Kinetic characterization of a basic peroxidase from garlic (Allium sativum L.) cloves

Metabolite Profile and In Vitro Beneficial Effects of Black Garlic (Allium sativum L.) Polar Extract

Over the centuries, humans have traditionally used garlic (Allium sativum L.) as a food ingredient (spice) and remedy for many diseases. To confirm this, many extensive studies recognized the therapeutic effects of garlic bulbs. More recently, black garlic (BG), made by heat-ageing white garlic bulbs, has increased its popularity in cuisine and traditional medicine around the world, but there is still limited information on its composition and potential beneficial effects. In this study, the metabolite profile of methanol extract of BG (BGE) was determined by high-performance liquid chromatography coupled to tandem mass spectrometry in high-resolution mode. Results allowed to establish that BGE major components were sulfur derivatives, saccharides, peptides, organic acids, a phenylpropanoid derivative, saponins, and compounds typical of glycerophospholipid metabolism. Characterization of the BGE action in cancer cells revealed that antioxidant, metabolic, and hepatoprotective effects occur upon treatment as well as induction of maturation of acute myeloid leukemia cells. These results are interesting from the impact point of view of BG consumption as a functional food for potential prevention of metabolic and tumor diseases.

In through the out door: Biochemical mechanisms affecting flavonoid glycoside catabolism in plants

Plants are the sole source of flavonoids, a chemical category that includes flavonols. For the most part, flavonols occur as glycosides with numerous postulated biological roles in plants, including photoprotection, modulation of hormone translocation, and sequestration of reactive oxygen species. Flavonol glycosides are often considered as dead-end metabolites because related flavonoids (i.e., anthocyanins) occur in terminal tissues such as flowers and fruit, but recent evidence points to their turnover in planta, including developing photosynthetic tissues. Although microbial degradation pathways for flavonol glycosides of plant origin are well described, plant catabolic pathways are little studied by comparison. This review will address our current understanding of biochemical processes leading to the loss of flavonol glycosides in plants, with a specific emphasis on the evidence for flavonol-specific β-glucosidases. Complete elucidation of these catabolic pathways is dependent on the identification of regiospecific modifying steps, including enzymes associated with the hydrolysis of rhamnosylated flavonols, as well as flavonol peroxidation and their encoding genes. Herein, we highlight challenges for the identification of hypothetical plant α-rhamnosidases and peroxidases involved in flavonol glycoside degradation, and the potential biological role of this catabolism in mitigating oxidative stress in developing and postharvest plant tissues.

Northeast red beans produce a thermostable and pH-stable defensin-like peptide with potent antifungal activity

A 5.4-kDa antifungal peptide was purified from Phaseolus vulgaris L. cv. "northeast red bean" using a protocol that entailed affinity chromatography, ion exchange chromatography, and gel filtration. The molecular mass was determined by matrix-assisted laser desorption ionization time-of-flight. The N-terminal amino acid sequence of the peptide was highly homologous to defensins and defensin-like peptides from several plant species. The peptide impeded the growth of a number of pathogenic fungi, including Mycosphaerella arachidicola Khokhr. (IC50 = 1.7 μM), Setosphaeria turcica Luttr., Fusarium oxysporum Schltdl., and Valsa mali Miyabe & G. Yamada. Antifungal activity of the peptide was fully preserved at temperatures up to 100 °C and pH values from 0 to 12. Congo red deposition at the hyphal tip of M. arachidicola was detected after exposure to the peptide, signifying that the peptide had suppressed hyphal growth. The antifungal peptide did not manifest antiproliferative activity toward human breast cancer MCF7 cells and hepatoma HepG2 cells, in contradiction to the bulk of previously reported plant defensins. The data suggest distinct structural requirements for antifungal and antiproliferative activities.

Asparagus byproducts as a new source of peroxidases

Soluble peroxidase (POD) from asparagus byproducts was purified by ion exchange chromatographies, and its kinetic and catalytic properties were studied. The isoelectric point of the purified isoperoxidases was 9.1, and the optimum pH and temperature values were 4.0 and 25 °C, respectively. The cationic asparagus POD (CAP) midpoint inactivation temperature was 57 °C, which favors its use in industrial processes. The Km values of cationic asparagus POD for H₂O₂ and ABTS were 0.318 and 0.634 mM, respectively. The purified CAP is economically obtained from raw materials using a simple protocol and possesses features that make it advantageous for the potential use of this enzyme in a large number of processes with demonstrated requirements of thermostable POD. The results indicate that CAP can be used as a potential candidate for removing phenolic contaminants.

Do vacuolar peroxidases act as plant caretakers?

Plant vacuolar peroxidases catalyze the reduction of toxic H(2)O(2) accumulated in the vacuoles by oxidizing a variety of secondary metabolites. The redundancy of peroxidases and their ability to react with a wide range of substrates have prevented the observation of a clear phenotypic effect by modifying a single gene. Here we review the correlative and partial data on vacuolar peroxidases, including evidence for genes encoding vacuolar localized peroxidases, and indications of peroxidase activity in the vacuole. Based on these data, we suggest that these enzymes are key players in the adaptation of plants to change and serve as plant caretakers. At the cellular level, peroxidases protect the plant by scavenging excess H(2)O(2) that accumulates in the vacuoles under stressful conditions. At the tissue level, they are responsible for the last steps in the synthesis of the phytoalexins that often accumulate following pathogen attack of the plant tissue. At the whole-plant level, we suggest that peroxidases are involved in controlling the quality and quantity of light reaching the photosynthetic apparatus as plants adapt to lower light intensities. Further characterization of peroxidases, based on high-throughput genomic and metabolomic data, will help elucidate the mechanisms by which plants adapt to change.

An antifungal peptide from Phaseolus vulgaris cv. brown kidney bean

A 5.4-kDa antifungal peptide, with an N-terminal sequence highly homologous to defensins and inhibitory activity against Mycosphaerella arachidicola (IC(50)= 3 μM), Setospaeria turcica and Bipolaris maydis, was isolated from the seeds of Phaseolus vulgaris cv. brown kidney bean. The peptide was purified by employing a protocol that entailed adsorption on Affi-gel blue gel and Mono S and finally gel filtration on Superdex 75. The antifungal activity of the peptide against M. arachidicola was stable in the pH range 3-12 and in the temperature range 0°C to 80°C. There was a slight reduction of the antifungal activity at pH 2 and 13, and the activity was indiscernible at pH 0, 1, and 14. The activity at 90°C and 100°C was slightly diminished. Deposition of Congo red at the hyphal tips of M. arachidicola was induced by the peptide indicating inhibition of hyphal growth. The lack of antiproliferative activity of brown kidney bean antifungal peptide toward tumor cells, in contrast to the presence of such activity of other antifungal peptides, indicates that different domains are responsible for the antifungal and antiproliferative activities.

Prevention and treatment of alopecia areata with quercetin in the C3H/HeJ mouse model

Alopecia areata (AA) is an autoimmune non-scarring hair loss disorder. AA can be acute, recurrent, or chronic. Current therapeutic options for AA are limited, and there is no effective prevention for recurrent AA. We have previously shown a correlation between the expression of HSP70 (HSPA1A/B), a heat shock protein involved in the inflammatory response, and the onset of AA in the C3H/HeJ mouse model. In this study, we tested the effects of quercetin, a bioflavonoid with anti-inflammatory properties, on AA development and HSP70 expression in the C3H/HeJ model. Mice with spontaneous AA were treated with subcutaneous quercetin or sham injections. Hair regrowth was observed in lesional areas in all the quercetin-treated mice, but in none of the sham-treated mice. In addition, non-alopecic C3H/HeJ mice were heat-treated to induce alopecia, along with quercetin or sham injections. Whereas 24% of the heat-treated mice with sham injections developed alopecia, none of the mice receiving quercetin injections did. As expected, the level of HSP70 expression in quercetin-treated areas was comparable to control. Furthermore, we showed that systemic delivery of quercetin by intraperitoneal injections prevented/reduced spontaneous onset of AA. Our results demonstrated that quercetin provided effective treatment for AA as well as prevention of onset of AA in the C3H/HeJ model, and warrant further clinical studies to determine whether quercetin may provide both treatment for preexisting AA and prevention of recurrent AA. The ready availability of quercetin as a dietary supplement may lead to increased patient compliance and positive outcomes for AA.