IngredientsOat (Avena sativa) is a cereal known since antiquity as a useful grain with abundant nutritional and health benefits. Oat is the only cereal crop that does not use benzoxazinoids as allelochemicals against fungi; instead, oat accumulates two distinct classes of saponins — avenacins and avenacosides. Avenacosides are therefore a chemotaxonomic signature of the genus Avena, distinguishing it from all other cultivated cereal crops.
Oats contain two unique steroidal saponins, avenacoside A and avenacoside B. Saponins are one type of widespread defense compound in the plant kingdom and have been exploited for the production of lead compounds with diverse pharmacological properties in drug discovery.
The revised structures of avenacosides A and B and a new sulfated steroidal saponin isolated from grains of Avena sativa L. were elucidated, with structures and complete NMR assignments based on 1D and 2D NMR studies and identified as nuatigenin 3-O-{α-L-rhamnopyranosyl-(1→2)-[β-D-glucopyranosyl...}
Oat leaves contain a different family of saponins from those found in roots: the steroidal molecules avenacosides A and B. Avenacoside A differs from avenacoside B only in that it lacks the terminal 1-3-linked D-glucose molecule.
The steroidal oat leaf saponins avenacosides A and B both have two sugar chains, one at C-3 and one at C-26. This bidesmosidic structure — meaning two separate sugar chains attached at two positions of the aglycone — is chemically significant because it governs their biological activity, as described below.
In response to pathogen attack, avenacosides are converted into 26-desglucoavenacosides (26-DGAs), which possess antifungal activity. These molecules are comprised of a steroidal backbone linked to a branched sugar chain consisting of one alpha-L-rhamnose and two (avenacoside A) or three (avenacoside B) beta-D-glucose residues.
Unlike other cereals, oats accumulate saponins, encompassing triterpenoid saponins and steroid saponins. Steroid saponins, such as avenacosides A and B, were first isolated from oat grains and leaves. The first isolation of avenacoside A was reported by Tschesche and co-workers in 1969 (in Chemische Berichte), with avenacoside B following in 1971.
More recently, a study directly purified five steroidal saponins (1–5) from a methanol extract of oat bran, characterized their structures by analyzing their MS and NMR spectra, and also tentatively identified 11 steroidal saponins (6–16) on the basis of their tandem mass spectra. Among the five purified saponins, compound 5 is a new compound and compound 4 is purified from oats for the first time.
Several types of saponins like triterpenoid saponins, avenacosides A and B from the leaves, and avenacin are reported from the root of A. sativa. Leaves have acylated and steroidal saponins, sterylglycosides (ASG), sterols, and sterylglycosides (SG).
These compounds have been detected in oat roots, leaves, and grain. In the grain, avenacosides A and B were revealed as the primary saponins, whereas in the husks, 26-desglucoavenacoside A was predominant. The elevated level of the active fungicidal form of saponin (26-desglucoavenacoside A) in the husks possibly indicates they are more prone to fungal attacks.
The absolute concentrations in plant tissue are notable: the total concentration of avenacoside A, avenacoside B and their desglucosides has been found to be 0.2 mg/100 mg fresh oat leaves.
The average content of avenacoside A and avenacoside B in three analysed oat bran products was 26 ± 7 mg/100 g and 8 ± 2 mg/100 g, respectively. In an oat drink, avenacoside A content was 4.6 ± 0.1 mg/100 g, avenacoside B was 2.7 ± 0.2 mg/100 g, and 26-desglucoavenacoside A was below the limit of quantification.
Avenacoside B represented 35.8%–55.2% of total saponin content in grain and 13.8%–49.0% in husks. The content of avenacosides varies due to differences in cultivars, growth conditions, and the sensitivity and precision of quantification methods used across different studies.
Oat-based milk alternatives (OMAs) may provide health benefits resulting from oat nutritional compounds; avenacosides are saponins with anti-bacterial and anti-fungal properties. Oats undergo multiple processing steps to ensure a sensory-appealing and safe product; however, little research has been carried out on the specific effects of these processing steps on these compounds. One study aimed to determine the concentration of avenanthramides, avenacoside A, and β-glucan throughout 12 stages of production.
The increased content of avenacosides in oat protein concentrate should be ascribed to the partial concentration of the oat saponins together with the protein fraction during the production process of oat protein concentrate.
For more than 4,000 years, Avena sativa has been recognized as a food, and its traditional use has been recorded since the 12th century. Oats have been used for personal care purposes since antiquity; wild oats (Avena sativa) were used in skin care in Egypt and the Arabian Peninsula as early as 2000 BC.
Traditionally, oats have been in use since long and are considered as stimulant, antispasmodic, antitumor, diuretic, and neurotonic. Oat possesses different pharmacological activities like antioxidant, anti-inflammatory, wound healing, immunomodulatory, antidiabetic, and anticholesterolaemic properties.
It is important to note that in the historical and traditional literature, health effects were attributed to oat preparations as a whole, not to isolated avenacosides. The specific contributions of avenacosides to these traditional uses have only become a subject of scientific inquiry in the modern era. Oats provide substantial levels of bioactive compounds such as phenolic acids, tocols, sterols, avenacosides, and avenanthramides. The saponin fraction — which includes avenacosides — was not differentiated from other oat constituents in pre-modern use.
The cleansing activity of oat is from the saponins. In traditional bathing and cosmetic practices, the foam-forming properties of oat-derived saponins (including avenacosides) were implicitly harnessed, though not identified by name.
One of the most thoroughly characterised features of avenacosides is their role as biologically inactive precursors that are enzymatically activated upon tissue disruption. Avenacosides are biologically inactive until they are converted to antifungal monodesmosidic saponins (26-desglucoavenacosides A and B) in response to tissue damage. The stem and leaves contain bidesmosidic steroidal saponins (e.g., avenacosides A and B); triterpenoid saponins and avenacin have also been reported in the root.
These glycosides are localized in the vacuole, and are believed to be preformed compounds which demonstrate activity against fungal infections; oat leaves contain a very active and specific β-glucosidase, known as avenacosidase, which immediately converts avenacoside A and avenacoside B into the antifungal 26-desgluco-derivatives upon cell damage.
A plastidal β-glucosidase from Avena sativa (oat) is activated during fungal infections. Antifungal precursors are stored in plant vacuoles, and the enzyme activates these avenacosides by hydrolysis to form antifungal 26-desglucoavenacosides. The enzyme is a globular α/β barrel with two catalytic glutamic acid residues that act as nucleophiles or as an acid/base catalyst. β-Glucosidase from oat hydrolyzes the β-glucoside avenacoside to C26-desgluco-avenacosides. This enzyme is nominally a homohexamer that hydrolyzes β1→4 glucose bonds; it also cleaves avenacosides as an antifungal defense.
Once activated to the desgluco- form, avenacosides exert their antifungal effects through a well-characterised membrane-disruption mechanism. The toxic mechanism of these saponins against fungi has been attributed to their lytic activity: when the saponins complex with membrane sterols, pores are formed, resulting in a loss of membrane integrity.
Isolates of pathogenic fungi that are capable of infecting oats can perform sequential hydrolysis of the sugar residues from the 26-desglucoavenacosides. Degradation is initiated by removal of the L-rhamnose, which abolishes antifungal activity. This demonstrates how some fungal pathogens have evolved counter-resistance mechanisms against the oat's chemical defense system.
An in vivo study performed in mice and an in vitro batch fecal fermentation study were used to investigate the potential metabolic routes of avenacosides B and A. Deglycosylation was identified as the major metabolic path for avenacosides B and A.
In an animal study, the pharmacokinetic parameters of avenacosides were studied in urine samples together with their gut microbiota metabolites. Neither the impact of the food matrix on their bioavailability and subsequent bioefficacy in vivo, nor their dose response in plasma, has been thoroughly investigated.
Saponins regulate fat absorption by inhibiting pancreatic lipase and modulate adipogenesis through the adenosine monophosphate-activated protein kinase signaling pathway, further contributing to the suppression of obesity. These mechanisms have been proposed for saponins broadly; whether they apply specifically to avenacosides at physiologically relevant concentrations in humans has not been confirmed in controlled clinical trials.
In in vivo allergic contact dermatitis models, by stimulating the mitogen-activated protein kinase signaling pathway, oat sprouts increased the expression levels of proteins associated with skin barrier formation, which are produced during the differentiation of keratinocytes.
In a lipopolysaccharide-induced skin irritation model using HaCaT cells, steroidal saponins (avenacoside B and 26-desglucoavenacoside B) and a flavonoid (isovitexin-2-O-arabinoside) of oat sprouts regulated the genetic expression of the same proteins located on the adjacent locus of human chromosomes known as the epidermal differentiation complex (EDC).
With filaggrin being the most powerful humectant among barrier proteins, one study proposes that the moisturizing effect of oat sprouts originates from the increased filaggrin expressed by its unique steroidal saponin, avenacoside B.
Evidence type: Biochemical, in vitro, and plant-model studies
The antifungal activity of the active metabolite 26-desglucoavenacoside B is the most extensively studied biological function of this compound family. Previous studies indicated that 26-desglucoavenacoside B and 26-desglucoavenacoside A are active antifungal compounds released by deglycosylation of avenacoside A and B in infested leaves. 26-desglucoavenacoside B shows the greatest inhibition of Pyrenophora mycelia, while 26-desglucoavenacoside A and avenacosides A and B showed minor inhibition of mycelia growth.
The avenacosides AveB and 26DGAveB were separated and purified from A. sativa green leaves, and their mycotoxic activity was confirmed against the fungus Trichoderma harzianum.
Evidence strength: The antifungal mechanism is well-characterised at a biochemical and plant-pathology level. There are no human clinical trials investigating avenacosides as antifungal therapeutic agents. Evidence is restricted to in vitro and plant-biology models.
Evidence type: In vitro assays and one mouse model
A study examined the molecular mechanisms behind the anthelmintic activity of the oat saponins avenacoside B (AveB) and 26-desglucoavenacoside B (26DGAveB) by evaluating their effect on Heligmosomoides bakeri, a parasitic nematode of mice.
Both compounds induced morphological changes in larvae and blocked Pgp (glycoprotein pump) activity; however, only 26DGAveB provoked expression of CED-9. The infected mice displayed changes in the molecular pattern of larval proteins and enhanced IL-4 production, indicating that avenacosides reduced the infectivity of H. bakeri larvae. In avenacosides, the residue without glucose at the C26 position demonstrated greater anti-nematode activity.
Avenacoside B, an oat saponin purified from Avena sativa green leaves, reduced the infectivity of Heligmosomoides bakeri larvae in a mouse model. Avenacoside B induced morphological changes in larvae, enhanced IL-4 production, and blocked glycoprotein pump (Pgp) activity.
Evidence strength: Preliminary. Studies are limited to one species of parasitic nematode in a mouse model. No human or large-animal clinical studies have evaluated avenacosides as anthelmintic agents.
Evidence type: In vitro cell models and in vivo animal (murine) models
Despite numerous studies on skin moisturisation, anti-inflammation, and antioxidation effects of oats, the precise molecular mechanisms are only partially understood. One study investigated the efficacy of oat sprouts in the treatment of allergic contact dermatitis (ACD) and identified their specific phytoconstituents and exact mechanisms of action.
In a lipopolysaccharide-induced skin irritation model using HaCaT cells, steroidal saponins (avenacoside B and 26-desglucoavenacoside B) and a flavonoid of oat sprouts regulated the genetic expression of proteins located on the epidermal differentiation complex. The expression levels of filaggrin were significantly diminished after LPS treatment, indicating that LPS greatly disrupted skin barrier function. However, many of these damages were repaired after treatment with the compounds. Filaggrin expression significantly recovered with avenacoside B and 26-desglucoavenacoside B to the level of the non-irritating controls.
In a lipopolysaccharide-induced skin irritation model, steroidal saponins (avenacoside B and 26-desglucoavenacoside B) regulated the genetic expression of proteins on the epidermal differentiation complex (EDC). Furthermore, oat sprouts showed immunomodulatory functions.
A separate line of research has examined protein-free oat plantlet extracts standardised for avenacoside content in the context of atopic dermatitis. Owing to their high content of flavonoids and saponins, plantlets of Avena sativa L. are likely to possess anti-inflammatory and immunoregulatory properties of value in the treatment of atopic dermatitis (AD). A protein-free plantlet extract was prepared and two flavonoids — isoorientin-2''-O-arabinoside (1) and isovitexin-2''-O-arabinoside (2) — and two saponins, avenacosides A (3) and B (4) were isolated from it.
Oat sprouts have been proposed for use as a therapeutic reagent for allergic contact dermatitis and other diseases such as atopic dermatitis or asthma, which are characterized by a disrupted skin barrier.
Evidence strength: Moderate preclinical evidence. The mechanistic role of avenacoside B in filaggrin upregulation is supported by in vitro and animal data. There are no controlled human clinical trials specifically isolating the contribution of avenacosides to skin health outcomes, separate from the broader oat extract matrix.
Evidence type: In vitro and animal studies; indirect epidemiological associations with whole oat consumption
Oats contain a unique phytochemical called steroidal saponin, mainly avenacins and avenacosides. Apart from plant defense mechanisms, oat saponins have a potential for cholesterol lowering, immunoregulatory, and anticancer activities.
Toxicity of oat saponins is considered low, although they can affect the absorption of other nutrients, e.g., lipid metabolism and digestion of carbohydrates.
The chemical composition, the levels of avenacosides in commercial oat products, and their health effects are still largely unknown.
Evidence strength: Weak for avenacosides specifically. The well-established cholesterol-lowering effect of oats in humans is primarily attributable to β-glucan, which has received regulatory approval from both the FDA and EFSA. Whether avenacosides contribute independently to lipid modulation in humans has not been tested in controlled clinical trials.
Evidence type: Animal model and computational (in silico) study
Using HPLC-MS techniques, 26-desglucoavenacoside A and B and avenacoside A in oats were found to lower the binding energy of growth differentiation factor-5 (GDF5) and insulin-like growth factor-1 receptor (IGF1R). After a 4-week treatment, serum growth hormone (GH) and osteoprotegerin concentrations in the high-dose combined oat and green onion group were similar to those of the positive control.
Evidence strength: Highly preliminary. This data comes from an in silico docking analysis combined with an animal model; no human studies have investigated this area.
Oat saponins have a potential for cholesterol lowering, immunoregulatory, and anticancer activities. Oat (Avena sativa L.) is rich in phytochemicals such as avenanthramides, avenacosides, and avenacins, which support intestinal health and exhibit antioxidative and anticancer properties.
Evidence strength: Very preliminary and largely indirect. Most evidence for oat-related anticancer activity in the scientific literature concerns avenanthramides (not avenacosides), and the evidence is predominantly in vitro and in animal models. No clinical trials have assessed avenacosides specifically for cancer prevention or treatment.
A distinct area of research has explored avenacosides not as therapeutic agents per se but as objective dietary biomarkers, exploiting their specificity to oats.
Avenanthramides (AVAs) and avenacosides (AVEs) are unique to oats (Avena sativa) and may serve as biomarkers of oat intake. A 2025 study aimed to investigate critical validation parameters such as half-lives, dose-response, matrix effects, and relative bioavailability under single dose and repeated dosing. Twenty-one healthy participants consumed two oat products (solid and liquid) in a non-blinded randomized crossover study for the pharmacokinetic assessment of multiple AVAs and AVEs (A and B).
Avenanthramides are promising candidates as compliance biomarkers of oat intake in intervention studies regardless of the tested food matrices. However, due to their short elimination half-lives, their applicability in nutritional epidemiology where long-term habitual intake is of main interest appears restricted.
Twelve healthy volunteers were recruited in a human urinary pharmacokinetic study; each participant received a single dose of oat bran as breakfast, 48-hour urine samples were collected at baseline and after treatment period, and avenacosides B and A were quantified by LC-MS/MS. Deglycosylation was identified as the major metabolic path for avenacosides B and A.
A review summarised current knowledge on the chemistry, stability, bioavailability, and health effects of two unique phytochemicals in oats, avenanthramides and avenacosides A and B. The review concluded that studies on the beneficial effects of avenanthramides and avenacosides A and B are still in their infancy, and additional health benefits of these unique oat components may yet be identified.
Avenacosides are not typically sold as isolated ingredients; they occur naturally within whole oat products and specialised oat extracts. The scientific literature contains dosage information primarily in the context of quantification studies, pharmacokinetic trials, and animal experiments rather than standardised therapeutic dosing in humans.
No standardised therapeutic dose for avenacosides in humans has been established by any regulatory or monograph body. The chemical composition, the levels of these saponins in commercial oat products, and their health effects are still largely unknown.
Toxicity of oat saponins is considered low, although they can affect the absorption of other nutrients, e.g., lipid metabolism and digestion of carbohydrates.
There are numerous reports of saponins with anthelmintic effects. Although most are too toxic for systemic treatment (due to haemolytic effects), their oral administration usually poses no toxicity problems. This general principle applies to the oat saponin class, as the bidesmosidic structure of intact avenacosides is believed to reduce their haemolytic potential compared to monodesmosidic saponins.
A key safety-relevant property of avenacosides A and B (the native, intact forms) is their biological inactivity prior to enzymatic conversion. Avenacosides are biologically inactive until they are converted to antifungal monodesmosidic saponins (26-desglucoavenacosides A and B) in response to tissue damage. This means that, in intact oat grain consumed orally, the primary forms present are the less-active bidesmosidic avenacosides, not the more bioactive desglucoavenacosides.
Saponins regulate fat absorption by inhibiting pancreatic lipase and modulate adipogenesis through the AMPK signaling pathway. However, the clinical application of these phytochemicals is often limited by factors such as bioavailability, solubility, and potential toxicity.
A safety assessment of Avena sativa (oat)-derived ingredients was conducted. The functions of these ingredients in cosmetics include abrasives, antioxidant, skin-conditioning agents, absorbents, and bulking agents. The Panel reviewed relevant animal and human data. Because final product formulations may contain multiple botanicals, each containing similar constituents of concern, formulators are advised to be aware of these constituents and to avoid reaching levels that may be hazardous to consumers. The Panel stated that industry should use good manufacturing practices to limit impurities and concluded that all but one of the A. sativa (oat)-derived ingredients are safe as cosmetic ingredients in the practices of use and concentration described in the safety assessment when formulated to be non-sensitizing.
The Panel noted that aflatoxins have been detected in A. sativa plants, seeds, dried hay, and/or in processed oat cereals. This is a quality-control consideration relevant to oat-derived ingredient suppliers rather than a specific safety concern intrinsic to avenacosides themselves.
One study correlated the abundance of Faecalibacterium prausnitzii to avenanthramide metabotypes and specifically their ability to transform avenanthramides to their dihydro-counterparts. Such metabotypes may exhibit different health benefits of consuming oats, which needs to be explored further in future studies. Whether analogous gut-microbiota-driven inter-individual variation exists for avenacoside metabolism has not been systematically characterised.
Neither the impact of the food matrix on avenacoside bioavailability and subsequent bioefficacy in vivo, nor their dose response in plasma, has been thoroughly investigated.
Avenanthramides are promising candidates as compliance biomarkers of oat intake in intervention studies, but due to their short elimination half-lives, their applicability in nutritional epidemiology where long-term habitual intake is of main interest appears restricted. Available evidence suggests avenacosides share similar pharmacokinetic constraints.
A review summarising current knowledge on the chemistry, stability, bioavailability, and health effects of avenacosides A and B concluded that studies on the beneficial effects of avenacosides A and B are still in their infancy, and additional health benefits of these unique oat components may yet be identified. This characterisation remains accurate: as of the most recent published data, no large-scale human clinical trials have been conducted on isolated avenacosides as dietary supplement or therapeutic agents.
Health conditions that Avenacosides may help support.
Body systems that Avenacosides may help support.
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