Luteolin and Chlorogenic Acid: The Science Behind Honeysuckle (Lonicera periclymenum)

Walk past any English hedgerow in June and you will smell it before you see it — that warm, sweet, almost honeyed scent that intensifies as evening comes. Honeysuckle. Lonicera periclymenum. It climbs through hawthorn and blackthorn and elder, reaching for the light, and in doing so produces one of the most biochemically interesting flowers in the British hedgerow. What it offers is not just scent and beauty. It is luteolin and chlorogenic acid — two compounds with a growing body of clinical and mechanistic evidence behind them, covering pathways from inflammation to blood glucose regulation.

This is Wednesday’s bioactive compound deep-dive, and honeysuckle is the subject. We will cover the two primary compounds, how they work, what the research shows, and why the flowers — available right now, for free, in almost every hedgerow in England — are worth paying attention to.

Identification

Lonicera periclymenum — wild honeysuckle, or woodbine — is a woody, deciduous climbing shrub in the Caprifoliaceae family. It climbs clockwise (always clockwise — this is reliable and distinctive) by twining its stems around supporting vegetation or structures. It is found in hedgerows, woodland edges, scrub, and open woodland across England, Wales, Scotland, and Ireland, and is at its peak flowering period right now through June and into July.

The leaves are oval to elliptical, paired opposite each other on the stem, dark green above and paler and slightly glaucous beneath. The uppermost pair of leaves directly below the flower cluster is fused at the base into a single disc shape — this is one of the most reliable identification features and distinguishes L. periclymenum from other honeysuckle species. The flowers emerge in a cluster or whorl from the centre of this fused disc. Each flower is a long, slender trumpet — typically 3–5cm — with a two-lipped opening and five prominent stamens and a single style that extend well beyond the tube. The corolla opens deep pink to purplish-red on the outside, cream to pale yellow within, fading further as the flower ages.

The berries that follow in late summer are bright red, produced in clusters, and are toxic — they must never be eaten. This point deserves emphasis: the flowers are edible and have a long history of culinary and medicinal use; the berries are not, and will cause vomiting and diarrhoea. The flowers can be distinguished from any dangerous plant by their unique structure, scent, and climbing habit — there is no realistic confusion species for L. periclymenum in the British flora.

Luteolin: the anti-inflammatory flavone

Luteolin is a flavone — one of the most studied subclasses of flavonoids — found in meaningful concentrations in honeysuckle flowers alongside chamomile, celery, thyme, and a range of other culinary and medicinal herbs. In honeysuckle it occurs primarily as luteolin-7-O-glucoside, the glycosylated form that survives digestion and is converted to free luteolin in the gut before absorption.

Its primary mechanism of action is the inhibition of NF-κB — nuclear factor kappa-light-chain-enhancer of activated B cells — one of the central transcription factors governing the inflammatory response. When NF-κB is activated (by infection, stress, oxidative damage, or chronic low-grade stimuli), it upregulates a cascade of pro-inflammatory cytokines: IL-1β, IL-6, TNF-α, and others. Luteolin suppresses this activation, effectively dampening the upstream signal before the inflammatory cascade gets going. A 2016 study in Industrial Crops and Products (PMC7127524, Hsu et al.) confirmed that luteolin-7-O-glucoside, alongside chlorogenic acid, is the primary active constituent responsible for the anti-inflammatory activity observed in Lonicera flower extracts, with water extraction (consistent with making a simple flower tea or syrup) producing the highest bioactive concentrations.

Beyond NF-κB suppression, luteolin has a second mechanism that is becoming increasingly relevant to clinical nutritionists: mast cell stabilisation. Mast cells are innate immune cells distributed throughout the body’s barrier tissues — skin, gut lining, respiratory mucosa — and are involved in allergic reactions, histamine release, and chronic inflammatory conditions. A 2019 review in Frontiers in Immunology (PMC6384425, Huang et al.) examined polyphenol effects on mast cell function and found that luteolin inhibited mast cell degranulation and histamine release more effectively than quercetin — the flavonol we associate with dog rose and other hedgerow plants — making it one of the most potent natural mast cell stabilisers identified to date. For anyone dealing with histamine intolerance, allergic conditions, or chronic skin or gut inflammation, this is a compound worth knowing about.

It is worth comparing luteolin to the other flavones we have covered on this site. Apigenin — found in chamomile and ox-eye daisy — shares the NF-κB suppression pathway and also has well-documented GABA-A receptor binding, making it useful for anxiety and sleep. Red clover provides isoflavones that act via oestrogen receptor pathways. Luteolin occupies a distinct niche: it is particularly potent for mast cell and histamine-related inflammation, and for gut barrier protection — two areas where the evidence is considerably stronger than for many more widely promoted supplements.

Chlorogenic acid: blood glucose, metabolism, and beyond

Chlorogenic acid is a phenolic acid — an ester of caffeic acid and quinic acid — that is perhaps best known as a primary bioactive compound in coffee (alongside apigenin-containing herbs and elderflower). In honeysuckle, it is present in the flowers at concentrations comparable to those found in green coffee beans — making the flowers a genuinely meaningful source, particularly given that they can be consumed as a cold or warm infusion that preserves the compound without the roasting degradation that reduces chlorogenic acid content in brewed coffee.

The mechanism relevant to blood glucose regulation is well characterised. Chlorogenic acid inhibits glucose-6-phosphatase — the enzyme responsible for releasing stored glucose from the liver — and also inhibits sodium-dependent glucose transporter 1 (SGLT1) in the intestinal lining, slowing the rate of glucose absorption from food. A comprehensive 2013 review in Nutrients (PMC3766985, Meng et al.) summarised the clinical evidence: chlorogenic acid ingestion significantly reduced early fasting glucose and insulin responses during oral glucose tolerance testing in overweight subjects, and regular consumption was associated with improved insulin sensitivity. The authors noted that the compound’s effects on glucose homeostasis were comparable in direction (though not magnitude) to those of metformin — acting on similar hepatic glucose output pathways.

The metabolic significance of this extends beyond blood sugar. Chronic postprandial glucose spikes drive insulin resistance, visceral fat accumulation, and — as part of the metabolic inflammation picture — systemic low-grade inflammation. Chlorogenic acid, by flattening the glucose absorption curve, reduces these downstream effects. A 2022 study in Nutrients (PMC9714618, Huang et al.) confirmed that chlorogenic acid improved glucose tolerance and insulin resistance in animal models, and described these effects as “similar to those of metformin” — a finding that has generated considerable interest in the functional nutrition research community.

Chlorogenic acid also has antioxidant activity via direct free radical scavenging, and has shown anti-inflammatory effects independent of the glucose pathway — inhibiting iNOS (inducible nitric oxide synthase) and COX-2, the same cyclooxygenase pathway targeted by aspirin and ibuprofen. This positions it alongside luteolin as a genuinely multi-pathway anti-inflammatory compound rather than a single-mechanism supplement.

The synergy between the two compounds is also worth noting. A study specifically on Lonicera extracts found that luteolin and chlorogenic acid have a synergistic antioxidant effect — their combined activity exceeds what would be predicted from either compound alone. This is consistent with the broader evidence base on polyphenol synergy: a diverse plant food matrix tends to produce effects greater than isolated compounds, which is one of the most consistent arguments the foraging and microbiome literature makes for whole-plant dietary diversity over supplementation.

How to use honeysuckle flowers

The flowers are the part used. The berries are toxic and must be avoided entirely. With that clearly stated, the flowers have several straightforward applications:

Honeysuckle flower infusion (cold or warm): The simplest and most bioactively faithful preparation. Cover a handful of fresh flowers with cold water and leave overnight — the resulting liquid carries both the scent and a meaningful proportion of the water-soluble phenolic compounds including chlorogenic acid. Alternatively, steep briefly in warm (not boiling) water. The 2016 study cited above specifically found that water extraction preserved the highest concentrations of chlorogenic acid and luteolin-7-O-glucoside — so a simple tea or cold infusion is, biochemically, the right preparation.

Honeysuckle syrup: Gently warm equal quantities of flowers and water (do not boil), steep for 20 minutes, strain, then dissolve sugar into the still-warm liquid at a ratio of roughly 1:1 with the liquid. The heat will reduce some volatile compounds but preserves most of the phenolics. Use over yoghurt, stirred into sparkling water, or as a base for salad dressings. The syrup will keep refrigerated for two to three weeks.

Honeysuckle-infused honey: Layer fresh flowers into a jar of good raw honey and leave in a warm place for a week. Strain out the flowers. The honey absorbs the aromatic compounds and takes on a floral complexity. Use as you would any flavoured honey — on oat cakes, with cheese, stirred into herbal tea. This is one of the most elegant preparations and requires almost no effort.

Fresh flowers as garnish: Scatter directly over salads, desserts, or drinks. Pull the base of the tube gently and a small drop of nectar appears — this is safe to consume and very sweet. Children find this irresistible, which is also a useful foraging education tool. Just ensure they understand that the red berries that follow are entirely different and must never be touched.

When and where to find it

Honeysuckle is in flower now — peak June in southern England, through July in the north. It is common throughout Britain in hedgerows, woodland edges, and scrub. The best-smelling flowers are in full evening sun — south-facing hedgerows on warm days produce the most volatile compounds — but harvest in the morning before the heat dissipates both scent and bioactive content.

Pick from plants you can clearly identify as Lonicera periclymenum: the fused leaf disc beneath the flower cluster is the key feature. Pick lightly — a few flowers from each plant — and leave plenty for the hawkmoths and bumblebees that depend on this plant as a high-value nectar source. Honeysuckle is listed as a particularly important plant for declining moth populations, and its ecological role matters considerably more than any syrup you might make from it.

References

• PMC7127524 — Hsu HF et al. Antioxidant and anti-inflammatory activities of Lonicera japonica flower bud extracts. Industrial Crops and Products. 2016.
• PMC6384425 — Huang J et al. Impact of polyphenols on mast cells with special emphasis on luteolin and quercetin. Frontiers in Immunology. 2019.
• PMC3766985 — Meng S et al. Roles of chlorogenic acid on regulating glucose and lipids metabolism. Evidence-Based Complementary and Alternative Medicine. 2013.
• PMC9714618 — Huang H et al. Chlorogenic acid improves glucose tolerance, lipid metabolism and insulin resistance. Nutrients. 2022.

Medical disclaimer

This content is for educational purposes only and does not constitute medical advice. Wild plants can be dangerous if misidentified. Never consume any wild plant unless you are completely confident in your identification. Note that honeysuckle berries (Lonicera periclymenum) are toxic and must never be eaten — only the flowers are used. Some wild plants can interact with medications. Always consult your GP before using wild plants medicinally, particularly if you are pregnant, breastfeeding, or taking medication.