Ana Paula Machado Bernardi

Antimicrobial activity of some Hypericum species

The crude methanolic extracts of six species of Hypericum [H. caprifoliatum Cham. & Schlecht., H. carinatum Griseb., H. connatum Lam., H. ternum A. St. Hil., H. myrianthum Cham. & Schlecht. and H. polyanthemum Klotzsch ex Reichardt] growing in southern Brazil were analyzed for antimicrobial activity against several microorganisms (bacteria and fungi). The most active plant was H. caprifoliatum, which showed activity against Staphylococcus aureus. Only H. polyanthemum and H. ternum extracts were active against Bacillus subtilis. None of the crude methanolic extracts showed activity against S. epidermidis, Escherichia coli or Saccharomyces cerevisiae. Extracts from these species were evaluated chemically and tannin, flavonoid and phenolic acids were the prominent compounds. The plants contained quercitrin, hyperoside (except H. connatum) and, less frequently, isoquercitrin and chlorogenic acid. In contrast to H. perforatum, which has high concentrations of rutin, these species do not produce this flavonoid or it appears as traces. The tannin concentration varied between 5.1 and 16.7% in H. myrianthum and H. ternum, respectively.

Germination and growth inhibitory effects of Hypericum myrianthum and H. polyanthemum extracts on Lactuca sativa L.

Germination and growth inhibitory effects of ethanolic crude extracts of Hypericum myrianthum and H. polyanthemum aerial parts on lettuce (Lactuca sativa) were investigated. The germination was retarded in all the tested concentrations. After seven days the final germination percentage of the most concentrated extracts was significantly reduced by both extracts in comparison with the control. The radicles length was significantly affected showing necrosis. Both species present phenolic compounds as the main components and they could be responsible for the inhibition of the germination and growth of Lactuca sativa.

ANTIOXIDANT ACTIVITY OF FLAVONOIDS ISOLATED FROM HYPERICUM TERNUM

In the present work we have studied the scavenging activity of several flavonoids isolated from Hypericum ternum A. St. Hil. The evaluation of the free radical scavenging capacity was based on the 2,2-diphenyl-l-picrylhydrazyl radical (DPPH) consumption elicited by their addition. Also, we have attempted to evaluate their capacity to delay pyrogallol red consumption promoted by peroxyl radicals. The compounds isolated and characterized were 13,118-biapigenin and five quercetin derivatives (quercetin 3-methyl ether, quercetin 3,7-dimethyl ether, hyperoside, isoquercitrin and guaijaverin). All compounds were able to scavenge DPPH radicals. The order in scavenging capacity (from highest to lowest) was: guaijaverin > hyperoside ≈ isoquercitrin > quercetin-3-methyl-ether. No protection of pyrogallol red was evidenced for all flavonoids derivatives at relatively high (100 µM) concentrations. This lack of protection contrasts with the efficient protection afforded by 10 µM quercetin, indicating that substitution at the 3-position in quercetin strongly reduces the capacity of the molecule to scavenge peroxyl radicals

Phenolic compounds profiles during ex vitro acclimatization of micropropagated Hypericum polyanthemum.

Accumulation of benzopyrans and total phenolic compounds were assessed in acclimatized field grown plants of Hypericum polyanthemum, an endemic species of southern Brazil, harvested at different developmental stages. The HPLC analysis of bioactive compounds 6-isobutyryl-5,7-dimethoxy-2,2-dimethylbenzopyran (HP1), 7-hydroxy-6-isobutyryl-5-methoxy-2,2-dimethyl-benzopyran (HP2) and 5-hydroxy-6-isobutyryl-7-methoxy-2,2-dimethyl-benzopyran (HP3) revealed that the three benzopyrans are accumulated both in the vegetative and reproductive parts with maximum contents observed after 18 weeks (in the former) and 20 weeks (in the later) of plant growth (1.92+/-0.085 g % DW and 2.62+/-0.13 g % DW in the vegetative and reproductive parts, respectively). Highest contents of HP1 (1.56+/-0.12 g % DW) and HP2 (0.19+/-0.01 g % DW) were quantified in the green floral buds of the plants, whereas HP3 reached the highest level (1.02+/-0.08 g % DW) in the overblown flowers. The evaluation of total phenolic compounds showed that the vegetative parts accumulated the highest levels of the metabolites (51.93+/-0.67 mg QE (g DW)(-1)) after 16 weeks of plant growth. Considering the reproductive parts, the open flowers accumulated the greatest levels of the bioactive compounds (75.99+/-0.95 mg QE (g DW)(-1)). The results show that H. polyanthemum can be efficiently propagated and acclimatized to produce benzopyrans and other phenolic compounds.

ANTIOXIDANT ACTIVITY IN SOUTHERN BRAZIL HYPERICUM SPECIES

The present study was conducted to assess the antioxidant activity of Hypericum species endemic to South Brazil, H. caprifoliatum, H. carinatum, H. myrianthum and H. polyanthemum. The free radical scavenging properties of plant extracts were evaluated employing different methodologies, including the bleaching of a stable free radical (2,2-diphenyl-1-picrylhydrazyl, DPPH) and the peroxyl reactivity indexes TRAP (Total Reactive Antioxidant Potential) and ORAC-pyrogallol red (Oxygen Radicals Absorbance Capacity). A fair correlation was found between total phenol content determined by Folin-Ciocalteau and DPPH consumption, both in crude methanol and n-hexane extracts. In particular, H. myrianthum and H. caprifoliatum showed the highest TRAP and ORACpyrogallol red values, respectively. This would imply that H. myrianthum contains a larger amount of antioxidants of lower reactivity.

Selective cytotoxicity and apoptosis induction in glioma cell lines by 5-oxygenated-6,7-methylenedioxycoumarins from Pterocaulon species

The coumarins 5-methoxy-6,7-methylenedioxycoumarin 1 5-(3-methyl-2-butenyloxy)-6,7-methylenedioxycoumarin 2 and 5-(2,3-dihydroxy-3-methylbutyloxy)-6,7-methylenedioxycoumarin 3 isolated from Pterocaulon species showed significant cytotoxicity against two glioma cells lines. Compound 1 presented IC(50) values of 34.6 μM and 31.6 μM against human (U138-MG) and rat (C6) glioma cells, respectively, and this compound was at least two times more potent than compounds 2 and 3. This result could be explained by the planar conformation adopted by 1 through a non-classical hydrogen bond between a hydrogen of the methoxy and the oxygen of the methylenedioxy groups. Another important finding was that the cytotoxic effect induced by 1 in glioma cells was not observed in organotypic cultures, indicating a selective cytotoxicity for tumor cells.