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Honeysuckle (Lonicera japonica Thunb.): A Comprehensive Reference

1. Identity and Botanical Classification

Botanical and Chemical Names

Lonicera japonica Thunb. (family Caprifoliaceae), commonly known in English as Japanese honeysuckle, bears the Chinese names Jin Yin Hua (金銀花, literally "gold-silver flower") and Ren Dong (忍冬, "winter-enduring vine"). In official Chinese pharmaceutical nomenclature, the dried flower bud or newly opened flower is designated Lonicerae Japonicae Flos (LJF), while the dried stem is designated Lonicerae Japonicae Caulis.

Natural Source and Botanical Description

Lonicera japonica is a perennial deciduous shrub native to East Asia and has spread throughout Argentina, Brazil, Mexico, Australia, New Zealand, and the Americas. Lonicera japonica is a twining vine able to climb up to 10 m (33 ft) high or more in trees. There are around 98 species of the genus Lonicera distributed in various provinces, and the southwest of China has the most species. Lonicera japonica is the most commonly used and studied plant of the genus Lonicera and has captured considerable attention in recent years as a health functional food.

The plant is a popular Chinese herbal medicine used for the treatment of inflammatory diseases and as a well-known dietary supplement; the medicinal part is the dried flower buds or flowers before blooming. Apart from the flower buds, the other parts of L. japonica — including roots, stem barks, leaves, fruits, and whole plants — are also used as traditional Chinese medicinal materials.

Common Preparations and Forms

Honeysuckle is used as a dietary supplement, tea, and beverage to clear heat and quench thirst. Preparations reported in the scientific literature and traditional practice include:

• Herbal decoction (water extract): Dried flower buds boiled in water, the traditional form of administration.
• Herbal tea: As an herbal tea, the dried buds create a vivid yellow-green decoction that is sweet and slightly bitter on the palate.
• Standardized extracts: Ethanol or aqueous extracts standardized to marker compounds such as chlorogenic acid and luteolin, used in clinical and preclinical research.
• Topical preparations: In TCM hospitals in China, extracts are injected directly into affected skin lesions.
• Compound formulas: Honeysuckle is a principal ingredient in renowned TCM blends like Yin Qiao Jie Du Pian, a formula designed for the early stages of colds and flu, where it works synergistically with herbs such as Forsythia, Mint, and Licorice.
• Effervescent tablets and beverages: Used in food-medicine contexts, particularly in China, where L. japonica holds homology-of-medicine-and-food status.

2. Traditional and Historical Use

Traditional Chinese Medicine (TCM)

Lonicera japonica is one of the oldest herbal medicines in China, with a medicinal history of more than 2,000 years. Physicians of all dynasties have used it as a key antipyretic and detoxifying drug. In China, as long as 1,500 years ago, Lonicera japonica was cultivated largely in Fengqiu county of Henan province, and the flowers were used as a local and traditional medicine for the treatment of exopathogenic wind-heat, epidemic febrile diseases, sores, carbuncles, furuncles, and various infectious diseases.

Originating from the ancient Chinese medical text Mingyi Bie Lu (Records of Famous Physicians), LJF is classified as a top-grade traditional Chinese medicine, known for its efficacy in clearing heat, detoxifying, dispersing wind, and alleviating heat. In TCM, the honeysuckle flower is linked with the lung, stomach, and large intestine meridians. It is considered to have cold properties, making it a remedy for removing heat from the body as well as toxins.

The Collective Notes to Canon of Materia Medica (around 480 to 498 AD) states: "It grows everywhere and is classified into liane, and does not fade over winter." It was taken to treat the exopathogenic wind-heat, epidemic febrile diseases, sores, carbuncles, and some infectious diseases.

Well-known TCM formulas employing honeysuckle include Yin Qiao San for early-stage measles, Cuo Chuan Jian Ji (Acne Decoction) of which honeysuckle is the chief herb, Xi Chuang Fang (Formula to Wash Sores) — a topical wash for bacterial skin infections such as impetigo — and Wu Wei Xiao Du Yin (Five-Ingredient Decoction to Eliminate Toxin) for purulent skin infections such as furuncles, mastitis, folliculitis, and erysipelas.

Many traditional Chinese medicinal texts, including Sasang Constitutional Medicine and Gwangje Bigeup, describe honeysuckle as beneficial for treating a variety of inflammatory abscesses inside and outside the human body. It has long been used as a folk remedy for upper respiratory infections such as colds, tonsillitis, and neuralgia.

Korean and Japanese Traditional Use

The plant grows naturally at the feet of mountains or levees in Japan, China, and Korea. Its flower buds and stems have been used as herbal medicines for promotion of urination, detoxification, hemostasis, blood purification, treatment of tumors, edema, colds, diarrhea, and emesis. Honeysuckle is a widely used traditional Korean natural herb with therapeutic properties including antiswelling, antiviral, antitumor, antipyretic, antiapoptotic, anti-inflammatory, and antibacterial effects.

Other Ethnomedical Traditions

Native to eastern Asia, L. japonica has become naturalized in Argentina, Brazil, Mexico, Australia, New Zealand, and the United States, where it has also been incorporated into local folk practices. In Thailand, the plant is widely used for its antipyretic effect.

3. Key Constituents and Active Compounds

Overall Chemical Profile

To date, 507 compounds have been isolated and identified from LJF, including volatile oils, organic acids, flavonoids, iridoids, triterpenes, and triterpenoid saponins. Earlier reviews catalogued a somewhat smaller number; more than 140 chemical compounds have been isolated, with the main compositions being essential oils, organic acids, and flavones. A more granular breakdown identifies at least 212 biologically active ingredients, including 27 flavonoids, 83 iridoids, 17 triterpenoids, 41 organic acids, and 45 other compounds.

Organic Acids

The most pharmacologically prominent organic acid is chlorogenic acid (5-caffeoylquinic acid). Chlorogenic acid and luteoloside are officially used as indicator compounds to characterize the quality of this herb and its related preparations; chlorogenic acid has demonstrated antibacterial, antiviral, anti-inflammatory, hypoglycemic activities, and allergy-preventive properties. Chlorogenic acid (CGA) and luteolosides are the leading secondary metabolites in L. japonica; additionally, secoiridoids such as loganin, secologanin, sweroside, and kingiside have been identified from extracts. CGA is a primary phenylpropanoid generated from the shikimic acid pathways with high antioxidant activities. Other identified organic acids include methyl caffeate, 3,4-di-O-caffeoylquinic acid, methyl 3,4-di-O-caffeoylquinic acid, protocatechuic acid, methyl chlorogenic acid, hyperoside, and caffeic acid.

Flavonoids

Lonicera japonica is rich in a variety of biologically active substances, and luteolin is its most representative flavonoid. Due to their good antibacterial, anti-inflammatory, and antitumor activities, chlorogenic acid and luteolin are used as indicator compounds to characterize the quality of Lonicera japonica and its preparations in the Chinese Pharmacopoeia. The two biflavonoids 3′-O-methyl loniflavone and loniflavone, along with luteolin and chrysin, can be isolated from the leaves. Additional flavonoids identified include rutin, luteoloside (luteolin-7-O-glucoside), hyperoside, and quercetin. LJF extract and its active components, such as chlorogenic acid, luteolin, rutin, luteoloside, hyperoside, and isochlorogenic acid, exhibit inhibitory effects on various cancers.

Iridoids and Secoiridoids

Two secoiridoid glycosides, loniceracetalides A and B, can be isolated together with 10 known iridoid glycosides from the flower buds. Wu suggested that the antibacterial activity of the flavones of fresh flower buds was 4 times that of chlorogenic acid, and iridoids also present marked biological activities.

Saponins

The plant also contains the saponins loniceroside A and B, and the anti-inflammatory loniceroside C. All parts of the plant other than the flower nectar have the potential to be toxic if consumed in very large quantities due to saponins.

Essential Oils (Volatile Compounds)

The important volatile compounds of honeysuckle flowers were identified as linalool, (Z)-jasmone, (Z)-jasmin lactone, and methyl jasmonate. An early analysis of essential oil from L. japonica flowers reported that linalool and linalool oxide C were the major identified constituents, with pinene, cis-3-hexen-1-ol, α-terpineol, geraniol, benzyl alcohol, β-phenylethanol, carvacrol, and eugenol present in lesser amounts.

4. Established Mechanisms of Action

Anti-inflammatory Mechanisms

In cell-based studies, Flos Lonicerae Japonicae water extract (FLJWE) and luteolin — but not chlorogenic acid — inhibited the production of iNOS, COX-2, and inflammatory cytokines in virus-infected macrophage cells. The extract and luteolin suppressed NF-κB activation by inhibiting the phosphorylation of STAT1 and STAT3, and FLJWE significantly upregulated the expression of pNrf2 and its downstream target gene heme oxygenase-1 (HO-1). This multi-pathway modulation — affecting NF-κB, JAK/STAT, and Nrf2/HO-1 axes simultaneously — is considered central to the anti-inflammatory activity.

In mast cell studies, luteolin isolated from Lonicera japonica flowers significantly inhibited the induction of TNF-α, IL-8, IL-6, and GM-CSF, attenuated COX-2 expression and intracellular Ca²⁺ levels, decreased the phosphorylation of ERK 1/2 and JNK 1/2, and inhibited NF-κB activation, IκB degradation, and luciferase activity.

In human neutrophil studies, L. japonica ethanol extract (LJEE) suppressed fMLF-activated superoxide anion generation, expression of CD11b, cell adhesion and migration, and the formation of neutrophil extracellular traps. It displayed dose-dependent ROS scavenger activity, with chlorogenic acids found to dominate the anti-inflammatory effects.

Antiviral Mechanisms

The flower or dry bud of honeysuckle is efficacious against various viral infections, including hepatitis B virus, adenovirus, influenza A virus, dengue virus, enterovirus, and respiratory syncytial virus. LJ water extract demonstrated an interrupting effect on the SARS-CoV-2 spike protein/ACE2 binding interaction in laboratory studies. Network pharmacology analysis identified core molecular targets including STAT3, TNF, and AKT1, with LJF's anti-RSV effects involving the PI3K-Akt signaling pathway, EGFR tyrosine kinase inhibitor resistance pathway, and FoxO signaling pathway.

Antibacterial Mechanisms

The main bacteriostatic active metabolites in Lonicera japonica are chlorogenic acid and flavonoids, with the bacteriostatic effect of flavonoids being more significant than that of chlorogenic acid. Lonicera japonica has shown in vitro efficacy against Staphylococcus aureus and Streptococcus haemolyticus.

Antioxidant Mechanisms

Phenolics and flavonoids in L. japonica have high antioxidant activities; pharmacological studies have proven their important role in removing harmful free radicals and in the prevention of diseases such as inflammation, cardiovascular disease, rheumatoid arthritis, and neurodegenerative disease. Antioxidant activities have been investigated by DPPH radical scavenging, ferric ion reducing antioxidant power assay, nitric oxide scavenging assay, and β-carotene bleaching assays.

Hepatoprotective Mechanisms

Lonicera japonica and related species have been confirmed to have liver-protective activities through various in vitro and in vivo trials. In one study using TUNEL assay, acetaminophen increased apoptotic hepatocyte number in mice (P < 0.001), while L. japonica water extract (350 mg/kg, administered orally) significantly decreased this tendency (P < 0.001).

5. Scientific Evidence by Area of Use

5.1 Inflammatory and Infectious Conditions (Respiratory Tract)

Lonicera japonica is widely used in the treatment of carbuncle, furunculosis, pharyngitis, erysipelas, bloody flux, common wind-heat cold, febrile disease, and fever. Lonicerae Japonicae Flos is considered superior to Lonicerae Japonicae Caulis in the prevention and treatment of respiratory diseases.

The clinical evidence base for honeysuckle in acute respiratory infections comes primarily from Chinese clinical practice, much of it in the context of compound TCM formulas rather than honeysuckle used in isolation. Some small clinical trials and observational studies have indicated potential benefits in managing symptoms of respiratory tract infections and supporting immune function, but large-scale, well-controlled human clinical trials are still limited. The evidence for single-herb preparations of L. japonica in respiratory infections remains preliminary.

5.2 COVID-19 (Add-on Therapy)

A systematic review aimed to evaluate the efficacy and safety of honeysuckle in the treatment of COVID-19 by searching seven electronic databases (PubMed, EMBASE, Cochrane Library, CNKI, and others) for RCTs involving adult patients. Nine RCTs involving 1,286 patients were enrolled. The honeysuckle preparations in these trials were predominantly used as add-on therapy to conventional care, not as standalone treatments, limiting interpretation of the findings. Evidence strength is currently rated as preliminary, given methodological limitations including small sample sizes and variability in preparations used.

At the preclinical level, LJ water extract demonstrated an interrupting effect on SARS-CoV-2 spike protein/ACE2 binding in laboratory assays. These are in vitro findings only and do not directly establish clinical efficacy.

5.3 EGFR Inhibitor–Induced Acneiform Rash (Oncology Supportive Care)

One of the more rigorously designed clinical studies concerns the use of honeysuckle to reduce skin toxicities from cancer treatment. In a prospective study, a total of 139 colorectal and lung cancer patients receiving EGFR inhibitor treatments were recruited. Patients were randomized to three arms: prophylactic honeysuckle treatment before rash occurred, symptomatic treatment when rash occurred, or conventional treatment with minocycline and a topical agent.

Honeysuckle treatment reduced incidences of EGFRI-induced acneiform rash (56.5%, 68.1%, and 71.7% in Arms A, B, and C, respectively; p = 0.280). Severities of rash (CTCAE grade 2 and 3) were significantly lower in prophylactic honeysuckle treatment (Arm A) compared to conventional treatment (Arm C) (p = 0.027), being 10% vs. 21%, respectively. Patients with honeysuckle treatment recovered more quickly from pruritus, with median times of 22, 36, and 58 days in Arms A, B, and C, respectively (p = 0.016). The study concluded that honeysuckle was effective in reducing incidences and severities of EGFRI-induced acneiform rash, especially for prophylactic treatment. This is considered one of the more controlled human studies, though it was a single center.

5.4 Inflammatory Bowel Disease (Preclinical)

Research into honeysuckle's effects on the gastrointestinal tract and gut inflammation is largely preclinical. L. japonica has demonstrated effective antioxidant activities, especially from its polyphenols and flavonoids. For example, the polyphenolic compound procyanidin B2, considered a bioactive metabolite of the honeysuckle flower, was found to ameliorate symptoms of inflammatory bowel disease (IBD) in experimental mice by inhibiting oxidative stress in colonic tissues via Nrf2/ARE signaling, promoting intestinal damage repair. These findings are animal-model data only; no direct clinical trials in human IBD populations have been reported in the reviewed sources.

5.5 Cardiovascular Disease (Preclinical)

The active compounds of honeysuckle have been extensively validated in fundamental research for anti-inflammatory properties relevant to cardiovascular disease (CVD), demonstrating considerable therapeutic potential. However, comprehensive studies on the active ingredients are necessary to clarify pharmacological effects, evaluate interactions with microorganisms in clinical trials, and determine metabolic benefits; and developing innovative dosage forms or delivery mechanisms to improve bioavailability is needed before honeysuckle can be firmly established as a natural medicinal agent for CVD prevention. Additional high-quality clinical trials and long-term follow-up assessments are required to furnish robust supporting evidence. All cardiovascular evidence at this time is preclinical.

5.6 Antimicrobial Activity (Preclinical / In Vitro)

Pharmacological studies of L. japonica flowering buds have shown wide biological activity including antibacterial, α-glucosidase inhibitory, antiviral, anti-inflammatory, antinociceptive, antiangiogenic, antioxidant, hepatoprotective, antifibrotic, and neuroprotective activities. The antibacterial and antiviral evidence, while voluminous, is primarily in vitro and animal-model based. Direct controlled human trials establishing clinical utility against specific bacterial or viral pathogens using single-herb preparations remain sparse.

5.7 Anticancer Activity (Preclinical)

Modern pharmacological studies have demonstrated that LJF exhibits a range of effects including antibacterial, anti-inflammatory, antiviral, liver-protective, intestinal-regulating, anti-depressive, antioxidant, anti-allergic, hypolipidemic, hypoglycemic, and immune-regulatory properties; LJF has also shown significant anti-tumor activity in preclinical work. Mechanisms include inhibiting cell proliferation, inducing cell apoptosis, blocking cell cycle, inhibiting cell metastasis, and regulating inflammation and immune function. However, there is a notable absence of systematic clinical reports detailing anti-tumor effects of LJF in human subjects. All anticancer evidence is currently preclinical.

5.8 Functional Dyspepsia (Human RCT)

A randomized, double-blind, placebo-controlled study evaluated the efficacy and safety of GCWB104 (Flos Lonicera Extract) in functional dyspepsia. Details of outcomes are not fully accessible in publicly available abstracts, and this study is cited as an example of the emerging human clinical work in gastrointestinal indications; it should not be extrapolated beyond its specific context.

6. Body Systems and Health Areas of Association

Based on the totality of pharmacological literature, honeysuckle has been associated with the following body systems, with the strength of evidence noted:

• Immune system / anti-infective: Most extensively studied; strong preclinical evidence, limited but growing human clinical data. Modern pharmacological studies have demonstrated antibacterial, anti-inflammatory, antiviral, liver-protective, intestinal-regulating, anti-depressive, antioxidant, anti-allergic, hypolipidemic, hypoglycemic, and immune-regulatory properties.
• Respiratory system: Traditional indication; some clinical data in compound formulas; LJF plays a significant role in antiviral, anti-inflammatory, antibacterial, immunomodulatory, and antioxidant effects relevant to respiratory infections.
• Skin / dermatology: Strong traditional use for skin infections and sores; one prospective RCT in EGFRI-induced rash (see Section 5.3).
• Gastrointestinal system: Preclinical IBD data; one human dyspepsia RCT identified.
• Liver (hepatoprotection): Preclinical evidence in acetaminophen-induced hepatotoxicity models.
• Cardiovascular system: Preclinical only; luteolin and chlorogenic acid studied as potential anti-atherogenic agents.
• Metabolic (glucose, lipid): Preclinical; chlorogenic acid has demonstrated hypoglycemic and hypolipidemic activity in laboratory models.
• Neurological (neuroprotection): Traditional claims and pharmacological studies have indicated that L. japonica may be a candidate for the treatment of various CNS disorders and neurodegenerative diseases, but direct human clinical evidence is absent.

7. Dosage Forms and Reported Dosages

Typical tea or decoction use for L. japonica is 6–20 g dried buds per day in the traditional context. Specific dosages reported in identified research include:

• Hepatoprotective animal model: L. japonica water extraction administered orally at 350 mg/kg in mice showed significant hepatoprotective activity versus acetaminophen-induced liver injury.
• Flower extract — oral safety window: Honeysuckle flower extract has been documented as possibly safe when used for up to 8 weeks in human oral use.
• EGFRI rash trial: The clinical trial protocol involved honeysuckle-based preparations in three arms (prophylactic, symptomatic, and conventional control), but specific dosage quantities used per arm were not disclosed in the available public source text.
• General note on dosage standardization: There is not yet enough reliable evidence to know what an appropriate dose of honeysuckle might be for specific clinical indications outside traditional decoction ranges, as most human trial data remain insufficient to establish evidence-based posology.

8. Safety Considerations and Interactions

General Toxicity Profile

In systematic toxicological evaluation, L. japonica was found to be fairly nontoxic, with high concentrations no longer having toxicological meaning. Despite some TCMs being reported to contain nephrotoxins and mutagens, honeysuckle showed safety without distinct toxicity or side effects in various studies.

Saponin Content and Large-Dose Toxicity

All parts of the plant other than the flower nectar have the potential to be toxic if consumed in a very large quantity due to saponin content. At typical supplemental or traditional decoction doses this risk has not been demonstrated in the reviewed literature, but the theoretical risk at extreme doses exists.

Species-Specific Toxicity

Not all honeysuckle species are equally safe. The North American red or coral honeysuckle (L. sempervirens), the dwarf honeysuckle (Diervilla lonicera), and Tartarian honeysuckle (Lonicera tatarica) are examples of honeysuckle plants with highly toxic berries, distinguishing them from L. japonica, whose berries and flowers are generally considered safe.

Reported Adverse Effects

Reported adverse effects from concentrated extracts in the literature include nausea and dizziness. Contact dermatitis from honeysuckle has been documented in the dermatological literature.

Potential Drug Interactions

Tannins isolated from Lonicera japonica have been found to exhibit differential inhibition of reverse transcriptase and cellular DNA polymerase-alpha activities in preclinical research, raising a theoretical concern for interactions with nucleoside analogue antiviral or antiretroviral medications, though clinical evidence for this interaction has not been established. Polyphenolic compounds from L. japonica have also been studied for effects on platelet activation, suggesting a potential pharmacodynamic interaction with anticoagulant agents at high doses, though this has not been confirmed in human trials.

Quality and Adulteration Concerns

Chlorogenic acid and luteolin — the official quality-control marker compounds in the Chinese Pharmacopoeia for L. japonica — have been found in other medicinal plants at even higher concentrations, meaning that use of these markers alone to verify product identity lacks specificity. This is a recognized challenge in standardizing commercial preparations. Due to the good antibacterial, anti-inflammatory, and anti-tumor activities of these compounds, they were designated quality indicators, but their presence alone does not confirm authentic Lonicera japonica sourcing.

Sustainability

Honeysuckle is at risk from overharvesting and habitat loss in its native range, which is relevant to the quality and supply consistency of commercial preparations.

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