Qualitative and Quantitative Secondary Metabolite Profiles in a Large Set of Sumatra Benzoin Samples.

Sumatra benzoin, a resin produced by Styrax benzoin and Styrax paralleloneurum, is used as an aromatic agent and may have the potential to be developed as a new agricultural fungicide. In this context, we performed a comprehensive metabolite profiling of a commercial grade A resin by high-performance liquid chromatography coupled with photodiode array detection, evaporative light scattering detection, and mass spectrometry (HPLC-PDA-ELSD-MS) analysis in combination with 1H NMR. Thirteen compounds including a new cinnamic acid ester containing two p-coumaroyl residues were identified after preparative isolation. These compounds accounted for an estimated 90% of the crude resin according to 1H NMR analysis. The two major constituents, p-coumaryl cinnamate (5) and sumaresinolic acid (11), were quantified by HPLC analysis. In a next step, the chemical profiles and the content in p-coumaryl cinnamate were compared in a large set of resin samples of different quality grades that were obtained from various commercial suppliers in Sumatra. The qualitative profiles of the samples were very similar, but significant quantitative differences were observed between different quality grades and origins of the samples for the relative contents.

Ingadosides A-C, acacic acid-type saponins from Inga sapindoides with potent inhibitory activity against downy mildew.

As part of a project aiming at the discovery of environmentally friendly alternatives to copper in organic agriculture, a 96% ethanolic extract from the leaves of Inga sapindoides showed potent inhibitory activity against grapevine downy mildew (Plasmopara viticola) in vitro (MIC100 25 µg/mL). Separation of the n-BuOH soluble fraction by silica gel column chromatography followed by a combination of RP18 and HILIC HPLC resulted in the isolation of a series of bidesmosidic saponins characterized by the presence of a monoterpenoid unit attached to a triterpenoid aglycone, a p-methoxycinnamoyl residue, and rare sugar residues such as N-acetyl-d-glucosamine, d-quinovose, and d-fucose. The isolated compounds inhibited the formation or activity of P. viticola zoospores with MIC100 values of 3 or 6 µg/mL, respectively. I. sapindoides, a tree which is often cultivated for shading coffee plantations in Central America, may represent a sustainable source of fungicidal products to be used in the replacement of copper.

Antiprotozoal Isoprenoids from Salvia hydrangea.

Fractionation of the n-hexane extract of Salvia hydrangea afforded seven isoprenoids including six new compounds (1-6) and salvadione A (7). Their structures were established by comprehensive spectroscopic and spectrometric data analysis (1D and 2D NMR, HRMS). The absolute configuration of salvadione A (7) was established by single-crystal X-ray diffraction analysis with Cu/Kα radiation. In addition, the absolute configuration of all compounds was determined by electronic circular dichroism spectroscopy. A biosynthetic pathway for the formation of the scaffold of 1 is proposed. The antiprotozoal activity of the compounds against Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovani, and Plasmodium falciparum was determined, and cytotoxicity was assessed in rat myoblast L6 cells. Perovskone C (2) exhibited good activity against P. falciparum (IC50 0.6 µM) and a selectivity index of 62.2.

Antiprotozoal Diterpenes from Perovskia abrotanoides.

As part of a screening for new antiparasitic natural products from Iranian plants, n-hexane and ethyl acetate extracts from the aerial parts of Perovskia abrotanoides were found to exhibit strong inhibitory activity against Trypanosoma brucei rhodesiense and Leishmania donovani. The activity was tracked by high-performance liquid chromatography (HPLC)-based activity profiling. Preparative isolation by a combination of silica gel column chromatography and HPLC afforded 17 diterpenoids (1: -17: ), including 14 abietane-, two icetexane-, and one isopimarane-type derivatives. Among these, (5R,10S)-11-hydroxy-12-methoxy-20-norabieta-8,11,13-triene (2: ), 12-hydroxy-norabieta-1(10),8,11,13-tetraene-1,11-furan (6: ), and 12-methoxybarbatusol (9: ) were new compounds, the structure of which was established by comprehensive spectroscopic data analysis (one- and two-dimensional nuclear magnetic resonance, high-resolution electrospray ionization mass spectrometry, electronic circular dichroism). The antiprotozoal activity of the isolated compounds was evaluated against T. b. rhodesiense, Trypanosoma cruzi, L. donovani, and Plasmodium falciparum. Selectivity indexes (SI) were calculated in comparison to cytotoxicity on rat myoblast (L6) cells. Particularly active were 7α-ethoxyrosmanol (4: ) with an IC50 of 0.8 µM against T. b. rhodesiense (SI 14.9) and an IC50 of 1.8 µM (SI 6.9) against L. donovani, ferruginol (8: ) with an IC50 of 2.9 µM (SI 19.2) against P. falciparum, and miltiodiol (10: ) with an IC50 of 0.5 µM (SI 10.5) against T. b. rhodesiense. None of the compounds exhibited selective toxicity against T. cruzi (SI ≤ 1.6).

Eudesmane Sesquiterpenes from Verbesina lanata with Inhibitory Activity against Grapevine Downy Mildew.

An in-house library of more than 3000 extracts of plant and fungal origin was screened against some major plant pathogens. As one of the hits, an ethyl acetate extract from inflorescences of Verbesina lanata showed significant inhibitory activity in vitro against grapevine downy mildew (Plasmopara viticola), with a MIC100 value of 35 µg/mL. An emulsifiable concentrate formulation with 50 mg/g of the extract was developed for in vivo evaluation. A suspension of the formulation containing 1 mg/mL of extract lowered leaf surface infection of grapevine seedling by 82% compared to the nontreated control. With the aid of HPLC-based activity profiling, the antifungal activity was correlated with a series of lipophilic compounds. Preparative isolation by a combination of chromatographic techniques afforded 16 eudesmane sesquiterpenes including eight new congeners. Nine compounds were obtained in sufficient quantities to be tested in vitro and were found to inhibit the zoospore activity of P. viticola with MIC100 values ranging from 4 to 50 µg/mL. The two major compounds, 6ß-cinnamoyloxy-4ß,9ß,15-trihydroxyeudesmane (9) and 6ß-cinnamoyloxy-1ß,15-dihydroxyeudesm-4-en-3-one (13), showed MIC100 values of 5 and 31 µg/mL, respectively.

Efficacy of a Juncus effusus extract on grapevine and apple plants against Plasmopara viticola and Venturia inaequalis, and identification of the major active constituent.

BACKGROUND: There is growing demand to replace chemical pesticides with alternatives owing to concerns related to impacts on human health and the environment. Plant-derived plant protection products could provide sustainable and environmentally friendly alternatives to chemical products. The aim of this study was to identify plant and fungal extracts with so far unknown activity against important plant pathogens by in vitro screening of a library of more than 3000 extracts. RESULTS: Several plant extracts with promising in vitro fungicidal activity (MIC100 ≤ 50 µg mL(-1) ) towards one or several of the investigated pathogens (Venturia ineaqualis, Phytophthora infestans, Plasmopara viticola) were identified by the screening. One of the hits, an ethyl acetate extract of Juncus effusus L. medulla, was further investigated, and dehydroeffusol (DHEF) was identified as its main active constituent. On susceptible grapevine and apple seedlings, efficacies of up to 100% were reached with the extract (EC50 123 or 156 µg mL(-1) ) and with DHEF (EC50 18 or 21 µg mL(-1) ) against P. viticola and V. inaequalis respectively. CONCLUSIONS: Our results demonstrate that plants can provide promising alternatives for integrated and organic farming. J. effusus shows high efficacy at low concentrations and, as an abundant perennial species, is an interesting candidate for the development of a novel plant protection product. © 2015 Society of Chemical Industry.