Location: Natural Products Utilization Research
2017 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
Plant or fungal extracts, and pure compounds constantly received under a continuing collaboration with China and Brazil were tested for activity against Colletotrichum species and/or Botrytis cinerea. Compounds isolated by Natural Products Utilization Research Unit (NPURU) visiting scientists, as well as samples from the Natural Products Center, University of Mississippi, were also assayed. One hundred semi-synthetic compounds derived from the commercial carboxamide fungicide penflufen submitted by visiting scientist from the University of Technology, Hangzhou, China, were initially tested in direct bioautography, and the best six compounds were subjected to micro-dilution broth assay. Cherry extracts received from Premier Botanicals were tested but showed no antifungal activity. Compound isolated from the methanol extract of leaves of Moringa oleifera were tested, but showed no antifungal activity.
Three larvicidal and 2 adulticidal compounds have been isolated from cashew nut shell liquid. The behavior of adult mosquitoes treated with these compounds was similar to that observed with permethrin, a commercial insecticide. The naturally occurring compounds have very similar structures and differ only in the number of double bonds. Methylation of these compounds caused reduction of activity. Further isolation of compounds is being carried out.
Several phytotoxic compounds were isolated and identified: i) phytotoxic compounds, including 4 new compounds, were isolated from the extract of adventitious roots of Vellozia gigantea a rare, ancient, and endemic neotropical plant present in the Brazilian Rupestrian grasslands. One of the known compounds isolated was especially phytotoxic with activity comparable to those of commercial herbicides clomazone, EPTC (s-ethyl dipropylthiocarbamate), and naptalam; ii) pyrichalasin H was identified as the phytotoxic compound from the culture broth of the fungus Pyricularia grisea that was isolated from infected Brachiaria eruciformis (signal grass), a common weed in the state of Mississippi; iii) a phytotoxic isochromene analog was identified from the culture broth of a fungus determined to be a member of the Phoma genus that was isolated from infected leaf of Malabar spinach (Basella alba), a popular green leafy vegetable native to tropical Asia; iv) two compounds (tyrosol and a compound having an isocoumarin core structure) were identified as the infected leaf of Hedera helix (English Ivy) exhibiting necrosis. Isocoumarin analogs were synthesized, and two of the analogs were two- to three-fold more phytotoxic than the naturally occurring compound in a Lemna paucicostata growth bioassay.
Significant progress was made from a subordinate project, which is related to Objective 1 in terms of identifying optimum production practices for the plant sources of bioactive compounds. An experiment was set up to test the feasibility of season extension methods on quantitative and qualitative production of spearmint, thyme, Greek oregano, and rosemary. These plants are sources of volatile oils, which contain some insect repellent components. The following season extension methods were tested: high tunnel (Ht), low tunnel (Lt), and low tunnel within high tunnel (LtHt). Except for rosemary, the herbage production of the studied herbs in LtHt was significantly higher than the herbage production in Lt and in Ht in the second harvest (late fall). The essential oil content of the herbs from this study did not vary significantly between the season extension methods. This study demonstrated that LtHt can provide optimal conditions for spearmint, thyme, and oregano fresh herbage and essential oil production in northern climates, even when the temperature falls below the freezing point. LtHt can also improve the antioxidant capacity of thyme and oregano.
Accomplishments
1. Phytotoxic compounds isolated from a rare plant in Brazil. Vellozia (V.) gigantean is a rare, ancient, and endemic neotropical plant present in the Brazilian Rupestrian grasslands. Extraction was performed by ARS scientists in Oxford, Mississippi. The dichloromethane extract of the adventitious roots of V. gigantea was phytotoxic against Lactuca sativa, Agrostis stolonifera, and Lemna paucicostata. Phytotoxicity assay-directed fractionation of the extract revealed four new compounds. One of the new compounds was especially phytotoxic with activity comparable to those of the commercial herbicides clomazone and naptalam. This study shows that ancient and unique plants, like the endangered narrowly endemic neotropical species V. gigantea present in the Rupestrian grasslands, should also be protected because they can be sources of new bioactive compounds.
2. Phytotoxic compound isolated from plant pathogenic fungus. Brachiaria (B.) eruciformis commonly known as Signal grass is a common weed in lawns and turfs in the state of Mississippi. ARS scientists in Oxford, Mississippi, collected Pyricularia (P.) oryzae from infected leaves of B. eruciformis showing necrosis. P. grisea, Magnaporthe (M.) gisea and Pyricularia oryzae are closely related fungi that are responsible for crop losses in rice and cereals worldwide. P. grisea was grown in culture broth. Extract of the culture broth was found to be phytotoxic. The phytotoxic constituent pyrichalasin H. This compound also showed antifungal activity against Colletotrichum species. This study provides not only further evidence that plant pathogenic fungi are good sources of herbicidal compounds but also provides a chemical basis for the necrosis in infected leaves.
Review Publications
Schrader, K., Cantrell, C.L., Midiwo, J.O., Muhammad, I. 2016. Compounds from Terminalli brownii extracts with toxicity against the fish pathogenic bacterium Flavobacterium columnare. Natural Product Communications. 11(11):1679-1682.
Shiwakoti, S., Zheljazkov, V.D., Schlegel, V., Cantrell, C.L. 2016. Growing spearmint, thyme, oregano, and rosemary in Northern Wyoming using plastic tunnels. Industrial Crops and Products. 94:251-258.
Travaini, M.L., Sosa, G.M., Ceccarelli, E.A., Walter, H., Cantrell, C.L., Carrillo, N.J., Dayan, F.E., Meepagala, K.M., Duke, S.O. 2016. Khellin and visnagin, furanochromones from Amni visnaga (L.) Lam., as potential bioherbicides. Journal of Agricultural and Food Chemistry. 64:9475-9487.
Weng, J., Ali, A., Estep, A., Becnel, J.J., Meyer, S.L., Wedge, D.E., Jacob, M., Rimando, A.M. 2016. Synthesis and biological evaluation of 3,5-dimethoxystilbene analogs. Chemistry and Biodiversity. 13(9):1165-1177.
Liu, X., Qiao, W., Sun, Z., Wedge, D.E., Becnel, J.J., Estep, A.S., Tan, C., Weng, J. 2017. Synthesis and insecticidal activity of novel pyrimidine derivatives containing urea pharmacophore against Aedes aegypti. Pest Management Science. 73:953–959. doi:10.1002/ps.4370.
Zhang, A., Rimando, A.M., Mizuno, C.S., Mathews, S.T. 2017. Alpha-glucosidase inhibitory effect of resveratrol and piceatannol. Journal of Agricultural and Food Chemistry. 47:86-93. doi:10.1016/j.jnutbio.2017.05.008.
Aguirre, L., Milton-Laskibar, I., Hijona, E., Bujanda, L., Rimando, A.M., Poetillo, M.P. 2017. Effects of pterostilbene in brown adipose tissue from obese rats. Journal of Physiology and Biochemistry. 73(3):457-464. doi:10.1007/s13105-017-0556-2.
Srivedavyasasri, R., White, M.B., Kustova, T.S., Gemeujiyeva, N.G., Cantrell, C.L., Ross, S.A. 2017. New tetranorlabdanoic acid from aerial parts of salvia aethiopis. Natural Product Research. doi:10.1080/14786419.2017.1324961.
Ferreira, M.C., Cantrell, C.L., Duke, S.O., Ali, A., Rosa, L.H. 2017. New phytotoxic diterpenoids from Vellozia gigantea (Velloziaceae), an endemic neotropical plant living in the endangered Brazilian biome Rupestrian grasslands. Molecules. 22:175. doi:10.339/molecules22010175.
Moreas, R.M, A.L. Cerdiera, S.O. Duke, F.E. Dayan, C.L. Cantrell, and S.C.N. Queiroz. 2016. Pesticidas Naturais Derivdos de Plantas: Descoberta et Usos (Natural Pesticides Derived from Plants: Discovery and Uses). In: Halfeld-Vieira, B.A, Marinho-Prado, J.S., Nechet, K.L., Morandi, M.A.B., Bettiol, W., editors. Defensivos Agrícolas Naturais: Uso e Perspectivas (Natural Agricultural Defenses: Use and Perspectives). Jaguariúa, Brazil: Emprapa Meio Ambiente. p. 505-541.
Ferreira, M.C., Cantrell, C.L., Wedge, D.E., Goncalves, V.N., Jacob, M., Khan, S., Rosa, C.A., Rosa, L.H. 2017. Diversity of the endophytic fungi associated with the ancient and narrowly endemic neotropical plant Vellozia gigantea from the endangered Brazilian rupestrian grasslands. Biochemical Systematics and Ecology. 71:163-169.
Duke, S.O., Rimando, A.M., Reddy, K.N., Cizdziel, J.V., Bellaloui, N., Shaw, D.R., Williams, M., Maul, J.E. 2017. Lack of transgene and glyphosate effects on yield, and mineral and amino acid content of glyphosate-resistant soybean. Pest Management Science. 74:1166-1173. https://doi.10.1002/ps.4625.
