Lilac (Syringa vulgaris L.): A Comprehensive Reference
1. Identity and Botanical Overview
Scientific Classification and Names
Common lilac is known scientifically as Syringa vulgaris L., belonging to the family Oleaceae (the olive family). It is a perennial deciduous shrub originally from Southeastern Europe, now widely distributed across Europe as an ornamental garden plant. The Latin genus name Syringa was formally assigned by Carl Linnaeus in 1753, deriving from the Greek myth of Pan and the river nymph Syrinx. Within the genus Syringa, there are between 20 and 30 species.
A plant sometimes called "French lilac" (Galega officinalis L.) — from which the drug metformin was originally developed — is not related to common lilac; it belongs to the pea family, not the olive family. This article addresses only Syringa vulgaris and related species of the genus Syringa unless otherwise stated.
Morphology and Distribution
Syringa vulgaris is a deciduous shrub or small tree native to the Balkan Peninsula, widely cultivated around the world for its fragrant, pale purple blossoms. It features ovate or heart-shaped leaves with full margins. The Oleaceae family encompasses 25 genera and approximately 600 species, comprising trees, shrubs, or woody climbers with almost worldwide distribution from northern temperate to southern subtropical regions.
Plant Parts Used and Common Forms/Preparations
Through the ages, many parts of S. vulgaris — including fruits, flowers, leaves, and branches — have been used in folk medicine due to their antimicrobial, immunomodulating, and anti-inflammatory activities. Lilac petals and flowers are edible. Popular products include honey, syrups, vinegars, teas, and infusions. Lilac flowers can also be used as an edible decoration in cakes or salads.
In terms of medicinal preparations, multiple forms have been documented:
- In traditional European medicine, common lilac bark has been used in the form of an infusion, decoction, or alcoholic extract as an antipyretic and a cold and cough treatment.
- The leaves and bark were sometimes made into teas or tinctures for treating fevers, mild infections, or digestive complaints.
- In folk medicine across rural Europe, lilac blossoms were soaked in alcohol to create tinctures or vinegars used externally for rheumatism, muscle aches, and minor skin irritations.
- Lilac flowers are the basis of many supplements available on the market.
- Volatile oils from Syringa have shown significant commercial value in the cosmetics industry.
2. Traditional and Historical Use
European Folk Medicine
In traditional European medicine, common lilac bark has been used in the form of an infusion, decoction, or alcoholic extract as an antipyretic and a cold and cough treatment. Locally, different parts of the plant are used to treat several ailments, including gastrointestinal disorders and skin wounds. In early American and European herbal texts, lilac was noted for its use in treating malaria and intermittent fevers, often via infusions of the bark or flowers — applications similar to the use of dogwood or willow bark during the same period.
In 19th- and early 20th-century American herbal practice, as recorded in Mrs. M. Grieve's A Modern Herbal, lilac was used as a vermifuge, and as a tonic anti-periodic and febrifuge, with suggestions it could be used as a substitute for aloes and in the treatment of malaria.
In Greece, flower infusions have been used internally to treat gastrointestinal problems and externally as a massage for gout and rheumatism. The flowers were also placed in sachets or baths to ease tension, anticipating some of the plant's aromatherapeutic potential.
Traditional Chinese and East Asian Medicine
Syringa vulgaris leaves are used in traditional Chinese medicine for their analgesic, pyretolysis (fever-reducing), anti-inflammatory, and stomachic properties. Lilac species have a long history in traditional Chinese medicine, where different parts of the plant were used to treat a wide range of ailments including coughs, bronchitis, diarrhea, vomiting, and abdominal pain; preparations were also used for acute liver inflammation (icteric hepatitis) and conjunctivitis.
As traditional medicine, Syringa has been applied to treat cough, diarrhea, acute icteric hepatitis, vomiting, abdominal pain, bronchitis, and other ailments. Blood stasis syndrome, known as oketsu in Japanese Kampo medicine, is considered an important pathology in traditional Chinese and Japanese medicine, and is related to diseases such as peripheral vascular disorders, blood vessel inflammation, and platelet aggregation. Lilac preparations have historically been used within this context for improving circulation and mitigating related symptoms.
Note on Nomenclature
It should be noted that in traditional Chinese medicine, the term "yuan hua" can refer to Daphne genkwa, a distinct and highly toxic species sometimes called "eastern lilac," which must not be confused with Syringa vulgaris. The two plants are taxonomically unrelated and have entirely different safety profiles.
3. Key Constituents and Active Compounds
Overview of Phytochemical Diversity
Until now, 302 compounds — including phenylpropanoids, iridoids, phenylethanols, flavonoids, triterpenoids, organic acids, and others — have been isolated and identified from Syringa species. Most of them belong to the phenolic class, which possesses a wide range of activities contributing either directly or indirectly to the biological effects of Syringa species. Phenylpropanoids and iridoids are the main constituents among these compounds and may be responsible for the activities directly or indirectly.
Secoiridoids
Studies on S. vulgaris metabolites in leaves and bark have revealed iridoids including syringopicroside, 8-epikingiside, syringalactone A and B; secoiridoids including oleuropein, ligstroside, isooleuropein, isoligustroside, neooleuropein, and nuezhenide. Three secoiridoid glycosides — isoligustroside, isooleuropein, and neooleuropein — were isolated from the leaves of Syringa vulgaris and structurally elucidated by carbon-13 nuclear magnetic resonance spectroscopy and other physicochemical methods.
Studies have found that secoiridoids exhibit strong antioxidant, anti-inflammatory, neuroprotective, and anti-cancer properties. Neooleuropein in particular has been identified as the most active compound in the inhibition of cytokine production by attenuating the MAP kinase pathways.
Phenylpropanoids
Syringin is a phenylpropanoid glycoside isolated from the bark of Syringa vulgaris. Syringin and oleuropein, representative compounds of phenylpropanoids and iridoids respectively, were found to be the most abundant in the plants and displayed extensive biological activities. Validated quantitative analyses show that syringin (2.52%) is the main phenolic compound in the bark, while rutin (1.13%) is the main phenolic compound in the leaf.
Other important phenylpropanoids include verbascoside (acteoside) and echinacoside. HPLC-DAD-ESI-MS analyses of flowers and fruits have led to the identification of syringin, echinacoside, verbascoside/acteoside, quercetin rutoside, oleuropein, and ligstroside.
Flavonoids
Significant amounts of free or glycosylated flavonoids including quercetin and kaempferol derivatives have been identified from flower, leaf, and bark extracts of S. vulgaris. Among the constituents of leaf extract, quercetin 3-glucoside, quercetin 3-rutinoside, and acteoside may play important roles in disease prevention, with flavonoids showing antioxidant, anti-inflammatory, and antiplatelet aggregation activities.
Volatile/Essential Oil Components
Syringa plants contain essential oils that form important constituents not only for their economic utility but also for their potential medicinal value as antimicrobial, antipyretic, and antiviral agents. Many compounds are responsible for the flowery aroma, such as benzyl alcohol, benzene acetaldehyde, cis-linalool oxide, linalool, phenylethyl alcohol, α-terpineol, myrtenol, cis-geraniol, p-vinylguaiacol, eugenol, and trans-nerolidol.
Other Compounds
The leaves and fruits of lilac contain phenylpropanoids, iridoids, sulphonic iridoids, flavonoids, and saponins, including eugenol, syringin, and oleuropein as main ingredients. Syringa vulgaris flowers are rich in bioactive compounds including flavonoids, essential oils, iridoid glycosides, organic acids, and lignan glycosides.
4. Established Mechanisms of Action
Anti-Inflammatory Mechanisms
In a study investigating extracts of different parts of Syringa vulgaris on pro-inflammatory functions of neutrophils, active compounds were isolated using bioassay-guided fractionation, and their activity and molecular mechanisms determined. Extracts were characterized using HPLC-DAD-MSn. Effects on ROS, MMP-9, TNF-α, IL-8, and MCP-1 production were measured using luminol-dependent chemiluminescence and ELISA methods, while effects on p38MAPK, ERK1/2, JNK phosphorylation, and NF-κB p65 translocation were determined using western blots.
Moderate anti-inflammatory activity was observed in a neutrophil model for all compounds compared with oleuropein. Syringin at a concentration of 50 μM significantly inhibited TNF-α production and stimulated TGF-β release in LPS-treated monocytes/macrophages. In the neutrophil model, all extracts and infusions were able to significantly reduce ROS production, likely related to the presence of compounds containing caffeic acid, p-coumaric acid, hydroxytyrosol, or tyrosol phenolic moieties.
Antioxidant Mechanisms
Syringa vulgaris flowers are rich in bioactive compounds with antioxidant potential. Lilac flowers have been shown to contain the highest content of phenolic, total flavonoid, and total phenolic acid compared to other parts of the plant. The in vitro antioxidant capacity of S. vulgaris extracts has been measured by ferric-reducing antioxidant power (FRAP), 2,2-diphenyl-picrylhydrazyl (DPPH•), and cupric ion reducing antioxidant capacity (CUPRAC) methods.
Verbascoside and its close metabolite teupolioside, major secondary metabolites in Syringa vulgaris meristem plant cells, are also known as potent chelators of Fe²⁺, a catalyst of the reaction of lipid peroxidation.
Cardiovascular Mechanisms
Syringin and kaempferol-3-O-rutinoside from S. vulgaris have been reported as antihypertensive compounds. Antihypertensive effects of syringin (33% reduction at 30 mg/kg dose) on blood pressure of anesthetized rats have been documented. Acteoside (obtained from violet flowers) was also studied in cardiovascular research for its effects on mean arterial blood pressure.
Sebum-Regulating Mechanisms (Cosmetic/Topical)
A botanical complex derived from lilac (Syringa vulgaris) cell culture has been shown to reduce sebum production by acting directly on sebocytes (the secreting cells responsible for oil production), making it relevant for skincare formulations targeting acne, seborrhea, and oily skin.
5. Scientific Evidence by Area of Use
5.1 Anti-Inflammatory Activity
Evidence type: Primarily in vitro and ex vivo; limited in vivo (animal); no published human clinical trials as of writing.
A key study demonstrated that common lilac, a traditionally used medicinal plant in Europe, is a valuable source of active compounds, especially neooleuropein. Research published in Frontiers in Pharmacology (2018) examined the effects of phytochemically characterized extracts from different parts of Syringa vulgaris — including bark, fruits, leaves, and flowers — on the pro-inflammatory functions of human neutrophils. Neooleuropein appeared to be the most active compound in the inhibition of cytokine production by attenuating MAP kinase pathways, with results suggesting a synergistic action of the active compounds in producing the final anti-inflammatory effect.
A separate study on bark (published in ScienceDirect, 2019) focused on bark-derived compounds' effects on human neutrophils and monocytes/macrophages. Moderate anti-inflammatory activity was observed in the neutrophil model for all compounds; syringin at 50 μM significantly inhibited TNF-α production and stimulated TGF-β release in LPS-treated monocytes/macrophages. The results demonstrated that common lilac bark is a valuable source of active compounds, especially syringin. These studies used ELISA-based measurement of pro-inflammatory cytokines and relied on isolated human immune cells. No randomized controlled trials in human subjects have been published for the anti-inflammatory use of lilac preparations.
5.2 Antioxidant Activity
Evidence type: In vitro; one study examined effects in human plasma.
Data about the antioxidant properties of various parts of S. vulgaris has been limited to in vitro antioxidant capacity of extracts; the effect of S. vulgaris flower extract on the parameters of oxidative stress in biological materials, including plasma, had not previously been demonstrated until more recent work. A 2026 study published in PMC investigated the protective effects of flower extract, noting that many parts of S. vulgaris have been used in folk medicine due to their antimicrobial, immunomodulating, and anti-inflammatory activities. Lilac flowers have been shown to contain the highest content of phenolic, total flavonoid, and total phenolic acid compared to other parts of the plant, with diversity in total content dependent on flower color.
A study characterizing chemical composition and antioxidant and cytotoxic properties of ethanolic extracts from S. vulgaris flowers, leaves, bark, and fruit found S. vulgaris to be a promising, not comprehensively studied source of bioactive compounds with important therapeutic potential. The study concluded that S. vulgaris extracts, particularly from flowers and leaves, represent valuable sources of compounds with antioxidant and antitumoral potential.
5.3 Cardiovascular Effects (Blood Pressure and Blood Stasis)
Evidence type: In vitro; animal models; one in vivo mouse study on blood stasis syndrome.
A study published in PMC (2020) employed an in vivo mouse assay to test whether leaves and flowers of S. vulgaris could prevent blood stasis syndrome (oketsu in Japanese). The study employed a previously developed in vivo assay to determine whether leaves and flowers of S. vulgaris could prevent blood stasis syndrome; the data confirmed their preventive activities, as administration of leaf and flower extracts significantly inhibited HEL-induced blood flow decrease. Quercetin 3-glucoside, quercetin 3-rutinoside, and acteoside were identified as active compounds, as they significantly mitigated blood flow reduction; the findings indicate that polyphenols from S. vulgaris could be useful for preventing oketsu and improving quality of life in individuals with peripheral circulatory disorders.
For blood pressure, Syringa vulgaris has been used to treat malaria, and its compounds syringin and kaempferol-3-O-rutinoside have been reported as antihypertensive. These findings are limited to animal and in vitro models.
5.4 Antimicrobial and Antifungal Activity
Evidence type: In vitro only.
Pharmacological experiments in vivo and in vitro have confirmed that extracts and pure compounds from Syringa possess anti-inflammatory, hepatoprotective, antimicrobial, antiviral, antioxidant, antitumor, and immunomodulatory activities. In terms of skin-relevant fungi, extracts of Syringa vulgaris (including compounds verbascoside and isoverbascoside) have been tested against strains of Malassezia furfur and Trichophyton rubrum using microbiological dilution assays. Malassezia furfur is the etiological agent responsible for seborrhoeic dermatitis and Pityriasis versicolor, while Trichophyton rubrum is the agent responsible for onychomycosis, athlete's foot, and tinea corporis. No published human clinical trials have established antimicrobial efficacy.
5.5 Cytotoxic and Antitumor Activity
Evidence type: In vitro cell line studies only.
Cytotoxic activity of S. vulgaris extracts was tested on two tumoral cell lines — HeLa and B16F10 — using the MTT assay. Significant amounts of phenylpropanoids (syringin, acteoside, echinacoside), flavonoids (quercetin, kaempferol derivatives), and secoiridoids were obtained from flower, leaf, and bark extracts. MTT tests pointed to a significant cytotoxic potential expressed in a non-dose-dependent manner toward the tumoral lines. These findings are preliminary and confined to cell culture; no clinical cancer research has been conducted with Syringa vulgaris.
5.6 Antipyretic Activity
Evidence type: Animal models; traditional use supported by phytochemical plausibility.
Scientific data has confirmed the antioxidant, anti-inflammatory, and antipyretic properties of S. vulgaris. Flowers are used in traditional medicine as antipyretic. Scientific data supporting the traditional use of S. vulgaris are connected with its antioxidant, anti-inflammatory, anti-nociceptive, and antipyretic properties. No published randomized controlled trials in humans specifically evaluating antipyretic activity have been identified.
5.7 Hepatoprotective Activity
Evidence type: Animal models; limited clinical observations in some Syringa species (not specifically S. vulgaris).
Research by the Henan Institute of Medical Sciences on Syringa microphylla (a related species) found that its crude extract had a certain preventive effect against chemical and immune liver injury in animals, as well as a significant anti-liver fibrosis effect, described as stable and long-lasting without toxic side effects. Pharmacological research in vitro and in vivo revealed that extracts and pure compounds possessed significantly hepatoprotective, anti-inflammatory, antimicrobial, antioxidant, antitumor, antiviral, cardioprotective, immunomodulatory, and other activities.
5.8 Skin and Cosmetic Applications
Evidence type: Proprietary cosmetic ingredient testing; in vitro studies; limited clinical cosmetic data.
A botanical complex derived from lilac (Syringa vulgaris) cell culture, marketed under the name Sebuless™, reduces sebum production by acting directly on sebocytes, and is positioned as a natural ingredient for skincare formulations targeting acne, seborrhea, and oily skin. Clinical tests of ingredient-containing applications showed that prolonged usage (a month or more) reduces the shiny appearance by up to 70%, with most participants reporting skin purification and overall improvement of the condition, complexion, and appearance. These are proprietary industry tests rather than independent peer-reviewed randomized trials, and should be interpreted accordingly.
Verbascoside, a major secondary metabolite in Syringa vulgaris meristem plant cells, is a potent chelator of Fe²⁺, a catalyst of lipid peroxidation, which may contribute to protective skin effects.
5.9 Blood Stasis and Circulatory Effects (Oketsu)
Evidence type: In vivo mouse model only.
Blood stasis syndrome is related to diseases such as peripheral vascular disorders, blood vessel inflammation, and platelet aggregation, whose severities are augmented owing to lipid peroxidation, free radicals, and oxidative stress; the assay system monitored blood flow decrease in the tail vein of mice. Through bioassay-guided fractionation of different S. vulgaris extracts, five polyphenols were isolated and identified; quercetin 3-glucoside, quercetin 3-rutinoside, and acteoside were identified as active compounds as they significantly mitigated blood flow reduction. The study was conducted in a sensitized mouse model; human clinical data are absent.
6. Overall Strength of Evidence
Recent scientific interest in Syringa vulgaris remains focused on its chemical composition rather than human clinical trials. Research has largely confirmed the presence of various bioactive compounds, but their therapeutic application remains theoretical. Phytochemical analyses continue to isolate secoiridoids, flavonoids, and phenolic compounds from lilac flowers and leaves, highlighting their antioxidant potential in in vitro settings.
There are currently no official monographs for Syringa vulgaris from the European Medicines Agency (EMA) or the World Health Organization (WHO). There is a profound lack of in vivo (animal or human) studies, and it is not known whether the effects observed in vitro translate to meaningful clinical outcomes in humans.
7. Body Systems Associated with Lilac
- Immune/Inflammatory system: Syringa vulgaris has documented anti-inflammatory, adaptogenic, and immunomodulatory properties.
- Digestive system: Traditional uses include treatment of diarrhea, vomiting, and abdominal pain.
- Respiratory system: Traditional use encompasses cold and cough treatment.
- Cardiovascular system: Syringin and kaempferol-3-O-rutinoside have been reported as antihypertensive compounds.
- Hepatic system: Acute icteric hepatitis has been historically treated with Syringa preparations in traditional Chinese medicine.
- Integumentary (skin): Lilac extract has found a growing role in skincare products targeting oily and acne-prone skin.
- Musculoskeletal system: Flower infusions have been used externally as a massage for gout and rheumatism in Greek folk practice.
8. Dosage Forms and Reported Dosages
There are currently no standardized or officially recommended dosages for Syringa vulgaris in any published pharmacopeial monograph or regulatory body guidance. The following dosage information reflects only what has been used or reported in experimental research:
- Syringin at a concentration of 50 μM was the dose at which significant inhibition of TNF-α production and stimulation of TGF-β release in LPS-treated monocytes/macrophages was observed in an in vitro model.
- Syringin and phillygenin significantly reduced lipid deposition in macrophages in a dose-dependent manner; for syringin, the greatest reduction in CD36 receptor expression was over 80% at a concentration of 50 μg/mL compared to cholesterol-stimulated controls.
- In animal studies, the antihypertensive effect of syringin was reported at a 30 mg/kg dose in anesthetized rats.
- In one oral toxicity study in animals, no obvious toxicity or side effects on major organs — including liver, kidney, blood system, and brain — were observed after oral administration of tablets at 250 times the therapeutic dose prepared from leaves.
For topical cosmetic preparations: Clinical tests of preparations containing lilac cell culture extract showed that prolonged usage of a month or more reduces shiny appearance, but the specific concentration or dose of the active ingredient was not disclosed in publicly available summaries.
9. Safety Considerations and Interactions
General Safety Status
There are currently no official monographs for Syringa vulgaris from the EMA or WHO, meaning formal safety assessments for the plant as a medicinal product are absent. Historically, herbalists have used its flowers, leaves, and bark for various ailments; however, it is crucial to distinguish between traditional practices and scientifically validated treatments, as many historical uses lack modern clinical support.
Potential for Toxic Compounds
A review of 23 edible flowers by the Danish Veterinary and Food Administration found that Syringa vulgaris was among nine flowers that contained compounds with toxic or potentially toxic effects if eaten. The food use of many of the flowers may be considered novel due to limited historical data on food use from ethnobotanical surveys.
Skin Sensitivity
Excessive topical use may lead to skin irritation, contact dermatitis, or allergic reactions.
Allergic Cross-Reactivity (Pollen)
Lilac belongs to the Oleaceae family, which also includes olive, ash, and privet. Cross-reactivity between the pollens of these species is well established, meaning that individuals allergic to olive or ash tree pollen may also react to lilac pollen.
French Lilac Confusion
The plant historically associated with the development of metformin is Galega officinalis, sometimes called French lilac or goat's rue, which is an entirely different plant in the pea family and should not be confused with common lilac. Their pharmacological profiles and safety characteristics are entirely different.
Absence of Formal Drug Interaction Data
No peer-reviewed clinical studies examining drug–herb interactions specific to Syringa vulgaris have been identified in the scientific literature. Given that syringin and related compounds have demonstrated effects on TNF-α, TGF-β, MAP kinases, and blood pressure in experimental models, theoretical interactions with immunomodulatory drugs, anti-inflammatory medications, and antihypertensives exist, but these have not been formally characterized in humans.
References
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