α-Glucosidase inhibitory activity and in vivo antihyperglycemic effect of secondary metabolites from the leaf infusion of Ocimum campechianum mill.

ETHNOPHARMACOLOGICAL RELEVANCE: Wild basil (Ocimum campechianum Mill.), an aromatic herb of the Lamiaceae family known as "albahaca de monte" (Spanish) or "x'kakaltun" (Mayan) in Yucatan, is used in Mayan traditional medicine to treat diabetes, as well as to alleviate fever symtoms, stomach pain, conjunctivitis, and various skin affections. AIM OF THE STUDY: To isolate and identify the bioactive metabolites responsible for the α-glucosidase inhibitory activity previously detected in the leaf infusion O. campechianum. MATERIALS AND METHODS: The bioassay-guided fractionation and purification of the lyophilized infusion was carried out using a liquid-liquid partition procedure, followed by successive chromatographic purifications of the semipurified fractions. The isolated metabolites were identified by comparing their spectroscopic data with those reported in the literature. The liophylized infusion, together with the semipurified fractions, and the pure metabolites were tested for their antioxidant and α-glucosidase inhibitory activities, as well as their antihyperglycemic effect. RESULTS: Chromatographic purification of the semipurified fractions led to the isolation of the polymethoxylated flavones 5-demethyl nobiletin (1) and 5-demethyl sinensetin (2), together with luteolin (3), methyl rosmarinate (4) and rosmarinic acid (5). Metabolites 4 and 5 appear to be responsible for the α-glucosidase inhibitory activity and the antihyperglycemic effect detected in the lyophilized infusion. A Lineweaver-Burk double reciprocal plot confirmed that the higher α-glucosidase inhibitory activity of 4 is of non-competitive nature. Both 4 and 5 caused a decrease in blood glucose higher than that caused by acarbose, a result that appears to be related to their strong α-glucosidase inhibitory activity. Even though flavonoids 1-3 did not show a good inhibition of α-glucosidase, these products decreased blood glucose in the in vivo model, suggesting a different antihyperglycemic mechanism. CONCLUSIONS: The results confirm both the traditional use of O. campechianum and the importance of the leaf infusion as a potential source of antihyperglycemic agents. The isolation of 5-demethyl nobiletin (1) and 5-demethyl sinensetin (2) from O. campechianum and other Ocimum spp. suggests that polymethoxyflavones can be considered chemotaxonomical markers for the genus.

Antidiabetic effect of Achillea millefollium through multitarget interactions: α-glucosidases inhibition, insulin sensitization and insulin secretagogue activities.

ETHNOPHARMACOLOGICAL IMPORTANCE: Achillea millefolium L. (Asteraceae) is a perennial herb used in Mexican folk medicine for treatment of several pathologies, including inflammatory and spasmodic gastrointestinal disorders, hepatobiliary complaints, overactive cardiovascular, respiratory ailments and diabetes. AIM OF THE STUDY: To evaluate the potential antidiabetic effect in vivo and to establish the potential mode of action through in vitro approaches of Achillea millefolium. MATERIALS AND METHODS: The antidiabetic effect of hydroalcoholic extract of Achillea millefolium (HAEAm) was evaluated on the oral glucose tolerance tests, in normoglycemic and experimental Type 2 diabetic mice models. In addition, we evaluated the possible mode of action in in vitro assays to determine α-glucosidases inhibition, the insulin secretion and calcium mobilization in RINm5F cells and PPARγ and GLUT4 expression in 3T3-L1 cells. RESULTS: HAEAm showed significant glucose diminution on oral glucose tolerance test and in acute experimental Type 2 diabetic assay with respect to the control (p < 0.05). In addition, HAEAm promoted the α-glucosidases inhibition by 55% at 1mg/ml respect to control. On the other hand, HAEAm increased the PPARγ (five-times) and GLUT4 (two-fold) relative expression than control (p < 0.05). Finally, HAEAm significantly increased the insulin secretion and [Ca2+]i compared with control. CONCLUSION: The HAEAm possesses in vivo antidiabetic effect, having such effect through multitarget modes of action that involve antihyperglycemic (α-glucosidases inhibition), hypoglycemic (insulin secretion) and potential insulin sensitizer (PPARγ/GLUT4 overexpression) actions.

Euphorbia dioeca Kunth as a novel source for alpha-glucosidase inhibitors / Euphorbia dioeca Kunth como una nueva fuente de inhibidores de alfa-glucosidasa

Euphorbia dioeca Kunth belongs to the Wanderer’s herb complex that is traditionally used for skin diseases and recently as antidiabetic. The methanol and aqueous extracts were evaluated for their in vitro alpha-glucosidase inhibitory activity and an oral starch tolerance test. These extracts showed an IC50 of 0.55 and 0.85 mg/mL, respectively. In diabetic Long Evans rats, the methanol and aqueous extracts reduced significantly the postprandial hyperglycemia peak in 15.2 percent and 12.8 percent, respectively. The alpha-glucosidase inhibitory activity is related with the presence of glycosides, phenolic compounds and flavonoids. Additionally, the safety parameters of both extracts were assessed by means of an acute toxicity test, being classified as innocuous. The traditional use of E. dioeca to control type 2 diabetes was confirmed, being an important source of alfa-glucosidase inhibitors.

Euphorbia dioeca Kunth, pertenece al complejo de plantas medicinales denominado Hierba de la Golondrina; el cual se utiliza para diversos padecimientos, destacando su uso como antidiabético. En dicho marco, se evaluó tanto la actividad inhibitoria de alfa-glucosidasa in vitro, como su desempeño en una prueba de tolerancia a una carga de almidón postprandial. Los extractos inhibieron la actividad de la alfa-glucosidasa con una CI50 de 0.55 y 0.85 mg/mL, respectivamente. Los extractos metanólico y acuoso disminuyeron significativamente el pico hiperglucémico postprandial en un 15.2 por ciento y un 12.8 por ciento, respectivamente, cuando se evaluó en ratas diabéticas. La actividad inhibitoria de alfa-glucosidasa, reflejada en ambas pruebas, está relacionada con la presencia de glicósidos, compuestos fenólicos y flavonoides. De manera adicional, ambos extractos fueron evaluados en una prueba de toxicidad aguda, siendo clasificados como inocuos. Se corroboró el uso tradicional de E. dioeca para el control de la diabetes tipo 2, siendo una importante fuente de compuestos inhibidores de alfa-glucosidasa.

In vitro fasciolicide activity of some plant extracts against newly excysted flukes.

The aim of the present study was to evaluate, under in vitro conditions, the activity of 20 plant extracts against newly excysted Fasciola hepatica metacercariae. The plants were selected on the basis of anthelmintic activity, traditional use, availability, solubility, and permanence in the liver. For the in vitro evaluation, 24-well Nunc-immunoplates containing RPMI-1640 culture medium bovine sera plus antibiotics were used. Extract concentrations of 500 and 50 mg/mL were placed in triplicate. Approximately 10 newly excysted flukes were placed in each well, and the plates were incubated in a CO(2) incubator at 5% atmosphere for 3 days. In each plate four control wells containing nontreated flukes were included. All procedures were undertaken under an air-flow cabinet. Efficacy was measured on days 1 and 3 by considering the motility of the live or dead trematodes evaluated with the aid of an inverted microscope. Results indicated that, from all extracts evaluated, Tilia mexicana showed an average efficacy for concentrations of 500 and 50 mg/mL, respectively, of 100 and 100%; Eriobotrya japonica, 100 and 95%; Coffea arabica, 100 and 100%; Crataegus mexicana, 95 and 90%; and Ternstroemia pringlei 100 and 100%. From this preliminary evaluation, we conclude that further and more detailed evaluations at lower concentrations should be undertaken to understand the real efficacy of these plant extracts.

Antimalarial 4-phenylcoumarins from the stem bark of Hintonia latiflora.

The EtOAc extract of the stem bark of Hintonia latiflora showed the suppression of total parasitemia and the chemosuppression of schizont numbers, when tested in vivo against Plasmodium berghei infection in mice. Bioassay-directed fractionation of the EtOAc extract, using the in vitro 16 h and the in vivo 4-day suppression tests on P. berghei schizont numbers, led to the isolation of the new compound 5-O-beta-D-glucopyranosyl-7,4'-dimethoxy-3'-hydroxy-4-phenylcoumarin (1), along with the known 5-O-beta-D-glucopyranosyl-7-methoxy-3',4'-dihydroxy-4-phenylcoumarin (2). The structure of compound 1 was established on the basis of spectroscopic data interpretation. Compounds 1 and 2 suppressed the development of P. berghei schizonts in vitro with IC50 values of 24.7 and 25.9 microM, respectively. Compound 2 suppressed the development of schizonts at the dose of 40 mg/kg by 70.8% in the in vivo assay.