests (31.6–316 mg/kg). CFOE was also active in both normoglycaemic and hyperglycaemic mice in the formalin test (10–100 μg/paw) revealing its antihyperalgesic property. Rutin reduced the nociceptive behaviour in the formalin test; its mechanism of action seems to involve GABAergic and opioid pathways. CFOE possessed noted hypoglycaemic and antihyperglycaemic effects in normoglycaemic and hyperglycaemic mice (31.6–316 mg/kg).

Conclusions

The antinociceptive, antihyperalgesic and hypoglycaemic effects of C. filaginoides found in this study support the contemporary uses of the plant in Mexican folk medicine.

Hypoglycemic and antihyperglycemic effects of phytopreparations and limonoids from Swietenia humilis

An aqueous extract from the seeds of Swietenia humilis (31.6-100mg/kg bw) lowered (p<0.05) blood glucose levels in normal and nicotinamide-streptozotocin (NA-STZ)-induced hyperglycemic mice. Furthermore, when administered to fructose-fed rats with metabolic syndrome, the decoction showed significant antihyperglycemic, hypoglycemic and hypolipidemic effects, as well as an augmentation of hepatic glycogen. Limonoids 2-hydroxy-destigloyl-6-deoxyswietenine acetate (1), humulin B (2), methyl-2-hydroxy-3-β-isobutyroxy-1-oxomeliac-8(30)-enate (3), methyl-2-hydroxy-3-β-tigloyloxy-1-oxomeliac-8(30)-enate (4), humilinolide G (5), humilinolide C (6), methyl-2-hydroxy-3-β-isobutyoyl-8α,30α-epoxy-1-oxo-meliacate (7), and humilinolide H (8), were isolated from a CH2Cl2-MeOH (1:1) extract of the seeds. Compounds 5 and 8 are analogs of compounds 6 and 7. The structure of 5 was unequivocally established by X-ray analysis. When tested in normal and NA-STZ-hyperglycemic mice, compounds 1, 2, and 4 (3.16-31.6 mg/kg bw) decreased glycemia during an oral glucose tolerance test. The present investigation sustains the contemporary popular uses of S. humilis seeds for treating metabolic disorders, including diabetes and dyslipidemia and demonstrates the potential of the mexicanolides as antihyperglycemic agents.

Quality control tests for the crude drug of Conyza filaginoides

CONTEXT

Conyza filaginoides (D.C.) Hieron (Asteraceae) is a medicinal Mexican plant highly prized in contemporary Mexico for the treatment of upset stomach and diabetes.

OBJECTIVE

This work was undertaken to develop a suitable high performance liquid chromatography (HPLC)-diode array detection (DAD) method for quantifying rutin (1), the main active principle from the aerial parts of C. filaginoides.

MATERIALS AND METHODS

The method was performed using a LiChrospher 100 RP-18 column. The mobile phase was water (containing 0.1% phosphoric acid)-methanol-acetonitrile (80:5:15, v/v) at a flow rate of 1.2 mL min⁻¹.

RESULTS

Limits of detection and quantification were 7.5 and 22.8 μg mL⁻¹, respectively. The main recoveries measured at three concentrations were higher than 98%, with RSD <2%. Quantitative analysis of a few samples showed the presence of high concentrations of 1 (3.6 ± 0.2 g/100 g of dry plant material). The volatile components were extracted by hydrodistillation or head space solid-phase microextraction (HS-SPME), and thereafter analyzed by gas chromatography coupled to mass spectrometry (GC-MS). Forty-three chemical constituents representing 90% of the total content of the oil were identified. The major light volatile compounds obtained by HS-SPME revealed a high content of monoterpene hydrocarbons.

CONCLUSIONS

A precise, reliable, and accurate analytical HPLC method to detect and quantify 1 in the crude drug and some preparations were developed and fully validated. The volatile components of the plant are described for the first time. The proposed method would be useful for quality control assurance of this important Mexican plant.