Main Antifungal Compound Research Articles

Detoxification Mechanism of Hinokitiol by Alternaria alternata and Its Application in Agricultural Antifungal Control.

Alternaria alternata is a common plant pathogen that can infect crops and reduce their production. In this work, an antagonism experiment between A. alternata and the essential oil of arborvitae (Platycladus orientalis) was performed, and it was proven that A. alternata had developed resistance to this plant-derived fungicide. A. alternata facilitated the biotransformation of hinokitiol (1), the main antifungal compound in the essential oil of arborvitae, into (R)-2-hydroxy-β-methylbenzeneethanol (2), which does not have antifungal activity against A. alternata. This biotransformation is an unusual ring-contraction reaction that was verified to be catalyzed by P450 enzyme hydroxylation and Baeyer-Villiger oxidation. In addition, the P450 enzyme inhibitors 1-aminobenzotriazole and piperonyl butoxide effectively prevented the destruction of the hinokitiol structure by A. alternata, and the combined use of these P450 enzyme inhibitors significantly increased the antifungal activity of hinokitiol. This work provides a theoretical reference for the further development of botanical fungicides.

Biocontrol Potential of Streptomyces odonnellii SZF-179 toward Alternaria alternata to Control Pear Black Spot Disease.

Pear black spot disease, caused by Alternaria alternata, is a devastating disease in pears and leads to enormous economic losses worldwide. In this investigation, we isolated a Streptomyces odonnellii SZF-179 from the rhizosphere soil of pear plants in China. Indoor confrontation experiments results showed that both SZF-179 and its aseptic filtrate had excellent inhibitory effects against A. alternata. Afterwards, the main antifungal compound of SZF-179 was identified as polyene, with thermal and pH stability in the environment. A microscopic examination of A. alternata mycelium showed severe morphological abnormalities caused by SZF-179. Protective studies showed that SZF-179 fermentation broth could significantly reduce the diameter of the necrotic lesions on pear leaves by 42.25%. Furthermore, the potential of fermentation broth as a foliar treatment to control black leaf spot was also evaluated. Disease indexes of 'Hosui' and 'Wonwhang' pear plants treated with SZF-179 fermentation broth were lower than that of control plants. Overall, SZF-179 is expected to be developed into a safe and broad-spectrum biocontrol agent. No studies to date have evaluated the utility of S. odonnellii for the control of pear black spot disease; our study fills this research gap. Collectively, our findings provide new insights that will aid the control of pear black spot disease, as well as future studies of S. odonnellii strains.

Suppressive soil microbiota inhibit wilting diseases and enhance growth in sesame

Biological control of pests and pathogens is one of the top priorities in plant protection. In particular, soil-borne pathogens, including wilting diseases, are notorious pathogens to control. Previously we noticed the lack of filamentous fungal growth on the rhizospheric samples that were collected from high-yield saffron crocus fields. We hypothesized that suppressive-soil microbiota are involved in this interesting phenomenon. Therefore, we isolated the rhizobacteria from the soil samples and tested their antifungal activities both in in vitro and in in vivo assays. From 10 rhizobacteria, two showed antifungal activity against Fusarium equiseti, Fusarium foetens, and Exserohilum mcginnisii, three fungal pathogens that cause wilting diseases in plants. In particular, Bacillus pumilus showed strong antifungal activity. Furthermore, this species significantly increased the biomass and height of sesame seedlings by 28% and 18%, respectively. Seeking for the antifungal mechanisms, we tested the antifungal properties of the extracellular substances and volatile organic compounds (VOCs) of B. pumilus. Results showed that VOCs, but not extracellular substances, are the main antifungal compounds of B. pumilus. The second bacteria, Metabacillus galliciensis, showed moderate antifungal activity, which is not reported before. Our results suggest B. pumilus as a biological agent to control wilting diseases, and also as a growth promoting bacteria.

Purification and characterization of antifungal lipopeptide produced by Bacillus velezensis isolated from raw honey.

Raw honey contains a diverse microbiota originating from honeybees, plants, and soil. Some gram-positive bacteria isolated from raw honey are known for their ability to produce secondary metabolites that have the potential to be exploited as antimicrobial agents. Currently, there is a high demand for natural, broad-spectrum, and eco-friendly bio-fungicides in the food industry. Naturally occurring antifungal products from food-isolated bacteria are ideal candidates for agricultural applications. To obtain novel antifungals from natural sources, we isolated bacteria from raw clover and orange blossom honey to evaluate their antifungal-producing potential. Two Bacillus velezensis isolates showed strong antifungal activity against food-isolated fungal strains. Antifungal compound production was optimized by adjusting the growth conditions of these bacterial isolates. Extracellular proteinaceous compounds were purified via ammonium sulfate precipitation, solid phase extraction, and RP-HPLC. Antifungal activity of purified products was confirmed by deferred overlay inhibition assay. Mass spectrometry (MS) was performed to determine the molecular weight of the isolated compounds. Whole genome sequencing (WGS) was conducted to predict secondary metabolite gene clusters encoded by the two antifungal-producing strains. Using MS and WGS data, we determined that the main antifungal compound produced by these two Bacillus velezensis isolates was iturin A, a lipopeptide exhibiting broad spectrum antifungal activity.

Lactic Acid Bacteria as Biopreservation Against Spoilage Molds in Dairy Products - A Review.

Mold spoilage of dairy products such as yogurt is a concern in dairy industry. Not only does it lead to substantial food waste, economic losses, and even brand image damage, but it may also cause public health concern due to the potential production of mycotoxin. Good hygiene practices are necessary to prevent contamination, but contamination may nevertheless occur at the production site and, not least, at the site of the consumer. In recent years, there has been a growing interest from consumers for “clean label” food products, which are natural, less-processed, and free of added, chemical preservatives, and a wish for shelf lives of considerable length in order to minimize food waste. This has sparked an interest in using lactic acid bacteria (LAB) or their metabolites as biopreservatives as a way to limit the growth of spoilage organisms in dairy products. A range of compounds produced by LAB with potential antifungal activity have been described as contributing factors to the inhibitory effect of LAB. More recently, growth inhibition effects caused by specific competitive exclusion have been elucidated. It has also become clear that the sensitivity toward both individual antifungal compounds and competition mechanisms differ among molds. In this review, the main spoilage molds encountered in dairy products are introduced, and an overview of the antifungal activity of LAB against different spoilage molds is presented including the main antifungal compounds derived from LAB cultures and the sensitivity of the spoilage molds observed toward these compounds. The recent findings of the role of competitive exclusion with emphasis on manganese depletion and the possible implications of this for biopreservation are described. Finally, some of the knowledge gaps, future challenges, and trends in the application of LAB biopreservation in dairy products are discussed.

Antifungal activity and mode of action of lactic acid bacteria isolated from kefir against Penicillium expansum

Penicillium expansum is the most common spoilage-associated organism found in fruit, which causes serious economic loss and public health concerns. The aim of this study was to isolate lactic acid bacteria (LAB) from kefir in order to study its antifungal effect on mold growth and further analyze the possible antifungal mode of action of LAB, including antifungal component, lytic enzymes activity and nutrient competition. Lactobacillus kefiri M4 and Pediococcus acidilactici MRS-7 were isolated from kefir, and the overlay method was used as a qualitative approach to evaluate their antifungal activities against Penicillium expansum , the results showed that all tested strains were inhibited by the isolates, except for P. expansum LPH6. Different treatments were carried out to characterize the nature of the molecules that contributed to the antifungal activity of the cell-free supernatants produced by the isolates, and it was shown that all supernatants were pH-dependent, partly heat sensitive, and were not influenced by proteinaceous treatment. The cell-free supernatants of both species of LAB were analyzed by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS), and it was found that the main antifungal compounds were organic acids and carboxylic acids. Both LAB species were able to produce lytic enzymes, such as cellulases, proteases, and glucanases, which formed a halo zone on the plate. L. kefiri M4 and P. expansum LPH10 exhibited nutrient competition when co-cultured together in a tissue culture plate insert. The results of this study showed that L. kefiri M4 and P. acidilactici MRS-7 isolated from kefir possess antifungal activity, which provides useful information of how P. expansum response to the LAB isolated from kefir. • Two LAB strains had antifungal effect on Penicillium expansum . • Organic acids and carboxylic acids were responsible for antifungal activity. • Both strains can produce cellulase, protease and glucanase. • L. kefiri M4 and P. expansum LPH10 have nutrients competition.

Control of Panama disease of banana by intercropping with Chinese chive (Allium tuberosum Rottler): cultivar differences

Panama disease (Fusarium wilt disease) caused by Fusarium oxysporum f. sp. cubense race 4 (FOC) severely threatens banana (Musa spp.) production worldwide. Intercropping of banana with Allium plants has shown a potential to reduce Panama disease. In this study, six cultivars of Chinese chive (Allium tuberosum Rottler) were selected to compare their differences in antifungal activity and active compounds. Three cultivars Duokang Fujiu 11, Fujiuhuang 2, and Duokang Sijiqing with higher levels of antifungal compounds were further used for intercropping with banana in the pots and field to compare their effects on growth and disease incidence of banana.The six cultivars showed significant differences in antifungal activity against FOC mycelia growth in both leaf volatiles and aqueous leachates. The aqueous leachates displayed stronger antifungal activity than the volatiles. FJH cultivar showed the best inhibitory effect among all six cultivars. Contents of three main antifungal compounds dipropyl trisulfide (DPT), dimethyl trisulfide (DMT), and 2-methyl-2-pentenal (MP) in volatiles and aqueous leachates varied considerably among cultivars. Pot and field experiments showed that intercropping with three selected Chinese chive cultivars significantly improved banana vegetative growth, increased photosynthetic characteristics and yield but decreased disease incidence of Panama disease.Our results indicate that intercropping with Chinese chive shows potential to reduce banana Panama disease and selection of appropriate cultivars is vital for effective disease control.

Chemical Composition and Antifungal In Vitro and In Silico, Antioxidant, and Anticholinesterase Activities of Extracts and Constituents of Ouratea fieldingiana (DC.) Baill.

Ouratea fieldingiana (Gardner) Engl is popularly used for wound healing. This study describes the main chemical compounds present in extracts of O. fieldingiana and evaluates their biological potential by investigating antifungal, antioxidant, and anticholinesterase activities. The action mechanism of main antifungal compound was investigated by molecular docking using the enzyme sterol 14-α demethylase, CYP51, required for ergosterol biosynthesis. The seeds and leaves were extracted with ethanol in a Soxhlet apparatus and by maceration, respectively. Both extracts were subjected to silica gel column chromatography for isolation of main constituents, followed by purification in sephadex. The structures of compounds were established by 1H and 13C-NMR spectroscopy and identified by comparison with literature data as amentoflavone and kaempferol 3-O-rutinoside, respectively. The antioxidant activities of the extracts were determined by the DPPH and ABTS free radical inhibition methods. In general, the extracts with the highest antioxidant activity corresponded to those with higher content of phenolic compounds and flavonoids. The ethanol extracts and two isolated compounds presented relevant antifungal activity against several Candida strains. The in silico findings revealed that the compound amentoflavone coupled with the CYP450 protein due to the low energy stabilization (-9.39 kcal/mol), indicating a possible mechanism of action by inhibition of the ergosterol biosynthesis of Candida fungi.

Antifungal activity of pomegranate peel extract against fusarium wilt of tomato

Pomegranate (Punica granatum) is an important source of bioactive compounds and has been used in folk medicine for many centuries. This paper describes the in vitro antifungal activity of pomegranate peel aqueous extract (pae) on the development of Fusarium wilt of tomato caused by Fusarium oxysporum, f. sp. lycopersici. HPLC-DAD-ESI/MS analysis was performed to identify punicalagins and ellagic acid, which are the main antifungal compounds. In vivo tests established the efficacy of pae treatments in controlling Fusarium wilt by evaluating improvements in growth variables of tomato plants. At high concentrations, pae showed allelopathic activity in tomato plants. The germination and the radicle growth of tomato seeds were significantly affected by pae. Increasing the extract concentration led to a progressive decrease in germination and in the length of the radicle. The reduction of the Fusarium population in soil and the increase in number of healthy plants obtained as a result of pae treatments indicate that this plant extract could have an important role in biologically-based management strategies for the control of Fusarium wilt in tomato crops.

Identification and quantification of antifungal compounds produced by lactic acid bacteria and propionibacteria

Fungal growth in bakery products represents the most frequent cause of spoilage and leads to economic losses for industrials and consumers. Bacteria, such as lactic acid bacteria and propionibacteria, are commonly known to play an active role in preservation of fermented food, producing a large range of antifungal metabolites. In a previous study (Le Lay et al., 2016), an extensive screening performed both in vitro and in situ allowed for the selection of bacteria exhibiting an antifungal activity. In the present study, active supernatants against Penicillium corylophilum and Aspergillus niger were analyzed to identify and quantify the antifungal compounds associated with the observed activity. Supernatant treatments (pH neutralization, heating and addition of proteinase K) suggested that organic acids played the most important role in the antifungal activity of each tested supernatant. Different methods (HPLC, mass spectrometry, colorimetric and enzymatic assays) were then applied to analyze the supernatants and it was shown that the main antifungal compounds corresponded to lactic, acetic and propionic acids, ethanol and hydrogen peroxide, as well as other compounds present at low levels such as phenyllactic, hydroxyphenyllactic, azelaic and caproic acids. Based on these results, various combinations of the identified compounds were used to evaluate their effect on conidial germination and fungal growth of P. corylophilum and Eurotium repens. Some combinations presented the same activity than the bacterial culture supernatant thus confirming the involvement of the identified molecules in the antifungal activity. The obtained results suggested that acetic acid was mainly responsible for the antifungal activity against P. corylophilum and played an important role in E. repens inhibition.

Biocontrol of Lasiodiplodia theobromae, which causes black spot disease of harvested wax apple fruit, using a strain of Brevibacillus brevis FJAT-0809-GLX

A strain of Brevibacillus brevis FJAT-0809-GLX that was isolated from the soil in Yongtai, Fujian Province, PR China, was evaluated for its potential to reduce the black spot decay of wax apple (Syzygium samarangense Merr. et Perry) fruit caused by Lasiodiplodia theobromae using in vitro and in vivo tests. The culture filtrate, unwashed cell suspension (1 × 108 CFU/mL) and washed cell suspension (1 × 108 CFU/mL) significantly suppressed the growth of mycelium in vitro. The culture filtrate was the most effective treatment for controlling wax apple fruit rot in vivo. The incidence of rot in wax apple fruits that were treated with culture filtrate for 8 days at 30 °C was 20% ± 6.67%, which was markedly lower than that of those that were treated with sterile distilled water (control). A better biocontrol was obtained with a longer incubation time of B. brevis. When the incubation time of B. brevis was 72 h, the disease incidence decreased to 14.44% ± 1.93%. Furthermore, the best biocontrol efficacy was obtained when the fruits were inoculated with the culture filtrate of B. brevis before inoculation with the pathogen. The chemical composition of the acetone extract from B. brevis culture filtrate by GC-MS analysis showed that there were three major antifungal compounds: ethylparaben, dibutyl phthalate, and 1,2-benzenedicarboxylic acid, mono(2-ethylhexyl) ester. The in vitro antifungal activities of these major components on L. theobromae showed that ethylparaben was the main antifungal compound. Isolated extracts could be used for the future development of antifungal agents. To the best of our knowledge, this is the first report demonstrating that the bacterium B. brevis could be used as a biocontrol agent against black spot disease by L. theobromae on wax apple fruit.

Urban propolis from San Juan province (Argentina): Ethnopharmacological uses and antifungal activity against Candida and dermatophytes

Propolis is widely used in the folk medicine of San Juan province (Argentina) to treat several diseases, including cold, cough, muscle aches and superficial mycoses. We report the in vitro antifungal activity of urban propolis, evaluated with CLSI protocols in addition to the evaluation of their chemical profile by HPLC-ESI-MS/MS techniques.The dermatophytes Microsporum gypseum, Trichophyton mentagrophytes and Trichophyton rubrum were the most susceptible species and guided the fractionation of urban propolis, which was performed with Sephadex LH-20 leading to eight fractions (I–VIII). These fractions showed high antifungal activities against dermatophytes (MICs=16.0–62.5μg/mL) and yeasts (MICs=31.2–125μg/mL) being III, V and VI the most active ones (MIC100=16–31.2μg/mL). They also, showed fungicidal capacity (a condition highly appreciated in antifungal drugs to avoid recurrence) with MFC values between 31.2 and 62.5μg/mL. From the most active fractions, two lignans: 3′-methyl-nordihydroguaiaretic acid (MNDGA) (1), and nordihydroguaiaretic acid (NDGA) (2), in addition to three flavonoids: chrysin (3), pinocembrin (4) and galangin (5), were isolated and quantified by HPLC–PDA-MS/MS as the main antifungal compounds. Lignans 1 and 2 showed strong activities against T. mentagrophytes, T. rubrum and Microsporum gypseum (MICs between 31.2 and 62.5μg/mL), and 1 showed strong activity against Candida albicans, Candida tropicalis and Cryptococcus neoformans (MICs between 31.2 and 62.5μg/mL). Regarding flavonoids, all yeasts were sensitive to 5 (MIC=31.2μg/mL), whereas the dermatophytes T. mentagrophytes and T. rubrum and all yeasts were moderately inhibited by 4 (MIC=31.2–250μg/mL). Finally, chrysin (3) showed low activity against yeasts and dermatophytes (MIC=250μg/mL). These results support that Argentinean urban propolis, which are frequently used by beekeepers for the preparation of syrups, tinctures and creams, are valuable natural product for the improving of human health, particularly fungal infections. It is also worthy to take into account that its chemical composition contains mainly two antifungal lignans, associated with the medicinal Larrea genus.

Acetone leaf extracts of Breonadia salicina (Rubiaceae) and ursolic acid protect oranges against infection by Penicillium species

The activity of acetone leaf extracts of Breonadia salicina and the main antifungal compound isolated from the extract, ursolic acid, was determined against three important plant fungal pathogens (Penicillium expansum, P. janthinellum and P. digitatum) to evaluate their potential use in combating post-harvest infections of oranges. In an in vitro assay, acetone extracts had good antifungal activity against P. janthinellum with an MIC (minimum inhibitory concentration) of 0.08mg/ml. P. digitatum and P. expansum were more resistant both with MICs of 1.25mg/ml. We evaluated the potential use of an acetone extract and ursolic acid against these fungal pathogens in artificially infected oranges. A crude leaf extract at a concentration of 1mg/ml gave the same level of protection as 1mg/ml ursolic acid indicating synergistic activities within the crude extract. The acetone extract had an MIC of 0.16mg/ml compared to the MIC of 0.08mg/ml of amphotericin B against P. digitatum. Cytotoxicity of the crude extract and ursolic acid was determined using a tetrazolium-based colorimetric assay (3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium bromide (MTT)) against Vero monkey kidney cells. The acetone extract had sufficient antifungal activity in vitro against these organisms to consider its use in the citrus industry after it has been tested under production and natural infection conditions and if it does not affect the fruit quality. The extracts were however more toxic to the kidney cells than to the fungi. The results show the potential use of plant extracts to combat plant fungal infections if extracts with lower cellular toxicity can be found or if the toxicity of the extract can be decreased without changing the antifungal activity.

P.2.a.010 Serotonin transporter-siRNA rapidly exerts antidepressant effects following internalisation into serotonergic neurons

Propolis is widely used in the folk medicine of San Juan province (Argentina) to treat several diseases, including cold, cough, muscle aches and superficial mycoses. We report the in vitro antifungal activity of urban propolis, evaluated with CLSI protocols in addition to the evaluation of their chemical profile by HPLC-ESI-MS/MS techniques.The dermatophytes Microsporum gypseum, Trichophyton mentagrophytes and Trichophyton rubrum were the most susceptible species and guided the fractionation of urban propolis, which was performed with Sephadex LH-20 leading to eight fractions (I–VIII). These fractions showed high antifungal activities against dermatophytes (MICs = 16.0–62.5 μg/mL) and yeasts (MICs = 31.2–125 μg/mL) being III, V and VI the most active ones (MIC100 = 16–31.2 μg/mL). They also, showed fungicidal capacity (a condition highly appreciated in antifungal drugs to avoid recurrence) with MFC values between 31.2 and 62.5 μg/mL. From the most active fractions, two lignans: 3′-methyl-nordihydroguaiaretic acid (MNDGA) (1), and nordihydroguaiaretic acid (NDGA) (2), in addition to three flavonoids: chrysin (3), pinocembrin (4) and galangin (5), were isolated and quantified by HPLC–PDA-MS/MS as the main antifungal compounds. Lignans 1 and 2 showed strong activities against T. mentagrophytes, T. rubrum and Microsporum gypseum (MICs between 31.2 and 62.5 μg/mL), and 1 showed strong activity against Candida albicans, Candida tropicalis and Cryptococcus neoformans (MICs between 31.2 and 62.5 μg/mL). Regarding flavonoids, all yeasts were sensitive to 5 (MIC = 31.2 μg/mL), whereas the dermatophytes T. mentagrophytes and T. rubrum and all yeasts were moderately inhibited by 4 (MIC = 31.2–250 μg/mL). Finally, chrysin (3) showed low activity against yeasts and dermatophytes (MIC = 250 μg/mL). These results support that Argentinean urban propolis, which are frequently used by beekeepers for the preparation of syrups, tinctures and creams, are valuable natural product for the improving of human health, particularly fungal infections. It is also worthy to take into account that its chemical composition contains mainly two antifungal lignans, associated with the medicinal Larrea genus.

Triterpenoid saponins from Lysimachia candida Lindl.

BackgroundIdentification of chemical constituents is very important for ensuring the function of traditional herbal medicine. The objectives of this study were to determine the activity chemical constituents of Lysimachia candida Lindl. MethodsSolvent fractionation and chromatographic separation techniques were used to isolate the chemical constituents of Lysimachia candida Lindl. ResultsThree triterpenoid saponins were isolated from the antifungal activity fraction of Lysimachia candida Lindl. Their structures were elucidated on the basis of spectroscopic data. They were established as a new compound 3-O-[β-d-Xylopyranosyl-(1→2)-β-d-Glucopyranosyl-(1→4)-[β-d-Glucopyranosy-(1→2)]-α-l-arabinopyranoside]-13,28-Epoxy-3,16,22-oleananetriol, named Lysimanoside (1), along with two known compounds Lysikokianoside I (2) and Anagallisin C (3). ConclusionAnagallisin C showed to be the main antifungal compound against Aspergillus flavu. in Lysimchia candida Lindl.

Identification of Antifungal Compounds Produced by Lactobacillus casei AST18

Lactobacillus casei AST18 was screened as an antifungal lactic acid bacteria which we have reported before. In this research, the antifungal properties of cell-free culture filtrate (CCF) from L. casei AST18 were detected, and the antifungal compounds of CCF were prepared by ultrafiltration, and semi-preparative HPLC, and then determined by GC-MS. CCF was sensitive to pH and heat treatment but it was not affected by the treatment of trypsin and pepsin. Through the treatment of ultrafiltration and semi-preparative HPLC there were two parts of CCF which showed antifungal activities: part 1 and part 4. Lactic acid was identified as the main antifungal compound in part 1. In part 4, three small molecular substances were detected with GC-MS. The three potential antifungal substances were cyclo-(Leu-Pro), 2,6-diphenyl-piperidine, and 5,10-diethoxy-2,3,7,8-tetrahydro-1H,6H-dipyrrolo[1,2-a;1',2'-d]pyrazine. The antifungal activity of L. casei AST18 was a synergistic effect of lactic acid and cyclopeptides.

Effect of biosynthetic intermediates and citrate on the phenyllactic and hydroxyphenyllactic acids production by Lactobacillus plantarum CRL 778

To evaluate the influence of biosynthetic precursors, intermediates and electron acceptors on the production of antifungal compounds [phenyllactic acid (PLA) and hydroxyphenyllactic acid (OH-PLA)] by Lactobacillus plantarum CRL 778, a strain isolated from home-made sourdough. Growth of fermentative activity and antifungal compounds production by Lact. plantarum CRL 778 were evaluated in a chemically defined medium (CDM) supplemented with biosynthetic precursors [phenylalanine (Phe), tyrosine (Tyr)], intermediates [glutamate (Glu), alpha-ketoglutarate (α-KG)] and electron acceptors [citrate (Cit)]. Results showed that the highest PLA production (0.26 mmol l(-1)), the main antifungal compound produced by Lact. plantarum CRL 778, occurred when greater concentrations of Phe than Tyr were present. Both PLA and OH-PLA yields were increased 2-folds when Cit was combined with α-KG instead of Glu at similar Tyr/Phe molar ratio. Similarly, glutamate dehydrogenase (GDH) activity was significantly (P < 0.01) stimulated by α-KG and Cit in Glu-free medium. Phe was the major stimulant for PLA formation; however, Cit could increase both PLA and OH-PLA synthesis by Lact. plantarum CRL 778 probably due to an increase in oxidized NAD(+). This effect, as well as the GDH activity, was enhanced by α-KG and down regulated by Glu. This is the first study where the role of Glu and GDH activity in the PLA and OH-PLA synthesis was evidenced in sourdough lactic acid bacteria (LAB) using a CDM. These results contribute to the knowledge on the antifungal compounds production by sourdough LAB with potential applications on the baked goods.

Argentinean Andean propolis associated with the medicinal plant Larrea nitida Cav. (Zygophyllaceae). HPLC–MS and GC–MS characterization and antifungal activity

The chemical profile and botanical origin of Andean Argentinian propolis were studied by HPLC–ESI–MS/MS and GC–MS techniques as well as the antifungal activity according to CLSI protocols. Dermatophytes and yeasts tested were strongly inhibited by propolis extracts (MICs between 31.25 and 125μg/mL). The main antifungal compounds were: 3′methyl-nordihydroguaiaretic acid (MNDGA) 1, nordihydroguaiaretic acid (NDGA) 2 and a NDGA derivative 3, showing strong activity against Trichophyton mentagrophytes, T. rubrum and Microsporum gypseum (MICs between 15.6 and 31.25μg/mL). The lignans 1 and 2 showed activities against clinical isolates of Candidas spp., Cryptococcus spp., T. rubrum and T. mentagrophytes (MICs and MFCs between 31.25 and 62.5μg/mL). The lignan and volatile organic compounds (VOCs) profiles from propolis matched with those of exudates of Larrea nitida providing strong evidences on its botanical origin. These results support that Argentinian Andean propolis are a valuable natural product with potential to improve human health. Six compounds (1–6) were isolated from propolis for the first time, while compounds 1 and 3–6 were reported for first time as constituents of L. nitida Cav.

Argentinean Propolis from Zuccagnia punctata Cav. (Caesalpinieae) Exudates: Phytochemical Characterization and Antifungal Activity

This paper reports the in vitro antifungal activity of propolis extracts from the province of Tucuman (Argentina) as well as the identification of their main antifungal compounds and botanical origin. The antifungal activity was determined by the microdilution technique, using reference microorganisms and clinical isolates. All dermatophytes and yeasts tested were strongly inhibited by different propolis extracts (MICs between 16 and 125 microg mL(-1)). The most susceptible species were Microsporum gypseum, Trichophyton mentagrophytes, and Trichophyton rubrum. The main bioactive compounds were 2',4'-dihydroxy-3'-methoxychalcone 2 and 2',4'-dihydroxychalcone 3. Both displayed strong activity against clinical isolates of T. rubrum and T. mentagrophytes (MICs and MFCs between 1.9 and 2.9 microg mL(-1)). Additionally, galangin 5, pinocembrin 6, and 7-hydroxy-8-methoxyflavanone 9 were isolated from propolis samples and Zuccagnia punctata exudates, showing moderate antifungal activity. This is the first study matching the chemical profile of Z. punctata Cav. exudates with their corresponding propolis, giving strong evidence on the botanical origin of the studied propolis.

Identification of an antifungal metabolite produced by a potential biocontrol Actinomyces strain A01.

Actinomyces strain A01 was isolated from soil of a vegetable field in the suburb of Beijing, China. According to the morphological, cultural, physiological and biochemical characteristics, and 16S rDNA sequence analysis, strain A01 was identified as Streptomyces lydicus. In the antimicrobial spectrum test strain A01 presented a stable and strong inhibitory activity against several plant pathogenic fungi such as Fusarium oxysporum, Botrytis cinerea, Monilinia laxa, etc. However, no antibacterial activity was found. In pot experiments in greenhouse, the development of tomato gray mold was markedly suppressed by treatment with the fermentation broth of the strain A01, and the control efficacy was higher than those of Pyrimethanil and Polyoxin. A main antifungal compound (purity 99.503%) was obtained from the fermentation broth of strain A01 using column chromatography and HPLC. The chemical structural analysis with U V, IR, MS, and NMR confirmed that the compound produced by the strain A01 is natamycin, a polyene antibiotic produced by S. chattanovgensis, S. natalensis, and S. gilvosporeus, widely used as a natural biological preservative for food according to previous reports. The present study revealed a new producing strain of natamycin and its potential application as a biological control agent for fungal plant diseases.