This contribution reviews the constituents of the pteridophytes (lycophytes and ferns), focusing on their occurrence, structures, and biological activities. It covers various classes of phytochemicals, including aromatic compounds (such as acylphloroglucinols, flavonoids, lignans, and selaginellins), and isoprenoids (monoterpenoids, norisoprenoids, sesquiterpenoids, diterpenoids, and steroids). The discussion includes the distribution of these compounds in different pteridophyte genera and species, their structural diversity, and their demonstrated biological activities. The volume also touches upon the phytochemical similarities and differences between algae, bryophytes, and the pteridophytes.

Two new labdane diterpenes, (4S,5R,10S,13S)-19-acetoxy-7-oxo-labd-8(9)-en-15-oic acid-15-methyl ester (1) and (4R,5R,10S,13S)-19-acetoxy-7-oxo-labd-8(9)-en-15-oic acid-15-methyl ester (2), along with two methyl ester derivatives of the known acid compounds, (4R,5S,9S,10R,13S)-ent-7-labden-17-acetoxy-18-hydroxy-15-oic acid (3), and (3R,5S,9S,10S,13S)-ent-7-labden-17-acetoxy-3-α-hydroxy-15-oic acid (4), were obtained from Grindelia puberula Hook & Arn, collected in northern Argentina. Their structures and absolute configurations were elucidated based on one- and two-dimensional nuclear magnetic resonance spectroscopy, mass spectrometry, and circular dichroism analysis. The CHCl3 sub-extract obtained from the aerial parts of this species, along with the pure compounds, were evaluated for antifungal activity against Botrytis cinerea, a widespread necrotrophic fungal pathogen responsible for significant economic losses worldwide. Among the tested compounds, 2 (IC50 = 27.7 ± 3.8 µg/mL) exhibited the highest antifungal activity, demonstrating greater efficacy compared to its C-4 epimer. Furthermore, an in silico structure-activity relationship study was conducted. Molecular docking simulations revealed that compound 2 displayed the highest binding affinity to the B. cinerea cytochrome b complex (-9.62 kcal/mol), a key target in antifungal therapy.

Natural products from the useful native species Flourensia fiebrigii S.F. Blake (Asteraceae, Heliantheae) were obtained from an Argentinean collection of Canon del Ocre at 2750 m a.s.l. Piceol/4-hidroxyacetophenone was one of the main volatile compounds isolated and identified for the first time in this species. F. fiebrigii chloroformic extract, a mid-polarity fraction, piceol, or 2,4-dihydroxychalcone (12.5-50 mu g/mL) increased bacterial auto-aggregation, biofilm formation, and surface/interfacial activity of Lactobacillus paracasei subsp. paracasei CE75. In fact, supernatants obtained from cultures grown with piceol (25 mu g/mL) reduced Pseudomonas aeruginosa HT5 and Staphylococcus aureus HT1 biofilms (72.01% and 43.39%, respectively) due to anti-adhesive effects. The ability of L. paracasei subsp. paracasei CE75 to degrade phenolic compounds was determined by GC-EIMS. After 5 days of static incubation, detoxification percentages were 99.89% for piceol (25 mu g/mL) and 100% for phenol (100 mu g/mL). This detoxifying capacity was correlated with the occurrence of phenoloxidases and glycoproteins with a significant surfactant activity. Scanning electron microscopy also showed bacterial surface protrusions as an adaptive response to chemical stress. Our results indicate that the stimulated lactic acid bacterium constitutes a novel strategy with a high detoxifying capacity of phenolic compounds and a promising tool against food- and waterborne pathogen biofilms.

Chemical investigation of the fern Pityrogramma trifoliata (L.) R. M. Tryon (Pteridaceae) yielded a new complex flavonoid, here named trifoliatol, and 4 known complex flavonoids in addition to known chalcones and flavanones. The absolute configuration of the complex flavonoids is proposed, based on circular dichroism (ECD), crystal x-ray diffraction, and [α]D measurements. White and yellow farinas, as well as 10 flavonoids were tested for antifungal activity against a panel of clinically important fungi, including yeast and dermatophytes. Both farinas and 2 of the flavonoids were notably active against Trichophyton rubrum and T. mentagrophytes (MICs and MFCs between 7.8 and 31.2 μg/mL). The localization of flavonoids in the plant trichomes was accomplished by use of scanning electron microscopy and histochemical methods.

Chemical investigation of the fern Pityrogramma trifoliata (L.) R. M. Tryon (Pteridaceae) yielded a new complex flavonoid, here named trifoliatol, and 4 known complex flavonoids in addition to known chalcones and flavanones. The absolute configuration of the complex flavonoids is proposed, based on circular dichroism (ECD), crystal x-ray diffraction, and [α] D measurements. White and yellow farinas, as well as 10 flavonoids were tested for antifungal activity against a panel of clinically important fungi, including yeast and dermatophytes. Both farinas and 2 of the flavonoids were notably active against Trichophyton rubrum and T . mentagrophytes (MICs and MFCs between 7.8 and 31.2 μg/mL). The localization of flavonoids in the plant trichomes was accomplished by use of scanning electron microscopy and histochemical methods. Keywords , , complex flavonoids , absolute configuration , antifungals , flavonoids histochemical localization

Chemical investigation of the fern Pityrogramma trifoliata (L.) R. M. Tryon (Pteridaceae) yielded a new complex flavonoid, here named trifoliatol, and 4 known complex flavonoids in addition to known chalcones and flavanones. The absolute configuration of the complex flavonoids is proposed, based on circular dichroism (ECD), crystal x-ray diffraction, and [α] D measurements. White and yellow farinas, as well as 10 flavonoids were tested for antifungal activity against a panel of clinically important fungi, including yeast and dermatophytes. Both farinas and 2 of the flavonoids were notably active against Trichophyton rubrum and T . mentagrophytes (MICs and MFCs between 7.8 and 31.2 μg/mL). The localization of flavonoids in the plant trichomes was accomplished by use of scanning electron microscopy and histochemical methods.

Chagas disease is caused by Trypanosoma cruzi and affects the poorest population in the Americas. Fourteen plant extracts and seventeen sesquiterpene lactones from the tribe Vernonieae (Asteraceae), were evaluated for the first time against T. cruzi. Cytotoxicity employing HeLa cells was also assessed. The best results were obtained with leaves and flowers rinse extracts from Vernonanthura nebularum (E-1 and E-3) and Elephantopus mollis (E-11 and E-13), with IC50 values <2 µg/mL, being E-1 the most active (IC50 = 0.8 µg/mL). Additionally, these extracts displayed a good selectivity (SI > 10). The most active sesquiterpene lactones, isolated from the extracts, were 2 (2-methoxy-2,5-epoxy-8-methacryloxygermacra-3Z,11(13)-dien-6,12-olide) and 6 (2-ethoxy-2,5-epoxy-8-angeloxygermacra-3Z,11(13)-dien-6,12-olide) from V. nebularum and 12 (8α-methacryloxyhirsutinolide 13-O-acetate) from V. pinguis, with IC50 of 1.5, 2.1 and 2.0 µM, respectively. These compounds showed SI values >14, better than those of the reference drug nifurtimox. Plants living in South American ecosystems could become a potential source of trypanocidal agents.

In the search for new plant‐derived products with antifeedant and insecticidal potential against economically important insects, 11 grindelanes (two as natural acids and nine as methylated derivatives) purified from the foliar tissue of Grindelia chiloensis (Cornel.) Cabrera (Asteraceae) were evaluated against the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae). Larvae of this moth are considered to be the main pest of maize that causes severe losses on local agricultural production. Remarkable alterations in feeding behavior, larval weight, larval and pupal stage lengths, and adult fertility, as well as malformations and mortality in specimens during their life cycle were noticed in the feeding preference tests and no‐choice diet assays. Antifeedant indexes (AI%) calculated in food preference bioassays reached up to 79% for the lipophilic grindelane 3b, the most potent antifeedant agent. Grindelane 7b showed a better insecticidal activity (median lethal dose, LD 50 = 26.49 µg g −1 ) and 8b was potentially neurotoxic due to acetylcholinesterase inhibition. Ultrastructure of the middle portion of the digestive tract of larvae fed with small amounts of natural grindelane 9a supplemented to the diet revealed cell damage, and thickening of the peritrophic membrane and a striking number of mitochondria, as evident signs of defense against toxic substances ingested by the larvae. Besides, this study demonstrated that these effective insecticides did not have inhibitory effects on beneficial plant and soil bacteria which would allow ecological pest management.

The effect of a natural sesquiterpene ketone, 9,10-dehydrofukinone (DHF), on pathogenic Staphylococcus aureus and Pseudomonas aeruginosa strains isolated from chronic infectious processes, was the focus of the present study. Lipophilic DHF produced important antibacterial synergistic effects in association with ciprofloxacin (CPX) against two biofilm-forming strains of S. aureus HT1 (FIC=0.21) and P. aeruginosa HT5 (FIC=0.05). Hence, this mixture constitutes an excellent strategy to combat these biofilm-producing bacteria that overexpress drug efflux pumps as a resistance mechanism. Additionally, a substantial rise in beneficial Lactobacillus biofilm biomass was determined as a very significant finding of this association. Particularly, a non-pathogenic biofilm increment of 119 % was quantified when the mixture was added to a probiotic L. acidophilus ATCC SD-5212 culture. A surface activity enhanced in 71 % with respect to untreated L. acidophilus culture was also generated by the DHF and CPX association, and therefore, a glycoprotein synthesis induction mediated by the mixture is discussed. The results obtained could help in the development of new selective antibiotics. From an ecological standpoint, the present study strongly suggests that DHF is a polyfunctional organic molecule produced with a high yield in Senecio punae that exerts a positive impact on a non-pathogenic plant bacterium L. plantarum CE105.

The morphology and distribution of glandular trichomes in fronds at different developmental stages were investigated in Notholaena sulphurea, and the main components of the secreted material (farina) were identified. In addition antifungal and molluscicidal activities of farinose exudate were tested. Trichomes were examined using conventional light and scanning electron microscopy (SEM). The histochemical studies were conducted using the following tests on hand-sections: Toluidine Blue, Calcofluor White, Ruthenium Red, Phloroglucinol/HCl, NADI reagent, Sudan black B, Sudan IV, Nile Blue, Neutral Red, ferric chloride, Vainillin/H2SO4, Vainillin/HCl, alumimium chloride and Benedict reagent. Antifungal activity was evaluated by broth microdilution techniques and molluscicidal activity by Adenusi, 2008. One type of glandular trichomes was found in both the adaxial and the abaxial surfaces. Young fronds were densely covered with trichomes; however, the density decreased progressively with frond maturity. Secretions flowed by diffusion through cuticle micropores, and no rupturring mechanism to release secretions was observed. Histochemical reactions revealed that the main components of the materials secreted by trichomes include polysaccharides, lipids, terpenes, phenols and flavonoids. The farina showed antifungal and molluscicidal activity. Our results strongly support an ecological role of farina as herbivore deterrent and resistance to fungi. Since N. sulphurea is a xeric adapted fern, flavonoids present in farinous secretions may also function as stress protection against harsh environmental conditions.

Background: Annonaceous acetogenins enclose a large number of biological activities, among which the insecticidal stands out. Methods: We report herein the biocide effects of natural acetogenins from Annona squamosa, A. muricata and A. montana seeds: annonacin, cis-annonacin, cis-annonacin-10- one, asimicin, rolliniastatin-2, cherimolin-1, cherimolin-2, almuñequin, and two β-OH acetogenins: laherradurin and itrabin on Spodoptera frugiperda Smith (Lepidoptera: Noctuidae). Also, some acetylated and methoxy methylated ACG derivatives were synthesized and evaluated: annonacin (3 OAc), annonacin (4 OAc), asimicin (3 OAc), rolliniastatin-2 (3 OAc), rolliniastatin-2 (MOM), laherradurin (3 OAc) and itrabin (3 OAc). Results: The natural acetogenin rolliniastatin-2 (100 μg·g-1 of diet) produced the most important toxic action causing 100% mortality of early instar larvae. Derivatization of ACG yielded compounds that produced nutritional alterations. The incorporation of rolliniastatin-2 (3 OAc) and rolliniastatin-2 (3 MOM) (100 μg·g-1) into the artificial diet of Spodoptera frugiperdadisplayed the strongest antifeedant effects causing marked decreasings in larval growth and adult lethal malformations. Conclusion: Natural acetogenins are promising metabolites for insect control. Derivatization of these compounds reduces their toxicity to early instar larvae.

Vernonanthura nebularum (Cabrera) H. Rob. (Asteraceae), an endemic species from the north of Argentina, is a rich source of elephantopus-type sesquiterpene lactones. These compounds have proved to be promising antiparasitic agents, but there is no report about their action against pest insects. In this work we studied for the first time the antifeedant and toxic effects of V. nebularum natural products against the fall army warm Spodoptera frugiperda Smith and the oviposition deterrent activity against the fruit fly Ceratitis capitata Wiedemann. As a result, we found that extracts, fractions composed of sesquiterpene lactones and pure sesquiterpene lactones altered larval feeding behavior in the food choice test. Nutritional parameters of S. frugiperda larvae were also affected. Fraction II (300 μg/g of diet.), containing compounds 1, 2 and 3, was the most toxic substance with 80% pupal mortality and wing malformations in adults. In oviposition deterrent experiments against Ceratitis capitata, we observed a moderate effect at 30 μg/cm2 of the test compound. The most active substances were the methanolic extract, dichloromethane subextract and lactone 2. According to our results, V. nebularum natural products could be used for maximizing the effectiveness and specificity in future insecticide design with specific or multiple target sites, while ensuring the economic and ecological sustainability, in addition to combat the increasing resistance rates developed by synthetic pesticides.

Quorum sensing (QS) is a cell-to-cell signaling communication system that controls the virulence behavior of a broad spectrum of bacterial pathogens, participating also in the development of biofilms, responsible of the antibiotic ineffectiveness in many infections. Therefore, QS system is an attractive target for antimicrobial therapy. In this study, we compare the effect of seven structurally related coumarins against bacterial growth, biofilm formation and elastase activity of Pseudomonas aeruginosa. In addition, the anti-pathogenic capacity of the seven coumarins was evaluated on the wild type and the biosensor strain of Chromobacterium violaceum. The comparative study of coumarins showed that molecules with hydroxyl groups on the aromatic ring displayed higher activity on the inhibition of biofilm formation of P. aeruginosa over coumarins with substituents in positions 3 and 4 or without the double 3,4-bond. These 3 or 4-hydroxylated positions caused a decrease in the anti-biofilm activity obtained for coumarin. However, the hydroxyl group in position 3 of the pyrone ring was important for the inhibition of C. violaceum QS and elastolytic activity of P. aeruginosa. The effects observed were active independently of any effect on growth. According to our results, coumarin and its hydroxylated derivatives represent an interesting group of compounds to use as anti-virulence agents against the human pathogen P. aeruginosa.

Squamocin belongs to a group of compounds called annonaceous acetogenins. They are secondary products of Annonaceae metabolism and can be isolated from Annona cherimolia seeds. This paper deals with the stimulation of biofilm formation of Bacillus atrophaeus CN4 by employing low squamocin concentrations to increase naphthalene degradation. Bacillus atrophaeus CN4, isolated from contaminated soil, has the ability to degrade naphthalene as the only source of carbon and energy. In the absence of additional carbon sources, the strain removed 69% of the initial concentration of naphthalene (approx. 0.2mmol/l) in the first 12h of incubation. The addition of squamocin in LB medium stimulated Bacillus atrophaeus CN4 biofilm formation and enhanced naphthalene removal. Squamocin (2.5μg/ml) does not affect planktonic growth and therefore, the observed increases are solely due to the stimulation of biofilm formation.

Eudesmanoids play an important role in the protection of plants against herbivores.Pluchea sagittalis (Lamarck) Cabrera (Asteraceae) is widespread in tropical South America and contains compounds that provide protection against phytophagous insects.In the present work we isolated seven sesquiterpenoids with eudesmane skeletons that were evaluated for their insecticidal activities against Spodoptera frugiperda and Ceratitis capitata, pests that cause serious damage to crops in the Argentine northwest.The Eudesmanes were incorporated at different concentrations to the diet of Spodoptera frugiperda.In the choice test, larval feeding behavior was altered.The eudesmanes 1, 5 and 7 showed the highest activity with feeding election indexes (FEI) of 50, 50, and 72 %, respectively at 200 µg/g of diet.When tested for insecticidal activity using neonate larvae with the nochoice artificial diet bioassays, eudesmane 1 was the most toxic in the larval stage (LD50 177.80 mg/g of diet).Compounds 5 lowered the percentage of adult emergence and produced the most malformations (72%) compared with control.Drastic effects were observed in the oviposition deterrence activity against C. capitata.The maximum oviposition deterrence (87 %) was recorded with eudesmane 5 at dose 30 µg/cm 2 of artificial fruit.Finally, eudesmanes 6 and 7 showed significant larval and pupal mortality against the first generation larvae of viable eggs oviposited by females fed with the treated diet (100 µg / g artificial diet).

Entomopathogenic fungi are fungal organisms extensively used in various parts of the world as biopesticides against insect pests that cause important economic damage. Various secondary metabolites produced by these fungi have many potential biological activities. The present study was undertaken to evaluate the insecticidal activity of extracts and pure compounds from Nomuraea rileyi (Farlow) Samson entomopathogenic fungi against Spodoptera frugiperda Smith (Lepidoptera), Ceratitis capitata Wiedemann (Diptera) and Tribolium castaneum Herbst (Coleoptera), three insect pests that generate serious economic losses in the northwest of Argentina. Diketopiperazines were extracted from the culture free supernatant of the media with ethyl acetate. Antifeedant properties were detected in all extracts under dietary choice conditions (300 ug/ g of diet). The maximum antifeedant activity was noted in cycles (Pro-Val) (86.02) and cycle (Pro-Phe) (73.47), while the rest of the extracts and metabolites exhibited varying degrees of moderate or less toxic effects. The maximum oviposition deterrence against C. capitata (55.86%) was recorded with cycle (Pro-Phe) at a 50 µm/cm2 dose. Culture medium extracts supplemented with insect remains and all pure compounds showed repellent action against T. castaneum. The main repellency was observed in phenylacetic acid and cycle (Pro-Val) with RI values of 42 and 41% respectively. The present study would suggest the possible utilization of entomopathogenic fungal metabolites as an effective agent for controlling insect pests that cause important economic losses.

The new methylated grindelane diterpenoid, 7β‐hydroxy‐8(17)‐dehydrogrindelic acid (1b), together with the known 7α‐hydroxy‐8(17)‐dehydrogrindelic acid (2a), 6‐oxogrindelic acid (3a), 4β‐hydroxy‐6‐oxo‐19‐norgrindelic (4a), 19‐hydroxygrindelic acid (5a), 18‐hydroxygrindelic acid (6a), 4α‐carboxygrindelic acid (7a), 17‐hydroxygrindelic acid (8a), 6α‐hydroxygrindelic acid (9a), 8,17‐bisnor‐8‐oxagrindelic acid (10a), 7α,8α‐epoxygrindelic acid (11a), and strictanonic acid (12a) as methyl esters were obtained from an Argentine collection of Grindelia chiloensis (Cornel.) Cabrera. Their structures and relative configurations were established on the basis of spectroscopic analysis. CHCl3 extract from the aerial parts and their pure compounds were evaluated for their antifungal and depigmenting effects. Methyl ester derivative of 10a (10b) exhibited a remarkable mycelial growth inhibition against Botritis cinerea with an IC50 of 13.5 μg ml−1. While the new grindelane 1b exerted a clear color reduction of the yellow‐orange pigment developed by Fusarium oxysporum against UV‐induced damage.

Three new compounds, a bicyclogermacrene ( 1 ) and two 2,3‐secoaromadendrane esters ( 2 and 3 ), together with (13 S )‐13‐hydroxylabda‐8,14‐diene ( 4 ), fusicogigantone B ( 5 ), 3 α ,14‐diacetoxy‐2‐hydoxybicyclogermacrene ( 6 ), fusicogigantone A ( 7 ), neofuranoplagiochilal ( 8 ), plagiochiline B ( 9 ), furanoplagiochilal ( 10 ), trans ‐nerolidol, spathulenol, α ‐tocopherol, and (+)‐globulol were isolated from an Argentine collection of Plagiochila diversifolia . Their structures were elucidated by extensive mono and bidimensional NMR studies. Compounds 4 , 5 , and 6 , incorporated to the larval diet at 100 μg per g of diet, reduced the larval growth of Spodoptera frugiperda (Lepidoptera: Noctuidae) by 70 ± 25, 57 ± 23, and 33 ± 16%, respectively. Compounds 4 and 5 produced 70% and 60% larval mortality at early instars. The latter also showed antifeedant properties in the Choice Test, with a feeding ratio of 0.54 ± 0.16.

Purification of a diethyl ether extract of the Argentinian fern Elaphoglossum lindbergii afforded five new prenylated acylphloroglucinols, lindbergins E-I (1-5), of which two showed significant in vitro leishmanicidal activity against promastigotes of Leishmania braziliensis and L. amazonensis. The structures of compounds 1-5 were elucidated based on analysis of their spectroscopic data and comparison with values previously reported for other phloroglucinol derivatives isolated from plant species of the genera Hypericum, Dryopteris, and Elaphoglossum. Fragmentation and rearrangement patterns of prenylated acylphloroglucinols were analyzed, and some mechanisms were proposed to rationalize the peaks observed in the mass spectra of these natural products produced by EI and FAB. Compounds isolated from E. lindbergii show the opposite absolute configuration when compared to those reported from E. crassipes. Empirical evidence indicates that acylphloroglucinols carrying a prenylated acylfilicinic acid residue possess a high-amplitude configuration-dependent Cotton effect centered at 350-360 nm in their CD curves, from which the absolute configuration of the sole chiral center of the prenylated acylfilicinic acid moiety can be deduced.