Advances in chemical and biological characterization of triterpenoid saponins from Anagallis arvensis L. using UHPLC-MS/MS and cell-based assays.

A fraction enriched in triterpenoid saponins (F4) from Anagallis arvensis L. was chemically characterized by UHPLC-ESI-QTOF-MS/MS and NMR analyses. The results proposed the presence of nine monodesmosidic saponins derived from oleanolic acid, including two reported for the first time for this species, 3: 3-O-{ß-D-glucopyranosyl (1→4)-[ß-D-xylopyranosyl (1→2)]-ß-D-glucopyranosyl (1→4)-[ß-D-glucopyranosyl (1→2)]-α-L-arabinopyranosyl}-13ß, 28-epoxy- 22 acetyl- 28 methoxy-16α, 24-oleananediol and 4: 3-O-{ß-D-glucopyranosyl (1→4)-ß-D-glucopyranosyl (1→4)-[ß-D-xylopyranosyl (1→2)]-ß-D-glucopyranosyl (1→4)-[ß-D-glucopyranosyl (1→2)]-α-L-arabinopyranosyl}-13ß, 28-epoxy- 16α, 30-oleananediol. Furthermore, haemolytic activity was determined by dot-blot autography, and cytotoxicity on human lymphocyte cultures was analysed according to metabolic activity (MTT assay) and membrane integrity (Trypan blue exclusion test). F4 showed mild cytotoxicity (%V > 50% at 100 µg/mL) on human lymphocytes under conditions of activation or not by LPS; moreover, showed haemolytic activity between 50 and 500 µg. This work contributed to phytochemical knowledge of the triterpenoid saponins from A. arvensis, and its cytotoxic effects on normal human cells.

Efficacy of Argentinean propolis extracts on control of potato soft rot caused by Erwinia carotovora subsp.

BACKGROUND: Erwinia carotovora subsp. cause the potato soft rot, which is a major disease in agriculture. Antibacterial agents currently applied on potato soft rot often offer a restricted control and have several disadvantages. Propolis has shown a wide range of antimicrobial activity, although its effect has not been investigated on E. carotovora subsp. In this work, we tested extracts from propolis samples of Northwest Argentina against E. carotovora subsp. RESULTS: Ethanolic propolis extracts (EPEs) from samples of Santiago del Estero province, particularly from sample 4 (EPE4), showed the highest antibacterial activity, which was associated with the highest content of flavonoids. 2',4'-Dihydroxychalcone, 2',4'-dihydroxy-3'-methoxychalcone, galangin, and pinocembrin were identified as antibacterial constituents of EPE4. 2',4'-Dihydroxychalcone showed an antibacterial activity (minimum inhibitory concentration, MIC = 0.3-1.2 µg gallic acid equivalents (GAE) mL-1 ; minimum bactericidal concentration, MBC = 0.6-4.8 µg GAE mL-1 ) lower than that of bacterimycin (MIC = 2.4-9.6 µg mL-1 ; MBC = 19.2-38.4 µg GAE mL-1 ) and streptocycline (MIC = 19.2-38.4 µg mL-1 ; MBC = 38.4-76.8 µg mL-1 ). Preventive assays on unwounded and wounded potatoes showed that their immersion in EPE4 containing 87.5 µg GAE mL-1 or streptocycline containing 40 µg mL-1 was equally effective in controlling potato soft rot, reducing the disease incidence by 64.6-67.0% (unwounded tubers) and 88.0-86.0% (wounded tubers) and the disease severity by 49.8-49.8% (unwounded tubers) and 54.5-68.5% (wounded tubers). CONCLUSIONS: Flavonoid-rich propolis extracts from Northwest Argentina efficiently reduced in vivo the incidence and severity of potato soft rot caused by E. carotovora subsp.

Antibacterial activity of native plants from Northwest Argentina against phytopathogenic bacteria.

Extracts from aerial parts of medicinal plants from northwest Argentina were screened for antibacterial activity against the phytopathogenic strains namely CECT 124 (Pseudomonas corrugata), CECT 126 (P. syringae pv. tomato), CECT 225 (Erwinia carotovora var. carotovora), CECT 472 (Agrobacterium tumefaciens) and CECT 792 (Xanthomonas campestres pv. vesicatoria). Leaves and stems of Aspidosperma quebracho-blanco, Schinus fasciculatus, S. gracilipes, Amphilophium cynanchoides and Tecoma stans were separately extracted with solvents of increasing polarity to obtain the dichloromethane (fCH2Cl2), ethyl acetate (fEtAc) and methanol extracts (fMeOH), respectively. Among the thirty extracts tested, only fEtAc from leaves and stems of S. fasciculatus reached the IC50 against the five bacterial strains tested (IC50 = 0.9 mg/ml). The fEtAc from the leaves contained kaempferol, quercetin and agathisflavone which had moderate to strong antibacterial activity. This extract and its identified flavonoids showed synergic (CECT 124,126 and 792) or additive effects (CECT 472 and 225) in mixtures with Kocide 3000.

Antifungal metabolites from Schinopsis balansae Engl (Anacardiaceae): isolation, identification and evidences of their mode of action on Fusarium graminearum Schwabe.

An antifungal activity-directed fractionation of leaf constituents from Schinopsis balansae on Fusarium graminearum yielded a fraction mainly made of a mixture of four 3-n-heptadec(en)ylcatechols (PALK). The PALK fraction showed on macroconidia germination a MIC100 value of 500 µg/mL which was twofold higher than that required for prothioconazole (MIC100 = 250 µg/mL). Sublethal concentrations of PALK modify the morphogenesis in germinating macroconidia, and decreased fungal production of H2O2 and deoxynivalenol biosynthesis at early fungal growth. Mixes of PALK and prothioconazole showed a synergic interaction. Our findings suggest that PALK constituents might restrict the adherence of F. graminearum to the surface of its hosts and its virulence on susceptible cereals. They deserve further research as additives of azole fungicides against F. graminearum.

Plant growth inhibitors isolated from sugarcane (Saccharum officinarum) straw.

Several compounds related with plant defense and pharmacological activities have been isolated from sugarcane. Straw phytotoxins and their possible mechanisms of growth inhibition are largely unknown. A bioassay-guided fractionation of the phytotoxic constituents leachated from a sugarcane straw led to the isolation of trans-ferulic (trans-FA), cis-ferulic (cis-FA), vanillic (VA) and syringic (SA) acids. The straw leachates and their identified constituents significantly inhibited root growth of lettuce and four weeds. VA was more phytotoxic to root elongation than FA and SA. The identified phenolic compounds significantly increased leakage of root cell constituents, inhibited dehydrogenase activity and reduced chlorophyll content in lettuce. VA and FA inhibited mitotic index while SA increased cell division. Additive (VA-FA and FA-SA) and synergistic (VA-SA) interactions on root growth were observed at the response level of EC(25). Although the isolated compounds differed in their relative phytotoxic activities, the observed physiological responses suggest that they have a common mode of action. HPLC analysis indicated that sugarcane straw can potentially release 1.43 (ratio 2:1, trans:cis), 1.14 and 0.14mmolkg(-1) (straw dry weight) of FA, VA and SA, respectively. As phenolic acids are often found spatially concentrated in the top soil layers under plant straws, further studies are needed to establish the impact of these compounds in natural settings.