Bitter Fennel Research Articles

Effectiveness of Oral Herbal in Postpartum and Breastfeeding

Background: Health care during the postpartum and breastfeeding periods fulfils the needs of the mother and baby. 'Jamu', or herbal medicine, is often used for this purpose, but there needs to be more evidence of its effectiveness. The public's insufficient understanding of herbal medicine necessitates a systematic review to assess its contents, benefits, and side effects. The systematic review aimed to examine oral herbal medicines during puerperium or breastfeeding, using the RCT method to provide evidence of IB levels in EBM. Methods: Inclusion criteria were articles in randomised controlled trials (RCTs) to investigate the effectiveness of oral herbs during the puerperium and lactation. The methodological quality of articles was tested with the Jadad Score. Results: The five (5) selected articles have good quality (the Jadad Score was 5–8). The study tested five herbs, including fenugreek, honey, bitter fennel, Brazilian propolis, barley malt, and Thai herbal tea "Wang Nam Yean" (a mixture of sappan wood (secang), bael (maja) fruit, licorice, ginger, and tuba (Derris scandens)). Comparators included placebo and other herbs or Domperidone. Most clinical outcomes involved successful breastfeeding, but complications, infant weight gain, and side effects were also observed. Conclusion: Herbs can aid in healthy breastfeeding, but they should be taken cautiously and in conjunction with the assessment, counselling, and support of healthcare professionals. No herbal medicine has the best evidence-based practices because the evidence has not been applied to clinical practice, so changes in clinical practice results have yet to be documented.

Analysis of Fennel Breeding Populations Based on Distinctness, Uniformity, and Stability (DUS) Testing via Morphological Descriptors and DNA Molecular Markers

AbstractA bred plant variety is a valuable tool for enhancing crop production and total yield. Recently, our breeding team developed three high seed yielding synthetic cultivars of bitter fennel. To characterize these newly breeding populations and differentiate them from each other and their parental populations, we conducted a Distinctness, Uniformity, and Stability (DUS) assessment using morphological traits evaluated over two consecutive years, as well as 20 Start Codon Targeted (SCoT) markers. The evaluation of morphological traits revealed that, five of qualitative traits exhibited monomorphism, while two other qualitative traits displayed polymorphism. Additionally, the investigation of eight quantitative traits showcased significant diversity. The Combined Over Years Distinctiveness analysis at a 1% significance level, based on eight quantitative characteristics, indicated distinctiveness for two breeding populations, namely Early and Medium Maturity Synthetic cultivars, compared to other populations. The Combined Over Years Uniformity analysis identified that all of the breeding populations and their parental populations were uniform in terms of the measured traits. The differences between Phenotypic Coefficients of Variation and Genotypic Coefficients of Variation were not particularly noticeable in the experimental material used currently. The majority of the measured traits showed high heritability, highlighting their stability over time. PCA utilized for quantitative morphological features, the first two principal components collectively accounted for more than 86.8% of the phenotypic variation. Subsequently, a dendrogram was constructed, which clustered breeding and parental populations into three distinct groups. The 15 SCoT markers produced a total of 164 extended fragments, with 139 (85%) of them showed polymorphic.The genetic similarity between the populations exhibited a range of 0.08–0.81, and cluster analysis utilizing Jaccard similarity coefficients and the Unweighted Pair Group Method with Arithmetic Mean (UPGMA) technique revealed clear distinctions among the three breeding populations and their parental populations. Altogether, the findings indicate that morphological DUS descriptors effectively distinguish some the populations, while others with overlapping expressions cannot be discriminated. Notably, SCoT markers demonstrate a fine ability to detect distinctions among fennel populations, suggesting the possibility of utilizing them as a complement to morphological traits in the DUS test. As a conclusion, these three newly breeding populations of fennel are distinct from each other and from their parental populations, and they can advance for registration and seed purity testing.

Evaluation of seed yield, essential oil compositions, and fatty acid profiles in advanced fennel (Foeniculum vulgare Mill) breeding populations

Metabolites derived from bitter fennel serve as flavoring and healing agents in the pharmaceutical, food, and cosmetic sectors. Previously, we developed three fennel breeding populations (Early, Medium, and Late Maturity Synthetic Cultivars) with the potential to produce higher seed yield. This investigation aimed to assess the quality and quantity of the important metabolites in these three cultivars alongside their elite parental populations. Our results showed that the highest amounts of essential oil yield and seed yield were produced by, two breeding populations, Medium and Late Maturity Synthetic Cultivars. These cultivars showed positive seed yield heterosis rates of 28% and 20%, respectively, above the averages of their parental populations. GC-MS analysis of the essential oil samples identified 24 components in total. The major compounds in all genotypes were trans-anethole (34.09–77.84%), limonene (4.99–12.66%), methyl chavicol (1.35–38.69%), and fenchone (6–13.07%). The highest amount of trans-anethole belonged to Fasa and the Medium Maturity Synthetic with 77.84 % and 73.10%, respectively. The analysis of fatty acid compositions in the genotypes was conducted using GC-FID, which revealed the presence of 19 unique fatty acids, of which ten were saturated, and nine were unsaturated fatty acids. Petroselinic acid (67.11–78.44%), and linoleic acid (9.14–11.60%) were the major unsaturated fatty acids in fennel seeds. The Early Maturity Synthetic exhibited the least saturated fatty acid content (7.24%), while the highest levels of unsaturated fatty acids were found in both the Early Maturity Synthetic (89%) and Hashtgerd (88.55%). The genotypes were categorized into four groups using a heat map analysis with hierarchical clustering. Overall, the results showed that the three synthetic cultivars of fennel have outperformed the elite parental populations for seed and essential oil yields, concentration of the major industrial secondary metabolites such as trans-anethole, and higher proportions of unsaturated fatty acids. These cultivars show potential for usage in the pharmaceutical and healthcare industries.

Safety and efficacy of feed additives consisting of essential oils from the fruit and stems of Foeniculum vulgare Mill. ssp. vulgare: Bitter fennel oil for use in all animal species and sweet fennel oil for use in dogs and cats (FEFANA asbl).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of essential oils from fruit and stems of Foeniculum vulgare Mill. (bitter fennel oil and sweet fennel oil), when used as sensory additives (flavourings). For long-living and reproductive animals, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) considered of low concern the use of bitter fennel oil (with a content of estragole up to 6.1%) at the proposed use level in complete feed: 0.6 mg/kg for laying hens and rabbits, 1.0 mg/kg for sows and dairy cows, 1.5 mg/kg for sheep/goats, horses and cats, 1.9 mg/kg for dogs and 7.1 mg/kg for ornamental fish. For short-living animals (animals for fattening), the Panel had no safety concern when bitter fennel oil is used at the proposed use level in complete feed of 18.2 mg/kg for chickens for fattening, 24.3 mg/kg for turkeys for fattening and 25 mg/kg for piglets, pigs for fattening, veal calves, cattle for fattening, sheep/goats, horses, rabbits and salmon. These conclusions were extrapolated to other physiologically related species. The use of sweet fennel oil (with a content of estragole up to 5.0%) was considered of low concern at the proposed use level in complete feed of 2.3 mg/kg for dogs and 1.9 mg/kg cats. The use of bitter fennel oil in animal feed is expected to be of no concern for consumers and the environment. The additives under assessment should be considered as irritants to skin and eyes, and as dermal and respiratory sensitisers. Due to the high concentration of estragole (> 1%), fennel oils are classified as suspected of causing genetic defects and of causing cancer and should be handled accordingly. Since the fruit of F. vulgare Mill. ssp. vulgare and its preparations are recognised to flavour food, no further demonstration of efficacy was necessary.

Protocol for the Scientific Opinion on the evaluation of the safety in use of preparations from the fruits of sweet and bitter fennel (Foeniculum vulgare Mill. and Foeniculum piperitum (Ucria) C.Presl)

Protocol for the Scientific Opinion on the evaluation of the safety in use of preparations from the fruits of sweet and bitter fennel (Foeniculum vulgare Mill. and Foeniculum piperitum (Ucria) C.Presl)

Determination of optimal harvesting time for essential oil and estragole yield in bitter fennel (Foeniculum vulgare Mill.) growing in culture conditions

Determination of optimal harvesting time for essential oil and estragole yield in bitter fennel (Foeniculum vulgare Mill.) growing in culture conditions

Seed yield stability with modified essential oil content and composition in self-compatible progenies of bitter fennel (Foeniculum vulgare Mill.)

Genetic progress as the mean yield increase within self (S1), and open-pollinated (OP) plants from eight bitter fennel populations were studied using the best nine full-sib (S1) and their corresponding nine half-sib (OP) plants from each population for agro-morphological traits and essential oil characteristics during two years. The average of S1 populations showed depression for all studied characteristics particularly the number of effective umbels per plant (NEUP) as the main yield component. However, some of the best S1 progenies performed well with stable and comparable yield to OP progenies. In addition, self-pollination interestingly increased the percentage of four major compounds including α-pinene, limonene, fenchone, and estragole in the essential oil (EO). In most populations, α-pinene, limonene, and fenchone were 2–4 times higher in selected S1 genotypes compared to OP counterparts. An inbred plant with more than 10-fold higher estragole content than the normal range was also identified among the selected genotypes. Conversely, the percentage of (E)-anethole decreased due to self-pollination in all selected plants in both years. Therefore, it may be concluded that although self-pollination has deleterious effects on the population’s general fitness, it may lead to improvement in the composition of EO in high-performing selected genotypes of bitter fennel for specific purposes and further utilization in pharmaceutical industries.

Changes in Bitter Fennel Essential Oils Exposed to Foliar Spray with L-Phenylalanine

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Characterization of lipid fraction of Apiaceae family seed spices: Impact of species and extraction method

The aim of this study was to investigate the potential of Apiaceae seeds - bitter fennel (Foeniculum vulgare Mill. var. vulgare), anise (Pimpinella anisum L.) caraway (Carum carvi L.) and coriander (Coriandrum sativum L.) as sources of high value lipophilic bioactive molecules. To evaluate the efficiency of extraction methods on seed oil yield and bioactive compounds content, seeds were extracted by both conventional methods (Soxhlet extraction and agitation-assisted extraction at room temperature) and pressurized liquid extraction (PLE) at 25 and 100 °C. Coriander was characterized by the highest yield of seed oil (12.30 %), the highest content of C18:1 fatty acids (sum of petroselinic acid and oleic acid) and the lowest content of lauric acid, while caraway seed oil contained 6.20 % of atypical caproic fatty acid. Although high levels of sterols were determined in all the seed oils analyzed, along with the dominance of stigmasterol and β-sitosterol, total sterols were highest in anise seed oil (903.9 mg/100 g) which contained particularly high levels of spinasterol and Δ7-stigmastenol. Significant levels of the triterpenes α- and β-amyrin were also detected in all extracted seed oils. Conventional methods resulted in higher oil yields, but the highest contents of total sterols and triterpenes were obtained by PLE at 100 °C. The lower yields of seed oil obtained with PLE were related to the relative decrease of C18:1 acids caused by their lower extractability and the subsequent increase od lauric acid. The obtained results show that PLE can be a useful tool for modulating the content and composition of bioactive molecules in lipid extracts from Apiaceae seeds.

Variation in a worldwide collection of fennel (

Fennel (Foeniculum vulgare Mill.) is an old medicinal plant and has been commonly used as a traditional food and medicine. This study aimed to evaluate genetic variation for agro-morphological traits and essential oil content and components in a worldwide collection of bitter fennel (F. vulgare var. vulgare). We examined production stability of different accessions, and identified associations between traits in order to find the best criteria for use in future breeding programs. The study evaluated 33 bitter fennel accessions from 11 countries in the field for morphological characters across 4 years (2015–18), and for important phytochemical characters in 2 years (2015 and 2016). Comparisons across years revealed varied responses from fennel genotypes. Highest mean production was observed in the third year, and highest essential oil content in the second year. Based on gas chromatography–mass spectrometry analysis, trans-anethole (59.86–78.82% of total oil content), estragole (3.61–24.39%), fenchone (9.58–18.26%) and limonene (0.52–3.66%) were detected as major essential oil components in the studied germplasm. Based on principal component and cluster analysis, genotypes were grouped into different clusters. Classification of genotypes was mainly in agreement with available information regarding their origins. The results support available information on the history of human establishments and the introduction of fennel from Mediterranean gene pools to other regions in ancient times. The negative correlation between some essential oil components indicates that some components are isomers and this could limit the simultaneous selection of components. Superior genotypes were identified in the studied germplasm, which can be used for future breeding programs with specific purposes.

Acı Rezene (Foeniculumvulgare Miller var. vulgare) Uçucu Yağ İçeriği ve Bileşenlerinde Morfogenetik, Ontogenetik ve Diurnal Varyabilite

The objective of this study was to determine morphogenetic, ontogenetic and diurnal variability in content and constituents of bitter fennel essential oil. Essential oils of various plant organs (leaf, root-bulb-stalk, flower and seed) of bitter fennel harvested at pre-, full- and post-flowering stages at different times (9 am, 1 and 5pm) were extracted by hydro distillation and analyzed by gas chromatography and mass spectrometry. Essential oil content differed significantly based on plant organ and growing stage, increasing in the order of leaf < flower <seed, with a nearly seven-fold increase occurring in seed essential oil as compared to that of leaf. Essential oil content increased from 1.68% at pre-flowering to 2.18% at full-flowering but decreased sharply to 0.81% at post-flowering. Trans-anethole was found to be the most prominent compound in all esssential oils, with decreasing order of seed > flower > root-bulb-stalk > leaf essential oil. Alpha-pinene, α–phellandrene, limonene and fenchone were the other major components, varying significantly with plant growth stages and organs. The present study reveals that the content and constituents of essential oil of bitter fennel from Turkey are predominantly dependent on ontogenetical phase and plant organ.

Production of more sustainable emulsions formulated with eco-friendly materials

Abstract Sustainable development involves the search for new products with a low environmental impact. Hence, the aim of this work is to obtain stable and concentrated aqueous emulsions containing bitter fennel oil and a biomass-derived emulsifier by studying different processing variables and techniques. Firstly, the effects of the application of a premix step previous to homogenization and of the geometry of the high-energy rotor-stator device used (Silverson L5M or Ultraturrax T50) on the droplet size distribution (DSD) and physical stability (PS) of emulsions were investigated. The use of a premix worsens both the physical stability and the average droplet diameters of the emulsions, the most stable emulsion being that obtained with the Silverson L5M alone. Secondly, the stability of this emulsion was improved. To achieve this goal, this coarse emulsion was microfluidized at different pressures (from 5000 to 25000 psi), reaching submicron sizes and monomodal distributions, except for that subjected to 25000 psi which resulted in clear overprocessing. Creaming and oiling off were the main destabilization processes. The emulsion exhibiting the lowest droplet sizes and the best physical stability was prepared at 20000 psi. This work contributes to the development of sustainable agrochemical prototypes.

The Safety of Mother's Milk® Tea: Results of a Randomized Double-Blind, Controlled Study in Fully Breastfeeding Mothers and Their Infants.

Various natural products are reported to improve maternal milk supply yet are not necessarily safe for infants. Researchers have not systematically studied galactagogue teas for safety. This study evaluates the safety of a galactagogue tea in breastfeeding women and their infants, assessing short- and long-term adverse effects. Healthy, exclusively/fully breastfeeding women ( N = 60) with no milk insufficiency were randomized into (1) an all-natural tea containing fruits of bitter fennel, anise, and coriander; fenugreek seed; and other herbs (Mother's Milk® herbal tea; test) group or (2) a lemon verbena leaf (placebo) group. Maternal diaries captured self-reported maternal and infant adverse effects, tea consumed, and perceived infant satisfaction. Maternal quality of life and psychological state were assessed at baseline and 2 and 4 weeks. Poststudy calls assessed adverse effects through the infants' age of 12 months. No adverse effects attributable to the interventions were reported at any time point. No differences were found between test and placebo groups in sociodemographic characteristics, maternal or infant adverse symptoms, quality of life, breastfeeding self-efficacy, maternal psychological measures, infant growth, and infant satisfaction (all p >.05). This double-blind, randomized controlled trial (RCT) of an herbal galactagogue versus placebo among healthy, exclusively/fully breastfeeding mothers and infants found no adverse events associated with the test tea across the 30-day study or the first year of their infant's life. This composite tea appears to present no safety risk for mothers or their young babies.

Morphogenetic, Ontogenetic and Diurnal Variability in Antimicrobial Activity of Bitter Fennel (Foeniculum vulgare Miller var. vulgare) Essential Oil

Abstract: Background: There has been considerable interest in antimicrobial activity of plant essential oils in recent years. Objectives: This research was carried out to determine morphogenetic, ontogenetic and diurnal variability in antimicrobial activity of bitter fennel essential oil. Methods: To specify morphogenetic variability, leaf and root-bulb-stalk samples taken at pre-, full and post-flowering, flower samples picked at full flowering and seed samples gathered at two seed growth stages were used. For ontogenetic and diurnal variability, whole plant samples were taken at pre-, full and post-flowering and at 9:00 am, 1:00 pm and 5:00 pm. A total of 10 microorganisms have been used to determine antimicrobial activity of essential oils with disc-diffusion and microdilution broth methods. Results: The highest inhibitory effect among leaf essential oils was observed from post-flowering samples, but essential oils of root-bulb-stalk samples of pre-flowering produced the highest antimicrobial activity. Whole plant essential oils of post-flowering samples produced higher antimicrobial activity than those of pre- and full flowering samples. Generally, inhibitory effect of seed essential oils extracted at the beginning of seed formation was higher than those of seed maturity. Daily harvesting time caused no effect on antimicrobial activity of essential oils of whole plant samples. Conclusion: The present study reveals that antimicrobial activity of bitter fennel essential oil significantly vary based on plant parts and growth stages. Key words: Antibacterial, Antifungal, Growth inhibition, Minimal inhibition concentration, Volatile oil.

Formulation and optimization of emulsions based on bitter fennel essential oil and EO/BO block copolymer surfactant

The influence of EO/BO block copolymer surfactant concentration in the range (1–5% (m/m)) and emulsification time on the emulsion stability and droplet size distribution of bitter fennel essential oil-in-water emulsions has been studied.Essential oils are promising material to be used for emulsion formulation with applications in cosmetics, food industry and agrochemicals. In the latter field these emulsions may be used as matrices for pesticides, where essential oils play the role of an eco-friendly solvent.A two-factor central composite design was conducted in order to optimize the emulsion formulation and processing. Emulsion stability has been studied as function of ageing time, by multiple light scattering (Turbiscan Lab-expert, Formulaction) and laser diffraction (Mastersizer X, Malvern). The surface response methodology allowed us to obtain a formulation comprising minimum droplet size and maximum stability by using a single step rotor/stator homogenization process.Creaming turned out to be the main destabilization mechanism. In order to improve emulsion stability the influence of high pressure homogenization (M110P, Microfluidics, MA, USA) and addition of a weighting agent (rosin gum) was studied. Although lower droplet sizes were obtained in both cases (D3,2 were in the range 0.30–0.35μm), emulsions were more unstable maybe due to Ostwald ripening phenomena.

Molluscicidal activity of four Apiaceae essential oils against the freshwater snail Radix peregra

Snails of the family Lymnaeidae are an essential link in the transmission of zoonotic diseases. Radix peregra is a European freshwater snail and a susceptible intermediate host of Fasciola hepatica, the causing agent of fascioliasis. Essential oils (EOs) extracted from Anethum graveolens (dill), Cuminum cyminum (cumin), Foeniculum vulgare var. vulgare (bitter fennel) and Petroselinum crispum (plain leaf parsley) were characterized by GC and GC–MS. Seven EOs and 11 constituents were first screened through a single-dose bioassay against R. peregra (10 mg L−1 for juveniles and 50 mg L−1 for egg masses and mature snails). EOs from parsley, cumin and bitter fennel (leaves plus stems) were highly active towards eggs and adults at 50 mg L−1. Subsequently, dose and time–lethality bioassays were performed against adults to determine lethal parameters (LC50;90 and LT50;90). Estimated 48 h LC50s varied from 13.7 to 46.5 mg L−1, with P. crispum fruits EO exhibiting the most significant activity. EOs from cumin fruits and bitter fennel infrutescences, and cuminaldehyde, were the most time-effective treatments when assessed by continuous exposure (LT50 for a 50 mg L−1 dose = 15.1, 19.3 and 19.5 h, respectively). A short-time exposure (8 h) to bitter fennel EOs was effective for the control of adults (LT50 ≤25 h). The present study uncovers the potential of four well-known Apiaceae species as natural sources of biomolluscicides.

The effect of Heights on Chemical Composition of Essential Oil of Bitter Fennel (Foeniculum vulgare subsp. piperitum) fruits

The essential oils of fruit of Foeniculum vulgare subsp. piperitum (Apiaceae) growing wild in South Anatolia were extracted by hydrodistillation, and analysed by GC and GC-MS. The percentage yields of the essential oils from fruits of bitter fennel harvested in different heights were 2.66 %, 2.0 % and 1.66 %, respectively. The major constituents varied depending on harvest years. The major constituents of bitter fennel fruit were methyl chavicol (estragol), fenchone and limonene. Methyl chavicol contents of oil changed between 50.2 % (600 m height) to 69.2 % (1600 m height). Fenchone contents of samples varied between 6.5 % and 32.8 %. The highest fenchone content was established at the level of 600 m height. While limonene contents of oil were found as 7.1 % and 8.2 % for 600 m and 1600 m heights, respectively, it was determined as 0.37 % for sea level.

Essential oil composition from sweet and bitter fennel fruits from Serbia

Fennel (Foeniculum vulgare Mill.) is aromatic plant from Apiaceae family. There are two types that have commercial importance, sweet fennel Foeniculum vulgare var. dulce, and bitter fennel – Foeniculum vulgare var. vulgare. The aim of this study was to examine the quality of essential oil of the fruits of these two varieties. Plants were grown in the experimental field in Mosorin for two years and from the produced fruits, essential oil was obtained by hydrodistillation method according to Clevenger apparatus, while the essential oil components were determined through GC/MS.Sweet fennel (variety “Fino”, Austrosaat AG, Austria) and bitter fennel (variety “Vojvođanski”, Dr Josif Pancic, Serbia) grown in Serbia, as most abundant compound of the essential oil had trans-anethole. In the var. dulceits part was from 77.2-80.0%, while the content of methyl-chavicol was 2.22.7 %, and fenchone 3.9-5.1%. The var. vulgarehad 61.1-67.1 % trans-anethole and fenchone 22.6-26.6 % depended on the year.

Larvicidal, molluscicidal and nematicidal activities of essential oils and compounds from Foeniculum vulgare

Plant-based products, namely essential oils (EOs), are environmentally friendly alternatives for the control of disease vectors, hosts and/or parasites. Here, we studied the general toxicity and biopesticidal potential of EOs and phenylpropanoids from Foeniculum vulgare var. vulgare (bitter fennel), a perennial plant well adapted to temperate climates. EO/compound toxicity was tested against a freshwater snail and potential intermediate host of Fasciola hepatica (Radix peregra), a mosquito and former European malaria vector (Anopheles atroparvus) and one of the most damaging plant-parasitic nematodes, the root-knot nematode (Meloidogyne javanica). Lethal concentrations (LC50; LC90) of EOs (infrutescences/stems with leaves) and compounds were calculated by probit analysis. All displayed noteworthy activity against R. peregra adults (LC50 21–39 µg ml−1) and A. atroparvus larvae (LC50 16–56 µg ml−1). trans-Anethole revealed acute nematicidal activity after 24 and 48 h (LC50 310 and 249 µg ml−1, respectively), and estragole (1,000 µg ml−1) showed some effectiveness against M. javanica hatching and juveniles after 15 days. Plant and EO yields were determined to evaluate the bitter fennel productivity. The chemical composition of the EOs was analyzed by gas chromatography coupled to mass spectrometry. EOs extracted from whole plants, infrutescences and stems with leaves were characterized by estragole-dominant profiles (28–65 %), considerable amounts of phellandrene (10–34 %) and fenchone (6–16 %), and minor trans-anethole contents (1–4 %). Although additional toxicological studies against nontarget organisms are required, our study demonstrates that bitter fennel is a productive source of molluscicides and larvicides, and thus a potential sustainable biological agent to control particular host species, namely freshwater snails and mosquitoes.

Variation in the essential oil constituents in indigenous populations of Foeniculum vulgare var. vulgare from different locations of Iran

The aim of this study was to determine the chemical variation in indigenous populations of bitter fennel originating from Iran. Essential oils isolated from the fruits of eight different populations of Foeniculum vulgare var. vulgare from different locations of Iran were analyzed by gas chromatography (GC) and GC/mass spectrometry (GC/MS). According to the results, the essential oil content in the fruit varied from 2.7% to 4%. The major chemical constituents exhibited higher differences between the populations. trans-Anethole was found to be the main component of the oil with rates of 46.5% and 84% in fruits and this component was followed by fenchone (9.1–23.8%), which is the second major phenylpropanoid detected in fennel oil. Limonene, estragol (methyl chavicol), γ-terpinene, α-pinene and β-mercene are other main components identified in the fennel oils. trans-Anethole was detected at the highest level (84%) in ‘Zanjan’ population oil and the ‘Marvdasht’ population contained the highest concentration (12.2%) of estragol compared with other populations. Fenchone, limonene, γ-terpinene, α-pinene and β-mercene were in higher concentrations in ‘Ardabil’ population oil than the other populations, while trans-anethole was the lowest in this population’s oil. The results suggest that there were important variations among the fennel population’s fruit in Iran concerning the essential oil content and composition.