Antioxidant activities of flavonol derivatives from the leaves and stem bark of Scutia buxifolia Reiss

Activity-guided isolation of antioxidant compounds from Rhizophora apiculata

Rhizophora apiculata (R. apiculata) contains an abundance of biologically active compounds due its special salt-tolerant living surroundings. In this study, the total phenolic content and antioxidant activities of various extract and fractions of stem of R. apiculata were investigated. Results indicated that butanol fraction possesses the highest total phenolic content (181.84 mg/g GAE/g dry extract) with strongest antioxidant abilities. Following in vitro antioxidant activity-guided phytochemical separation procedures, lyoniresinol-3α-O-β-arabinopyranoside (1), lyoniresinol-3α-O-β-rhamnoside (2), and afzelechin-3-O-L-rhamno-pyranoside (3) were separated from the butanol fraction. These compounds showed more noticeable antioxidant activity than a BHT standard in the DPPH, ABTS and hydroxyl radical scavenging assays. HPLC analysis results showed that among different plant parts, the highest content of 1–3 was located in the bark (0.068%, 0.066% and 0.011%, respectively). The results imply that the R. apiculata might be a potential source of natural antioxidants and 1–3 are antioxidant ingredients in R. apiculata.

Influence of the traditional Brazilian drink Ilex paraguariensis tea on glucose homeostasis

In this study we examined the acute in vivo effect and short- and long-term in vitro effects of samples from native and commercial Ilex paraguariensis on glucose homeostasis. Also, the potential effect of I. paraguariensis on serum insulin secretion was investigated. The chemical identification and quantification of methyl xanthines and polyphenols in CH₂Cl₂, EtOAc and n-BuOH fractions of native I. paraguariensis as well as infusions of green and roasted I. paraguariensis from a commercial source was verified by high-performance liquid chromatography. The results for the serum glucose-lowering indicated that both fractions and both infusions were able to improve significantly the oral glucose tolerance curve. Additionally, both the EtOAc and n-BuOH fractions induced-insulin secretion, but EtOAc induced an early (at 15 min) and late (at 60 min) biphasic peak of insulin secretion similar to glipizide stimulatory effect. Both fractions increased liver glycogen content compared with fasted normal rats. Also, EtOAc and n-BuOH fractions inhibited in vitro disaccharidases activities after an acute treatment. The maximum inhibitory effect of the EtOAc and n-BuOH fractions on maltase activity (at 5 min) was around 35%. The evident reduction of protein glycation by glucose or fructose with EtOAc and n-BuOH fractions increased from 7 to 28 days of in vitro incubation. Inhibition of bovine serum albumin glycation by glucose and fructose, by around 50% and 90%, respectively, was observed. Additionally, the green and roasted mate infusions reduced the formation of AGEs in a characteristic long-term effect. In conclusion, this study shows that I. paraguariensis has an anti-hyperglycemic potential role able to improve the diabetic status and is probably a source of multiple hypoglycemic compounds.

Endothelium-dependent and independent vasorelaxation induced by an n-butanolic fraction of bark of Scutia buxifolia Reiss (Rhamanaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Scutia buxifolia has been widely used in Brazilian folk medicine as an anti-hypertensive agent. We evaluated the vascular effects and mechanism involved in the relaxation of aorta induced by an n-butanolic fraction (BuOH) from Scutia buxifolia.

MATERIALS AND METHODS

Rat aortic rings precontracted by phenylephrine (1 μM) were exposed to cumulative concentrations (3–3000 μg/ml) of crude extracts or fractions obtained from bark or leaves of Scutia buxifolia. Classical receptor antagonists, channel and enzymatic inhibitors were used to check the mechanisms involved.

RESULTS

The crude extracts of both leaves and bark of Scutia buxifolia, as well as several fractions, were able to induce partial or total relaxation of rat aortic rings. The BuOH fraction of bark of Scutia buxifolia was the most potent in endothelium-intact (E+) preparations, and also induced a partial, but very significant relaxation in endothelium-denuded (E−) vessels. The non-selective nitric oxide synthase inhibitor L-NAME, as well as the soluble guanylate cyclase inhibitor ODQ, vanished the relaxation in E+. In E− preparations, K+ channel blockers, such as tetraethylammonium, glibenclamide, 4-aminopyridine, and the large-conductance calcium-activated K+ channel blocker iberiotoxin, were able to significantly reduce the maximum relaxation elicited by BuOH fraction.

CONCLUSION

Our results demonstrated that BuOH fraction obtained from barks of Scutia buxifolia induced both endothelium-dependent and -independent relaxation in rat aortic rings. The endothelium-dependent relaxation is fully dependent on NO/cGMP system, while direct activation of K+ channels may explain, at least in part, the endothelium-independent relaxation induced by BuOH fraction of Scutia buxifolia.

Protective effects of extracts and flavonoids isolated from Scutia buxifolia Reissek against chromosome damage in human lymphocytes exposed to hydrogen peroxide

Flavonoids are claimed to protect against cardiovascular disease, certain forms of cancer and ageing, possibly by preventing initial DNA damage. Therefore, we investigated the protective effects of crude extract, ethyl acetate fraction and flavonoids (quercetin, quercitrin, isoquercitrin and rutin) isolated from the leaves from Scutia buxifolia against chromosome damage induced by H₂O₂ in human lymphocytes by analyzing cellular growth rate, cell viability, mitotic index and chromosomal instability. We found a differential response among the compounds tested, with the ethyl acetate fraction being more effective than the crude extract, a difference perhaps related to the presence of the antioxidants identified and quantified by HPLC/DAD. In general, quercetin, isoquercitrin and rutin recovered the mitotic index and chromosomal instability more than quercitrin after treatment with hydrogen peroxide.

Antioxidant effect of Stryphnodendron rotundifolium Martius extracts from Cariri-Ceará State (Brazil): potential involvement in its therapeutic use

Stryphnodendron rotundifolium is a phytotherapic used in the northeast of Brazil for the treatment of inflammatory processes which normally are associated with oxidative stress. Consequently, we have tested the antioxidant properties of hydroalcoholic (HAB) and aqueous extracts (AB) from the bark and aqueous extract (AL) from the leaves of Stryphnodendron rotundifolium to determine a possible association between antioxidant activity and the popular use of this plant. Free radical scavenger properties were assessed by the quenching of 1',1'-diphenil-2-picrylhydrazyl (DPPH) and the calculated IC(50) were: HAB = 5.4 ± 0.7, AB = 12.0 ± 2.6, and AL = 46.3 ± 12.3 µg/mL. Total phenolic contents were: HAB = 102.7 ± 2.8, AB = 114.4 ± 14.6, and AL = 93.8 ± 9.1 µg/mg plant). HPLC/DAD analyses indicated that gallic acid, catechin, rutin and caffeic acid were the major components of the crude extracts of S. rotundifolium. Plant extracts inhibited Fe(II)-induced lipid peroxidation in brain homogenates. Iron chelation was also investigated and only HBA exhibited a weak activity. Taken together, the results suggest that S. rotundifolium could be considered an effective agent in the prevention of diseases associated with oxidative stress.

Comparative studies on antioxidant activities of extracts and fractions from the leaves and stem of Epimedium koreanum Nakai

The antioxidant potency of various extracts and fractions from the leaves and stem of Epimedium koreanum Nakai was evaluated using three esteblished methods, specifically the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radica-scavenging activity assay, the inhibitory effect on lipid peroxidation induced by Fe(2+)/ascorbate (MDA) assay and the ferric reducing power (FRP) assay. The amounts of total phenolics and total flavonoids in the extracts and fractions were determined by spectrophotometric methods and the content of icariin was determined by HPLC. The results showed that all the extracts and fractions exhibited antioxidant activities at different magnitudes of potency. The leaf extract and fractions demonstrated superior antioxidant activity in most of the assays. The decreasing order of antioxidant activities among the extracts/fractions assayed through the three methods were found to be n-BuOH fraction>ethyl acetate fraction>ethanol extract>petroleum ether fraction>water fraction. A positive correlation was found between the amounts of total phenolics, total flavonoids and icariin and DPPH radical scavenging activity (R(2) = 0.9935, 0.9944 and 0.9997, respectively) and inhibitory activity on lipid peroxidation (R(2) = 0.9987, 0.9830 and 0.9886, respectively). The results suggested that Icariin was one of the main constituents contribute to the antioxidant activity of Epimedium koreanum Nakai and the n-BuOH fractions of leaf extract might be valuable antioxidant natural sources.

Antiplasmodial, anti-inflammatory and cytotoxic activities of various plant extracts from the Mascarene Archipelago

AIM OF THE STUDY

Antiplasmodial activity, inhibition of nitric oxide (NO) overproduction, and anti-proliferative activity were investigated in vitro to evaluate the bioactive potential of the traditional pharmacopoeia of the Mascarene Archipelago, which is known for its biodiversity and for the richness of its endemic flora.

MATERIALS AND METHODS

A total of 45 methanol (MeOH) and dichloromethane (DCM) extracts were prepared from 19 plant species collected on Réunion and Mauritius Islands. Ninety-six-well microplate assays were performed on chloroquine sensitive Plasmodium falciparum 3D7 strain, on LPS-stimulated Raw 264.7 murine macrophages and on A-549, DLD-1 and WS1 human cells. Activity was evaluated through spectrophotometric methods.

RESULTS

Activity was attributed to plant extracts expressing IC(50)<50μg/ml for antiplasmodial response, IC(50)<100μg/ml for cytotoxicity, and IC(50)<130μg/ml for anti-inflammatory reaction. The majority of the extracts tested (69%) exhibited potency in at least one of these three types of activity. This is the first report describing promising antiplasmodial activity (IC(50)<15μg/ml) for Psiadia dentata DCM extract and Terminalia bentzoe MeOH bark extract. NO inhibition assay revealed seven interesting plants, described for the first time as anti-inflammatory: Aphloia theiformis, Buddleja salviifolia, Eupatorium riparium, Hiptage benghalensis, Psiadia arguta, Psiadia dentata, and Scutia commersonii. Finally, anti-proliferative activity was observed for two endemic species, Geniostoma borbonicum and Nuxia verticillata.

CONCLUSION

Using the criterion of endemism as part of the criteria for traditional medicinal use raises the chances of finding original active principles. In our case, 86% of the endemic plants tested displayed pharmacological interest.