Location: Natural Products Utilization Research
2018 Annual Report
Objectives
The main objective of this project is to isolate and identify compounds from natural sources with pesticidal activity or have properties that are beneficial for human health. The overall goal is to be able to provide compound(s) amenable for commercial development as a pesticide or identify a “high value” plant with unique bioactive compounds. Over the next 5 years, we will focus on the following objectives:
Objective 1: Enable, from a technological standpoint, new commercial biopesticides; and identify optimum production practices for the plants from which these biopesticides are derived.
Subobjective 1.1: Identify nematicidal compounds from tall fescue.
Subobjective 1.2. Discover natural product based fungicides from plant extract collections or other useful sources for US agriculture.
Subobjective 1.3: Investigation of cashew nut shell liquid for insecticide activity and synthetic modification of the isolated compounds to gain insights into structure-activity relationship.
Sub-objective 1.4: Discover natural product based herbicidal and insecticidal compounds from crude plants and plant endophyte extract collections.
Objective 2: Identify human bioactive compounds in select plants and herbs, and determine plant growth conditions to enhance or optimize bioactive compound concentrations.
Subobjective 2.1: Identify anti-adipocyte compound(s) in Scutellaria ocmulgee and determine the effect of various growth conditions on the bioactive compound(s).
Approach
An “activity-guided” isolation approach will be employed in efforts to discover novel bioactive compounds. Focus will be on isolating single compounds from active fractions. The che mical structure of bioactive compounds isolated will be elucidated using a combination of spectroscopic techniques such as ultraviolet, infrared, mass spectrometry and nuclear magnetic resonance spectroscopy. Simple structure modification of the bioactive constituent(s) and synthesis of analogs will be performed for activity optimization. In general, four projects are included in the plan, employing specific approaches. These include: 1) Identification of nematotoxic compound(s) from tall fescue cultivar Jesup (Max-Q). Isolation will be guided by an in vitro assay on inhibition of nematodes. The activity of the isolated nematotoxic compound will be tested in soil. 2) Identification of fungicidal compound(s) from select plants from China. Isolation will be guided using in vitro assays against Botrytis cinerea, Colletotrichum species, Fusarium species, and Phomopsis species. The activity of isolated compounds will be tested in detached leaf assays. 3) Identification of compound(s) from cashew nut shell liquid with insecticidal activity. Isolation will be performed using assays to determine activity against mosquito (Aedis egypti) larvae and adult. Analogs of the mosquito larvicidal/adulticdal compound(s) will be synthesized following standard synthetic procedures such as Friedel-Crafts acylation reaction. 4) Identification of anti-obesity compound from Scutellaria ocmulgee. Isolation of compounds will be performed using inhibition of adipocyte differentiation as acidity indicator. Anti-adipocyte compounds isolated will be used as chemical markers in associated study determining the appropriate agronomic practices to generate highest amount of anti-adipocyte compound(s) and biomass.
Progress Report
We evaluated the antifungal potential of cytochalasins produced by Diaporthe taxa against phytopathogenic fungi. Cytochalasins H and J were evaluated for activities against the fungal plant pathogens Colletotrichum fragariae, C. gloeosporioides, C. acutatum, Botrytis cinerea, Fusarium oxysporum, Phomopsis obscurans, and P. viticola using microdilution broth assays. Cytochalasin H and J exhibited the most potent activities against the Phomopsis species tested. Our results showed that Diaporthe species were potential producers of different cytochalasins, which exhibit potential for controlling fungal diseases in planta and/or maintaining antagonism.
We also examined the essential oils of three aromatic plants, Zanthoxylum armatum, Juniperus communis, and Dysphania ambrosioides, which are used by the local population of the western Himalayan region for medicinal purposes. These plants were studied for their antifungal, larvicidal and biting deterrent activities. Antifungal activity was evaluated against three Colletotrichum species. Dyspania ambrosioides oil showed the best activity against these strawberry anthracnose causing fungi. It also demonstrated biting deterrent activity against Aedes aegypti similar to DEET as positive control, whereas Z. armatum and J. communis were less effective against Colletotrichum and mosquitoes.
The larvicidal constituents from cashew nut shell liquid were isolated and we still have to isolate adulticide constituents from a more polar fraction. Synthetic analogs have also been produced and are awaiting insecticidal evaluations.
A systematic bioassay-guided fractionation of methylene chloride extracts of the aerial part of Artemisia arborescens was performed in order to identify its phytotoxic compounds. Two lignans were isolated, sesamin and ashantin, that inhibited growth of Agrostis stolonifera (bentgrass), a monocot, and Lactuca sativa (lettuce), a dicot, at 1 mg mL-1.
Aedes aegypti is a major mosquito vector for the transmission of serious diseases, especially dengue and yellow fever. In order to maintain mosquito control gains, it is critical to develop and evaluate novel bioactive molecules that differ in mode of action from currently used products. A series of novel pyrimidine derivatives were designed and synthesized. The biological activities of these compounds were tested against Ae. aegypti. Many of them exhibited insecticidal activity against adult and larval mosquitoes. This study suggests that these pyrimidine derivatives exhibit some activity against the yellow fever mosquito and, with further structure modification, could be novel lead compounds for the development of insecticides against mosquitoes.
We have been working on plant pathogenic fungi in search for herbicidal, insecticidal and antifungal constituents. We were able to isolate and identify three fungi and a bacterium from the leaves of dollar weed (Hydrocotyle spp.). Dollar weed is a highly invasive species that is affecting lawns and golf courses in the US. These microbes were isolated from a leaf of dollar weed that showed severe necrotic lesions. The fungi Diaporthe ceratozamiae, Alternaria alternate and Epicoccum sorghi were isolated and identified as the fungi affecting the dollar weed leaves together with the bacterium Pantoea ananatis. Isolation and identification of the active metabolites are in progress.
Hymnoclea salsola, a weed species that is found in the arid regions of Utah, Texas and Arizona was investigated in search of phytotoxic, antifungal and insecticidal compounds. Confertin and several analogs of confertin and two novel chalcones that showed phytotoxic and antifungal activities were isolated and identified by spectroscopic techniques. These bioactive compounds are being evaluated further in our in-house bioassays.
Plants in the Rutaceae family are known for their biologically active compounds. We have investigated ethyl acetate extract of the leaves of an Amyris species collected in South Florida. Bioassay guided isolation led to isolation and identification of a novel phytotoxic furanocoumarin. The absolute configuration was determined by X-ray data. The IC50 value for this novel compound was determined on duckweed assay to be around 26 µM. The alcohol analog of this compound was found to be less active with IC50 value around 100 µM in the same assay.
Pertaining to the optimization of the bioactive constituents, in vitro propagation of S. ocmulgee during first half of the year has been completed. Year-1 of field studies has yet to be performed. We have no results thus far on the anti-adipocyte bioactives and yield.
The remaining progress made thus far falls more broadly, evaluating species for double utilization is a new approach to add value to lignocellulosic feedstock production. We evaluated selected essential oil crops peppermint (Mentha x piperita L.), ‘Scotch’ spearmint (M. x gracilis Sole), Japanese cornmint (M. canadensis L.), sweet sagewort (Artemisia annua L.), and compared them to switchgrass (Panicum virgatum L.) as lignocellulosic feedstock for ethanol production and for production of high-value natural products. Estimated ethanol production from the alternative crops were similar to the one from switchgrass. Additional incomes from the essential oil sells would be $1,055 - 5,132 ha-1 from peppermint, $1,309 - 5,580 ha-1 from spearmint, $510 - 2,460 ha-1 from Japanese cornmint, and $3,613 ha-1 from sweet sagewort. The tested species could be used as supplemental crops for biofuel feedstock in irrigated areas. The advantage of the proposed crops over other lignocellulosic species is the production of high-value natural products, which may offset production costs, foster the development of new value-added products, and be more attractive to growers.
Pertaining to the identification of human bioactive compounds in select plants and herbs, pterostilbene, a bioactive component of blueberries and grapes, shows structural similarity to resveratrol, and exhibits antioxidant, anti-inflammatory, anti-cancer, hypoglycemic, and cholesterol lowering effects. Recent evidence indicates that pterostilbene is an agonist of the nuclear receptor, peroxisome proliferator-activated receptor-alpha (PPAR-a). Taken together, our studies demonstrate that pterostilbene, a natural compound and PPAR-a agonist, modulate several AMPK-dependent metabolic functions. The results of the present study suggest that pterostilbene may have beneficial effects in the prevention and management of type 2 diabetes and related disorders. In this study, we found that pterostilbene activated AMP-activated kinase (AMPK) and increased the expression of fatty acid oxidation genes, including acyl CoA oxidase and carnitine palmitoyl transferase-1.
Age-related declines in motor function may be due, in part, to an increase in oxidative stress in the aging brain leading to dopamine (DA) neuronal cell death. In this study, we examined the neuroprotective effects of natural antioxidants resveratrol and pinostilbene against age-related DAergic cell death and motor dysfunction using SH-SY5Y neuroblastoma cells and young, middle-aged, and old male C57BL/6 mice. Resveratrol and pinostilbene protected SH-SY5Y cells from a DA-induced decrease in cell viability. Dietary supplementation with resveratrol and pinostilbene inhibited the decline of motor function observed with age. These data suggest that resveratrol and pinostilbene alleviate age-related motor decline via the promotion of DA neuronal survival and activation of the ERK1/2 pathways.
Accomplishments
1. Evaluating species for double utilization is a new approach to add value to lignocellulosic feedstock production. ARS researchers at Oxford, Mississippi, evaluated selected essential oil crops peppermint (Mentha x piperita L.), ‘Scotch’ spearmint (M. x gracilis Sole), Japanese cornmint (M. canadensis L.), sweet sagewort (Artemisia annua L.), and compared them to switchgrass (Panicum virgatum L.) as lignocellulosic feedstock for ethanol production and for production of high-value natural products. For each crop, the field experiment had a split-plot experimental design nested in year, with 3 blocks, 2 levels of irrigation, and 4 N application rates (0, 60, 120, and 180 kg ha-1). The biomass yields range (in kg ha-1) were 9,500 - 43,430 in Japanese cornmint, 9,300 - 33,870 in peppermint, 7,190 - 33,830 in ‘Scotch’ spearmint, and 11,867 in sweet sagewort. Oil content was 0.31 - 0.4% in Japanese cornmint, 0.23 - 0.26% in peppermint, 0.38 to 0.5% in spearmint, and 0.34% in sweet sagewort, and oil yields were (in kg ha-1) 34- 165 in Japanese cornmint, 25 - 108 in peppermint, 29.3 - 126 in spearmint, and 39.7 in sweet sagewort. Treatments affected the concentration of essential oil constituents, however, the oil composition remained within the normal range for the respective species. Estimated ethanol production from the alternative crops were similar to the one from switchgrass. Additional incomes from the essential oil sells would be $1,055 - 5,132 ha-1 from peppermint, $1,309 - 5,580 ha-1 from spearmint, $510 - 2,460 ha-1 from Japanese cornmint, and $3,613 ha-1 from sweet sagewort. The tested species could be used as supplemental crops for biofuel feedstock in irrigated areas. The advantage of the proposed crops over other lignocellulosic species is the production of high-value natural products, which may offset production costs, foster the development of new value-added products, and be more attractive to growers.
Review Publications
Morimoto, M., Cantrell, C.L., Khan, S., Tekwani, B.L., Duke, S.O. 2017. Antimalarial and antileishmanial activities of phytophenolics and their synthetic analogues. Chemistry and Biodiversity. DOI: 10.1002/cbdv.201700324.
Ren, G., Rimando, A.M., Mathews, S.T. 2018. AMPK activation by pterostilbene contributes to suppression of hepatic gluconeogenic gene expression and glucose production in H4IIE cells. Biochemical and Biophysical Research Communications. 498:640-645.
Allen, E.N., Potdar, S., Tapias, V., Parmar, M., Mizuno, C.S., Rimando, A.M., Cavanaugh, J.E. 2017. Resveratrol and pinostilbene confer neuroprotection against aging-related deficits through an ERK1/2 dependent-mechanism. Journal of Nutritional Biochemistry. 54:77-86.
Butt, N.A., Kumar, A., Dhar, S., Rimando, A.M., Akhtar, I., Hancock, J.C., Lage, J.M., Pound, C.R., Lewin, J.R., Gomez, C.R., Levenson, A.S. 2017. Targeting MTA1/HIF-1a signaling by pterostilbene in combination with histone deacetylase inhibitor attenuates prostate cancer progression. Cancer Medicine. 6(11):2673-2685.
Nakano, H., Seiji, K., Mamonov, L.K., Cantrell, C.L. 2016. 8-0-Acetyl-7-0-Methylgossypetin from Atraphaxis laetevirens. Chemistry of Natural Compounds. 52(1):127-129. doi: 10.1007/s10600-016-1567-x.
Gadetskaya, A.V., Mohamed, S.M., Tarawneh, A.H., Mohamed, N.M., Ma, G., Ponomarev, B.N., Zhusupova, G.E., Cantrell, C.L., Cutler, S.J., Ross, S.A. 2017. Phytochemical characterization and biological activity of secondary metabolites from three Limonium species. Medicinal Chemistry Research. 26:2743-2750. 10.1007/s00044-017-1973-z.
Ferreira, M.C., Cantrell, C.L., Wedge, D.E., Goncalves, V.N., Jacob, M.R., Khan, S., Rosa, C.A., Rosa, L.H. 2017. Antimycobacterial and antimalarial activities of endophytic fungi associated with the ancient and narrowly endemic neotropical plant Vellozia gigantea from Brazil. Memorias Do Instituto Oswaldo Cruz. 112(10):692-697.
Labruzzo, A., Cantrell, C.L., Carrubba, A., Ali, A., Wedge, D.E., Duke, S.O. 2018. Phytotoxic Lignans from Artemisia arborescens. Natural Product Communications. 13(3):237-240.
Meepagala, K.M., Estep, A.S., Clausen, B.M., Becnel, J.J. 2018. Mosquitocidal activity of a naturally occurring isochroman and synthetic analogs from the plant pathogenic fungus, Diaporthe eres against Aedes aegypti (Diptera: Culicidae). Journal of Medical Entomology. 55(4):969–974. doi:10.1093/jme/tjy016.
Meepagala, K.M., Briscoe, W.E., Techen, N., Johnson, R.D., Clausen, B.M., Duke, S.O. 2017. Isolation of a phytotoxic isocoumarin from Diaporthe eres-infected Hedera helix (English Ivy) and synthesis of its phytotoxic analogs. Pest Management Science. 74:37-45.
Jeliazkov, V.D., Cantrell, C.L. 2016. Medicinal and aromatic crops: Production, phytochemistry, and utilization. In: ACS Symposium Series. Ed(s) Jeliazkov and Cantrell, American Chemical Society, Washington, DC., Volume 1218.
Carvalho, C.R., D'Silva, A.F., Wedge, D.E., Cantrell, C.L., Rosa, L.H. 2018. Antifungal activities of cytochalasins produced by Diaporthe miriciae, an endophytic fungus associated with tropical medicinal plants. Canadian Journal of Microbiology. 64:835-843. https://doi.org/10.1139/cjm-2018-0131.
Stappen, I., Tabanca, N., Ali, A., Wedge, D.E., Wanner, J., Gochev, V., Jaitak, V., Lal, B., Kaul, V.K., Schmidt, E., Jirovetz, L. 2017. Biological activity of Bunium persicum essential oil from western Himalaya. Planta Medica International Open. e52-e58. https://dx.doi.org/10.1055/s-0043-106857.
Shen, Z., Sun, Z., Becnel, J.J., Estep, A.S., Wedge, D.E., Tan, C., Weng, J., Liu, X. 2018. Synthesis and mosquiticidal activity of novel hydrazone containing pyrimidine derivatives against Aedes aegypti. Letters in Drug Design & Discovery. 15(9):951-956. doi:10.2174/1570180815666180102141640.
Meepagala, K.M., Schrader, K.K. Antibacterial activity of constituents from Mangosteen Garcinia mangostana fruit pericarp against several channel catfish pathogens. Journal of Aquatic Animal Health. 2018;30:179-184. https://doi.org/10.1002/aah.10021.
