Loquat

Loquat (Eriobotrya japonica): A Comprehensive Reference

1. Identity and Botanical Classification

Eriobotrya japonica (Thunb.) Lindl., commonly known as loquat, is a plant belonging to the Rosaceae family. It is a member of the Eriobotrya genus within the subfamily Maloideae of the Rosaceae family. A more recent taxonomic synonym, Rhaphiolepis bibas (Lour.) Galasso & Banfi, places it within the same family; the plant is an evergreen, subtropical fruit tree native to China and Japan, but cultivated in southern countries of Europe.

An economically important subtropical evergreen fruit tree from the Rosaceae family, it is native to southeast China. E. japonica has been cultivated in China for more than 2000 years, and its cultivation has spread to many countries, including Japan, Turkey, Brazil, and Spain. Native to China, it is extensively cultivated in southern regions and globally, including Japan, the United States, India, Spain, Brazil, Mexico, Argentina, and Italy, among others.

Common names for the plant vary by language and region. In Chinese traditional medicine, the leaf drug is known as Pi Pa Ye (枇杷叶), and the plant is also called pipa (Chinese lute) in Chinese, a reference to the resemblance of its leaves to the traditional string instrument. In Japanese it is called biwa, and in Spanish-speaking countries it is known as níspero.

Plant Parts Used

As a traditional medicinal plant, loquat has been used for thousands of years for its nutritional and pharmaceutical value. Loquat flowers, fruit, leaves, roots, and bark can all be used as traditional drugs. Flowers can cure headaches and runny nose; fruit can moisturize viscera; and the root can cure consumptive cough and joint pain. The most important medicinal part is the loquat leaf, the main medicinal ingredients of which include nerolidol and farnesol volatile oils, organic acids, amygdalin, and vitamin B.

Common Forms and Preparations

The fruits of E. japonica are primarily consumed fresh or used in making jams and alcoholic beverages. The loquat tree produces fruits that are not only consumed fresh but also processed into various products such as jams, jellies, and juices. Loquat fruits are often eaten raw or as an extract, but the fruit is also found in jams, pies, and juices. The loquat leaf and flower are also sometimes used in teas. In medicinal and supplement contexts, loquat is commercially available as standardized leaf extracts (in capsule or tablet form), dried leaf powders, herbal teas (decoctions and infusions), syrups, and topical preparations. Currently, there are dietary supplements and herbal medicines on the market derived from loquat.

2. Traditional and Historical Use

China

Loquat is a subtropical fruit tree with high medicinal value native to China. Different organs of loquat have been used historically as folk medicines and this has been recorded in Chinese history for thousands of years. Loquat extracts have been used for the treatment of cough, chronic bronchitis, inflammation, diabetes, and cancer in Chinese folk medicine. Ancient literature, such as the Compendium of Materia Medica, described the origin, classification, breeding methods, and medicinal value of the loquat tree, and laid the foundation for the development and cultivation of loquat. The Compendium of Materia Medica (Bencao Gangmu), compiled by Li Shizhen, dates to 1578 CE, representing one of the most important historical records of loquat's medicinal role.

Traditional Chinese medicine has extensively used loquat leaves to alleviate coughs and respiratory conditions such as chronic bronchitis and asthma. In China, loquat flowers and leaves are frequently utilized as medicinal herbs, purportedly offering benefits such as wind dispersal, cough relief, and nasal decongestion. They are traditionally employed for symptoms such as headaches, nasal obstruction, rhinorrhea, persistent cough due to fatigue, and blood-streaked sputum. As a traditional Chinese medicine, loquat leaf has been widely used in the treatment of respiratory diseases for centuries, such as pharyngolaryngitis, bronchitis, chronic bronchitis cough, and chronic obstructive pulmonary disease.

Japan

In Japanese Kampo medicine, loquat — known as biwa — has been incorporated into herbal formulations addressing respiratory and digestive complaints. Loquat is an Asian evergreen tree commonly cultivated for its fruit, and its leaf has long been used as an important material for both functional and medicinal applications in the treatment of lung disease in China and Japan.

Morocco and North Africa

Loquat leaves have been used in Moroccan traditional medicine to manage diabetes and its complications. In Moroccan traditional medicine, loquat leaves have been used to treat diabetes and its complications. In African traditional medicine, loquat extracts have been noted for their beneficial health effects, including antifungal properties against Cryptococcus neoformans.

Other Regions

Originating from Southeast China, loquat has been utilized in traditional medicine across countries like Indonesia, Japan, India, and Turkey. Different plant parts are being used in traditional medicine to treat many diseases including diabetes, respiratory disorders, cardiovascular diseases, and digestive disorders. Ethnobotanical studies reveal that loquat has been a staple in folk medicine across different cultures.

Preparations Used Traditionally

Across the cultures in which it has been used, loquat has been prepared in several characteristic ways. The most important medicinal part is the loquat leaf, and loquat leaf extract has been used for the treatment of cough originating in the lung for thousands of years. Traditional preparations include decoctions of dried leaves taken as a tea for respiratory complaints, loquat-based syrups combined with other botanicals for coughs and sore throats, and fruit-based preparations consumed for general nutrition and digestive support. At present, loquat extracts are used for treating inflammation, diabetes, chronic bronchitis, and cancer.

3. Key Constituents and Active Compounds

The phytonutritional composition of extracts of different organs varies considerably: loquat leaf and flower are rich in phenolics and triterpenes; fruit is rich in sugars, organic acids, carotenoids, flavonoids, phenolic acids, and vitamins; the kernel is a good source of proteins, starch, tannins, and minerals.

Triterpenoids

Triterpenoids are a class of chemical compounds composed of three terpene units, known for their diverse biological activities. In loquat, triterpenoids such as ursolic acid and oleanolic acid have been identified. These compounds exhibit a range of pharmacological properties, including anti-inflammatory, antitumor, and antioxidative activities.

Twelve triterpene acids — including seven ursane-type (ursolic acid, corosolic acid, 3-O-cis-p-coumaroyltormentic acid, 3-O-trans-p-coumaroyltormentic acid, 3-epicorosolic acid, euscaphic acid, and 1β-hydroxyeuscaphic acid), four oleanane-type (oleanolic acid, maslinic acid, methyl arjunolate, and 2α,3α,23-trihydroxyolean-12-en-28-oic acid), and one lupane-type (betulinic acid) — have been isolated from the ethyl acetate-soluble fraction of loquat leaf. Additional triterpenoid compounds identified in loquat include tormentic acid, 3-O-cis-p-coumaroyltormentic acid, and methyl chlorogenic acid.

Flavonoids and Phenolic Compounds

Phytochemical analysis of E. japonica leaves identified 30 compounds, including flavonoids, phenolics, and megastigmanes. The flavonoids isolated from the leaves include flavones, flavans, flavolignans, flavonoid glycosides, and coumaroyl flavonoid glycosides.

The polyphenols contained in loquats can be categorized into phenolic acids, flavonoids, lignans, coumarins and hydroxycinnamic acids, stilbenes, and proanthocyanidins. The flavonoids in loquats mainly include fourteen kinds of flavonoids, such as kaempferol, quercetin, galangal, nerol, and rutin, and fourteen kinds of phenolic compounds, including chlorogenic acid, caffeic acid, ferulic acid, gallic acid, and protocatechuic acid.

Phytochemical studies indicate that flavonoids are among the main chemical components of loquat leaf, and most of them contain quercetin and kaempferol as the parent nucleus, such as rutin (quercetin-3-O-rutinoside) and kaempferol-3-O-glucoside.

Polysaccharides

Polysaccharides in loquat have been studied for their immunomodulatory and antidiabetic effects, highlighting the broad spectrum of bioactive compounds in this versatile plant. A galacturonic acid (GalA)-containing polysaccharide isolated from loquat leaves showed potential anti-inflammatory and antioxidant effects.

Carotenoids and Vitamins

Vitamins, particularly vitamin C, are present in loquat fruits, enhancing its nutritional value and contributing to its overall antioxidant properties. Carotenoids, such as beta-carotene and lutein, are also present and play a role in eye health and immune function. Red cultivars of loquat fruit generally have higher levels of carotenoids compared to white fruit cultivars.

Organic Acids and Minerals

The organic acids responsible for the titratable acidity of loquat juice are mainly represented by malic acid (610.08 ± 19.55 mg/100g), followed by tartaric acid (73.17 ± 5.22 mg/100g), succinic acid (26.11 ± 1.83 mg/100g), and oxalic acid (15.93 ± 1.13 mg/100g). The mineral content in loquat juice is essentially represented by potassium (261.58 ± 10.23 mg/100g), sodium (36.20 ± 1.93 mg/100g), phosphorus (23.66 ± 1.41 mg/100g), calcium (17.62 ± 3.01 mg/100g), magnesium (18.02 ± 2.11 mg/100g), and iron (3.99 ± 0.16 mg/100g).

Sesquiterpene Glycosides and Volatile Oils

Sesquiterpene glycosides have been identified as key contributors to loquat's medicinal properties, particularly in managing hyperglycemia and inflammation. Modern purification technology has successfully isolated multiple effective components from loquat, including volatile oils such as nerolidol and farnesol, as well as tartaric acid.

Amygdalin (Cyanogenic Glycoside)

Amygdalin is the main saponin component in loquat, distributed in various parts of the plant. It can be decomposed into hydrocyanic acid, phenylacetic acid, and glucose in the body. Among these, prussic acid (hydrocyanic acid) is a toxic substance capable of inhibiting cell respiration and causing cell death. Amygdalin is most highly concentrated in the seeds.

4. Mechanisms of Action

Anti-inflammatory Mechanisms

Loquat leaf extract and its triterpene ursolic acid inhibit LPS-induced cytokines and inducible enzyme production (iNOS, COX-2, TNF-α, IL-1β, and IL-8) in A-549 human lung epithelial cells via the NF-κB signaling pathway. The anti-inflammatory effect of loquat leaf extract might result from the inhibition of expression of iNOS and COX-2 through the downregulation of NF-κB activation and MAPK phosphorylation in LPS-stimulated RAW264 cells and in the LPS-activated murine peritoneal macrophage model.

Anti-inflammatory effects of loquat tea extract may rely on the inhibition of the production of iNOS, nitric oxide (NO), IL-6, TNF-α, and on the downregulation of the transforming growth factor-β (TGF-β)-activated kinase-mediated MAPK and NF-κB pathways in mouse macrophage-like RAW 264.7 cells.

The compounds targeting the cysteinyl leukotriene receptor-1 (CysLTR1) from loquat fruit were identified as corosolic acid, ursolic acid, and oleanolic acid. A high-dose combination of the three exhibited stronger anti-inflammatory activity than any triterpene acid alone and the loquat extract, significantly decreasing inflammatory cell counts and inhibiting the production of pro-inflammatory mediators. These three triterpene acids exhibited anti-inflammatory activities by attenuation of CysLTR1 expression.

Antidiabetic Mechanisms

The pharmacological effectiveness of loquat leaf extract and its important component ursolic acid in the treatment of diabetes mellitus has been explored in traditional medicine. Research has evaluated their protective effects against hyperglycemia-induced advanced glycation end product (AGE) formations and hepatic pro-inflammation.

Ursolic acid and loquat extract suppressed hepatic oxidative stress and AGE formation in diabetic mice, accompanied by downregulated mitogen-activated protein kinase signaling and nuclear factor κB (NF-κB) activity. Docking simulation predicted ursolic acid to bind to liver kinase B1 (LKB1), an upstream regulator of the AMP-activated protein kinase (AMPK)/transcription factor forkhead box O3 (FOXO3) axis. Ursolic acid reversed the high-glucose-induced downregulation of LKB1-AMPK-FOXO3 activation and antioxidant gene transcription.

Sesquiterpene glycosides have been shown to improve insulin sensitivity, reduce blood glucose levels, and modulate gut microbiota, thereby offering a natural therapeutic option for managing type 2 diabetes mellitus. Loquat leaf extracts and their isolated triterpenoids also show inhibitory activity against α-glucosidase and α-amylase, two key enzymes involved in postprandial blood glucose elevation. The leaf methanolic extract exhibited antidiabetic potential due to its potent α-glucosidase inhibition, and the presence of diverse phenolic compounds, including flavonoids and their glycoside derivatives, further supports the traditional use of E. japonica as an herbal medicine with antidiabetic properties.

Antioxidant Mechanisms

Loquat exhibits significant antioxidant properties, primarily attributed to its high content of bioactive compounds such as flavonoids, phenolic acids, and vitamins. The main sources of antioxidant activity in loquat and its by-products are vitamin C, vitamin E, polyphenolic compounds, and carotenoids. These compounds act by scavenging free radicals and up-regulating endogenous antioxidant enzyme systems. Loquat leaf extract significantly increased antioxidant enzyme activities of superoxide dismutase, catalase, glutathione-S-transferase, glutathione peroxidase, glutathione reductase, and reduced glutathione in HepG2 cells.

Hepatoprotective Mechanisms

Loquat leaf extracts showed hepatoprotective effects in HepG2 cells overexpressing CYP2E1 by improving the hepatic antioxidant activity and decreasing the formation of intracellular reactive oxygen species (ROS). As a result, loquat leaf extract increased HepG2 cell viability in a concentration-dependent manner and showed protective activity against ethanol-induced toxicity in HepG2 cells.

Antimicrobial Mechanisms

In addition to antioxidant, anti-inflammatory, and hypoglycemic effects, loquat has a wide array of other functional activities. For example, the polyphenols in loquat can have a significant inhibitory effect on the growth and activity of bacteria and fungi. Studies have indicated that polyphenol extracts affect normal microbial activity by enhancing the permeability of microbial cell membranes.

5. Scientific Evidence by Area of Use

5.1 Respiratory Health

Loquat leaf's use for respiratory conditions represents one of the oldest and most investigated traditional applications. Its leaf has long been used as an important material for both functional and medicinal applications in the treatment of lung disease in China and Japan. As the principal functional components of loquat leaf, triterpene acids have shown notable anti-inflammatory activity.

Animal and cellular evidence is more robust than human clinical evidence in this area. In a study where male C57BL/6 mice were challenged with cigarette smoke for 12 weeks and then fed triterpene acids from loquat leaf (50 and 100 mg/kg) for 6 weeks, triterpene acids suppressed lung histological changes in cigarette smoke-exposed mice, as evidenced by diminished generation of pro-inflammatory cytokines including IL-1β, IL-2, IL-6, and TNF-α. Moreover, treatment significantly inhibited malondialdehyde levels and increased superoxide dismutase activity. Triterpene acids also increased phosphorylation of AMPK and Nrf2 expression, while inhibiting phosphorylation of NF-κB and iNOS expression in CS-induced COPD. The study concludes that triterpene acids could be considered as a promising candidate for treating COPD-related inflammation. This is an animal study and its results cannot be directly applied to humans.

Loquat leaf extracts enriched with triterpene acids, especially ursolic acid, showed anti-inflammatory effects on alveolar macrophages in rats with LPS-induced chronic bronchitis. Again, this is preclinical evidence only.

Evidence strength: Preclinical (animal and cellular) evidence for respiratory anti-inflammatory effects is consistent; controlled human clinical trials specifically evaluating loquat-only preparations for respiratory conditions are currently lacking in the peer-reviewed literature. The traditional use in Chinese and Japanese medicine is well documented historically, but this does not substitute for controlled clinical evidence.

5.2 Blood Glucose Regulation and Antidiabetic Effects

The antidiabetic potential of loquat is among the most extensively studied pharmacological properties of this plant. Research spans in vitro enzyme inhibition assays, animal models, and limited molecular mechanistic studies.

Extracts of methanol from loquat leaves recorded DPPH free radical scavenging activity of 87% and gave the lowest IC50 of 0.5336, which was below that of ascorbic acid used as a control. Hexane extract had a higher α-amylase inhibitory activity of 24% at 1 μg/ml as compared to other extracts. Generally, hexane extracts of Eriobotrya japonica exhibit mild inhibitory activity against the α-amylase enzyme. The results obtained support the use of the plant as an anti-diabetic agent at higher concentrations. This study is in vitro only.

Mice fed a high-fat and high-glucose diet for 10 weeks were used as a model to assess the antidiabetic and antihyperlipidemic effects of a daily administration of loquat leaf aqueous extract (LLE) at three different doses: 150, 200, and 250 mg/kg body weight/day. This constitutes in vivo animal evidence.

Oral administration of ursolic acid and loquat leaf extract at a dose of 50 mg/kg/day for 15 days yielded no significant hypoglycemic effect in diabetic db/db mice. This indicates that the antidiabetic benefit in some models may relate more to anti-inflammatory and anti-AGE activity than to direct blood glucose lowering, and that results across animal models are not uniform.

Loquat is known to be rich in bioactive constituents such as triterpenoids, flavonoids, phenolics, and polysaccharides, which exhibit antioxidant, anti-diabetic and anti-cancer activities.

Evidence strength: Preclinical (in vitro and animal model) evidence for antidiabetic mechanisms (α-glucosidase/α-amylase inhibition, insulin sensitization, AGE suppression) is substantial and mechanistically informative. No well-designed, randomized controlled human trials evaluating loquat extracts specifically for blood glucose control in humans were identified in the peer-reviewed literature. The evidence remains at the preclinical stage.

5.3 Anti-inflammatory Effects

Research shows that loquat extracts contain many antioxidants, and different extracts exhibit bioactivity capable of counteracting inflammation, diabetes, cancer, bacterial infection, aging, pain, allergy, and other health issues.

The leaves and fruits of Eriobotrya japonica are known for their expectorant, anti-inflammatory, and antidiabetic effects, among others.

The mechanistic basis for anti-inflammatory activity is well-characterized in preclinical models. As noted above, inhibition of NF-κB, MAPK, iNOS, COX-2, and CysLTR1 pathways by triterpene acids (particularly ursolic acid, corosolic acid, and oleanolic acid) has been demonstrated in cell-line and animal studies. Loquat seed extracts also showed anti-inflammatory effects in vivo. By using a chemotherapy drug (5-fluorouracil)-induced mucositis model in hamsters, the loquat seed extract significantly inhibited the chemotherapy-induced mucositis, and the epithelial injury and bacterial infection were greatly inhibited, together with a much lower plasma lipid peroxide level.

Evidence strength: Strong preclinical mechanistic evidence across multiple cell and animal models; no well-powered randomized human trials specifically on loquat anti-inflammatory effects were identified.

5.4 Antioxidant Activity

The profile of phenolic constituents of E. japonica fruits and leaves from Tuscany (Italy) was evaluated for in vitro antioxidant and chemopreventive activities. Results revealed that the extract of leaves displayed higher antioxidant and anticancer potential than the fruit extract and contained 25 individual phenolic compounds characterized and quantified by the UPLC-PDA-MS method.

Loquat juice is a good source of vitamin C (10.52 ± 0.29 mg/100g), carotenoids (53.18 ± 4.09 μg/g), and polyphenols (153.67 ± 8.33 mg/g), of which flavonoids represent 56 ± 1.22 mg/g, making the juice a good functional food with a low calorie content (43.12 ± 0.28 kcal/100g).

Phenolic acids, including chlorogenic acid and caffeic acid, contribute to the antioxidant capacity of loquat and play a role in protecting cells from oxidative damage.

Evidence strength: Strong in vitro evidence of high antioxidant capacity across multiple assays and cultivars. In vivo human antioxidant biomarker studies are very limited. The antioxidant content is well-characterized analytically.

5.5 Anticancer and Antiproliferative Effects

A growing body of preclinical research has examined the antiproliferative and anticancer properties of loquat extracts and isolated constituents.

In an evaluation of 14 oriental medicinal herbs for antiproliferative activities, loquat leaf showed strong cytotoxicity in cell lines of estrogen receptor-negative breast cancer (MDA-MB-231), cervix epitheloid (HeLa), and lung (A549) carcinoma. Ursolic acid and oleanolic acid isolated from loquat leaf significantly suppressed the proliferation of human lymphoid Molt 4B cells, which may result from the depletion of polyamines by inhibiting ornithine decarboxylase and S-adenosylmethionine decarboxylase activities.

Hydrophilic loquat extracts also showed in vivo anticancer activity in Meth-A-fibrosarcoma-bearing mice, operating through immunomodulatory activity, as indicated by factors such as interferon-gamma, interleukin-17, and TGF-β1. The possible constituents of such immunomodulatory activity require further investigation. Loquat leaf and seed extracts also showed significant anti-metastatic properties by inhibition of the migration and invasion of MDA-MB-231 human breast cancer cells and B16F10 melanoma cells, partially through the inhibition of matrix metalloproteinase-2 (MMP-2) and MMP-9.

Several other bioactive compounds extracted from loquat leaves, such as euscaphic acid, 1β-hydroxyeuscaphic acid, procyanidin B-2, and roseoside, have exhibited significant anticancer activity.

Modern science studies have demonstrated at the protein and gene level that loquat extracts can suppress cell carcinogenesis at different progression stages, such as cancer initiation, proliferation, and metastasis. Both water and ethanol extracts of loquat leaf inhibited 7,12-dimethylbenz[α]anthracene (DMBA)-induced breast cancer in rats, and water extracts showed a higher inhibitory activity. Both extracts inhibited the development of breast cancer by significantly suppressing the initiation stage.

Evidence strength: In vitro (cell line) and in vivo (animal tumor model) evidence exists demonstrating antiproliferative and anti-metastatic activity. There are no human clinical trials on loquat for cancer treatment or prevention. The evidence is preliminary, and no clinical conclusions can be drawn.

5.6 Hepatoprotective Effects

Extracts of loquat leaf have shown bioactivities including anti-diabetic, hypolipidemic, and anti-obesity activities. As a hepatic manifestation of the metabolic syndrome, loquat leaf extracts also have therapeutic effects on non-alcoholic fatty liver disease (NAFLD).

In a PM2.5-induced NAFLD mouse study, body weight, ratio of liver to body weight, and blood lipids increased significantly compared with the control group. Total flavonoids (TF) from loquat leaf significantly reduced these parameters in PM2.5-induced NAFLD mice. TF treatment alleviated oxidative stress by preventing the accumulation of oxidative product malondialdehyde and by strengthening the anti-oxidative capacity of superoxide dismutase.

Loquat seed extracts also showed protective activity against non-alcoholic steatohepatitis.

Evidence strength: All hepatoprotective evidence is from animal and cell-line models; no human trials were identified. The mechanistic basis is consistent with the anti-inflammatory and antioxidant profile of the plant's active compounds.

5.7 Lipid Metabolism and Cardiovascular Health

Nutritionally, loquat is rich in sugars such as glucose, fructose, and sucrose, and it also contains dietary fibers, organic acids, vitamins, and minerals. Loquat is also a significant source of various nutritional bioactive compounds, including polyphenols, carotenoids, and triterpenoids, known for their pharmacological activities. Numerous experimental studies have demonstrated the potential health benefits of loquat in animal and cell line models, such as its hypoglycemic, anti-inflammatory, antioxidative, and hypolipidemic properties.

Loquat contains several bioactive compounds that contribute to cardiovascular health. These include flavonoids, carotenoids, and phenolic acids, known for their antioxidant properties. The presence of these compounds helps in reducing oxidative stress, which is a significant factor in cardiovascular diseases.

Evidence strength: Hypolipidemic activity has been observed in animal dietary models. Human evidence is absent. The nutritional composition (potassium, fiber, polyphenols, low caloric density) is consistent with general cardiovascular dietary recommendations but no specific cardiovascular outcome studies in humans using loquat have been identified.

5.8 Antimicrobial Activity

The antifungal activity of loquat extracts against clinical isolates of Cryptococcus neoformans points to its potential in developing new antifungal agents. The leaves of loquat are rich in polyphenols and other bioactive compounds, which have been shown to possess antioxidant, anti-inflammatory, and antimicrobial properties.

Evidence strength: In vitro antimicrobial and antifungal data are available. No human clinical evidence was identified for loquat as an antimicrobial agent.

5.9 Potential Neuroprotective and Antidepressant Effects

Loquat tree has been used in traditional medicine to treat respiratory ailments, inflammation, and skin diseases; however, its potential antidepressant-like effects have not been extensively investigated. A study evaluated the antidepressant-like effects of E. japonica fruit extract (EJFE) in a mouse model of corticosterone (CORT)-induced depression. HPLC analysis revealed that chlorogenic acid is the major compound in EJFE. Male ICR mice were injected with corticosterone (40 mg/kg intraperitoneally) once daily for 21 days to induce depressive-like behaviors. Behavioral tests were conducted 1 hour after oral administration of EJFE at different doses (30, 100, and 300 mg/kg) and chlorogenic acid (30 mg/kg).

In a cell model using β-amyloid-induced oxidative stress in neuronal PC12 cells, treatment with loquat leaf efficiently suppressed the formation of intracellular ROS by Aβ1-42 peptide.

Evidence strength: Entirely preclinical (animal and cell models). No human trials on neurological or mood effects have been identified. This area remains highly exploratory.

6. Body Systems Associated with Loquat

• Respiratory system: Traditional and preclinical evidence for expectorant, antitussive, and anti-inflammatory effects in bronchitis, COPD, and asthma-related models.
• Metabolic/endocrine system: Preclinical evidence for blood glucose-lowering (α-glucosidase/α-amylase inhibition), insulin sensitization, and antidiabetic properties.
• Hepatic system: Preclinical evidence for protection against NAFLD, alcoholic liver injury, and non-alcoholic steatohepatitis via antioxidant and anti-inflammatory pathways.
• Cardiovascular system: Preclinical and nutritional evidence for antioxidant, hypolipidemic, and anti-atherosclerotic potential.
• Immune system / oncology: Preclinical antiproliferative and immunomodulatory activity across multiple cancer cell lines and animal tumor models.
• Neurological system: Very early preclinical evidence for neuroprotective and antidepressant-like effects.
• Integumentary system: The ethanolic extract of loquat leaves was found to be non-irritating to the skin and eyes in animal replacement tests, and it also significantly inhibited melanogenesis.

7. Dosage Forms and Dosages Reported in Studies

Dosages reported in the peer-reviewed scientific literature are derived almost exclusively from preclinical (animal and cell) studies. No standardized human clinical doses have been established for loquat preparations. The following dosages are those reported in the cited sources:

• Loquat leaf extract (LE) and ursolic acid (UA) — animal study: Oral administration of UA and LE at a dose of 50 mg/kg/day for 15 days in diabetic db/db mice.
• Triterpene acids from loquat leaf — animal study (COPD model): Male C57BL/6 mice were fed with triterpene acids (TAs) at 50 and 100 mg/kg for 6 weeks from the seventh week of cigarette smoke exposure.
• Loquat leaf aqueous extract (LLE) — antidiabetic animal study: Mice fed a high-fat and high-glucose diet for 10 weeks received a daily administration of LLE at three different doses: 150, 200, and 250 mg/kg body weight/day.
• Loquat fruit extract (EJFE) — antidepressant animal study: Behavioral tests were conducted after oral administration of EJFE at different doses (30, 100, and 300 mg/kg) and chlorogenic acid (30 mg/kg) in mice.
• Loquat leaf hexane extract — in vitro antidiabetic: Hexane extract had a higher α-amylase inhibitory activity of 24% at 1 μg/ml as compared to other extracts.

These dosages are species-specific and cannot be extrapolated directly to human dosing without appropriate clinical pharmacokinetic and safety studies. No human pharmacokinetic data for standardized loquat preparations were identified in the peer-reviewed literature.

8. Safety Considerations

Cyanogenic Glycosides in Seeds

The most significant documented safety concern associated with loquat relates to the cyanogenic glycoside content of the seeds. Loquat seeds contain cyanogenic glycosides, mainly amygdalin. When these compounds break down, they can release cyanide.

Amygdalin, prunasin, total cyanide, and free cyanide concentrations in 12 powdered loquat seeds were investigated. The mean concentrations of amygdalin, prunasin, total cyanide, and free cyanide in powdered loquat seeds were 5900, 760, 410, and 44 mg/kg, respectively. The range of each quantitative value was extensive. Seven out of twelve samples were at risk for exceeding the acute reference dose (ARfD) of cyanide.

Amygdalin is a natural cyanogenic glycoside occurring in the seeds of some edible plants, such as bitter almonds and peaches. It is a medically interesting but controversial compound as it has anticancer activity on one hand and can be toxic via enzymatic degradation and production of hydrogen cyanide on the other hand. Despite numerous contributions on cancer cell lines, the clinical evidence for the anticancer activity of amygdalin is not fully confirmed. Moreover, high dose exposures to amygdalin can produce cyanide toxicity.

In recent years, amygdalin has been regarded as a promising natural substance with diverse anticancer effects. In addition, amygdalin can be used to treat respiratory diseases such as cough and asthma. However, there are still some urgent and serious problems related to toxicity due to its cyano fraction, as well as poor oral bioavailability.

Loquat seeds are not appropriate for home remedies, powdered supplements, or self-treatment plans. Public safety warnings have specifically addressed powdered loquat seed products because their cyanide exposure can become meaningful. The idea that loquat seeds are a natural anticancer treatment is not supported by reliable human evidence and creates unnecessary risk.

Leaves and Fruit — Lower Cyanogenic Risk

Leaves also contain cyanogenic compounds, but in much lower amounts than seeds. Properly prepared loquat leaf infusions appear to pose a much lower cyanide risk than seed powders.

Toxicology Data

As the identification of compounds progresses, studies investigating the in vivo metabolism, bioavailability, and structure–activity relationships, as well as potential toxicity of loquat extracts in animal or cell models are receiving more attention. Formal acute and chronic toxicity studies in humans are limited; the available traditional use record for loquat leaves and fruit over centuries provides some indirect evidence of general tolerability at customary food or tea amounts, but this does not validate the safety of concentrated extracts or seed preparations.

Skin Sensitivity

The ethanolic extract of loquat leaves was found to be non-irritating to the skin and eyes in animal replacement tests. It also significantly inhibited melanogenesis. These preclinical data are encouraging for topical applications but require human confirmation.

General Research Gaps

Drug interaction data for loquat preparations and human pharmacokinetic studies are notably absent from the published peer-reviewed literature. Further research is needed to better understand the correlation between loquat's bioactive compounds and their biological activities. The broad preclinical evidence base has not yet been matched by controlled clinical trials in humans, and this represents the primary evidence gap for this plant.

References

• Structural Diversity and Anti-Diabetic Potential of Flavonoids and Phenolic Compounds in Eriobotrya japonica Leaves — PMC (2025)
• Eriobotrya japonica: A review — Phytochemical constituents, traditional uses, and therapeutic potentials — ScienceDirect (2025)
• Traditional uses, phytochemistry, pharmacology, and toxicity of Eriobotrya japonica leaves: A summary — ScienceDirect (2022)
• Biological Activities of Extracts from Loquat (Eriobotrya japonica Lindl.): A Review — PMC / Int J Mol Sci (2016)
• Phytochemicals, Extraction Methods, Health Benefits, and Applications of Loquat (Eriobotrya japonica Lindl.) and Its By-Products: A Comprehensive Review — PMC (2025)
• Antioxidant and Antiproliferative Activities of Phenolic Extracts of Eriobotrya japonica (Thunb.) Lindl. Fruits and Leaves — PMC / Plants (2023)
• Protective mechanisms of loquat leaf extract and ursolic acid against diabetic pro-inflammation — PubMed / Journal of Molecular Medicine (2022)
• Triterpene Acids of Loquat Leaf Improve Inflammation in Cigarette Smoking Induced COPD by Regulating AMPK/Nrf2 and NFκB Pathways — PMC (2020)
• Phytochemical screening, anti-oxidant activity and α-amylase inhibition study using different extracts of loquat (Eriobotrya japonica) leaves — PMC (2020)
• Loquat (Eriobotrya japonica (Thunb) Lindl.): Evaluation of nutritional value, polyphenol composition, antidiabetic effect, and toxicity of leaf aqueous extract — ScienceDirect / Journal of Ethnopharmacology (2022)
• Protective mechanisms of loquat leaf extract and ursolic acid against diabetic pro-inflammation — Journal of Molecular Medicine / Springer (2022)
• Hepatoprotective Effect of Loquat Leaf Flavonoids in PM2.5-Induced Non-Alcoholic Fatty Liver Disease via Regulation of IRs-1/Akt and CYP2E1/JNK Pathways — PMC / Int J Mol Sci (2018)
• Dried Loquat Fruit Extract Containing Chlorogenic Acid Prevents Depressive-like Behaviors Induced by Repeated Corticosteroid Injections in Mice — PMC (2023)
• Nutritional Composition and Effect of Loquat Fruit on Lipid Metabolism and Liver Steatosis in High-Fat High-Sucrose Diet-Fed Mice — PMC (2024)
• Phytochemical Analysis and Antifungal Potentiating Activity of Extracts from Loquat (Eriobotrya japonica) against Cryptococcus neoformans Clinical Isolates — PMC (2022)
• Quantification of amygdalin, prunasin, total cyanide and free cyanide in powdered loquat seeds — Food Additives & Contaminants: Part A (2020)
• Quantification of amygdalin, prunasin, total cyanide and free cyanide in powdered loquat seeds — PubMed (2020)
• Amygdalin: Toxicity, Anticancer Activity and Analytical Procedures for Its Determination in Plant Seeds — PMC / Molecules (2021)
• The screened triterpene acids from Loquat fruit by CysLTR1-immobilized column could serve as alternative anti-inflammatory agents — BMC Complementary Medicine and Therapies (2025)
• Eriobotrya japonica (Thunb.) Lindl.: Ethnomedicinal uses, phytochemical and pharmacological review — Ethnobotany Research and Applications
• Loquat — an overview — ScienceDirect Topics
• Metabolic Effects of Loquat Juice on Lipid Homeostasis, Liver Steatosis, and Oxidative Stress in Hyperlipidemic Mice — PMC (2024)
• Comprehensive Review of Bioactive Compounds in Loquat and Their Pharmacological Mechanisms — Medicinal Plant Research (2024)
• Key Bioactive Constituents in Loquat and Their Potential Applications in Modern Medicine — Biological Evidence (2025)
• Phenolic Composition from Different Loquat (Eriobotrya japonica Lindl.) Cultivars Grown in China and Their Antioxidant Properties — PMC (2018)
• Genetic Tendency Analysis and Comprehensive Antioxidant Activity Evaluation of Leaves and Flowers of Loquat F1 Generation — PMC (2025)
• Loquat and its phytochemical potential: A promising application in food technology — eFood / Wiley (2024)