Effectiveness of tiger milk mushroom (Lignosus rhinocerus) on asthma: a systematic review

Abstract

Asthma is a chronic inflammatory airway disease with a rising global prevalence and impact on quality of life. Conventional therapeutics such as corticosteroids and β2-agonists are associated with various long-term adverse effects and are costly. This has prompted the exploration of natural therapies such as the tiger milk mushroom (TMM), also known as Lignosus rhinocerus. Native to Southeast Asia, this medicinal mushroom has been traditionally used for respiratory health. TMM is known to be rich in bioactive compounds including polysaccharides and polyphenols, and has shown anti-inflammatory and immunomodulatory properties. This systematic review aimed to investigate its effects in asthma. Animal studies demonstrated significant suppression of eosinophil infiltration, Th2 cytokines (IL-4, 5, and 13), IgE levels, and attenuated airway remodeling. In vitro studies confirmed bronchorelaxation effects mediated through calcium channel modulation. A single human study reported a decrease in inflammatory and antioxidant markers (IL-1β, IL-8, and MDA), improved lung function and quality of life. Overall, TMM has shown promising potential as an anti-asthmatic agent. However, current evidence is largely preclinical and has a limited scope. Further high-quality larger scale trials are needed to validate its efficacy and safety in humans.

Introduction

Asthma is a complex respiratory condition that is characterized by reversible airway constriction, inflammation, and in severe cases, results in structural changes of bronchial tissues. It imposes a significant health burden worldwide. Around 1 in 10 people are diagnosed with asthma in developed countries, with an estimate of 100 million people to be affected by 2025 [1]. The widespread nature of the condition affects the quality of life of patients. Medication compliance, fear of hospitalization and exacerbations, and persistent symptoms all impose physical, mental, and even financial burdens [2].

Conventional therapies such as inhaled corticosteroids and beta-2 agonists remain as the mainstay medications [3]. While they remain essential for symptomatic relief and control, their long-term use is associated with adverse effects such as tachycardia, cough, and oral candidiasis. Additionally, the use of biologics (e.g. omalizumab) in severe presentations of asthma can be costly, and the Food and Drug Administration has issued a box warning for risk of anaphylaxis [4]. This has spurred interest to dive into complementary therapies as they provide easy access to treatments across all socioeconomic classes and display good renewability globally [5]. Various natural products such as turmeric, Nigella sativa, and licorice have risen as promising adjunctive alternatives to palliate airway inflammation as well as to improve respiratory health with lesser adverse effects [6]. Besides, many natural therapeutic agents have also shown to significantly increase and improve predicted FEV1 [7].

One such candidate is the tiger milk mushroom (TMM), also known as Lignosus rhinocerus, from the Polyporaceae family. This medicinal mushroom, originating in Southeast Asia and predominantly in Malaysia, is one of the 38 currently reported types of edible mushrooms in the country. The mushroom comprises three parts: the pileus (cap), the stipe (stem), and the sclerotium. The sclerotium is of most importance as it contains its nutrient reserves in the mycelium. The mushroom tends to grow in solitude underground [8]. Although once difficult to obtain, TMM has been successfully cultivated on a large-scale, allowing for ease in commercialization and reducing costs [9]. It has been widely used in traditional medicine for its potential benefits in treating respiratory ailments, such as asthma. Evaluation of its phytochemical profile revealed compounds ranging from triglycerides, to phenols and polysaccharide-protein complexes. Hence, recent studies have suggested that tiger milk mushroom could exert bronchoprotective and anti-inflammatory effects through these phytochemicals [10–12]. These bioactive phytochemicals are β-glucans, polysaccharides and phenolic compounds that could mediate anti-inflammatory, antioxidant and creates immunomodulatory effects via modulation of key signaling pathways such as the production of Th2 cytokines and IgE synthesis. This forms a mechanistic basis for its potential therapeutic use in asthma beyond symptomatic relief. However, despite these promising findings, literature remains fragmented and limited. Hence, a systematic review is warranted to evaluate and assess the current evidence available on TMM.

Methods

Search strategy

This is a systematic review that reviewed and analyzed articles that fulfilled the specific criteria to evaluate the effectiveness of Lignosus rhinocerus in asthma. Between January to April 2025, a literature search was conducted using five search engines namely, PubMed, ScienceDirect, EBSCOHost, Scopus, and Google Scholar. Table 1 shows the search terms and boolean operators used.

Table 1.

Search strategy

Source	The Effectiveness of Tiger Milk Mushroom (Lignosus rhinocerus) on Asthma
PubMed	Keywords
Search #1	"tiger milk mushroom"[All Fields] OR (("tigers"[MeSH Terms] OR "tigers"[All Fields] OR "tiger"[All Fields]) AND ("agaricales"[MeSH Terms] OR "agaricales"[All Fields] OR "mushroom"[All Fields] OR "mushrooms"[All Fields])) OR "Lignosus rhinocerus"[All Fields] OR "Lignosus rhinocerotis"[All Fields] OR "l rhinocerus"[All Fields]
Search #2	"asthma"[MeSH Terms] OR "asthma"[All Fields] OR "asthmas"[All Fields] OR "asthma s"[All Fields] OR "lung"[MeSH Terms] OR "lung"[All Fields] OR "pulmonary"[All Fields] OR "respiratory"[All Fields]
Search #3	Search #1 AND Search #2
ScienceDirect	(“tiger milk mushroom” OR “Tiger mushroom” OR “Lignosus rhinocerus” OR “Lignosus rhinocerotis” OR “L. rhinocerus”) AND (“asthma” OR “respiratory” OR “pulmonary”)
EBSCOHost	((“tiger milk mushroom” OR “Tiger mushroom” OR “Lignosus rhinocerus” OR “Lignosus rhinocerotis” OR “L. rhinocerus”)) AND ((“asthma” OR “respiratory” OR “pulmonary”))
Scopus	TITLE-ABS-KEY (("asthma" OR "respiratory" OR "pulmonary")) AND TITLE-ABS-KEY (("tiger milk mushroom" OR "Tiger mushroom" OR "lignosus rhinoceros" OR "lignosus rhinoceros" OR "l. rhinoceros"))
Google Scholar	((“tiger milk mushroom” OR “Tiger mushroom” OR “Lignosus rhinocerus” OR “Lignosus rhinocerotis” OR “L. rhinocerus”)) AND ((“asthma” OR “respiratory” OR “pulmonary”))

Inclusion and exclusion criteria

The inclusion criteria focused on research articles evaluating the effects of L. rhinocerus on asthma including both preclinical and clinical studies. Preclinical studies included animal models and in vitro experiments, while clinical studies included human trial such as randomized controlled trials (RCTs), cohort studies and case–control studies. Only studies published in English and accessible in full text were considered to ensure comprehensibility. The publishing year was kept at a 10-year range from 2015–2025 to maintain relevance and applicability of findings. Studies that were reviews, editorial pieces, letters to editors, brief communications, personal opinions, and study protocols were excluded from consideration.

Study population

This systematic review focused on animals and animal models that replicated an asthmatic environment, as well as humans diagnosed with asthma.

Study selection

The process of selection involved several steps to ensure a comprehensive and unbiased review of the literature. The process began by firstly identifying potentially relevant articles using their titles and abstracts after conducting the search using the key terms. All articles were uploaded onto the Rayyan online platform and a search was run to detect and remove duplicates by automatically identifying similarities based on the title, author, and publication year. Manual verification was subsequently performed to enhance accuracy. Two independent reviewers screened titles and abstracts using the Rayyan siftware. Inter-rater agreement was assessed using Cohen’s kappa statistics, demonstrating agreement (κ = 0.72). Any disagreement were resolved through discussion or involving a third reviewer when necessary.

A total of 132 articles were excluded at various stages of screening, primarily due to not meeting the study objectives, not having the appropriate study design, and lacking sufficient data for inclusion.

Quality assessment

The quality of the selected studies was assessed using validated risk of bias tools. For animal in vivo studies, the SYRCLE Risk of Bias tool was applied. This tool is an adaptation of the Cochrane Risk of Bias (RoB) tool that is specifically developed to address bias found in preclinical animal studies. It consists of ten domains and assesses biases in relation to variables such as animal housing, allocation, and assessor blindness. This tool has been widely adopted and has helped improve the transparency and reproducibility of preclinical studies [13]. The QUIN tool was used for in vitro studies. It is a validated tool that was recently developed by Sheth et al. in 2024 [14]. There are twelve criteria that assess the overall quality of the paper as well as any risk of bias. Judgement of papers is determined by a scoring system. A score of 0–2 was given for each criterion based on whether the information was adequately sufficient. The total score was calculated based on the formula provided, with a percentage of > 70% indicating a low risk of bias; 50–69% moderate; and < 50% indicating a high risk of bias. The ROBINS-I V2 tool was used for non-randomized human intervention studies. This tool was developed by the Cochrane Bias Methods Group as well as the Cochrane Non-Randomised Studies Methods Group. The tool has been validated and is widely considered the gold-standard for assessing the risk of bias in individual domains of non-randomized studies, rather than providing a overall “quality” score [15]. It consists of seven domains with signaling questions and provides a judgement of risk of bias for each domain (low, moderate and serious). Overall risk of bias is determined by considering the combination of domain-level judgments rather than a numerical or total score. Throughout the critical appraisal process, all included studies were independently assessed by two reviewers. Any discrepancies in assessment were resolved through discussion with a third reviewer to achieve a consensus. This ensured a consistent evaluation of study quality.

Data synthesis

Data synthesis involved a thorough approach to compile and interpret the findings from the included studies. Key data was extracted from each study including sample type, TMM formulation, dosage, and measured outcome. Quantitative findings were synthesized descriptively and organized into summary tables to facilitate cross-study comparisons. A narrative synthesis was also conducted to qualitatively summarize the pharmacological effects of TMM, with emphasis on its anti-inflammatory, immunomodulatory, and bronchodilatory properties and potential. Patterns and discrepancies in outcomes were analyzed to identify emerging trends and variations across the studies.

Results

The initial search retrieved 182 articles from EBSCOHost, ScienceDirect, Pubmed, Google Scholar, and SCOPUS. In all, 41 duplicates were excluded as well as 132 studies whose title and abstract did not meet the pre-established criteria. 9 articles were considered relevant for a full-text screening. A total of 9 studies were selected for the review that included 8 animal studies and 1 human study. Figure 1 shows a flowchart of the study selection process which has been divided into the steps of identification, screening, and inclusion. The process was followed in accordance with the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) recommendations for writing systematic reviews.

Fig. 1.

PRISMA flowchart showcasing the study selection process

Animal studies

Table 2 summarizes the key findings from in vivo animal studies evaluating the effects of TMM in asthma models. Four studies used hot water L. rhinocerus extract (LRE) while one study used L. rhinocerus polysaccharide (LRP). The dosage of TMM extract used ranged from 1–500 mg/kg. Three studies administered the active compound orally while the others used an intranasal mode of delivery. All studies showed that TMM extracts produced significant reduction in inflammatory cell infiltration, including eosinophils, down-regulated Th2 cytokines (IL-4, IL-5, and IL-13) and serum IgE levels. Histopathological alterations including mucus hypersecretion and goblet cell hyperplasia were markedly reduced. Furthermore, TMM extracts also modified the markers of airway remodeling, including TGF-β1 and Activin A as well as downregulated genes associated with asthma pathophysiology.

Table 2.

Animal studies

Author, year	Animal (Mice/Rats)	Active ingredient	Dosage	Administration (Oral/Intranasal)	Outcome
[16]	Female Balb/C mice	Hot water L. rhinocerus extract (LRE)	125, 250, 500 mg/kg	Oral	LRE significantly suppressed inflammatory cells and eosinophil infiltration, reduced Th2 cytokines (IL-4, IL-5, and IL-13) in BALF and serum IgE levels, and attenuated goblet cell hyperplasia and airway remodelling through inhibition of TGF-β1 and Activin A expression at Weeks 2 and 10 compared with the ovalbumin (OVA) -sensitized/challenged group (p < 0.05)
[17]	Female Balb/C mice	Hot water L. rhinocerus extract (LRE)	125, 250, 500 mg/kg	Intranasal	LRE treatment reduced Th2 cytokines in a dose-dependent manner, with significant suppression of IL-4 and IL-5 at 500 mg/kg and IL-13 at 250 mg/kg versus the OVA group (p < 0.01)
[18]	Male Sprague Dawley rats, female Balb/C mice	Hot water L. rhinocerus extract (LRE)	125, 250, 500 mg/kg	Oral	Oral LRE treatment at 500 mg/kg significantly reduced IL-4, IL-5, and IL-13 levels relative to the OVA group (p < 0.05). At lower doses, LRE125 and LRE250 also reduced IL-5 significantly (p < 0.05) with partial reduction of IL-4 and IL-13, p < 0.05 vs OVA where indicated
[11]	Male Sprague Dawley rats	Hot water L. rhinocerus extract (LRE)	500 mg/kg	Oral	LRE extract at 500 mg/kg significantly reduced serum IgE, IL-4, and IL-5 levels compared with the untreated OVA group (p < 0.05). IL-13 also tended to decrease in the LRE group, but this change did not reach statistical significance (p ≥ 0.05 vs OVA). Treatment with dexamethasone similarly reduced IgE and all measured Th2 cytokines (p < 0.05 vs OVA)
[19]	Female Balb/C mice	L. rhinocerus polysaccharides (LRP)	1,10,100 mg/kg	Intranasal	LRP significantly reduced the percentage of eosinophils in OVA-induced mice, with the 10.0 and 100.0 mg/kg LRP groups and the DEX group showing eosinophil percentages of 19.1% ± 1.2, 15.8% ± 1.9, and 9.0% ± 1.5, respectively, compared to the OVA group, decreased serum IgE levels, with 1.0, 10.0, and 100.0 mg/kg LRP groups and the DEX group showing concentrations of 6.5 ± 1.5 (p < 0.05), 5.5 ± 1.8 (p < 0.01), 3.6 ± 0.7 (p < 0.001), and 1.9 ± 0.7 (p < 0.001) ng/mL, respectively, compared to the OVA group. Gene expression analysis demonstrated a significant downregulation of inducible nitric oxide synthase (iNOS) relative to the OVA group (p < 0.05)

In vitro studies using isolated animal airways

Three studies explored the effects of L. rhinocerus on isolated animal airway models; two on Sprague–Dawley rats; one on guinea pig tracheal rings (Table 3). Two of these studies utilized cold-water extracts of TMM (LRE) while the third used a purified polysaccharide extract. All three studies used different strengths to analyze the outcomes. All three papers consistently demonstrated that TMM significantly exhibited bronchodilatory effects. LRE caused maximum tracheal ring relaxation by primarily inhibiting calcium-induced contractions via extracellular blockage of calcium ion influx. Besides that, molecular fractionation of LRE revealed that high and medium molecular weight fractions were superior to low molecular weight fractions and crude extract in relaxing contracted airway tissues. Such effects were β2-adrenergic pathway-independent, therefore suggesting a new mechanism of bronchodilation possibly through modulation of calcium channels. The third study used LRP and displayed a dose-related relaxation effect on carbachol and histamine pre-contracted guinea pig tracheal rings. The result showed that the relaxing effect was mediated at least partly through muscarinic and histaminergic receptor modulation.

Table 3.

In vitro studies using isolated animal airways

Author, year	Sample type	Active ingredient	Dosage	Outcome
[20]	Isolated airway of male Sprague-Dawl ey rats	Cold water L. rhinocerus extract (LRE)	0.0–3.75 mg/ml	CWE of LRE produced full relaxation of carbachol-precontracted trachea at 3.75 mg/mL and bronchus at 2.5 mg/mL (p < 0.0001 vs baseline control) by inhibiting calcium ion influx
[21]	Isolated airway of male Sprague-Dawle y rats	Cold water L. rhinocerus extract (LRE)	2.5 mg/ml of various fraction strengths (High, Medium, Low molecular weight) and cold-water extract	HMW and MMW fractions of L.rhinocerotis shows more bronchodilation than CWE in isolated rat airway, Eₘₐₓ values of 117.32 ± 24.62% and 105.84 ± 17.58% in trachea and 101.67 ± 16.34% and 108.30 ± 19.98% in bronchus, respectively, compared with vehicle control (39.68 ± 5.47%) (p < 0.05). LMW fraction did not significantly relax airways (p > 0.05 vs vehicle). In pre-incubation experiments, HMW markedly suppressed carbachol- and 5-HT-induced contractions (Eₘₐₓ: 44.52 ± 36.61% and 2.48 ± 3.41% vs vehicle 241.20 ± 24.41% and 85.24 ± 30.95%, respectively; p < 0.05), while CWE also attenuated carbachol responses though less potently and ipratropium (177.30 ± 46.88%) served as a mechanistic reference control
[22]	Isolated guinea pig trachea (GPT) ring	L. rhinocerus polysaccharides (LRP)	10 mg/mL to 100 mg/mL	LRP treatment produced concentration-dependent relaxation of airway smooth muscle in guinea pig trachea pre-contracted with EC₄₀ carbachol or EC₅₀ histamine, compared with vehicle-contracted controls (carbachol or histamine), indicating statistically significant bronchodilation (p < 0.05 relative to contracted baseline)

Human studies

Table 4 presents the findings from a human clinical study evaluating the effects of TMM supplementation on respiratory health. Till date, there is only one study which studies the effectiveness of TMM on the human respiratory system. The participants in the study received a twice-daily standardized oral dosage of 300 mg encapsulated TMM over three months. The analysis showed that supplementation of TMM significantly reduced the levels of IL-1β, IL-8, and malondialdehyde (MDA), which may have reduced systemic inflammation and oxidative stress. It was also statistically significant to show an increase of IgA and total antioxidant capacity, which may suggest increased mucosal immunity and antioxidant capacity. Moreover, this study shows improvements in pulmonary function test outcomes (FEV1/FVC) as well as self-reported respiratory symptom scores.

Table 4.

Human study

Author, year	Active ingredient	Dosage, route	Outcome
[23]	TMM capsules (TigerPro™)	300 mg twice-daily, oral	TMM significantly improved pulmonary function, with FEV₁ increasing (p < 0.01) and FEV₁/FVC ratio rising (p < 0.001) compared with baseline. Respiratory symptom scores significantly reduced (p < 0.001). Inflammatory markers IL-1β and IL-8 from nasal lavage markedly decreased (p < 0.001), while salivary IgA increased (p < 0.01)

Risk of bias assessment

ROBINS-I tool

The human study conducted by Tan et al. [23]. demonstrated good methodological quality as assessed by the ROBINS-I tool (Fig. 2). The study showed low risk of bias in five out of seven domains, with moderate risk in the remaining two domains. Therefore, this study indicated moderate confidence in the study findings.

Fig. 2.

Risk assessment using the ROBINS-I tool [24]

SYRCLE risk of bias

Of the five studies reviewed using SYRCLE's tool, the table below shows that the majority of the domains were marked as having uncertain risk of bias, particularly on allocation concealment, blinding strategies, and random housing. This suboptimal reporting in preclinical animal studies could compromise reproducibility and validity of findings. Full low-risk scores were demonstrated by a few studies across the majority of domains (Fig. 3).

Fig. 3.

Risk assessment using the SYRCLE Risk of Bias tool [24]

QUIN tool

It is worth noting that three in vitro studies that were assessed using the QUIN tool showed a total score of above 70% each. This indicated a low risk of bias. Thus these articles were considered to be of satisfactory quality, providing reliable evidence for further interpretation and application (Table 5).

Table 5.

Risk assessment using the QUIN tool

	Objec tives	Sample size calcula tion	Sampl ing techni que	Details of compa rison group	Metho dology	Opera tor details	Rando mizati on	Measu remen t of outco me	Assess or details	Blindi ng	Statistical analysis	Presen tation of results	Total Score %
[20]	2	0	2	2	2	NA	NA	2	NA	0	2	2	77.8
[22]	2	0	2	2	2	NA	NA	2	NA	0	2	2	77.8
[21]	2	0	2	2	2	NA	NA	2	NA	0	2	2	77.8

A score of > 70% indicates low risk of bias

Discussion

In the studies investigated, Lignosus rhinocerus was studied using different approaches to extraction and delivery methods in animal models of asthma. The majority of the animal studies have used a hot-water extract or aqueous extract, otherwise referred to as L. rhinocerus extract (LRE). This method was used to extract bioactive compounds that are water-soluble such as β-glucans and polysaccharide-protein complexes with immunomodulatory effects [25]. However, the study done by Bushra et al. [19], used cold-water extraction to get purified polysaccharides (LRP). Polysaccharides are thermolabile and extracting with cold-water preserves more structural integrity potentially offering enhanced bioactivity [26]. Cold-water extraction methods help retain natural compounds, including high molecular weight polysaccharides and glycoproteins. By preserving these compounds, biological effects may be achieved at lower doses compared to crude hot-water extracts [27]. These differences highlight the importance considering both phytochemical and biological activity when evaluating efficacy. Variation in extraction processes may alter potency and lead to under or over estimation true efficacy of TMM.

Furthermore, variations in routes of administration, specifically, oral and intranasal were used as the mode of delivery of TMM. Oral administration, which has been utilized by several researchers [16, 18, 23], mirrors human dietary supplementation and is a feasible, systemic delivery method [28]. Conversely, intranasal administration, as used by Muhamad et al. [17] and Bushra et al. [19], is designed for direct deposition of bioactive compounds on the respiratory mucosa to avoid first-pass metabolism, allowing more localized effects on the airways [29, 30]. Studies using intranasal routes reported substantial reductions in eosinophilia, Th2 cytokines and IgE levels similar or lower doses than oral delivery, suggesting greater local bioavailability. However, these findings are limited by small sample size, variable extraction methods and inconsistent dosing. These methodological differences emphasize the need for standardization to improve reproducibility and translational relevance.

Airway inflammation is the main feature of asthma, with eosinophils being one of the major regulators of inflammation and, in the long-term, airway remodelling [31]. Upon infiltration, activated eosinophils release pro-inflammatory mediators such as major basic protein and leukotriene C4, and synthesize interleukins such as IL-4, IL-5, and IL-13 [32]. Across all animal studies, LRE reduced inflammatory cell count including eosinophil infiltration significantly, with reported doses of 500 mg/kg of LRE, 10 and 100 mg/kg as well as other inflammatory cells, indicating early attenuation of the airway inflammatory cascade [11, 16–19].

Prolonged ovalbumin induction increased Th2 cytokines, but both the LRE and LRP shoes significant suppression of IL-3, IL-4 and IL-5 [11, 16–19]. For LRE at 500 mg/kg was the most effective dose while LRP was active at lower doses (1–100 mg/kg) [19]. The reduction of Th2 cytokines is vital during asthma responses as each interleukin is involved in key features of inflammation [33], including IgE production, eosinophil survival, mucus hypersecretion and airway hyperresponsiveness [34, 35]. Collectively these findings indicate that TMM modulated Th2 predominant immune activity central to asthma pathogenesis.

Tan et al. [23] examined IL-1β and IL-8 in clinical study and found that TMM supplementation significantly reduced both cytokines, indicating improved inflammatory status. IL-1β and IL-8 are key mediators in the initiation and persistence of airway inflammation [36]. IL-1β is upregulated in asthma and promoted tissue injury and fibrosis [37, 38], while IL-8 drives neutrophil recruitment and is amplified by IL-1β signaling [35]. Thus, TMM mediated suppression of these cytokines supports its anti-inflammatory potential in human airway disease.

Elevated IgE is closely linked to Th2 cytokine activity [39]. As all animal model studies reported significant IgE reduction, which supports TMM’s ability to attenuate allergic airway inflammation. However, IgE was not measured in the human study, instead IgA doubled after three months of supplementation, suggesting enhanced respiratory immunity [23]. Future clinical studies should link immune outcomes to specific phytochemicals, like β-glucans and polyphenols to strengthen mechanistic interpretation.

Airway inflammation is associated with lipid peroxidation, where reactive oxygen species (ROS) were found to be generated by several inflammatory cells and their production amplifies inflammation [40]. MDA is the main product of lipid peroxidation and is often used as a biomarker to assess oxidative damage. It has also been correlated with pulmonary function and severity of respiratory disease [41]. Tan et al. [23] studied pre-post levels of MDA and found that TMM exerted a significant suppressive effect on its production. The phenomenon could be linked to the high phenolic content found in TMM [42]. Polyphenols have been proven to produce protective effects against inflammation by several mechanisms such as: attenuating endoplasmic reticulum stress signalling,suppressing pro-inflammatory cytokine; and activating transcription factors that antagonize chronic inflammation [43]. However, further studies are needed to determine the potential antioxidant effects of TMM.

Johnathan et al. [18] showed that 16 asthma-related genes (IL-17A, ADAM33, CHIA, IL4, CCR3, CCL5, CCL17, PMCH, CLCA1, Cma1, CCR8, FCER1A, IFNG, CCR4, CCL22, and PRG2) upregulated by ovalbumin were significantly down-regulated after treatment with 500 mg/kg of LRE. These genes are central to Th2 cells, mast cells, NK cells, as well as eosinophils [44]. Key severity related genes such as IL-17A and ADAM33 were suppressed suggesting reduced neutrophilic signaling and airway remodeling potential [45, 46]. Similarly, LRP suppressed nitric oxide synthase (iNOS) expression at 10 and 100 mg/kg doses [19]. However, the iNOS leads to nitric oxide secretion, promoting intracellular calcium uptake, and causes airway contraction [47]. However, due to the limited gene expression data these findings require confirmation in future studies.

Airway remodeling involves goblet cell hyperplasia, mucus overproduction and smooth muscle thickening [48]. Epithelial injury triggers an increased secretion of IL-4 and IL-13, which causes basal epithelial cells to differentiate into goblet cells that secrete mucus to trap pathogens [49]. Hence, prolonged inflammation leads to goblet cell hyperplasia and mucus hypersecretion resulting in airway obstruction [50]. The LRE consistently inhibited goblet cell hyperplasia at 500 mg/kg reducing PAS staining [16–18]. LRP showed similar results, however the results were insignificant compared to the ovalbumin-challenged group [19]. The studies overall suggest the capabilities of LRE and LRP to reduce airway obstruction which is line with results from a similar study by Xu et al. [51] that reported Scutellaria baicalensis reduced mucin secretion in ovalbumin-induced airway inflammation.

Additionally, transforming growth factor (TGF-β1) activin A contribute to fibrosis and smooth muscle remodelling [52, 53]. Thickening of the airway smooth muscle layer results in a restricted lumen, leading to increased dynamic and fixed resistance [54]. Treatment with LRE and LRP was shown to have reduced both cytokines and smooth muscle remodelling significantly [16–19], improve airway remodelling. Comparison with other botanicals such as curcumin support the plausibility of this effect [55]. Another study by Hardy et al. [56] reported a reduction of TGF-β1 and Activin A was related with the resolution of remodeling after cessation of the allergen.

All three in vivo studies tested TMM’s bronchorelaxation activity, where study done by M Lee et al. [20] and M.K. Lee et al. [21] both used isolated bronchus and trachea of male Sprague Dawley rats, whereas Daku et al. [22], isolated trachea from guinea pigs. The rat studies pre-contracted tissue with carbachol and compared LRE effects to bronchodilators (ipratropium bromide, salmeterol) and calcium channel blocker (nifedipine) using water or DSMO as controls. LRE and its high and low molecular wight fractions significantly reduce calcium induced contractions. This happens via a mechanism independent of β2 receptors, nitric oxide, potassium channel or muscarinic antagonism, suggesting a calcium modulating pathway [57]. Similar results was seen with 2.5 mg/ml of LRE and the high molecular fraction and similar non competitive antagonistic effect were observed for carbachol and 5-HT [20]. Longer incubation enhanced bronchodilation, indicating potential for late-phase asthma prevention. Additionally, study by Daku et al. [22] showed LRP induced relaxation even with β2 receptor blockade. However, there are a few limitations to consider such as interspecies variation (rat vs. guinea pig models) isolated tissues under laboratory-controlled environments, potentially not accurately reflecting in vivo biological models of the airway environment, including immune cell and inflammatory component interactions and differences in sample processing, highlighting the need for standardized in vivo studies and dose–response evaluations.

Importantly, clinical studies involving inhaled calcium channel blockers such as verapamil, diltiazem, and nifedipine have shown that localized delivery to the lungs can effectively reduce bronchoconstriction without producing significant cardiovascular side effects [58, 59]. Given that TMM’s bronchodilatory activity may operate through a similar calcium-modulating pathway, there is a strong rationale for exploring TMM-based inhaled formulations. Such an approach could maximize airway-specific effects while avoiding gastrointestinal degradation and systemic side effects associated with oral delivery.

Tan et al. [23] carried out spirometry tests on participants and reported a 27.2% improvement in FEV1/FVC ratio after TMM supplementation, along with marked symptom reduction and improved quality of life scores. A low FEV1 and ratio is a risk factor of chronic lung disease development [60]. Meanwhile, two self-administered tests were provided to determine symptoms and quality of life: nasal symptom questionnaire (NSQ) and visual analogue scale (VAS). The results dropped in symptoms drastically and enhanced quality of life after TMM supplementation. As such, TMM has the potential to improve both pulmonary function and quality of life.

Limitations

Although the findings on TMM are promising, there are several limitations to be accounted for. The majority of evidence of TMM’s efficacy came from animal in vivo and in vitro studies which are limited in their ability to predict such results on human populations. Preclinical studies cannot fully replicate the complexity of human asthma such as its heterogeneity, comorbidities, and the influence of the external environment. Furthermore, only one study was conducted on humans, which limits the ability to direct the findings to clinical practice or into asthma management guidelines.

Future recommendations

Future research should focus on human application by conducting large-scale randomized controlled trials that investigate the clinical efficacy of TMM in asthma in order to strengthen the relevance of current findings. These studies will need to proceed with standardized protocols on factors such as extraction, dosing, route of administration, and outcome measurement. In this way, the results will be comparable and reproducible. The combined synergistic effects of TMM with conventional therapies such as β2 agonists and inhaled corticosteroids can also be explored to determine its viability as an adjunct agent. Additionally, studies could make direct comparisons between oral vs inhalation routes of administration to identify the optimal and most practical delivery system in humans.

Conclusion

This systematic review demonstrates that Lignosus rhinocerus, also known as tiger milk mushroom (TMM), holds promising preclinical therapeutic potential as an adjunct agent for asthma treatment. This is supported by both in vivo and in vitro data consistently showing significant anti-inflammatory, bronchodilatory and immunomodulatory effects. Particularly, TMM shows a reduction in eosinophil infiltration, Th2 cytokines, and airway remodeling in animals with preliminary supportive findings in a single human study.

The observed mechanism of action of TMM, the calcium channel-modulating activities suggest a biologically plausible and distinct mode of action compared with conventional asthma therapies. However, the current evidence base remains predominantly preclinical and limited human study as well as lack of methodological standardization precludes conclusion regarding clinical efficacy for routine clinical use. Further well designed, more clinical trials are required to establish safety, efficacy and the therapeutic role of TMM in asthma management.

Abbreviations

BALF

Bronchoalveolar lavage fluid

DMSO

Dimethyl sulfoxide

FEV1

Forced expiratory volume in 1s

FVC

Forced vital capacity

HMW

High molecular weight

iNOS

Inducible nitric oxide synthase

LMW

Low molecular weight

LRE

L. rhinocerus Extract

LRP

L. rhinocerus Polysaccharides

MDA

Malondialdehyde

MMW

Medium molecular weight

NSQ

Nasal symptom questionnaire

PAS

Periodic Acid-Schiff

PCR

Polymerase chain reaction

PRR

Pattern recognition receptors

ROS

Reactive oxygen species

TGF-β1

Transforming growth factor beta 1

TMM

Tiger milk mushroom

VAS

Visual analogue scale

Authors’ contributions

G.S.P. conceptualized the study, contributed to the methodology, data analysis, and interpretation of results, and led the manuscript drafting.. S.A.A conducted the literature search, data extraction, and synthesis of results, drafted the original manuscript, and contributed to manuscript revisions. A.K.K. contributed to the study design, literature review, and data collection, and provided critical revisions to the manuscript. K.S.L. assisted with the literature search, data extraction, and synthesis of results. M.J.F. contributed to the analysis and revised the manuscript for accuracy L.C.M. provided supervision, methodological insights, and critically reviewed the manuscript for scientific rigor. All authors read and approved the final manuscript.

Funding

Open access funding provided by Datta Meghe Institute of Higher Education and Research.

Data availability

Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable. The manuscript does not contain any individual person’s data in any form (including individual details, images, or videos).

Competing interests

The authors declare no competing interests.