Monday, 5 August 2019

July phytochemicals - chemotheraputics from plants and more

Camptothecin - an alkaloid discovered during a natural products anticancer activity screen - is a topoisomerase inhibitor originally isolated from Camptotheca acuminata, a plant in traditional Chinese medicine. Structural analogs are current chemotheraputics!

This week: quassin, a (degraded) triterpenoid found in Quassia amara that is apparently one of the most bitter compounds in the world - as many as 50 times more bitter than quinine! It and its structural relatives exhibit a variety of biological activites.

Podophyllotoxin - a lignan derivative from above ground roots of mayapple. It can be converted into etoposide, a chemotheraputic on the WHO's list of essential medicines.

Today: (iso)masticadienonic acids - two compounds in mastic, a resin from the tree Pistacia lentiscus. These compounds may contribute to the resin's many reported bioactivites, for which it is featured on today's @nytimes front page.

Tuesday, 2 July 2019

June phytochemicals: the start of Project #ChemicalBlooms!

Did you know that capsaicin is not the only spicy molecule in peppers (Capsicum)? Several structural variants can also accumulate to substantial levels: dihydrocapsaicin is about as spicy as capsaicin itself; nordihydrocapsaicin, about half as spicy.

Aristolochic acid, a biosynthetic relative of morphine: found in the birthwort family Aristolochiaceae, it toxifies some butterflies that grow up on such plants. Birthworts are used in traditional medicine, but the acid is linked to kidney issues and cancer.

CALLING ALL BIOPROSPECTORS! Seen white coatings on plants? Each is unique, on Dudleya brittonii, it's mainly amyrins - bioactive & protective compounds. Help advance our understanding of these coatings: join Project #ChemicalBlooms: Please send pics of chemical blooms on twitter (@PlantsRChemists), instagram (@chemical_blooms), or email for a bioprospecting kit - sample the blooms yourself and send them in for analysis using the included stamped envelope. Best #FirstDayofSummer ever!

Reserpine, used in combo with other compounds to treat high blood pressure. Structurally, a combo of aromatic amino acid and terpenoid pathway products. Found in Rauvolfia serpentina (indian snakeroot; milkweed family) occurring in combo with other alkaloids.

Thursday, 20 June 2019

May phytochemicals - spring scents and conifer essential oils

Is it #SpringTime where you live? If lawn mowing has begun, think cis-3-Hexenal. A primary contributor to the smell of freshly cut grass, this small aldehyde is enzymatically derived from the tail end of linoleic acid. Thanks @chdiep for the #PhytochemicalFriday suggestion!

Recent discovery! A gene from Leucosceptrum canum (mint family) underlying the synthesis of the tricyclic sesquiterpene cedrol, an important aroma compound found in conifer essential oils and some mints = potential for a synthetic biology-based cedrol supply.

Kainic and domoic acids: compounds from some Ceramiales (red algae) that accumulate in shellfish & sardines. As neuronal stimulants, these acids can affect marine predators (inspiring scenes in Hitchcock's "The Birds"?) & are used in neurological research.

Hyperforin, a compound from the genus Hypericum (which includes the medicinal herb St. John's Wort) that scientists suspect is involved in the plant's various reported pharmacological effects. Seems derived from prenylation of phloroglucinol.

Pinoresinol, a lignan made of two monomers by oxidase enzymes. Cooccurring dirigent proteins (first discovered during study of Forsythia intermedia lignans) are not catalytically active themselves, but control a coupling reaction's stereochemical outcome.

Thursday, 16 May 2019

April Phytochemicals - complex and psychedelic structures

Taxol - found by a @USDA botanist screening plants for new cancer drugs - enhances microtubule stability, interfering with cell division. Originally isolated from the bark of Taxus brevifolia, then chemically synthesized, now grown in cell culture.

Another complex structure: moroidin - a bicyclic peptide with unusual leu-trp and trp-his links (in yellow). Found in Dendrocnide moroides (Urticaceae), it's a tubulin polymerization inhibitor that gives the plant's silica-tipped hairs a sting!

Two harmala alkaloids - harmine and harmaline - from (among others) Banisteriopsis caapi, aka ayahuasca (Malpighiales). These fluorescent beta-carbolines are monoamine oxidase inhibitors - an activity that promotes the psychoactive effects of DMT.

Thinking about garden layout? Don't forget companion Chrysanthemums. Several species produce pyrethrins - a group of biodegradable, insecticidal (terpenoid!) compounds. These alternatives to synthetic pyrethroids (permethrin) can reduce aquatic poisonings.

Wednesday, 6 March 2019

March Phytochemicals - toxins and medicines

"Locoweeds" (some Astralagus and Oxytropis spp. - Fabaceae) produce the indolizidine alkaloid swainsonine, a compound causing neurological disorders in cattle. The compound inhibits glycoside hydrolases and is being investigated as a potential chemotheraputic.

The classic alkaloid morphine: used since ~400AD, and believed to be the first active ingredient isolated from a plant, Papaver somniferum (+ other Papaverales, mammals). The latex of some P. somniferum varieties contain ~25% morphine (or ~0%!).

Inspired by @LegumeFed: daidzein. Apparently exclusive to legumes, including Trifolium spp. (the clovers that inspired St. Patrick's analogy between the shamrock and the holy trinity), these compounds are believed to protect against pathogens.

Pilocarpine - an imidazole alkaloid from tropical Pilocarpus spp. ("jaborandi", Rutaceae). This compound is on the WHO's List of Essential Medicines as a treatment for glaucoma, among other things. Genetic basis of biosynthesis still unknown!

Arbutin, a simple glycosylated hydroquinone from Arctostaphylos dwarf shrubs in the Ericaceae (tho found in other plants) that inhibits tyrosinase - the rate-limiting enzyme in melanin biosynthesis and toxic to insects.

Friday, 1 February 2019

February Phytochemicals - malic acid and more!

Malic acid: gets its name from common apple (Malus domestica), the plant from which the acid was first isolated in the 1700s. Though an important acid in many fruits, it is also central to #CAM (an arid climate photosynthesis variant) as a CO2 storage unit. .

Inspired by @GoogleDoodlesaromatic heterocycles discovered by Friedlieb F. Runge, including quinoline (the core of the plant molecule quinine), pyrrole (a structure found in chlorophyll), and caffeine (evolved independently in tea, coffee, and cacao).

This week’s idea from @mishaploid: a prenylated furanocoumarin bergamottin found in some citrus spp. (grapefruit, pomelo, bergamot organge) that irreversibly inhibits drug-metabolizing P450 enzymes and can lead to accidental drug overdoses. Watch out!

Phorbol esters: acylated diterpenoids found in Euphorbiaceae (for example, Croton and Jatropha spp.). These poisonous compounds promote the growth of cancerous tumors and are used in biomedical studies of tumor formation and proliferation.

Thursday, 3 January 2019

December phytochemicals - poison tipped arrows and holiday highlights

Glaziovianin: a flavonoid compound from Ateleia glazioviana that belongs to a family of tubulin polymerization inhibitors. By inhibiting microtubule assembly, these compounds interfere with cell division = potential chemotheraputics.

Ouabain:The poison-tipped arrow: brought to you by biochemical pathways in the Apocyanace! Species in this lineage such as Acokanthera schimperi twist and modify squalene into this potent cardiac glycoside. In small doses it can treat low blood pressure, but when delivered by arrow, inhibits the sodium-potassium ion pump and can cause cardiac arrest.

Pinenes: Happy holidays! If you enjoy the smell of a Christmas tree this season (mainly Pinaceae and Cupressaceae spp.), you are likely smelling a mixture of compounds that contains pinenes. Isolated, these monoterpenes smell a bit like turpentine and repel insects.

Ethyl lactate: Impress friends on #NYE2018: tout ethyl lactate, a volatile ester (union of an alcohol - ethanol, and acid - lactic acid) that contributes a buttery, creamy aroma to champagne. Also a green solvent that can be used to clean and degrease your post-party pans.