Antiradical Potency Research Articles

Extracts of Brocchia cinerea (Delile) Vis Exhibit In Vivo Wound Healing, Anti-Inflammatory and Analgesic Activities, and Other In Vitro Therapeutic Effects.

The plant Brocchia cinerea (Delile) (B. cinerea) has many uses in traditional pharmacology. Aqueous (BCAE) and ethanolic extracts (BCEE) obtained from the aerial parts can be used as an alternative to some synthetic drugs. In vitro, DPPH, FRAP and TAC are three tests used to measure antioxidant efficacy. Antibacterial activities were determined against one Gram positive and two Gram negative strains of bacteria. The analgesic power was evaluated in vivo using the abdominal contortion model in mice, while carrageenan-induced edema in rats was the model chosen for the anti-inflammatory test; wound healing was evaluated in an experimental second degree burn model. The results of the phytochemical analysis showed that BCEE had the greatest content of polyphenols (21.06 mg AGE/g extract), flavonoids (10.43 mg QE/g extract) and tannins (24.05 mg TAE/g extract). HPLC-DAD reveals the high content of gallic acid, quercetin and caffeic acid in extracts. BCEE has a strong antiradical potency against DPPH (IC50 = 0.14 mg/mL) and a medium iron reducing activity (EC50 = 0.24 mg/mL), while BCAE inhibited the growth of the antibiotic resistant bacterium, P. aeruginosa (MIC = 10 mg/mL). BCAE also exhibited significant pharmacological effects and analgesic efficacy (55.81% inhibition 55.64% for the standard used) and the re-epithelialization of wounds, with 96.91% against 98.60% for the standard. These results confirm the validity of the traditional applications of this plant and its potential as a model to develop analogous drugs.

Pyrazolone-type compounds (part II): in vitro and in silico evaluation of antioxidant potential; structure-activity relationship.

The pyrazolone class comprises a variety of hybrid compounds displaying diverse biological actions. Although studied for decades, these compounds are still of interest due to their facile chemical transformations. In our previous work, we presented the synthetic route of functionalised pyrazolone derivatives. The presence of pyrazolone structural motif in many drugs, such as edaravone, prompted us to investigate the antioxidant features of the selected compounds. In this paper, we provide an extensive in vitro and in silico description of the antioxidant properties of selected pyrazolone analogues. The obtained in vitro results revealed their great antiradical potency against the DPPH radical (IC50 values in the 2.6-7.8 μM range), where the best results were obtained for analogues bearing a catechol moiety. Density functional theory (DFT) was used to assess their antioxidant capacity from the thermodynamic aspect. Here, good agreement with in vitro results was achieved. DFT was employed for the prediction of the most preferable radical scavenging pathway, also. In polar solvents, the SPLET mechanism is a favourable scavenging route, whereas in nonpolar solvents the HAT is slightly predominant. Furthermore, antioxidant mechanisms were studied in the presence of relevant reactive oxygen species. The obtained values of the reaction enthalpies with the selected radicals revealed that HAT is slightly prevailing in polar solvents, while the SPLET mechanism is dominant in nonpolar solvents. Regarding the well-known antioxidant features of the drug edaravone, these findings represent valuable data for this pyrazolone class and could be used as the basis for further investigations.

In Vitro and In Silico Antioxidant Efficiency of Bio-Potent Secondary Metabolites From Different Taxa of Black Seed-Producing Plants and Their Derived Mycoendophytes

Oxidative stress is involved in the pathophysiology of multiple health complications, and it has become a major focus in targeted research fields. As known, black seeds are rich sources of bio-active compounds and widely used to promote human health due to their excellent medicinal and pharmaceutical properties. The present study investigated the antioxidant potency of various black seeds from plants and their derived mycoendophytes, and determined the total phenolic and flavonoid contents in different extracts, followed by characterization of major constituents by HPLC analysis. Finally, in silico docking determined their binding affinities to target myeloperoxidase enzymes. Ten dominant mycoendophytes were isolated from different black seed plants. Three isolates were then selected based on high antiradical potency and further identified by ITS ribosomal gene sequencing. Those isolated were Aspergillus niger TU 62, Chaetomium madrasense AUMC14830, and Rhizopus oryzae AUMC14823. Nigella sativa seeds and their corresponding endophyte A. niger had the highest content of phenolics in their n-butanol extracts (28.50 and 24.43 mg/g), flavonoids (15.02 and 11.45 mg/g), and antioxidant activities (90.48 and 81.48%), respectively, followed by Dodonaea viscosa and Portulaca oleracea along with their mycoendophytic R. oryzae and C. madrasense. Significant positive correlations were found between total phenolics, flavonoids, and the antioxidant activities of different tested extracts. The n-butanol extracts of both black seeds and their derived mycoendophytes showed reasonable IC50 values (0.81–1.44 mg/ml) compared to the control with significant correlations among their phytochemical contents. Overall, seventeen standard phenolics and flavonoids were used, and the compounds were detected in different degrees of existence and concentration in the examined extracts through HPLC analysis. Moreover, the investigation of the molecular simulation results of detected compounds against the myeloperoxidase enzyme revealed that, as a targeted antioxidant, rutin possessed a high affinity (−15.3184 kcal/mol) as an inhibitor. Taken together, the black seeds and their derived mycoendophytes are promising bio-prospects for the broad industrial sector of antioxidants with several valuable potential pharmaceutical and nutritional applications.

The reactivity of neurotransmitters and their metabolites towards various nitrogen-centered radicals: Experimental, theoretical, and biotoxicity evaluation

In the past few years, there has been a certain interest in nitrogen-centered radicals, biologically important radicals that play a vital role in various processes and constitute many important biological molecules. In this paper, there was an attempt to bridge a gap in the literature that concerns the antiradical potency of monoamine neurotransmitters (dopamine, epinephrine, and norepinephrine) and their metabolites towards these radicals. The most probable radical quenching mechanism was determined for each radical out of three common mechanisms, namely Hydrogen Atom Transfer (HAT), Single Electron Transfer followed by the Proton Transfer (SET-PT), and Sequential Proton Loss Electron Transfer (SPLET). Marcus’ theory was then used to determine the reaction rates for the electron transfer process. SPLET was the most probable mechanism for both reactions with the aminyl and hydrazyl radicals, while HAT and SPLET were plausible mechanisms for reactions with the imidazolyl radical. Special emphasis was put on the investigation of the substituent effect on the preferred mechanism. The necessity of both thermodynamic and kinetic parameters for the comparison of the antiradical potency of compounds was discussed. The same methodology was applied for the theoretical investigation of the reactivity towards DPPH⦁, a member of the hydrazyl radicals. An ecotoxicity analysis was performed to assess the impact the investigated radicals have on the ecosystem. Except for histidine, every other neutral form was either toxic or highly toxic to some of the analyzed marine organisms.

Effect of Steric Structure on the Mechanism of Antioxidant Activity of Alkyl Gallates in Soybean Oil Triacylglycerols—A Kinetic Approach

AbstractFrom an interfacial phenomena standpoint, the effect of the alkyl chain length is evaluated on the mechanism of antioxidant activity of gallic acid ester derivatives (methyl, propyl, octyl, dodecyl, and stearyl gallates) in bulk phase oil. A combinational kinetic model is used to estimate the oxidation kinetic parameters, such as induction period, the maximum concentration of lipid hydroperoxides, and critical reverse micelle concentration. These kinetic parameters are estimated much better with the combinational model compared to the tangent method. The nonlinear behavior is observed for inhibitory activities of homologous series of antioxidants in soybean triacylglycerols. In terms of different kinetics parameters, including antioxidant effectiveness and activity, methyl gallate has the highest inhibitory effect during lipid peroxidation. Gallic acid and alkyl gallates are able to protect bulk oils against peroxidation (induction period > 336 h) in terms of the extent of their participation in the main reaction of chain termination and pro‐oxidative side reactions of chain initiation, and anti‐oxidative side reactions of chain propagation.Practical Applications: This work explains the effect of the esterification in the inhibitory activity of alkyl gallates, mechanism action of alkyl gallates in bulk oil systems, antiradical potency as a function of the interfacial phenomena, and free radical chain mechanism, the impact of antioxidant activity on critical reverse micelle concentration of hydroperoxides. Moreover, in this study, it is confirmed that the combinational kinetic model can be employed as a reliable method for determining the oxidation kinetic parameters.

Combined Effect of Cultivar and Peel Chromaticity on Figs’ Primary and Secondary Metabolites: Preliminary Study Using Biochemical and FTIR Fingerprinting Coupled to Chemometrics

Simple SummaryPrimary and secondary metabolites are among the markers for addressing fig chemotypic variability. These compounds are mainly driven by the cultivar factor besides chromatic coordinates color as they are highly correlated to these biomarkers. Combined use of chemical analytical procedures and vibrational spectroscopy is of great importance for a better understanding of network connections within the dataset. In this study, we screened 11 fig tree cultivars for their biochemical and spectral fingerprints in a comparative scheme for high resolution discrimination. Analytical methods herein used were also evaluated for their greenness aspects using GAPI eco-scale tool.Figs are a traditional pantry staple for healthy eating in Middle Eastern and North African countries as fig trees grow abundantly in such hot and dry climates. Despite the importance of this species, chemotypic diversity has gone unheeded and therefore its valorization pathways remain poorly documented. For this reason, high-pressure liquid chromatography (HPLC) alongside vibrational spectroscopy were used to investigate the changes of antiradical potency and primary and secondary metabolites in fresh figs with regard to the combined effect of the cultivar factor and the fruit peel chromatic coordinates. Fourier-transform infrared spectroscopy (FTIR) fingerprinting displayed six major peaks assigned to functional groups of the investigated samples with significant differences in their vibration intensities. Biochemical screening revealed highly significant variability (p < 0.05) among the investigated cultivars. Antioxidant activity was found to be higher in free radical scavenging using 2,2-diphenyl-1-picrylhydrazyl (DPPH) compared to ferric reducing ability (FRAP). Chemometric investigations of both biochemical and FTIR fingerprinting showed satisfactory resolutions, and the total phenol contents and chromatic coordinates had the highest scores in the dataset. However, the cultivars’ geographical origin seemed not to have a clear impact on the clustering results. The aforementioned analytical procedures were found to be equally important and can be jointly used for high-resolution screening and discrimination of fig trees.

Ultrasound-Assisted Water Extraction of Mastocarpus stellatus Carrageenan with Adequate Mechanical and Antiproliferative Properties.

Ultrasound-assisted water extraction was optimized to recover gelling biopolymers and antioxidant compounds from Mastocarpus stellatus. A set of experiments following a Box–Behnken design was proposed to study the influence of extraction time, solid liquid ratio, and ultrasound amplitude on the yield, sulfate content, and thermo-rheological properties (viscoelasticity and gelling temperature) of the carrageenan fraction, as well as the composition (protein and phenolic content) and antiradical capacity of the soluble extracts. Operating at 80 °C and 80 kHz, the models predicted a compromise optimum extraction conditions at ~35 min, solid liquid ratio of ~2 g/100 g, and ultrasound amplitude of ~79%. Under these conditions, 40.3% carrageenan yield was attained and this product presented 46% sulfate and good mechanical properties, a viscoelastic modulus of 741.4 Pa, with the lowest gelling temperatures of 39.4 °C. The carrageenans also exhibited promising antiproliferative properties on selected human cancer cellular lines, A-549, A-2780, HeLa 229, and HT-29 with EC50 under 51.9 μg/mL. The dried soluble extract contained 20.4 mg protein/g, 11.3 mg gallic acid eq/g, and the antiradical potency was equivalent to 59 mg Trolox/g.

Antioxidative potential of ferulic acid phenoxyl radical

The vast majority of previous studies dealing with antioxidant potency of (poly)phenols does not investigate the fate of phenoxyl radical obtained after single free radical scavenging. We investigated possible pathways of inactivation of ferulic acid phenoxyl radical (FAPR) using DFT method. Direct coupling with a set of 10 physiologically important free radicals, H-atom donation and dimerization were analysed by estimation of Gibbs free energy changes related to these processes. The former two processes are thermodynamically feasible to inactivate more dangerous free radicals such as hydroxyl, alkoxyl and carbon-centered radicals. Among dimerization reactions, the least energy demanding is formation of C-5−C-5 dimer of ferulic acid (FA), which has higher antiradical potency than FA itself. Obtained results reveal that FAPR, a priori considered as stable and unreactive, may contribute to the overall antioxidant activity of FA. This is a beneficial behavior, which makes FA a particularly valuable protector against oxidative stress. Hence, the contribution of phenoxyl radicals to the antioxidant activity of (poly)phenolic compounds should be taken into account, what has been scarcely considered until now.

Influence of molecular weight on the properties of Sargassum muticum fucoidan

The crude fucoidan extracted during hydrothermal treatment of Sargassum muticum was fractionated in a sequence of membranes (100 to 5 kDa) operating at a volume concentration ratio (VCR) of 5. The retentates and final permeate were further characterised for molecular weight, oligosaccharide content, sulfate and phenolic content, as well as for radical scavenging properties, expressed as Trolox equivalent antioxidant capacity (TEAC). The 50–100 kDa fraction contained 25% of solubles in the hydrolysates. The highest oligosaccharide content (69.34 g 100 g−1) was found in the 50–100 kDa fraction, whereas the maximal sulfate (12.30 g 100 g−1) and phenolic (6.63 g 100 g−1) content occurred in the >100 kDa fraction, which also presented the highest antiradical potency, 47 g Trolox-eq 100 g−1. However, the 10–30 kDa fraction was the most cytotoxic against cervix cancer HeLa 229 cells (EC50 = 44 μg mL−1). As a consequence, the membrane fractionation of the liquid phase obtained by autohydrolysis could provide fucoidans with different composition, molecular weight and properties.

Thermodynamic and kinetic analysis of the reaction between biological catecholamines and chlorinated methylperoxy radicals

ABSTRACTThe antiradical potency of catecholamines (dopamine, epinephrine, norepinephrine, L-DOPA), metabolites of dopamine (homovanillic acid, 3-methoxytyramine and 3,4-dihydroxyphenylacetic acid) and catechol towards substituted methylperoxy radicals is investigated. The thermodynamic parameters, together with the kinetic approach, are used to determine the most probable mechanism of action. The natural bond orbital and quantum theory of atoms in molecules are utilised to explain the highest reactivity of trichloromethylperoxy radical. The preferred mechanism is dependent both on the thermodynamic and kinetic parameters . The number of chlorine atoms on radical, the presence of intra-molecular hydrogen bond and number of hydroxy groups attached to the aromatic ring significantly influence the mechanism. The results suggest that sequential proton loss electron transfer (SPLET) is the most probable for reaction with methylperoxy and hydrogen atom transfer (HAT) for reaction with trichloromethylperoxy radicals, with a gradual transition between SPLET and HAT for other two radicals. Due to the significant deprotonation of molecules containing the carboxyl group, the respective anions are also investigated. The HAT and SPLET mechanisms are highly competitive in reaction with MP radical, while the dominant mechanism towards chlorinated radicals is HAT. The reactions in methanol and benzene are also discussed.

Theoretical study of the thermodynamics of the mechanisms underlying antiradical activity of cinnamic acid derivatives

The role of antiradical moieties (catechol, guaiacyl and carboxyl group) and molecular conformation in antioxidative potency of dihydrocaffeic acid (DHCA) and dihydroferulic acid (DHFA) was investigated by density functional theory (DFT) method. The thermodynamic preference of different reaction paths of double (2H+/2e−) free radical scavenging mechanisms was estimated. Antiradical potency of DHCA and DHFA was compared with that exerted by their unsaturated analogs − caffeic acid (CA) and ferulic acid (FA). Cis/trans and anti-isomers of studied cinnamic acid derivatives may scavenge free radicals via double processes by involvement of catechol or guaiacyl moiety. Carboxyl group of syn-isomers may also participate in the inactivation of free radicals. Gibbs free energies of reactions with various free radicals indicate that syn-DHCA and syn-DHFA, colon catabolites that could be present in systemic circulation in low μM concentrations, have a potential to contribute to health benefits by direct free radical scavenging.

Free radical scavenging potency of quercetin catecholic colonic metabolites: Thermodynamics of 2H+/2e− processes

Reaction energetics of the double (2H+/2e−), i.e., the first 1H+/1e− (catechol→ phenoxyl radical) and the second 1H+/1e− (phenoxyl radical→ quinone) free radical scavenging mechanisms of quercetin and its six colonic catecholic metabolites (caffeic acid, hydrocaffeic acid, homoprotocatechuic acid, protocatechuic acid, 4-methylcatechol, and catechol) were computationally studied using density functional theory, with the aim to estimate the antiradical potency of these molecules. We found that second hydrogen atom transfer (HAT) and second sequential proton loss electron transfer (SPLET) mechanisms are less energy demanding than the first ones indicating 2H+/2e− processes as inherent to catechol moiety. The Gibbs free energy change for reactions of inactivation of selected free radicals indicate that catecholic colonic metabolites constitute an efficient group of more potent scavengers than quercetin itself, able to deactivate various free radicals, under different biological conditions. They could be responsible for the health benefits associated with regular intake of flavonoid-rich diet.

Antimicrobial and antiradical activities of Corylus cornuta (marsh.,betulacea) kernel extracts

Hazelnut (Corylus cornuta) is good source of natural antioxidants. Natural antioxidants are very important in the food industry for preparation of functional foods. The aim of this study was to evaluate antimicrobial activity against selected bacteria and antiradical potency of ethyl acetate and methanol extracts of dehulled hazelnut kernel. Dried sample powder was extracted with ethyl acetate and methanol. The antimicrobial activity of the extracts on Streptococcus pneumonia, Klebsiella pneumonia and Candida albicans was evaluated by the disk diffusion method. Total phenolic content and antiradical potency of the extracts against 2,2-diphenyl-1-picryhydrazyl (DPPH) radical were determined. Fingerprints of the extracts were developed by using HPLC. Total phenolic content of the methanol and ethyl acetate extracts were 0.67 and 0.58 mg gallic equivalent/g, respectively. Minimum inhibition concentrations (MIC) of the methanol and ethyl acetate extracts on S. pneumonia were 0.15 mg/ml and 0.76 mg/ml. Similar MIC values of 100 mg/ml on K. pneumonia were obtained for each extract. The extracts were inactive against Candida albicans. Observation of bacteria under light microscope revealed lower cell count and morphology changes as compared to control. The extracts exhibited free radical scavenging activity against DPPH radical. Qualitative HPLC analysis of the extracts showed the presence of caffeic acid, gallic acid, and vanillic acid. This study shows that hazelnut has antimicrobial and antiradical activities hence, eating the nuts may help to prevent infectious diseases.

In vitro study of anti-glycation and radical scavenging activities of the essential oils of three plants from Morocco: Origanum compactum, Rosmarinus officinalis and Pelargonium asperum

Introduction: We have carried out our study on the chemical composition; anti-glycation andradical scavenging activities of Origanum compactum, Rosmarinus officinalis and Pelargonium asperum essential oils (EO) that were harvested in the northeast of Morocco. These plants have been traditionally used in medicine as a chief ingredient of many polyherbal formulations for the treatment of several pathologies. Method: The phytochemical study was revealed by GC-MS. The protein glycation inhibitory activity of EO extracted from these plant tissues was evaluated in vitro using the model system of bovine serum albumin and methylglyoxal. The measure of DPPH • radical reducing power was used to evaluate the antiradical activity. To test each fraction, we used the IC50 value previously obtained for the crude oils. Results: The phytochemical study of these essential oils showed that p-Thymol, Eucalyptol and Citronellal were respectively the major components in the three investigated EO of O.compactum, R. officinal is and P. asperum. More than 90% of the total components were detected. The extracts and fractions with glycation inhibitory activity also showed antiradical activity when the DPPH • radical reducing power was measured. Conclusion: The glycation inhibitory activity was correlated with the antiradical potency of the extracts. Thus, the positive glycation inhibitory and antiradical activities of these plants might suggest a possible role in targeting aging and diabetic complications.The presence of various bioactive compounds confirms the application of these plants for various diseases by traditional practitioners. However, isolation of individual phytochemical constituents may proceed to find a novel drug.

Identification of polyphenols in leaf extracts of Lawsonia inermis L. with antioxidant, antigenotoxic and antiproliferative potential

Background: Keeping in view the importance of natural plant products, bioactivity‑guided isolation of phytoconstituents was attempted from Lawsonia inermis L. Materials and Methods: Various polar and non‑polar extract/fractions were isolated and evaluated for the genotoxic and antigenotoxic potential against mutagens viz., 4‑nitroquinoline‑1‑oxide and nitrofurantoin in SOS chromotest using Escherichia coli PQ37 tester strain and against H2O2 in DNA protection assay. In order to decipher mode of action, antioxidant activity was evaluated using different assays. The extract/fractions were also investigated for their antiproliferative potential against PC‑3 and Colo 205 cancer cell lines. Major polyphenolic constituents were identified using high-performance liquid chromatography (HPLC) technique. Results: All the extract/fractions except Hex‑Li significantly decreased the SOS‑inducing potency of both the mutagens. In various in vitro assays, the polar fractions exhibited marked antioxidant activity. HPLC analysis of the extract/fractions showed that gallic acid, catechin, chlorogenic acid, epicatechin, rutin, ellagic acid, quercetin and kaempferol are the major constituents. The marked antigenotoxic activity of extract/fractions may be attributed to the polyphenolic compounds. The fractions viz., Hex‑Li and CHCl3‑LI were found to be highly cytotoxic against Colo‑205 cancer cell line. Conclusions: This is the first report of antigenotoxic and anticancer activities of Lawsonia inermis L. phytoconstituents. The antiradical potency of these extract/fractions may be responsible for the above activities. Key words: 4‑Nitroquinoline‑1‑oxide, antioxidant activity, cancer cell lines, nitrofurantoin, SOS chromotest

Phenolics, Antiradical Assay and Cytotoxicity of Processed Mango (Mangifera indica) and Bush Mango (Irvingia gabonensis) Kernels

Phenolic constituents (total phenols, flavonoids, tannins, and anthocyanins), comparative antiradical potency and cytotoxicity of processed mango (Mangifera indica) kernel (PMK), processed bush mango (Irvingia gabonensis) kernel (PBMK) and their mixture (MKK) at 50:50 were evaluated. Antiradical assay of the samples was conducted using three different methodologies (lipid peroxidation, nitric oxide and ferric reducing anti-oxidant power (FRAP)). The three samples contained negligible amounts of anthocyanins (< 0.67 ng/g) compared with the other constituents (1.4 to 2.2 mg/g), largely of gallotannins and flavonoids. However, PBMK had the least flavonoid content, averaging 43%. Due to relative sensitivity of assay techniques to phenolic composition of sample extracts, results from FRAP assay favourably complemented those of another technique to give better reflection of sample’s radical scavenging capacity. Mean inhibitory concentration (IC 50 ) values obtained, showed that the three samples had higher antioxidant capacity than reference quercetin. Similarly, the mean lethal concentration (LC 50 ) values obtained from cytotoxicity assay indicated that the phenolic acid and flavonoid content of the three processed kernel samples were more tolerable physiologically compared with reference dichromate. Both observations were statistically significant (p < 0.05). Processed kernels of mango (Mangifera indica) (PMK) and bush mango (Irvingiagabonensis) (PBMK), therefore, could find application as neutraceuticals and antimicrobials.

Caffeic Acid phenethyl ester: consequences of its hydrophobicity in the oxidative functions and cytokine release by leukocytes.

Numerous anti-inflammatory properties have been attributed to caffeic acid phenethyl ester (CAPE), an active component of propolis. NADPH oxidases are multienzymatic complexes involved in many inflammatory diseases. Here, we studied the importance of the CAPE hydrophobicity on cell-free antioxidant capacity, inhibition of the NADPH oxidase and hypochlorous acid production, and release of TNF-α and IL-10 by activated leukocytes. The comparison was made with the related, but less hydrophobic, caffeic and chlorogenic acids. Cell-free studies such as superoxide anion scavenging assay, triene degradation, and anodic peak potential (E pa) measurements showed that the alterations in the hydrophobicity did not provoke significant changes in the oxidation potential and antiradical potency of the tested compounds. However, only CAPE was able to inhibit the production of superoxide anion by activated leukocytes. The inhibition of the NADPH oxidase resulted in the blockage of production of hypochlorous acid. Similarly, CAPE was the more effective inhibitor of the release of TNF-α and IL-10 by Staphylococcus aureus stimulated cells. In conclusion, the presence of the catechol moiety and the higher hydrophobicity were essential for the biological effects. Considering the involvement of NADPH oxidases in the genesis and progression of inflammatory diseases, CAPE should be considered as a promising anti-inflammatory drug.

The antimicrobial, antioxidative, anti-inflammatory activity and cytotoxicity of different fractions of four South African Bauhinia species used traditionally to treat diarrhoea

Ethnopharmacological importanceMany Bauhinia species, including those indigenous to South Africa, are used in traditional medicine across the world for treating ailments such as gastrointestinal tract (GIT) disorders, diabetes, infectious diseases and inflammation. AimsSeveral relevant aspects of different fractions of leaf extracts of Bauhinia bowkeri (BAB), Bauhinia galpinii (BAG), Bauhinia petersiana (BAP), and Bauhinia variegata (BAV) used in South African traditional medicine to alleviate diarrhoea related symptoms were evaluated. Materials and MethodsThe antioxidative activities of the extracts were determined using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS+) radical scavenging and ferric reducing antioxidant power (FRAP) methods. In vitro antimicrobial activities of the extracts were determined against bacterial strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis) and clinical isolates of the opportunistic fungal strains (Aspergillus fumigatus, Candida albicans, and Cryptococcus neoformans) using a serial dilution microplate method. The polyphenolic contents were quantified using standard methods, and anti-inflammatory activities of the crude extracts were determined using the cyclooxygenase and soybean 15-lipoxygenase enzyme inhibitory assays. The safety of the extracts was evaluated by determining the cytotoxicity against Vero cell lines. ResultsThe acidified 70% acetone crude extract and their fractions had good antiradical potency against the DPPH and ABTS radicals. The methanol soluble portions of the butanol fractions were more potent (EC50 ranges from 0.64±0.05 to 1.51±0.07 and 0.88±0.18 to 1.49±0.09μg/ml against DPPH and ABTS radical respectively) compared to the standard, trolox and ascorbic acid (EC50 ranges from 1.47±0.24 to 1.70±0.27μg/ml) for both DPPH and ABTS. The crude extracts contained variable quantities of phenolic content. The crude extracts and their fractions had weak to good antimicrobial activities, inhibiting the growth of the organisms at concentrations ranging from 39 to 2500μg/ml. The BAG crude extract and its fractions were the most active against the fungi (MICs ranging from 39 to 625μg/ml) while the BAB extract and its fractions were the least active with the MICs ranging between 39 and 2500μg/ml. Aspergillus fumigatus was the least susceptible fungus while Cryptococcus neoformans was the most susceptible.The phenolic-rich crude extracts of BAB, BAG, and BAP had moderate to good dose-dependent cyclooxygenase-1 enzyme inhibitory activity with inhibitions between 22.8% and 71.4%. The extracts were however, inactive against cyclooxygenase-2. The extracts had some level of cytotoxicity towards Vero cell lines, reducing cell viability to less than 10% at concentrations more than 50μg/ml. ConclusionThe biological activities observed in Bauhinia species provide a scientific basis for the use of the plants in traditional medicines to treat diseases with multi-factorial pathogenesis such as diarrhoea, with each aspect of activity contributing to the ultimate therapeutic benefit of the plants. However, the use of the phenolic-rich extracts of these plants to treat diarrhoea or any other ailments in traditional medicine needs to be monitored closely because of potential toxic effects and selective inhibition of COX-1 with the associated GIT injury.

Phenolic acids and derivatives: studies on the relationship among structure, radical scavenging activity, and physicochemical parameters.

The antiradical activity of caffeic acid (1), dihydrocaffeic acid (5), and their corresponding n-alkyl esters was evaluated by using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*)) method. Dihydrocaffeic acid (5) was the most potent compound, having an antiradical effect higher than that of (+/-)-alpha-tocopherol, whereas caffeic acid (1) was less efficient. Esterification of the carboxyl group of dihydrocaffeic acid (5) had a dramatic effect on its antiradical potency, but similar effects were not observed for caffeic acid (1) derivatives. The n-alkyl esters of both phenolic series had similar potencies, and their antiradical activities were independent of the alkyl chain length. Dose-dependent scavenger effects were found in both series. Acid-base properties of the compounds, evaluated by using potentiometry and spectrophotometry, showed that the catechol moiety had pK(a2) and pK(a3) values of 9. 24-9.02 and 11.38-10.99 in the dihydrocaffeic series and 8.48-8.24 and 11.38-11.07 in the caffeic series, respectively. Antiradical activity and pK(a) values of the compounds were not related.