Nutritional composition and antioxidant capacity of Urtica hyperborea: A phytofood of Trans-Himalayan region of Ladakh, India

Urtica hyperborea Jacquem. ex Wedd., a perennial plant of Urticaceae family is considered as a wild vegetable in the mountainous region of Ladakh. Due to its application in many forms of traditional culinary in every household during the harsh winter season, the plant ensures the food security. However, the nutritional composition and phytochemical analysis of U. hyperborea responsible for these beneficial features have not been explored widely. The present study aims to determine the nutritional composition (e.g., macromolecules, pigments, minerals, phenolics and flavonoid contents), antioxidant activity and the phytochemical analysis of this plant species present in Ladakh, India. The radical scavenging and antioxidant potential of the plant were evaluated by assays like 2,2‒diphenyl‒1‒picrylhydrazyl (DPPH), hydrogen peroxide (H2O2), hydroxyl (ºOH), and ferric ion reducing antioxidant power (FRAP) for different extracts prepared in water, methanol, ethyl acetate, and petroleum ether. Macromolecules such as protein, carbohydrate, total phenolic and flavonoid contents in U. hyperborea were found to be 62.28±6.67, 170.80±3.98, 24.47±0.39 and 5.43±0.97 mg g-1, respectively. Similarly, dried powder of U. hyperborea was found to be rich in different mineral contents such as potassium, magnesium, sodium, manganese, zinc and iron. Among the various solvents used for exploring scavenging and antioxidant potential, aqueous extracts showed highest activity with 79.2% in DPPH assay as compared to other extracts. Similar trend was observed for other assays where aqueous extracts exhibited higher activity followed by methanolic, ethyl acetate and petroleum ether extracts. Significant positive linear correlations were observed between the radical scavenging/antioxidant activity of aqueous extracts and their content of phenolic/flavonoid compounds. The identification of phenolic compounds such as coumarin, quercetin, and ferulic acid confirm the antioxidative nature of the plant. Overall, rich macromolecule and mineral contents, as well as higher radical scavenging/antioxidant activities in aqueous extracts of U. hyperborea revealed that the plant has significant potential to be utilized as a phytofood source in harsh environmental conditions

Alternative control of littleseed canary grass using eucalypt oil

Globally, huge amounts of synthetic herbicides are used to manage weeds in arable lands. However, their widespread use has resulted in various toxicological effects on the environment and human health, besides resulting in the emergence of herbicide-resistant weed biotypes. To overcome these problems, there is an urgent need to search for novel compounds, particularly natural plant products, with potential herbicidal activity. In this area, we studied the phytotoxic effect of volatile oil from lemon-scented eucalypt on littleseed canary grass, a noxious weed of wheat fields. Our findings show that under laboratory conditions the emergence and earlier growth of the weed decreased and completely ceased using a very low concentration of eucalypt oil (0.0714%, v/v). Treatment with eucalypt oil of the 4-week-old pot-raised weeds caused visible damage such as chlorosis and necrosis, wilting and even plant death. The effect was concentration-dependent. At low concentrations, 2.5 and 5%, v/v of eucalypt oil, plants were damaged but recovered later, whereas at concentrations higher than 5%, v/v, of eucalypt oil plants showed severe injury with little or no sign of recovery, and death. There was a severe effect on the photosynthetic and respiratory ability of treated plants 7 and 21 days after treatment. Eucalypt oil treatment caused a rapid electrolyte leakage in the P. minor leaf tissues, indicating a loss of membrane integrity. The study concludes that lemon-scented eucalypt oil offers a good option for control of littleseed canary grass and could be included as a viable component of integrated weed management under sustainable agricultural practices

Chemical composition and inhibitory activity of essential oil from decaying leaves of Eucalyptus citriodora

A study was undertaken to explore the content and composition of volatile oil from decaying leaves of lemon-scented eucalypt (Eucalyptus citriodora Hook.) not analyzed earlier. GC and GC-MS analysis of the oil (yield 0.6%) revealed the monoterpenoid nature with citronellal (52.2%), citronellol (12.3%) and isoisopulegol (11.9%) as the major constituents. Overall, 17 components were identified that accounted for over 94% of the decaying leaf oil. Surprisingly, the decaying leaf oil contained nearly 1.8% of trans-rose oxide, which is generally absent in eucalypt essential oil. Decaying leaf oil and its major 2 components (citronellal and citronellol) inhibited the germination and root elongation of two weeds Ð Cassia occidentalis (broad-leaved) and Echinochloa crus-galli (grassy weed). Based on the dose-response studies, I 50 values were determined for decaying leaf oil and the effect was more on germination only of broad-leaved weed (C. occidentalis), whereas that of citronellal and citronellol were on germination as well as root length of E. crus-galli (grassy weed). Based on I 50 values it was observed that citronellal was more phytotoxic and germination inhibiting in nature, whereas citronellol was a more potent root inhibitor, thereby indicating a possible different mode of action. The study concludes that decaying leaf oil hold a good commercial value for exploitation as weed management agent

Eucalyptus essential oil as a natural pesticide

Eucalyptus (family Myrtaceae), an Australian native, represented by around 700 species is a genus of tall, evergreen and magnificent trees cultivated world over for its oil, gum, pulp, timber, medicine and aesthetic value. Among the various wood and non-wood products, essential oil found in its foliage is the most important one and finds extensive use in food, perfumery and pharmaceutical industry. In addition, the oil possesses a wide spectrum of biological activity including anti-microbial, fungicidal, insecticidal/insect repellent, herbicidal, acaricidal and nematicidal. The present paper discusses this environmentally benign pest control using eucalyptus oils against bacteria, fungi, insects, nematodes, weeds and mites. The use of eucalyptus oil as a natural pesticide is of immense significance in view of the environmental and toxicological implications of the indiscriminate use of synthetic pesticides and overcoming/reducing the problem of increasing pest resistance

Role of root-mediated interactions in phytotoxic interference of Ageratum conyzoides with rice (Oryza sativa)

Ageratum conyzoides L. (billy goat weed; Asteraceae) is an annual invasive weed native of tropical America and has now naturalized worldwide, particularly in Southeast Asia. The present study investigated the nature and potential of root-mediated allelopathic interference of A. conyzoides against rice (Oryza sativa). Root and shoot length and biomass accumulation of rice were significantly reduced (by 18-30%) when grown in the rhizosphere soil of the weed indicating the release of putative allelochemicals from the weed into the soil. The growth of rice was also progressively reduced in the soil amended with increasing amounts of root residues (5, 10 and 20 g kg-1 soil) of A. conyzoides. The addition of activated charcoal, an inert material with high affinity for organic biomolecules, partly ameliorated the negative effects of root residues amended in the soil. Further, there was no negative effect on the availability of soil nutrients in the root-amended soils. These were rather nutrient rich with greater electrical conductivity, and higher amount of organic matter, thus indicating no role in observed growth reduction. The reduction in allelopathic effects of root residue upon charcoal addition further indicated that putative phytotoxins released from the weed roots are water-soluble phenolic compounds. A significant amount of water-soluble phenolics were present in rhizosphere (~6-times higher) and root-amended soils (∃ 5-10-fold higher) and their content was reduced (to ∃ 3.6-7.0-fold higher) when charcoal was added. The observed growth reduction in Ageratum rhizospheric or root-amended soils was concomitant with the amount of phenolic compounds. Upon HPLC analyses, these were identified as p-coumaric acid, gallic acid, ferulic acid, p-hydroxybenzoic acid and anisic acid. Under laboratory conditions, these phenolic acids reduced the root length and seedling weight of rice individually as well as in equimolar mixture, though no synergistic effect was noticed. The study concludes that root exudates and residues of A. conyzoides suppress the growth of rice by releasing phenolic allelochemicals into the soil rhizosphere and not through alteration of soil nutrients, and allelopathy plays a significant role in root-mediated negative interference of A. conyzoides

Crop allelopathy and its role in ecological agriculture

A number of crops exhibit allelopathic interactions that play a significant role in the complex environment of agroecosystems. Several studies have shown that allelopathic crops reduce growth, development and yield of other crops growing simultaneously or subsequently in the fields. Another aspect of interest regarding crop allelopathy is that allelochemicals may exhibit inhibitory effect on the same crop which is commonly called as crop autotoxicity. It is predominantly common in fields where sole cropping under reduced or no-tillage system is practiced. Though any crop part can be allelopathic, including even the pollens, but decomposing crop residues exhibit more influence on other plants. Furthermore, the extent of allelopathy by a crop plant varies with age, part and type of cultivar being used. Nowadays allelo-pathic crops are being used as an important tool in managing weeds and harmful pests under sustainable pest management programs. In this context several cover/smother and green manure crops with allelopathic nature hold a good promise as well as challenge for the future as they have a potential to suppress noxious weeds. Likewise, the decomposing residues of such crops can also be used for managing harmful weeds and pests vis-à-vis maintaining the sustainability of the system. The traditional practice of crop rotation which declined with the discovery of synthetic herbicides can also be revived, if allelopathic potential of rotational crops is well understood. Selection of cultivars with high allelopathic potential/high competitiveness is another possible way by which crop allelopathy can be better utilized for weed control and yield enhancement. Crops with less allelopathic potential can be genetically improved by incorporating desired genes encoding the synthesis of allelochemicals. Pure allelochemicals extracted and identified from some crop plants can also be used as bioherbicides

Phytotoxic effects of volatile oil from Artemisia scoparia against weeds and its possible use as a bioherbicide

A study was conducted to assess the bioherbicidal activity of volatile oil hydrodistilled from Artemisia scoparia Waldst et Kit. (red stem wormwood; Asteraceae) against five weed species, viz. Achyranthes aspera, Cassia occidentalis, Parthenium hysterophorus, Echinochloa crus-galli, and Ageratum conyzoides. Emergence and seedling growth (in terms of root and shoot length) were significantly reduced in a dose-response bioassay conducted in sand impregnated with Artemisia oil (at ≥10, 25, and 50 µg Artemisia oil/g sand). In general, the root length was inhibited more as compared to the shoot length and the inhibitory effect was greatest in P. hysterophorus followed by A. conyzoides and least in C. occidentalis. Post-emergence application of Artemisia oil (2%, 4%, and 6%, v/v) on 6-week-old weed plants caused visible injury (1- and 7-days after spray) ranging from chlorosis to necrosis to complete wilting of plants. Among the sprayed test weeds, the effect was greatest on E. crus-galli and P. hysterophorus. Artemisia oil treatment resulted in a loss of chlorophyll content and cellular respiration in test weeds thereby implying interference/impairment with photosynthetic and respiratory metabolism. Artemisia oil caused a severe electrolyte leakage from E. crus-galli (a monocot) and C. occidentalis (a dicot) indicating membrane disruption and loss of integrity. The study concludes that Artemisia oil has bioherbicidal properties as it causes severe phytotoxicity and interferes with the growth and physiological processes of some weed species

α-Pinene Inhibits Growth and Induces Oxidative Stress in Roots

• Background and Aims Determining the mode of action of allelochemicals is one of the challenging aspects in allelopathic studies. Recently, allelochemicals have been proposed to cause oxidative stress in target tissue and induce an antioxidant mechanism. α-Pinene, one of the common monoterpenoids emitted from several aromatic plants including forest trees, is known for its growth-inhibitory activity. However, its mechanism of action remains unexplored. The aim of the present study was to determine the inhibitory effect of α-pinene on root growth and generation of reactive oxygen species, as indicators of oxidative stress and changes in activities of antioxidant enzymes