Plant secondary metabolite diversity reflects both phylogeny and ecological adaptation

A phylogenetic framework explaining plant secondary metabolite diversity is lacking, but metabolite classes could represent adaptations to habitat resource availability. We test the hypothesis that primary adaptive strategies (competitors, C; stress-tolerators, S; ruderals, R) are associated, respectively, with nitrogenous metabolites synthesized in persistent organs (alkaloids), nitrogen-lacking aromatic terpenes and phenolics, and nitrogenous compounds prevalent in reproductive tissues (cyanogenic glucosides and glucosinolates). A matrix was compiled of 1019 species for which secondary metabolite pathways and CSR strategies are known. Accounting for phylogenetic relatedness and native biomes, we found that most phytochemical pathways did not correlate with strategy axes, but certain key associations were evident. C-selection was positively associated with amino acid-derived phenylpropanoids (low phylogenetic relatedness; λ<0.5) and pyrrolizidine alkaloids and galloyl derivatives (high λ), and negatively with N-lacking linear monoterpenes (low λ). Nitrogenous cyanogenic glucosides positively correlated with R-selection (low λ). Terpenoids were widely distributed, but correlated positively with S- and negatively with R-selection (low λ). Twenty-six correlations between phytochemicals and biomes (low λ) were evident. Most secondary metabolite synthesis pathways are widespread, reflecting common roles and obligate defence, and strong phylogenetic effects are often evident. However, the character of phytochemical/adaptive strategy associations agrees with ecological theory and thus reflects adaptation.

Plant-Derived Pesticides as an Alternative to Pest Management and Sustainable Agricultural Production: Prospects, Applications and Challenges

Pests and diseases are responsible for most of the losses related to agricultural crops, either in the field or in storage. Moreover, due to indiscriminate use of synthetic pesticides over the years, several issues have come along, such as pest resistance and contamination of important planet sources, such as water, air and soil. Therefore, in order to improve efficiency of crop production and reduce food crisis in a sustainable manner, while preserving consumer’s health, plant-derived pesticides may be a green alternative to synthetic ones. They are cheap, biodegradable, ecofriendly and act by several mechanisms of action in a more specific way, suggesting that they are less of a hazard to humans and the environment. Natural plant products with bioactivity toward insects include several classes of molecules, for example: terpenes, flavonoids, alkaloids, polyphenols, cyanogenic glucosides, quinones, amides, aldehydes, thiophenes, amino acids, saccharides and polyketides (which is not an exhaustive list of insecticidal substances). In general, those compounds have important ecological activities in nature, such as: antifeedant, attractant, nematicide, fungicide, repellent, insecticide, insect growth regulator and allelopathic agents, acting as a promising source for novel pest control agents or biopesticides. However, several factors appear to limit their commercialization. In this critical review, a compilation of plant-derived metabolites, along with their corresponding toxicology and mechanisms of action, will be approached, as well as the different strategies developed in order to meet the required commercial standards through more efficient methods.

Activation and detoxification of cassava cyanogenic glucosides by the whitefly Bemisia tabaci

Two-component plant defenses such as cyanogenic glucosides are produced by many plant species, but phloem-feeding herbivores have long been thought not to activate these defenses due to their mode of feeding, which causes only minimal tissue damage. Here, however, we report that cyanogenic glycoside defenses from cassava (Manihot esculenta), a major staple crop in Africa, are activated during feeding by a pest insect, the whitefly Bemisia tabaci, and the resulting hydrogen cyanide is detoxified by conversion to beta-cyanoalanine. Additionally, B. tabaci was found to utilize two metabolic mechanisms to detoxify cyanogenic glucosides by conversion to non-activatable derivatives. First, the cyanogenic glycoside linamarin was glucosylated 1–4 times in succession in a reaction catalyzed by two B. tabaci glycoside hydrolase family 13 enzymes in vitro utilizing sucrose as a co-substrate. Second, both linamarin and the glucosylated linamarin derivatives were phosphorylated. Both phosphorylation and glucosidation of linamarin render this plant pro-toxin inert to the activating plant enzyme linamarase, and thus these metabolic transformations can be considered pre-emptive detoxification strategies to avoid cyanogenesis.

Chemical Characterization and Acceptability of Eight Cassava Varieties Introduced in Rwanda

Cassava is a staple food and an important and cheap source of carbohydrate in Rwanda. However, the nature and chemical composition of cassava roots limit its proper use as food due to its toxicity and short shelf life. The cyanogenic glucosides found in the cassava roots are responsible for the toxicity. The aim of the study was to characterize the chemical profile and consumer acceptability of paste from eight cassava varieties processed into flour using four processing methods. The cassava samples were harvested from trials conducted at Rubona Station of Rwanda Agriculture and Animal Resources Development Board. Four processing methods were used, namely, Cassava grated fermented, Cassava roots fermented, Cassava grated no fermented and Cassava roots no fermented. Pressing was done before drying the products to obtain the flour. At each stage of processing, the samples were prepared for laboratory analysis of dry mater, titratable acidity, cyanhydric acid and crude fiber by Rwanda Standards Board laboratory. Cassava flour was made into paste and sensory evaluation was conducted to evaluate the acceptability of the eight cassava varieties. The sensory attributes for the Ugali tested was significantly different (P&lt;0.05). The method of grating before fermentation gave the most tasty Ugali than cassava root fermented. The more prefered varieties were GAHENE/2 and SEMAK 150/452 followed by BULK 13, MH95/0091 and NASE 14. The chemical analysis done for the 8 cassava varieties flour from the 4 processing methods exhibited the acceptable acidity and the NASE 14, Gahene/2 and Bulk 13 had the lowest cyanide hydrogen.

Phenotypic plasticity in chemical defence of butterflies allows usage of diverse host plants

Host plant specialization is a major force driving ecological niche partitioning and diversification in insect herbivores. The cyanogenic defences of Passiflora plants keep most herbivores at bay, but not the larvae of Heliconiu s butterflies, which can both sequester and biosynthesize cyanogenic compounds. Here, we demonstrate that both Heliconius cydno chioneus and H. melpomene rosina have remarkable plasticity in their chemical defences. When feeding on Passiflora species with cyanogenic compounds that they can readily sequester, both species downregulate the biosynthesis of these compounds. By contrast, when fed on Passiflora plants that do not contain cyanogenic glucosides that can be sequestered, both species increase biosynthesis. This biochemical plasticity comes at a fitness cost for the more specialist H. m. rosina , as adult size and weight for this species negatively correlate with biosynthesis levels, but not for the more generalist H. c. chioneus . By contrast, H. m rosina has increased performance when sequestration is possible on its specialized host plant. In summary, phenotypic plasticity in biochemical responses to different host plants offers these butterflies the ability to widen their range of potential hosts within the Passiflora genus, while maintaining their chemical defences.

Effect of Sprouting on Chemical, Fatty Acid Composition, Antioxidants and Antinutrients of Flaxseeds

The objective research investigated the effect of flaxseed sprouting on chemical composition, fatty acid composition, antioxidants and flaxseed antinutrients during the four-day sprouting period. For attempts to reduce flaxseed levels of some antinutritional factors, such as cyanogenic glucosides, and improve nutrient palatability and availability, the sprouting technique has been used. After 4 days of sprouting, the dry matter content of the seeds was decreased by 5.54%. Significant decreases in oil content were observed during the sprouting period, but there were increases in protein, fibre, P, Ca, Fe and Zn content. During sprouting, the content of cyanogenic glucosides as antinutrients has decreased, thus increasing the nutritional quality and the economic demand for flaxseed sprouts. Increases were also found in the value of free fatty acids, peroxide and saponification. In addition, unsaponifiable matter has been reduced. Among fatty acids, while linoleic and oleic were increased during the sprouting period, linolenic was decreased. The results revealed that in extracted oils, total phenols and antioxidant activity decreased during and at the end of sprouting, whereas flavonoids, carotenoids and chlorophylls increased.

Phytochemical profile and pharmacological properties of Trifolium repens

Trifolium repens belongs to the family Leguminosae and has been used for therapeutic purposes as traditional medicine. The plant is widely used as fodder and leafy vegetables for human uses. However, there is a lack of a detailed review of its phytochemical profile and pharmacological properties. This review presents a comprehensive overview of the phytochemical profile and biological properties of T. repens. The plant is used as antioxidants and cholinesterase inhibitors and for anti-inflammatory, antiseptic, analgesic, antirheumatic ache, and antimicrobial purposes. This review has summarized the available updated useful information about the different bioactive compounds such as simple phenols, phenolic acids, flavones, flavonols, isoflavones, pterocarpans, cyanogenic glucosides, saponins, and condensed tannins present in T. repens. The pharmacological roles of these secondary metabolites present in T. repens have been presented. It has been revealed that T. repens contain important phytochemicals, which is the potential source of health-beneficial bioactive components for food and nutraceuticals industries.