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Phytochemical investigation led to the isolation of three alkaloids [skimmianine (1), vulcanine (2) and evoxine (3)] from the aerial parts of Haplophyllum tuberculatum, and two diacetylenic spiroketal enol ethers [spiroketalenolether polyyne (4) and [7-hexa-2,4-diynylidene-1,6-dioxaspiro[4.4]nona-2,8-dien-4-yl] acetate (5)] and a sesquiterpene lactone [8α acetoxy-11β,13dihydrokauniolide (6)] from the aerial parts of Chrysanthemum coronarium. The chemical structures of the isolated compounds were determined by using spectral data of 1H NMR, 13C NMR, as well as by comparison with literature data. Compounds 4, 1 and 5 were the most potent inhibitors against plant pathogenic bacteria Rhizobium radiobacter, Ralstonia solanacerum and Pectobacterium carotovorum ss. carotovorum with minimum inhibitory concentration (MIC) values of 31.3, 62.5 and 31.3 µg/ml, respectively. In antifungal assay, compounds 1 (MIC 62.5 µg/ml), 2 (MIC 62.5 µg/ml) and 5 (MIC 125 µg/ml) caused the highest inhibitory effects against phytopathogenic fungi Verticillium dahliae, Fusarium oxysporum and Alternaria solani, respectively. Moreover, crude extract of H. tuberculatum and 4 were significantly the most potent inhibitors of seed germination, root and shoot growth of Echinochloa crus-galli.

This study was undertaken to evaluate the herbicidal activity of twelve natural compounds belonging to monoterpenes, phenylpropenes, and sesquiterpenes against Echinochloa crus-galli under laborato...

Six monoterpenes, ((−)-citronellal, p-cymene, (−)-menthone, α-pinene, α-terpinene and (−)-terpinen-4-ol) and two phenylpropenes, (trans-cinnamaldehyde and eugenol) were tested for their insecticidal activity against the rice weevil, Sitophilus oryzae under laboratory conditions. The bioassays were carried out on wheat at the concentrations of 0.5, 1.0 and 5.0 g/kg. Adult mortality was assessed after 14 days of exposure. After this interval, the treated wheat was retained for an additional period of 90 days, in order to evaluate progeny production and wheat loss. At the concentrations of 0.5 and 1.0 g/kg, trans-cinnamaldehyde and eugenol achieved highest adult mortality. At 5.0 g/kg, all compounds except for p-cymene and α-pinene caused complete (100%) adult mortality. Generally, trans-cinnamaldehyde was the most potent compound causing complete inhibition of progeny at the three concentrations. Similarly, no progeny were observed in the wheat treated with (−)-citronellal, eugenol, p-cymene, (−)-menthone, and (−)-terpinen-4-ol at 5.0 g/kg after 45 and 90 days. Similar trends were noted for wheat weight loss and damage as the treatment with monoterpenes and phenylpropenes at the highest rate preserved the wheat intact and free from damage by S. oryzae for 90 days. Our findings suggest the tested compounds except p-cymene and α-pinene could be recommended for use as part of an integrated pest management program for S. oryzae control in stored wheat.

In the present study, six monoterpenes [(−)-citronellal, p-cymene, (−)-menthone, α-pinene, α-terpinene, and (−)-terpinen-4-ol] and two phenylpropenes [trans-cinnamaldehyde and eugenol] were evaluated for their contact and fumigant toxicities against Sitophilus oryzae adults. The effects of these compounds on the mortality of S. oryzae adults in stored wheat and their inhibitory effects on acetylcholinesterase (AChE) and adenosine triphosphatases (ATPases) were examined. The tested compounds showed varying degrees of contact toxicity, with trans-cinnamaldehyde (LC50 = 0.01 mg/cm2) being the most potent compound, followed by (−)-menthone (LC50 = 0.013 mg/cm2) and eugenol (LC50 = 0.015 mg/cm2). In a fumigant toxicity assay, the monoterpenes α-terpinene, p-cymene, and (−)-menthone showed the highest toxicities (LC50 = 50.79, 52.37, and 54.08 μl/L air, respectively). Trans-cinnamaldehyde, (−)-citronellal, and eugenol were the least toxic (LC50 > 100 μl/L air). In general, the oxygenated compounds exhibited high contact toxicities while the hydrocarbon compounds exhibited high fumigant toxicities. When tested for their insecticidal activities against S. oryzae in stored wheat, trans-cinnamaldehyde was found to be the most potent compound, with 73.9% mortality at an application rate of 0.5 g/kg and complete mortality (100%) at 1 and 5 g/kg after 1 week of treatment. All of the tested compounds showed AChE inhibition, although (−)-citronellal and trans-cinnamaldehyde presented the strongest enzyme inhibition, with IC50 values of 18.40 and 18.93 mM, respectively. On the other hand, (−)-terpinene-4-ol exhibited the highest inhibition of ATPases, followed by α-pinene and α-terpinene.

Endophytes are promising bio-control agents and rich sources of secondary metabolites known for their biological activities. Two medicinal plants, Pelargonium graveolens and Melia azedarach, and two weeds, Chenopodium album and Malva parviflora, were selected to isolate endophytic fungi. Spore suspension of Alternaria alternata (MG786545), Alternaria solani (MG786543), Curvularia lunata (MF113056), Nigrospora sphaerica (MF113055), and Stemphylium sp. endophytes was tested for their pathogenicity to the third-instar larvae of the cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae). Two techniques were used: dipping in spore suspension and residual film assay. Secondary metabolites were extracted, and ethyl acetate extracts of A. alternata (MG786545), C. lunata (MF113056), and N. sphaerica (MF113055) were tested for their insecticidal activity by both techniques. C. lunata (MF113056) showed the most potent pathogenicity causing 60% mortality after 7 days by dipping bioassay, while A. solani (MG7865453) and A. alternata (MG786545) caused 40 and 33.3% mortality, respectively. All tested endophytes showed no effect against S. littoralis by residual film method. N. sphaerica ethyl acetate extract activated larval feeding on castor leaves causing 25% mortality by residual film at 2000 mg/l.

Monoterpenes, the major constituents of essential oils, are known for their diverse biological activities. This study was conducted to assess the herbicidal effect of six monoterpenes viz. (R)-carvone, 1,8-cineole, cuminaldehyde, (S)-fenchone, geraniol, (S)-limonene, and (R)-linalool on barnyardgrass under laboratory and glasshouse conditions with a view to explore the possibility of their utilization for future weed management. The effect of monoterpenes on chlorophyll contents and total phenolic compounds was also evaluated. The inhibitory effects of monoterpenes on seed germination and seedling growth were tested at concentrations of 1, 2, 4, 6, and 8 mM. The results showed that geraniol and (R)-carvone caused greatest reduction of seed germination with complete inhibition at the concentrations > 2 mM. Similarly, these two compounds were the most potent inhibiters for root and shoot growth. In general, monoterpenes were less effective against seed germination than seedling growth. Furthermore, the inhibition of root growth by all compounds was greater than that of shoot growth. In foliar application treatments under glasshouse conditions, the monoterpenes reduced the fresh and dry weights, and shoot length of two-leaf stage barnyardgrass at concentrations of 1 and 2%. In addition, the tested monoterpenes caused phytotoxicity symptoms, mainly chlorosis and necrosis, followed by weed death. Complete weed control was observed in the treatments with 1 and 2% of geraniol, and 2% of cuminaldehyde. Further, a reduction of chlorophyll contents and total phenolic compounds of barnyardgrass leaves was noticed, indicating that the monoterpenes cause adverse effect on photosynthesis and weed metabolism. Based on the results of this study, it can be concluded that the monoterpenes, particularly geraniol, (R)-carvone, and cuminaldehyde, can be used as potential natural herbicides.