Seasonal variation on the contents of coumarin and kaurane-type diterpenes in Mikania laevigata and M. glomerata leaves under different shade levels.

Coumarin (1) and kaurane-type diterpenes are considered the bioactive constituents of Mikania glomerata and M. laevigata, used in Brazil to treat respiratory affective disorders. The seasonal variation of 1, ortho-coumaric acid (2), benzoylgrandifloric acid (3), cinnamoylgrandifloric acid (4), and kaurenoic acid (5) in leaves of both species, cultivated in full sunlight and under shade levels of 40 and 80%, was quantified by HPLC. Compound 2 was detected solely in M. laevigata in concentrations below the limit of quantification. Coumarin was not found in M. glomerata, whereas its concentration reached 0.94±0.24% (w/w) in M. laevigata farmed in summer under 80% shading. Both Mikania species produced higher amounts of kaurane diterpenes when cultivated in plenty of sunlight. Hence, maximum contents of 1 are reached in M. laevigata cultivated under high shading, but with reduced concentrations of 3-5. Conversely, M. glomerata should be cultivated under full sunlight and harvested in winter for highest concentrations of kaurane-type diterpenes.

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-ß-(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-ß-(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.

Hancornia speciosa Gomes (Apocynaceae) as a potential anti-diabetic drug.

ETHNOPHARMACOLOGICAL RELEVANCE: The leaves of Hancornia speciosa Gomes are traditionally used to treat diabetes in Brazil. The aim of the study is to evaluate the potential anti-diabetic effect of Hancornia speciosa extract and derived fractions. MATERIALS AND METHODS: The ethanolic extract from Hancornia speciosa leaves and chromatographic fractions thereof were evaluated on α-glucosidase assay, on hyperglycemic effect and glucose uptake. The chemical composition of the extract and its most active fraction was investigated by ESI-LC-MS. RESULTS: The ethanolic extract and derived fractions inhibited α-glucosidase in vitro. However, only the crude extract and the dichloromethane fraction inhibited the hyperglycemic effect induced by starch or glucose. Both the extract and dichloromethane fraction were also able to increase glucose uptake in adipocytes. Bornesitol, quinic acid, and chorogenic acid were identified in the extract, along with flavonoid glycosides, whereas the dichloromethane fraction is majorly composed by esters of lupeol and/or α/ß-amirin. CONCLUSIONS: Hancornia speciosa has a potential anti-diabetic effect through a mechanism dependent on inhibition of α-glucosidase and increase on glucose uptake. These results give support to the use on traditional medicine of this medicinal plant.