Assessment of Allelopathic Potential of Senna garrettiana Leaves and Identification of Potent Phytotoxic Substances

Senna garrettiana (Craib) Irwin & Barneby (Fabaceae) is a medicinal plant known to be rich in biologically active compounds that could be exploited to produce bioherbicides. The present study was conducted to explore the allelopathic potential and phytotoxic substances of S. garrettiana. Extracts of S. garrettiana leaves were found to significantly inhibit the growth of Lepidium sativum L. and Echinochloa crus-galli (L.) P. Beauv. (p ≤ 0.05). The phytotoxic substances were isolated and identified as vanillic acid and ferulic acid by bioassay-directed fractionation and spectral data analysis. The two compounds were shown to significantly inhibit the seed germination, seedling growth, and dry biomass of L. sativum. Based on the concentration required for 50% growth inhibition (defined as IC50), the roots of L. sativum were the most sensitive to the compounds, and the inhibitory effect of ferulic acid (IC50 = 0.62 mM) was >1.3 times more potent than that of vanillic acid (IC50 = 0.82 mM). In addition, a mixture of the two compounds (0.3 mM) resulted in synergistic inhibitory activity against the L. sativum roots compared with the individual compounds. These results suggest that the extracts of S. garrettiana leaves and their phytotoxic compounds have potential as candidate natural herbicides.

Agave Steroidal Saponins as Potential Bioherbicides

Agave saponins are a valuable resource for the prospective development of new forms of agrochemicals. The extraction method was optimized and applied to 17 Agave species. Thirteen saponin fractions (SFs) were assayed on wheat etiolated coleoptiles, and analysed using UPLC-QTOF-MSE, NMR spectroscopy and the HMBC method for aglycone identification (HMAI). Six SFs were assayed on standard target species (STS) and weeds. The new extraction method reduces costs to obtain SFs with the same activity. The tested SFs assayed on etiolated wheat coleoptiles that belong to the subgenus Agave were among those with the highest activity levels. The combination of HMAI together with UPLC-MS allowed the identification of 20 aglycones in the SFs, and no isolation or hydrolysis of the saponins was required. A Principal Component Analysis (PCA) showed that for the active SFs the structural key would be the length of their sugar chain. The presence of a carbonyl group at C-12 implied an enhancement in phytotoxic activity. Six SFs were assayed on seeds, and no activity on Solanum lycopersicum (tomato) was observed; however, good activity profiles were obtained on weed E. crus-galli (IC50 < 80 ppm), better than the commercial herbicide Logran®. These findings represent a possible lead for the development of natural herbicides through the use of saponins of subgenus Agave species.

Potensi Murraya keonigii sebagai Herbisida Alami

Various kinds of agricultural products are needed to support organic farms to produce superior quality products, one of it was natural herbicides. Some plants have the potential to become natural herbicides by producing chemical compounds, namely allelopathy which can inhibit the growth of surrounding plants and Murraya keonigii is one of it. This study aims to see the potential of M. keonigii to become a natural herbicide. Grass seeds were given M keonigii’s extract at a dose of 0 gr / l (control / M0), 50 gr / lt (M1), 60 gr / lt (M2), and 70 gr / lt (M3). The results showed that the aromatic or allelopathic compounds in M ​​keonigii affected the germination. Germination was slower at doses of 60 gr / l (M2) and 70 gr / lt (M3) compared to controls (M0) and 50 gr / lt (M1). Radicle length did not increase rapidly in M2 and M3 treatment. Germination power of grass seeds in control and M0 had a value of 100% or all germinated, while M1 and M2 had 67% germination. The higher the dose of M keonigii extract, the slower the process of grass seed germination.

Bioactive Diterpenes from the Brazilian Native Plant (Moquiniastrum pulchrum) and Their Application in Weed Control

Even today, weeds continue to be a considerable problem for agriculture. The application of synthetic herbicides produces serious environmental consequences, and crops suffer loss of their activity due to the appearance of new resistant weed biotypes. Our aim is to develop new effective natural herbicides that improve the problem of resistance and do not harm the environment. This work is focused on a bioassay-guided isolation and the characterization of natural products present in Moquiniastrum pulchrum leaves with phytotoxic activity and its preliminary application in weeds. Moquiniastrum pulchrum was selected for two reasons: it is an abundant species in the Cerrado region (the second most important ecosystem in Brazil, after the Amazon)—the explanation behind its being a dominant species is a major focus of interest—and it has traditional employment in folk medicine. Six major compounds were isolated in this plant: one flavone and five diterpenes, two of which are described for the first time in the literature. Four of the six compounds exhibited phytotoxic activity in the bioassays performed. The results confirmed the phytotoxic potential of this plant, which had not been investigated until now.

Chemical composition, phytotoxicity and cytogenotoxicity of essential oil from leaves of Psidium guajava L. cultivars

Natural products with biological activity, such as essential oils, can be used in the search for and development of ecological herbicides as an alternative to reduce the damage caused by synthetic herbicides. This work to aimed to determine the chemical composition and phytotoxic properties of the essential oils, at concentrations of 3000, 1500, 750, 375 and 187.5 µg/mL, of four cultivars of Psidium guajava (guava) evaluated on germination and root growth of plant models Lactuca sativa and Sorghum bicolor, as well as in the L. sativa cell cycle. Exposure to essential oils reduced germination and root growth in bioassays, especially at the highest concentration (3000 µg/mL). The essential oils interfered in the normal dynamics of the cell cycle of L. sativa at most concentrations, causing a decrease in the mitotic index and increasing of chromosomal alterations, evidencing aneugenic and clastogenic action. The biological activity of the oils was associated with the presence of sesquiterpenes and monoterpenes found here, such as caryophyllene oxide, (E) -caryophyllene, and limonene. Thus, the essential oils of cultivars of guava demonstrated the promising potential for use as natural herbicides.

Phytotoxic activity of aqueous extracts of ruderal plants and its potential application to tomato crop

Background: The application of synthetic pesticides to the tomato crop (Solanum lycopersicum -Solanaceae-) increases fruit production, but also carries risks for the environment, human and animal health. Hypothesis: local ruderal plant extracts could be an alternative for weed control, with potential applications in agroecology and organic agriculture. Methods: Organic and aqueous extracts (1 and 10% w/v) were prepared with the fresh (FAE) and dry (DAE) aerial parts of five ruderal species from Tlaxcala, Mexico: Argemone mexicana L. (Papaveraceae), Baccharis salicifolia Pers. (Asteraceae), Lepidium virginicum L. (Brassicaceae), Leucena leucocephala S. Zárate (Fabaceae) and Reseda luteola L. (Resedaceae). Their phytotoxic activity was evaluated in vitro with the seeds of three model plants (amaranth, lettuce, and tomato). Results: DAE of B. salicifolia and L. virginicum (1 % w/v) showed the highest potential as natural herbicides. These inhibited 100 % seed germination and radicle elongation in the three model plants but did not affect the growth of tomato seedlings of 8 and 12 weeks in greenhouse conditions. Both extracts analyzed by HPLC-ESI-QTOF-MS showed two major peaks. Bacharis salicifolia with m/z 432.9 and 725.4. Lepidium virginicum with m/z 532.9 and 527.1. Conclusions:DAE of local ruderal plants B. salicifolia and L. virginicum (1 % w/v) are potential natural herbicides, without harmful effects on tomato cultivated seedlings, awaiting the precise identification of their active compounds.

Synthesis and extraction routes of allelochemicals from plants and microbes: A review

Allelopathy, a complex phenomenon has unveiled both stimulatory and inhibitory effects in plant processes that are mediated by the release of certain chemical compounds commonly known as allelochemicals. Allelochemicals, a form of bioactive secondary metabolites are produced by a diverse group of plants and microbes in response to biotic and abiotic stress. It ranges from a simple hydrocarbon to complex polycyclic aromatic compounds like phenol, flavonoids, tannins, steroids, amino acids, alkaloids and quinones. These plant bioactive compounds are released into the environment via decomposition, exudation, leaching and volatilization that play a significant role in regulating the intra-specific or inter-specific relations with counterparts. A wide variety of methods has been proposed for analyzing the basic mechanism and overall effect of allelochemicals. However, the lack of a reliable and effective method to identify their molecular mode of action and their modulation in the metabolic pathway still remains as a great challenge. From a commercial perspective, these allelochemicals are deemed to be better candidates for green natural herbicides and weedicides that are proven to be environment friendly, unlike synthetic chemicals. In order to pave a way for the economic viability of these chemicals, a basic understanding of their chemistry is inevitable. This review article is focused to give an in-depth understanding of metabolic pathways genes responsible for the elicitation/secretion and the adoption of a suitable downstream process and analytical techniques that can intensify the process.

Assessment of allelopathic compounds to develop new natural herbicides : A review

Herbicides are a crucial tool for weed control in crops. However, their continuous and indiscriminate uses have caused environmental pollution and development of weed resistance. Hence, there is an urgent need to minimise the dependence on synthetic herbicides. Allelopathy may be used to develop new bioherbicides to inhibit germination and growth of weeds. There is a great potential to develop eco-friendly herbicides from plants, but little research has been done so far in this context. Identification and quantification of natural weed control compounds (allelochemicals) of plants may help to develop natural herbicides (based on indigenous/invasive weed species), to reduce the dependence on synthetic herbicides and improve the integrated weed management programme in crops. This review describes thepotential allelochemicals present in plants, which may be used as a tool to develop new natural herbicides.