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Dr Winnie Shiu

@the.creative.chemist

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🇬🇧Phytochemist •Pharmacist •PhD phytochem UCL
🌿Medicinal plant chemistry learning resources
🌟SciComm •Making everyday science accessible
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Dandelion (Taraxacum officinale) is a herbaceous perennial in the daisy family (Asteraceae). Its name comes from the French dent de lion (lion’s tooth), referring to the serrated leaf edges. It has a deep, resilient taproot and produces bright yellow flowers which develop into silvery, wind-dispersed seeds. A single plant can produce over 5,000 seeds per year, which can travel up to 5 miles on their tiny, parachute-like pappus. Although often regarded as a weed, the leaves, flowers and roots can be used in herbal medicine or as food. 🌿 Bioactive phytochemicals Dandelion is rich in bioactive phytochemicals, including sesquiterpene lactones (taraxacin, taraxinic acid β-D-glucopyranoside), triterpenoids (taraxasterol, β-sitosterol, stigmasterol), flavonoids (quercetin, luteolin, apigenin), phenolic acids (chicoric, caffeic, chlorogenic acids) and polysaccharides (inulin). These compounds contribute to various health benefits of dandelion herb and extracts. 🌿 Therapeutic applications Dandelion has been used as traditional medicine to support detoxification and improve liver function. Sesquiterpene lactones contribute to its bitter taste and diuretic effect, promoting urination to reduce fluid retention and high blood pressure. It is rich in vitamins and minerals, especially potassium, which facilitates water excretion while maintaining electrolyte balance. Dandelion root is high in inulin, a dietary fibre that supports gut health. The bioactive compounds have also been shown to demonstrate antioxidant, anti-inflammatory, anti-cancer and anti-diabetic properties. 📖 Further reading: The phytochemical and pharmacological profile of dandelion. Yan et al., Biomedicine & Pharmacotherapy, 2024, https://doi.org/10.1016/j.biopha.2024.117334 Dandelion science chemistry | garden plant | phytochemistry natural product science communication| pharmacognosy | medicinal plant infographics | sci comm | everyday science | stem home education | GSCE A Level BSc MSc chemistry pharmacy | Dr Winnie Shiu | the creative chemist #dandelion #science #chemistry #phytochemistry #scicomm by @the.creative.chemist
Molecule Monday. The chemistry of autumn leaves colour: carotenoids - pigments responsible for yellow and orange colours in autumn leaves. 🍁 Chemistry of carotenoids Carotenoids are a group of naturally occurring pigments that include lutein (a xanthophyll), and beta-carotene which are responsible for yellow and orange colours respectively. Lutein and β-carotene are tetraterpenoids each with 40 carbon atoms, featuring extended conjugated polyene chains with alternating single and double carbon-carbon bonds. These conjugated systems absorb light primarily in the blue and blue-green regions of the visible spectrum (approximately 400–500 nm). Yellow, orange and some red wavelengths are absorbed less strongly and are therefore reflected or transmitted, giving carotenoids their characteristic yellow and colours. 🍁 Why does the colour of leaves change Carotenoids are present in leaves but are masked by the dominant green colour from chlorophyll. In autumn, shorter days and cooler temperatures trigger chlorophyll breakdown, revealing the yellow and orange carotenoids. It is important to note that red and purple hues primarily result from anthocyanins, which are newly produced in late summer and fall, rather than carotenoids. Carotenoids lutein beta-carotene | autumn leaves colour science chemistry| phytochemistry natural product science communication| pharmacognosy pharmacy health | medicinal plant infographics | sci comm | everyday science | molecule monday | Dr Winnie Shiu | the creative chemist #carotene #autumn #science #chemistry #scicomm by @the.creative.chemist
Did you know that saffron is the most expensive spice in the world? Its high cost is not due to the difficulty in cultivation, but due to the labour-intensive harvesting process: saffron must be harvested entirely by hand. Saffron yields are extremetly low: about 150-200 flowers are needed to produce just one gram of dried saffron threads! Saffron comes from the dried stigmas of the Crocus sativus flower. It adds a vibrant golden colour, delicate flavour and aroma to dishes such as paella. Let’s explore the chemistry of saffron (Crocus sativus) 🌱 Phytochemicals in saffron Carotenoids (e.g. crocin and crocetin) are responsible for the bright yellow-orange colour of saffron. The multiple hydroxyl groups (-OH) in crocin contributes to its solubility in water and antioxidant activity. Anthocyanins (e.g. delphinidin and petunidin derivatives) give the purple colour of the petals. The monoterpene glycoside, picrocrocin, is responsible for the taste. Safranal, a monoterpenoid aldehyde, is the primary volatile compound contributing to the distinct aroma. 🌱 Biological activites of saffron Saffron demonstrates potent antioxidant, anti-inflammatory, neuroprotective and anti-depressant activities, driven by the compounds described above. These compounds help support mental health, cognitive function and cardiovascular health. 🌱 Saffron is a true autumn-flowering crocus. However, autumn crocus can also refer to Colchicum autumnale, a different medicinal plant from which the toxic alkaloid colchicine (used to prevent and treat gout) is derived. Saffron Crocus sativus chemistry | garden plant | phytochemistry natural product plant science communication| pharmacognosy | everyday science infographics | sci comm | stem education | Dr Winnie Shiu | the creative chemist #crocus #science #chemistry #scicomm #phytochemistry by @the.creative.chemist
Chamomile has been recognized as a medicinal plant for thousands of years. German chamomile (Matricaria chamomilla) is the variety commonly used for herbal tea due to its sweet, fruity flavour. Roman chamomile (Chamaemelum nobile) can also be used for tea, but it has a stronger aroma and is more bitter. Both species belong to the daisy family (Asteraceae). 🌿Bioactive phytochemicals Bioactive compounds in chamomile (both M. chamomilla and C. nobile) are concentrated in the flower heads. Key compounds include flavonoids (e.g. apigenin, luteolin, quercetin, caffeic acid), sesquiterpenoids (e.g. chamazulene, α-bisabolol and its oxides). These compounds contribute to the anti-inflammatory, antioxidant, antispasmodic and sedative properties. 🌿Therapeutic applications Chamomile is commonly consumed as a tea infusion and is used to treat gastrointestinal disorders, including cramps and spasms. It acts as a mild sedative and helps improve sleep quality: the compound apigenin binds to benzodiazepine receptors in the brain and produces a calming effect. Chamomile can also be applied topically to manage inflammatory skin conditions. Studies showed that chamomile may be approximately 60% as effective as 0.25-0.5% hydrocortisone cream in the treatment of eczema. Chamomile science chemistry | phytochemistry natural product | medicinal plant science communication| pharmacognosy | gardening | everyday science infographics | sci comm | stem education | Dr Winnie Shiu | the creative chemist #chamomile #science #chemistry #scicomm #phytochemistry by @the.creative.chemist
Molecule Monday: this week’s molecule is resveratrol: key antioxidant compound in the skin of red and purple grapes 🌿 Chemistry Resveratrol is a naturally occurring polyphenolic compound concentrated in the skin of grapes (particularly red and purple varieties), berries, peanuts and Japanese knotweed (Reynoutria japonica). It is a phytoalexin (plant defense compound) produced by plants to protect against fungal infections, UV radiation and environmental stress. Japanese knotweed contains the highest concentration of resveratrol among all plants. It is an important commercial source, as its roots and rhizomes contain high concentrations of resveratrol for extraction. Chemically, resveratrol is a stilbene (3,5,4′-trihydroxystilbene) comprising two aromatic rings connected by an ethylene bridge, with three substituted hydroxyl groups. Trans-resveratrol is the predominant natural isomer and is more stable than the cis isomer. 🌿 Biological activities Resveratrol exhibits diverse biological activities, including antioxidant, anti-inflammatory, antimicrobial, cardioprotective and potential anticancer effects. It modulates oxidative stress, inflammatory pathways and cellular signalling mechanisms. Grapes wine resveratrol Japanese knotweed science chemistry| phytochemistry natural product science communication| pharmacognosy pharmacy health | medicinal plant infographics | sci comm | everyday science | molecule monday | Dr Winnie Shiu | the creative chemist #resveratrol #science #health #chemistry #scicomm by @the.creative.chemist
Lemon balm (Melissa officinalis) is an aromatic, perennial herb in the mint family (Lamiaceae). Also known as melissa, it is characterized by its lemony fragrance. The genus name Melissa derives from the Greek word for “honeybee”, reflecting the plant’s ability to attract pollinators due to its high nectar content. Its leaves are traditionally valued for its calming and therapeutic properties. Native to parts of Europe and the Mediterranean region, it is now widely cultivated for use in herbal medicine, aromatherapy, perfumes, foods and teas 🌿 Bioactive phytochemicals Bioactive phytochemicals in the volatile essential oil of lemon balm include monoterpene aldehydes (citronellal, geranial, neral) and sesquiterpenes (β-caryophyllene). Triterpenes (ursolic acid, oleanolic acid), flavonoids (quercetin, apigenin, kaempferol) and phenolic compounds (caffeic and chlorogenic acids) are also present in the herb. The key bioactive compound is the phenolic rosmarinic acid, which serves as the main biomarker for plant standardization for medicinal use. 🌿 Therapeutic applications Rosmarinic acid is the key compound responsible for the herb’s calming and stress-relieving effects. It acts as an inhibitor of the enzyme gamma-aminobutyric acid (GABA) transaminase, which breaks down GABA in the brain. The herb also demonstrates potent antioxidant, anti-inflammatory and antimicrobial activities. Topical lemon balm extract has been shown to have antiviral activity against Herpes simplex virus type 1 (HSV-1). Lemon balm Melissa officinalis science chemistry | phytochemistry natural product science communication| pharmacognosy pharmacy | medicinal plant herb infographics | sci comm | everyday science | stem home education | aromatherapy | GSCE A Level BSc MSc MPharm | Dr Winnie Shiu | the creative chemist #lemonbalm #science #chemistry #phytochemistry #scicomm by @the.creative.chemist
Echinacea, also known as the purple coneflower, is a member of the Asteraceae (daisy) family. Echinacea species are widely distributed in North America and have a long tradition of use, both by the Indigenous peoples and the settlers, who developed the first commercial preparations in the 19th century. Three species, E. purpurea, E. pallida, and E. angustifolia, are used as immunostimulants to treat and prevent colds and other respiratory infections. Bioactive phytochemicals Key bioactive phytochemicals of the three medicinal Echinacea species include caffeic acid derivatives (e.g. chlorogenic acid, cichoric acid, echinacoside), alkylamides, and polysaccharides. These compounds, which vary by species and plant parts, are responsible for the immunostimulatory, anti-inflammatory, and antioxidant properties. Alkylamides are lipophilic compounds which exhibit significant immunomodulatory activity. Therapeutic applications Echinacea preparations are used to relieve the symptoms of the common cold and influenza-type infections. They appear to be effective both therapeutically (reducing symptoms and duration) and preventatively. It has been suggested that the alkylamides bind to the cannabinoid-2 (CB2) receptor to exert anti-inflammatory and immunostimulatory effects. However, Echinacea preparations tested in clinical trials differ considerably due to standardisation issues, such as species and parts of plant used and the method of production. Echinacea purpurea science chemistry | garden medicinal plant | phytochemistry natural product plant science communication| pharmacognosy phytotherapy | everyday science infographics | sci comm | stem education | Dr Winnie Shiu | the creative chemist #echinacea #science #chemistry #scicomm #phytochemistry by @the.creative.chemist
Molecule Monday: this week’s molecule is thymol - the main phytochemical in thyme essential oil 🌿 Chemistry Thymol is a naturally occurring phenolic monoterpene commonly found in plants belonging to the mint family (Lamiaceae), especially in the genus Thymus. It was first isolated from common thyme (Thymus vulgaris) by German chemist Caspar Neumann in 1719. Thymol typically makes up approximately 10-64% of the volatile essential oil extracted from common thyme. It is biosynthesized through the terpenoid pathway in the plant and contributes to the characteristic aroma and biological activity of many medicinal herbs. Chemically, thymol is a phenol substituted with a methyl group and an isopropyl group. It is a colourless to white crystalline solid at room temperature and is slightly soluble in water. 🌿 Biological activities Thymol exhibits diverse biological activities, including antimicrobial, antifungal, antioxidant and anti-inflammatory properties. It is widely used in dental hygiene products (e.g. Listerine mouthwash) to reduce plaque and freshen breath. For essential oil therapy, always mix the essential oil with a carrier oil to prevent skin irritation and never apply undiluted oil directly to the skin. Thyme thymol science chemistry| phytochemistry natural product science communication| pharmacognosy pharmacy health | essential oil | medicinal plant infographics | sci comm | everyday science | molecule monday | Dr Winnie Shiu | the creative chemist #thyme #thymol #science #health #scicomm by @the.creative.chemist
Lavender (genus Lavandula) is an aromatic, evergreen herb in the mint family (Lamiaceae), native to the Mediterranean. Its name originates from the Latin lavare, meaning "to wash", as the Romans used its fragrant essential oil for bathing and medicinal purposes. Of the 47 known species, English lavender (L. angustifolia) is the most common and widely cultivated species, valued for its sweet scent, hardiness and high quality oil used in perfumes, aromatherapy and cooking. 🌿 Phytochemicals in lavender essential oil Linalool and linalyl acetate are the main phytochemicals in lavender essential oil, which is extracted through steam distillation of fresh or dried lavender. These compounds are produced in the flowers, leaves and stems, especially the flowering tops where tiny oil glands are present. Linalool is a terpene alcohol contributing to the signature floral scent of lavender. It acts on the nervous system, causing relaxation and sedation. The acetyl ester of linalool, linalyl acetate, gives a sweet, fruity scent and overall mildness of the oil. Both compounds are volatile - they evaporate readily at room temperature, so the scent can be detected by our sense of smell. Other bioactive compounds include terpenoids such as camphor, 1,8-cineole, limonene and terpinen-4-ol. 🌿 Biological activities of lavender Not only lavender offers relaxing and sedating effects, it is also an anti-inflammatory and antioxidant. Its antimicrobial activity is potent and broad spectrum, effective against Gram-positive bacteria S. aureus, Gram-negative bacteria E. coli and fungus C. albicans. Common herbal preparations include tea infusion, tincture and infused oil. 📖 Further reading: Lavender: phytochemistry, pharmacology, cross-disciplinary applications, and clinical efficacy. Jiang et al., Phytomedicine, 2025. https://doi.org/10.1016/j.phymed.2025.157274 Lavender science chemistry | garden plant | phytochemistry natural product science communication| pharmacognosy | medicinal plant infographics | sci comm | everyday science | stem home education | aromatherapy essential oil | Dr Winnie Shiu | the creative chemist #lavender #science #chemistry #phytochemistry #scicomm by @the.creative.chemist
Molecule Monday: this week’s molecule is capsaicin - the compound that gives chilli peppers their signature heat 🌶️ Chemistry Capsaicin is the principal pungent compound mainly found in the fruits of chilli (genus Capsicum), such as C. annuum and C. frutescens. Chemically, it is a capsaicinoid biosynthesised through the phenylpropanoid and fatty-acid pathways in plants. Its chemical structure consists of a vanillyl aromatic ring with a methoxy group, a hydroxyl group, an amide bond and a long unsaturated hydrocarbon chain. Capsaicin is lipophilic: it is insoluble in water but soluble in fatty oils. It is heat-stable at temperatures below 190 °C, so cooking methods like boiling, steaming and simmering generally result in limited degradation. However, cooking can disrupt chilli’s plant cell walls, releasing capsaicin into the surrounding liquids and altering the perceived pungency. 🌶️ Biological activities Capsaicin produces a burning sensation by activating TRPV1 receptors in mucous membranes. It demonstrates antioxidant, antimicrobial, anti-inflammatory and analgesic properties and is widely used in pharmaceutical and food applications. Topically, it is used in creams (e.g. Deep Heat and Zacin) to relieve muscle pain, neuropathic pain and osteoarthritic pain. Chilli pepper capsaicin science chemistry| phytochemistry natural product science communication| pharmacognosy pharmacy health | essential oil | medicinal plant infographics | sci comm | everyday science | molecule monday | Dr Winnie Shiu | the creative chemist #chilli #capsaicin #science #health #scicomm by @the.creative.chemist
Matcha (Camellia sinensis) Did you know: In Japan, samurai warriors historically drank matcha to increase their physical stamina and stay alert yet calm before battle. Matcha is the only tea in the world that you consume the whole tea leaves. Normally, tea is consumed as an infusion of tea leaves. For matcha, the powdered tea leaves are mixed with water and then served. Technically, matcha tea is a suspension, not a solution. 🍵 Chemistry of matcha Matcha contains phytochemicals such as caffeine, L-theanine, chlorophyll, catechins and phenolic acids. While caffeine contributes to alertness, L-theanine is an amino acid that provides calm focus. The result of this combination is a smooth and sustained energy, without the typical coffee jitters or energy crash. 🍵 Health benefits of matcha Matcha contains a high concentration of beneficial phytochemicals as whole tea leaves are consumed. It is rich in antioxidants and is anti-inflammatory, providing protective effects on the heart, gut and liver. It boosts brain health, function and alertness. Its calming effect may have a stress-relieving effect. Matcha science chemistry | Camellia sinensis | phytochemistry natural product science communication| pharmacognosy | medicinal plant infographics | sci comm | everyday science | stem home education | Dr Winnie Shiu | the creative chemist #matcha #science #chemistry #phytochemistry #scicomm by @the.creative.chemist
Molecule Monday: this week’s molecule is rosmarinic acid - the main bioactive ingredient of rosemary and lemon balm 🌿 Chemistry Rosmarinic acid is a naturally occurring polyphenolic compound widely distributed in medicinal and aromatic plants of the mint (Lamiaceae) family, including mint, basil, sage, and oregano. It is the main bioactive compound found in rosemary (Salvia rosmarinus) and lemon balm (Melissa officinalis). The compound was first isolated and characterised in 1958 by Italian chemists Scarpati and Oriente from rosemary, after which the acid was named. Chemically, rosmarinic acid is a hydroxycinnamic acid derivative consisting of two aromatic rings, each containing a catechol group (two adjacent hydroxyl groups in a benzene ring), linked by an ester bond. Rosmarinic acid is a white to light-beige solid with a melting point of approximately 171–175 °C. 🌿Biological activities Rosmarinic acid is a potent antioxidant and anti-inflammatory compound which modulates oxidative stress and inflammatory signalling pathways. It is antimicrobial and antiviral, and displays virostatic activity against virus like HSV-1. It also demonstrates neuroprotective potential against neuroinflammation and cognitive impairment. Rosemary lemon balm rosmarinic acid science chemistry| phytochemistry natural product science communication| pharmacognosy pharmacy health | essential oil | medicinal plant infographics | sci comm | everyday science | stem home education | molecule monday | Dr Winnie Shiu | the creative chemist #rosemary #lemonbalm #science #health #scicomm by @the.creative.chemist

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