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secondary metabolites Archives - The Global Plant Council

Image: Yew tree with fruits. Paclitaxel and its precursors are produced in the needles and bark of various trees in the Taxus genus. Credit: Alexa / Pixabay

Biosynthesis of paclitaxel unravelled

By | News, Plant Science

Part of modern cancer therapy is the use of chemicals that kill the tumor. Unfortunately, these chemicals are often very complex, difficult to obtain and thus expensive. Researchers have unravelled the biosynthetic pathway of paclitaxel in Yew plants. This discovery might facilitate the production of this very complex molecule which is currently produced with great efforts and high costs.

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Arabidopsis_thaliana_root_growth_in_vitro Credit: Alena Kravchenko / Wikimedia

Plants recruit distinct chemical activities of coumarins under different soil pHs

By | News, Plant Science

Iron is an essential micronutrient for plants and is generally found in large quantities in the Earth’s crust. However, its availability to plants is highly dependent on the pH value of the soil. When suffering from iron deficiency, certain plant species release coumarins. Which type of these small secondary metabolites is mainly released depends on the pH value of the soil. Now, a research team has shown how different coumarins are used to maximize iron uptake under acidic and alkaline conditions.

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Treatment of COVID-19 pandemic with indigenous knowledge of medicinal plants: A Folklore

By | Blog, ECRi, Post

Two years ago, in 2020, the entire world was engulfed in the COVID19 pandemic, which is caused by the severe acute respiratory syndrome coronavirus SARSCoV2. As everyone knows by now, the most common symptoms of this disease are fever, dry cough, fatigue, and headache, and can turn into a progressive and severe pneumonia. However, evidence suggests that COVID-19 patients may also develop a variety of neurological complications. Thousands of people died each day because there was no known treatment. The search for treatments and vaccines for this novel coronavirus disease was on.

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Terpen-tales: The mystery behind the unique fragrance of the lovely lavender

By | Agriculture, News, Plant Science

Even the mention of lavender evokes the distinct fragrance of the flower. This beautiful flower has been used to make perfumes and essential oils since time immemorial. The aesthetics of the flower have captured the imagination of hundreds, worldwide. So, what makes this flower so special? What are the “magical” compounds that gives it its unique fragrance? What is the genetic basis of these compounds? These questions have long puzzled scientists.

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Scientists Discover Plants’ Roadblock to Specialty Oil Production

By | News, Plant Science

Hundreds of naturally occurring specialty fatty acids (building blocks of oils) have potential for use as raw materials for making lubricants, plastics, pharmaceuticals, and more—if they could be produced at large scale by crop plants. But attempts to put genes for making these specialty building blocks into crops have had the opposite effect: Seeds from plants with genes added to make specialty fatty acids accumulated dramatically less oil. No one knew why.

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A new analytic method for identifying bioactive compounds in complex plant extracts

By | ASPS, News, Plant Science, Research

A group of scientists from Sechenov University, Russia, and La Trobe University, Australia, have developed a fast and cost-effective method of detecting and identifying bioactive compounds in complex samples such as plant extracts. They successfully applied the method to examine Mediterranean and Australian native culinary herbs. Three articles on this work were published in Applied SciencesJournal of Pharmaceutical and Biomedical Analysis and Journal of Chromatography A.

Since ancient times, people have been using herbs as food additives and medicines, though a search for useful compounds and a study of their properties remain a difficult task. It is possible to examine a compound if it is stable enough and can be separated from other substances in a sample. However, plant extracts contain hundreds of compounds. In the past, only known compounds were investigated by target analysis and most bioactive compounds were left undiscovered. Thus, the number of compounds that are yet to be explored is so huge that methods that can both screen mixtures and identify the compounds responsible for bioactivity are of greater value.

The authors of the papers used an Effect Directed Analysis (EDA) approach, which is a combination of chromatographic separation with in situ (bio)assays and physico-chemical characterisation to discover and identify bioactive compounds in complex plant samples. Thin-layer chromatography (TLC) and high performance thin-layer chromatography (HPTLC) are well established, chromatographic separation techniques ideally suited for high-throughput screening of bioactive compounds in crude samples. 

To separate substances, TLC uses the fact that various compounds are transported by a solvent and absorbed by a sorbent at different speeds. A sorbent-coated plate with a studied mixture is immersed with one end in the solvent, and under the action of capillary forces, it begins to rise along the plate, taking the substances of the mixture with it. As they move upward, the compounds are absorbed by the sorbent and remain as horizontal bands that can be distinguished in visible, infrared or ultraviolet light. Using this method, crude extracts can be analysed directly with no preparation and possible loss of sample components. 

Bioassays allow to determine the properties of compounds, such as toxicity, observing how model organisms (bacteria, plants or small animals) react to them. In this way, one can select extracts able to inhibit the action of individual enzymes or reactive oxygen species.

Combination of TLC chromatography with microbial (bacteria and yeast) tests and biochemical (enzyme) bioassays enables rapid and reliable characterization of bioactive compounds directly on the chromatographic plates, without isolation/extraction. The advantage of HPTLC is that plates/chromatograms can be directly immersed into enzyme solution (bioassays), incubated for up to several hours, followed by visualization of the (bio)activity profile via an enzyme substrate reaction as bioactivity zones. This approach is more cost effective, enabling a more streamlined method to detect and characterise natural products that are suitable candidates for further investigation as potential new drug molecules.

Using this method, scientists examined the properties of bioactive compounds from culinary herbs commonly used in the Mediterranean diet: basil, lavender, rosemary, oregano, sage and thyme. Australia’s native plants were added to the list: lemon myrtle (Backhousia citriodora), native thyme (Prostanthera incisa), sea parsley (Apium prostratum), seablite (Suaeda australis) and saltbush (Atriplex cinerea). Some of the secondary metabolites from these plants exhibit significant antioxidant activity and enzyme inhibition, like α-amylase inhibition. Therefore, these herbs may be preventive not only against cardiovascular diseases but also type 2 diabetes. The enzyme α-amylase breaks down polysaccharides, thereby increasing blood sugar levels. Recent studies suggest that hyperglycemia induces generation of reactive oxygen species, alteration of endogenous antioxidants and oxidative stress. It was found that patients with uncontrolled sugar levels in addition to diabetes also suffer from accelerated cognitive decline independent of their age. Although Australian native herbs are used as a substitute for related European plants, their medicinal properties are much less studied.

After preparing the extracts, the scientists began to study their composition and qualities. Rosemary and oregano extracts showed the greatest antioxidant activity, while sage, oregano and thyme were the best at slowing down reactions involving α-amylase (extracts from lavender flowers and leaves were the only ones not to show this effect). Among the studied Australian native herbs, lemon myrtle showed the strongest antioxidant properties, with the best α-amylase inhibition observed with extracts of native thyme (this property was noticed for the first time), sea parsley and saltbush.

The study of plant extracts using bioassay and thin-layer chromatography allows scientists to examine a variety of compounds, find mixtures that have the desired properties and isolate substances that exhibit them to the greatest extent. This fast and cost-effective method will be useful for finding new drug compounds.

Read the papers: Applied SciencesJournal of Pharmaceutical and Biomedical Analysis and Journal of Chromatography A.

Article source: Sechenov University via Eurekalert

Image credit: Melburnian / Wikimedia