Effects of Sparassis crispa in Medical Therapeutics: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

In this study, we investigated the therapeutic potential and medical applications of Sparassis crispa (S. crispa) by conducting a systematic review of the existing literature and performing a meta-analysis. The original efficacy treatment of the mushroom extract is considered primarily and searched in electronic databases. A total of 623 articles were assessed, 33 randomized controlled experiments were included after the manual screening, and some papers, review articles, or editorials that did not contain data were excluded. A comparative standard means difference (SMD) and a funnel plot between control and S. crispa groups were used as parameters to demonstrate the beneficial effects of S. crispa for diabetes and cancer treatment, as well as anti-inflammatory, anti-fungal and antioxidant activities. The meta-analysis was carried out using Review Manager 5.1 software. Although for therapeutic diabetes there was heterogeneity in the subgroup analysis (I2 = 91.9%), the overall results showed statistically significant SMDs in major symptoms that decreased serum insulin levels (SMD = 1.92, 95% CI (1.10, 2.75), I2 = 0%), wound rates (SMD = 3.55 (2.56, 4.54), I2 = 40%) and contributions to an increase in nutrient intake content (SMD = 0.32 (−0.15, 0.78), I2 = 0%). Simultaneously, the study confirmed the utility of S. crispa treatment in terms of not only anti-cancer activity (reduction of tumor activity and survival of cancer cells I2 = 42 and 34%, respectively) but also anti-inflammatory, anti-fungal and antioxidant activities (I2 = 50, 44, and 10%, respectively). Our findings suggest that S. crispa extracts are useful for prevention and treatment of human diseases and might be the best candidates for future medicines.


Introduction
Medical mushrooms have been approved as cures in traditional East Asian therapies [1,2]. Scientists around the world have verified the unique properties of compounds extracted from mushrooms in the prevention and treatment of cancer and other chronic diseases [3].

Risk of Bias
To explore the validity of eligible randomized studies, the quality of bias assessment of the included studies was determined by evaluating the bias of the random sequence generation, allocation concealment, selective reporting, blinding of participants and outcome assessment, and incomplete outcome data based on three levels following the Cochrane guideline (low and high risk of bias that may indicate either lack of information or uncertainty over the potential for bias) [46]. According to Table 2 and Figure 2, almost all criteria showed a low risk of bias, especially in studies where homogeneity in the random sequence generation criteria was used. Resulting in an evident enhanced of the statistical significance of the meta-analysis.

Diabetes Treatment
Anti-diabetic activity was evaluated by seven studies [6,12,14,[28][29][30][31] (Figure 3 and Table 3). Most of the assays were performed in diabetic rat and mouse cells, and the treatment was assessed in five aspects: serum glucose levels (mg/dL), serum insulin levels (mg/dL), nutrition intake (mL), body weight (g) of mice or tissues before and after treatment, as well as wound healing ability (%). In addition, some individual studies have identified and demonstrated the beneficial effects of S. crispa in several healing aspects, so they were evaluated in various separate analyses. For instance, Yamamoto et al. showed that S. crispa could prevent human diabetes by reducing serum glucose levels, insulin levels, and increasing the body weight of diabetic mice [14]. In addition, Jeong et al. indicated the capability of S. crispa in four aspects including serum glucose and insulin levels, nutrition intake, and body weight [29].

Diabetes Treatment
Anti-diabetic activity was evaluated by seven studies [6,12,14,[28][29][30][31] (Figure 3 and Table 3). Most of the assays were performed in diabetic rat and mouse cells, and the treatment was assessed in five aspects: serum glucose levels (mg/dL), serum insulin levels (mg/dL), nutrition intake (mL), body weight (g) of mice or tissues before and after treatment, as well as wound healing ability (%). In addition, some individual studies have identified and demonstrated the beneficial effects of S. crispa in several healing aspects, so they were evaluated in various separate analyses. For instance, Yamamoto et al. showed that S. crispa could prevent human diabetes by reducing serum glucose levels, insulin levels, and increasing the body weight of diabetic mice [14]. In addition, Jeong et al. indicated the capability of S. crispa in four aspects including serum glucose and insulin levels, nutrition intake, and body weight [29]. A subgroup analysis was conducted to quantify the effect of S. crispa in all therapeutic approaches comparing to the control group. Anti-diabetic activity was significantly higher in the S. crispa group than in the control group, and results showed a significant effect of S. crispa in the treatment (SMD = 1.29, 95% confidence interval (CI) (0.47, 2.11), p < 0.00001), although a heterogeneity was observed in the subgroup analysis (heterogeneity X 2 = 50.24, p < 0.00001, I 2 = 91.9%). However, when was considered each aspect of the diabetes treatment, the comparison between serum insulin levels and wound healing rates showed significant homogeneities in all reported symptoms and presented a large SMD between the two groups ((SMD = 1.92, 95% CI (1.10, 2.75), I 2 = 0%) and (SMD = 3.55, 95% CI (2.56, 4.54), I 2 = 40%), respectively). Neither nutrition intakes showed heterogeneity SMD (SMD = 0.32, 95% CI (−0.15, 0.78), I 2 = 0%). Nevertheless, serum glucose levels and body weights of rats showed high heterogeneity (I 2 = 94% and I 2 = 78%, respectively).

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of oxidative protection than the control group, with evidence of improving antioxidant activity ( Figures 10  and 11). The inhibitory activity indicated a significant homogeneity with I 2 = 0% and X 2 = 1.   of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see .    A subgroup analysis was conducted to quantify the effect of S. crispa in all therapeutic approaches comparing to the control group. Anti-diabetic activity was significantly higher in the S. crispa group than in the control group, and results showed a significant effect of S. crispa in the treatment (SMD = 1.29, 95% confidence interval (CI) (0.47, 2.11), p < 0.00001), although a heterogeneity was observed in the subgroup analysis (heterogeneity X 2 = 50.24, p < 0.00001, I 2 = 91.9%). However, when was considered each aspect of the diabetes treatment, the comparison between serum insulin levels and wound healing rates showed significant homogeneities in all reported symptoms and presented a large SMD between the two groups ((SMD = 1.92, 95% CI (1.10, 2.75), I 2 = 0%) and (SMD = 3.55, 95% CI (2.56, 4.54), I 2 = 40%), respectively). Neither nutrition intakes showed heterogeneity SMD (SMD = 0.32, 95% CI (−0.15, 0.78), I 2 = 0%). Nevertheless, serum glucose levels and body weights of rats showed high heterogeneity (I 2 = 94% and I 2 = 78%, respectively).

Cancer Treatment
From nine-teen studies [7,13,15,21,23,24,26,28,30,[32][33][34][35][36][37][38][39][40][41], seven reported an anti-tumor activity, five showed an inhibition of cancer cell viability, and nine indicated IFN-γ induction of S. crispa extracts. On the other hand, there are several reports which showed appropriate data in many respects [3,7]. In addition, when considering the capability of healing, researchers performed experiments to describe the effect of S. crispa extract in various types of cells [3,15,23] or to determine the therapeutic potential of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see .
of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see .

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of oxidative protection than the control group, with evidence of improving antioxidant activity ( Figures 10  and 11). The inhibitory activity indicated a significant homogeneity with I 2 = 0% and X 2 = 1.   of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see .  of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see .

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see .

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of oxidative protection than the control group, with evidence of improving antioxidant activity ( Figures 10  and 11). The inhibitory activity indicated a significant homogeneity with I 2 = 0% and X 2 = 1.

Sensitivity Analysis
Studies that used the same S. crispa extract, similar dosages and the same experimental objects were included in the sensitivity analysis. Wound healing rates in diabetes treatment and survival of cancer cells after anti-tumor activity were analyzed (Figures 12 and 13). All cases showed a high homogeneity and a high reduction of the percentages of cancer cells (SMD = 16.08 (1.83, 27.32), I 2 = 0%), as well as an improved wound healing ability of the objects (SMD = 2.89 (1.87, 3.90), I 2 = 13%) after treatment with S. crispa. of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see .   A comparison between the control and S. crispa group showed a lower tumor cell activity (SMD = 2.22, 95% CI (1.69, 2.75), p < 0.00001); that reduction was relevant to the homogeneity in seven studie [7,13,15,24,30,34,35] (X 2 = 24.27, I 2 = 42%). Additionally, the heterogeneity was not significant for the survival of cancer cells (X 2 = 12.11, I 2 = 34%) in five studies [7,23,30,33,36], resulting in a dramatical decrease in the cancer cell viability after exposure to S. crispa (SMD = 21.36, 95% CI (17.91, 24.81), p < 0.00001). The SMD between these two groups did not show a significant of the IFN-γ induction aspect (SMD = −0.34, 95% CI (−0.37, −0.31), X 2 = 1168.88, I 2 = 99%).

Anti-Fungal Activity
Anti-fungal compounds are produced by S. crispa in cultures and in wood decomposed naturally, as reported in three studies [19,29,43]. According to these studies, results of the meta-analysis ( Figure  9) there was a favorable effect in the S. crispa group; the numbers of bacteria and fungi were reduced in the treatment group compared with the control group. A significant difference was found between these two groups (SMD = 0.20, 95% CI (−0.23, 0.62), X 2 = 8.86, I 2 = 44% < 50%).

Anti-Fungal Activity
Anti-fungal compounds are produced by S. crispa in cultures and in wood decomposed naturally, as reported in three studies [19,29,43]. According to these studies, results of the meta-analysis ( Figure  9) there was a favorable effect in the S. crispa group; the numbers of bacteria and fungi were reduced in the treatment group compared with the control group. A significant difference was found between these two groups (SMD = 0.20, 95% CI (−0.23, 0.62), X 2 = 8.86, I 2 = 44% < 50%).

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of oxidative protection than the control group, with evidence of improving antioxidant activity (Figures 10  and 11). The inhibitory activity indicated a significant homogeneity with I 2 = 0% and X 2 = 1. of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see .

Anti-Fungal Activity
Anti-fungal compounds are produced by S. crispa in cultures and in wood decomposed naturally, as reported in three studies [19,29,43]. According to these studies, results of the meta-analysis (Figure 9) there was a favorable effect in the S. crispa group; the numbers of bacteria and fungi were reduced in the treatment group compared with the control group. A significant difference was found between these two groups (SMD = 0.20, 95% CI (−0.23, 0.62), X 2 = 8.86, I 2 = 44% < 50%).

Anti-Fungal Activity
Anti-fungal compounds are produced by S. crispa in cultures and in wood decomposed naturally, as reported in three studies [19,29,43]. According to these studies, results of the meta-analysis ( Figure  9) there was a favorable effect in the S. crispa group; the numbers of bacteria and fungi were reduced in the treatment group compared with the control group. A significant difference was found between these two groups (SMD = 0.20, 95% CI (−0.23, 0.62), X 2 = 8.86, I 2 = 44% < 50%).

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of oxidative protection than the control group, with evidence of improving antioxidant activity (Figures 10  and 11). The inhibitory activity indicated a significant homogeneity with I 2 = 0% and X 2 = 1.

Sensitivity Analysis
Studies that used the same S. crispa extract, similar dosages and the same experimental objects were included in the sensitivity analysis. Wound healing rates in diabetes treatment and survival of cancer cells after anti-tumor activity were analyzed (Figures 12 and 13). All cases showed a high homogeneity and a high reduction of the percentages of cancer cells (SMD = 16.08 (1.83, 27.32), I 2 = 0%), as well as an improved wound healing ability of the objects (SMD = 2.89 (1.87, 3.90), I 2 = 13%) after treatment with S. crispa. of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see Figures 4-6).

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of oxidative protection than the control group, with evidence of improving antioxidant activity (Figures 10 and 11). The inhibitory activity indicated a significant homogeneity with I 2 = 0% and X 2 = 1.

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of oxidative protection than the control group, with evidence of improving antioxidant activity (Figures 10  and 11). The inhibitory activity indicated a significant homogeneity with I 2 = 0% and X 2 = 1.

Sensitivity Analysis
Studies that used the same S. crispa extract, similar dosages and the same experimental objects were included in the sensitivity analysis. Wound healing rates in diabetes treatment and survival of cancer cells after anti-tumor activity were analyzed (Figures 12 and 13). All cases showed a high homogeneity and a high reduction of the percentages of cancer cells (SMD = 16.08 (1.83, 27.32), I 2 = 0%), as well as an improved wound healing ability of the objects (SMD = 2.89 (1.87, 3.90), I 2 = 13%) after treatment with S. crispa.

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of oxidative protection than the control group, with evidence of improving antioxidant activity (Figures 10  and 11). The inhibitory activity indicated a significant homogeneity with I 2 = 0% and X 2 = 1. of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see Figures 4-6).

Antioxidant Activity
According to six studies [8,[25][26][27]44,45], the antioxidant activity was performed through DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity and the oxidative-inhibitory capacity of phenolic compounds derived from S. crispa. In both cases, the S. crispa group reported a higher level of oxidative protection than the control group, with evidence of improving antioxidant activity (Figures 10  and 11). The inhibitory activity indicated a significant homogeneity with I 2 = 0% and X 2 = 1.

Sensitivity Analysis
Studies that used the same S. crispa extract, similar dosages and the same experimental objects were included in the sensitivity analysis. Wound healing rates in diabetes treatment and survival of cancer cells after anti-tumor activity were analyzed (Figures 12 and 13). All cases showed a high homogeneity and a high reduction of the percentages of cancer cells (SMD = 16.08 (1.83, 27.32), I 2 = 0%), as well as an improved wound healing ability of the objects (SMD = 2.89 (1.87, 3.90), I 2 = 13%) after treatment with S. crispa. of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated and appeared multiple times in a comparison of this analysis. An individual analysis was applied to two groups for each of those aspects, showing significant inter-group differences (see .

Sensitivity Analysis
Studies that used the same S. crispa extract, similar dosages and the same experimental objects were included in the sensitivity analysis. Wound healing rates in diabetes treatment and survival of cancer cells after anti-tumor activity were analyzed (Figures 12 and 13). All cases showed a high homogeneity and a high reduction of the percentages of cancer cells (SMD = 16.08 (1.83, 27.32), I 2 = 0%), as well as an improved wound healing ability of the objects (SMD = 2.89 (1.87, 3.90), I 2 = 13%) after treatment with S. crispa.

Sensitivity Analysis
Studies that used the same S. crispa extract, similar dosages and the same experimental objects were included in the sensitivity analysis. Wound healing rates in diabetes treatment and survival of cancer cells after anti-tumor activity were analyzed (Figures 12 and 13). All cases showed a high homogeneity and a high reduction of the percentages of cancer cells (SMD = 16.08 (1.83, 27.32), I 2 = 0%), as well as an improved wound healing ability of the objects (SMD = 2.89 (1.87, 3.90), I 2 = 13%) after treatment with S. crispa. of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evaluated an appeared multiple times in a comparison of this analysis. An individual analysis was applied to tw groups for each of those aspects, showing significant inter-group differences (see Figures 4-6).

Bias Analysis
Funnel plots were drawn to assess the publication bias of studies on the medical applications of S. crispa. Figures 14 and 15 are approximately symmetrical but small studies showing diabetes and cancer treatment effects of S. crispa remain unpublished. In contrast, Figure 16 estimated that the most important studies on anti-inflammatory activity of S. crispa have been missing, so the outcomes of the anti-inflammatory treatment were not highly significant statistically. Even though the funnel plots in Figures 17 and 18 also demonstrated that many relevant studies have not been published yet, all the published data were statistically significant for the anti-fungal and antioxidant activity of S. crispa extracts.  of different S. crispa extracts on a cell type [7]. Therefore, these studies have been evalua appeared multiple times in a comparison of this analysis. An individual analysis was applie groups for each of those aspects, showing significant inter-group differences (see

Bias Analysis
Funnel plots were drawn to assess the publication bias of studies on the medical applications of S. crispa. Figures 14 and 15 are approximately symmetrical but small studies showing diabetes and cancer treatment effects of S. crispa remain unpublished. In contrast, Figure 16 estimated that the most important studies on anti-inflammatory activity of S. crispa have been missing, so the outcomes of the anti-inflammatory treatment were not highly significant statistically. Even though the funnel plots in Figures 17 and 18 also demonstrated that many relevant studies have not been published yet, all the published data were statistically significant for the anti-fungal and antioxidant activity of S. crispa extracts.

Discussion
In this systematic review and meta-analysis of thirty-three studies on the medical application of S. crispa extracts were confirmed that S. crispa is not only an edible mushroom but also a medicinal mushroom that has been increasingly cultivated because of its potential value in traditional medicine. Indeed, S. crispa contains highly physiological active substances (e.g., β-glucan, phenolic compounds, chloroform extract, and some antibiotic compounds) that can support a healthy level of blood-sugar and recovery of the normal cellular immunization [3]. The beneficial effects have been demonstrated by anti-diabetic, anti-tumor, anti-inflammatory, anti-fungal, and anti-oxidant activities [1,3,11,20,47]; almost all of the typical therapeutic effects of S. crispa showed significant differences, relative to the control groups.
As an immunomodulating substance, β-glucan plays an important role in most healing modalities [48]. Mainly, involving an enhance of the immune response against cancer and stimulating the cells of the innate immune system [48][49][50][51]. The discovery of specific receptors for glucans in cells, as well as interactions with other receptors mainly expressed by innate immune cells, have been reported as the primary mechanism of β-glucan for regulation of anti-tumor therapy and some associated medical treatments [51]. Our meta-analysis indicated that S. crispa extracts had a large influence in reducing significantly cancer cells viability and tumor cells suppression (Figures 4 and 5). Although, here there was not a high homogeneity in the IFN-production aspect ( Figure 6). Moreover, the estimate as clinical evidence for a relationship between structure and activity, suggested the contributions of multiple receptor-ligand interactions in glycan-mediated immunopotentiation.
Diabetes that has been caused by a single high dose of streptozotocin is typically accompanied by symptoms such as weight loss, polyuria, hyperglycemia, and neuroendocrine dysfunction 6,14].On the other hand, whereas wound healing progresses at an optimal rate in healthy individuals, patients with diabetes usually exhibit delayed or impaired wound healing, which is a serious highblood-glucose-related clinical problem [52]. The present subgroup analysis did not report any significant difference (I 2 = 91.9%) between S. crispa and control groups ( Figure 3 and Table 3), suggesting that mushroom extracts have not had complete effects on all the diabetes symptoms. However, an individual analysis for each aspect, two topical therapy symptoms (incidence of wounds and serum insulin levels in the blood) were eliminated after treatment with S. crispa. In summary, S. crispa showed a slightly beneficial influence on diabetes therapeutics. Meanwhile, we expect that additional studies on S. crispa treatments will improve the accuracy of the analysis.
Additionally, the mushroom has shown an anti-inflammatory activity [1,2,47]. The present analysis estimates (Figures 7 and 8, and Table 3) that studies on anti-inflammatory therapy were

Discussion
In this systematic review and meta-analysis of thirty-three studies on the medical application of S. crispa extracts were confirmed that S. crispa is not only an edible mushroom but also a medicinal mushroom that has been increasingly cultivated because of its potential value in traditional medicine. Indeed, S. crispa contains highly physiological active substances (e.g., β-glucan, phenolic compounds, chloroform extract, and some antibiotic compounds) that can support a healthy level of blood-sugar and recovery of the normal cellular immunization [3]. The beneficial effects have been demonstrated by anti-diabetic, anti-tumor, anti-inflammatory, anti-fungal, and anti-oxidant activities [1,3,11,20,47]; almost all of the typical therapeutic effects of S. crispa showed significant differences, relative to the control groups.
As an immunomodulating substance, β-glucan plays an important role in most healing modalities [48]. Mainly, involving an enhance of the immune response against cancer and stimulating the cells of the innate immune system [48][49][50][51]. The discovery of specific receptors for glucans in cells, as well as interactions with other receptors mainly expressed by innate immune cells, have been reported as the primary mechanism of β-glucan for regulation of anti-tumor therapy and some associated medical treatments [51]. Our meta-analysis indicated that S. crispa extracts had a large influence in reducing significantly cancer cells viability and tumor cells suppression (Figures 4 and 5). Although, here there was not a high homogeneity in the IFN-γ production aspect ( Figure 6). Moreover, the estimate as clinical evidence for a relationship between structure and activity, suggested the contributions of multiple receptor-ligand interactions in glycan-mediated immunopotentiation.
Diabetes that has been caused by a single high dose of streptozotocin is typically accompanied by symptoms such as weight loss, polyuria, hyperglycemia, and neuroendocrine dysfunction [6,14]. On the other hand, whereas wound healing progresses at an optimal rate in healthy individuals, patients with diabetes usually exhibit delayed or impaired wound healing, which is a serious high-blood-glucose-related clinical problem [52]. The present subgroup analysis did not report any significant difference (I 2 = 91.9%) between S. crispa and control groups ( Figure 3 and Table 3), suggesting that mushroom extracts have not had complete effects on all the diabetes symptoms. However, an individual analysis for each aspect, two topical therapy symptoms (incidence of wounds and serum insulin levels in the blood) were eliminated after treatment with S. crispa. In summary, S. crispa showed a slightly beneficial influence on diabetes therapeutics. Meanwhile, we expect that additional studies on S. crispa treatments will improve the accuracy of the analysis. Additionally, the mushroom has shown an anti-inflammatory activity [1,2,47]. The present analysis estimates (Figures 7 and 8, and Table 3) that studies on anti-inflammatory therapy were statistically significant, achieving a small homogeneity in the analysis. Furthermore, results also demonstrated that S. crispa extracts played an inhibitory role in inflammatory responses via regulation of NO production; suggesting a potential role as a component of inflammatory drugs.
Recently, some evidence has suggested that the biological actions of phenolic compounds are associated with their antioxidant capacity based on their ability to chelate metals and lipoxygenase inhibitors [19,26]. The present survey also considered and evaluated antioxidant activities of the medical mushroom by meta-analysis (Figures 10 and 11). According to the coefficient of heterogeneities of the analysis (I 2 = 0% and 10%), it was confirmed that phenolic compounds and other S. crispa extracts could significantly contribute to antioxidant properties; explaining the relationship between phenolic compounds and antioxidant activities, as well as anti-fungal ability.
Finally, anti-bacterial and anti-fungal compounds have been identified in S. crispa [43], though their utilities were reported in only three studies [19,29,43]. The analysis showed that after exposure to S. crispa extracts the numbers of bacteria and fungi were reduced, indicating that the mushroom, as a component of pharmaceuticals, can protect humans from bacterial and fungal contamination.

Methods
The study followed the Cochrane Collaboration method [46], as well as the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [53] to report a systematic review and meta-analysis. Also, this work was based on the protocols and reviews on medical applications of S. crispa. It included all the researches that assessed the ability of S. crispa extracts on human health treatment (i.e., diabetes and cancer treatment, anti-fungal, antioxidant, and anti-inflammatory activity). It excluded ineligible studies such as studies of the effects of mushroom in other application fields and contained inappropriate data for the analysis. It compared and analyzed the statistical significance of individual studies of the same effect of S. crispa for the specific therapeutics using meta-analysis. Outcomes provided an overview and a systematic assessment about the clinical efficacies of S. crispa based on comparing SMDs between control and S. crispa groups, as well as the heterogeneity coefficient (I 2 ) of each analysis [54].

Database Research Strategy
The searched literature on medical applications of S. crispa extracts was performed in the databases PubMed (National Library of Medicine, Bethesda, MD, USA), EMBASE (Excerpta Medica database, Amsterdam, Netherlands), Elsevier (Information and Analytics, Amsterdam, Netherlands), CENTRAL (Cochrane Central Register of Controlled Trials, New York, NY, USA), and Web of Science (Institute of Scientific Information and Clarivate Analytics, Philadelphia, PA, USA), considering articles published between 1990 and 2018. Also, we made a hand searching for important conference papers, as well as checking reference lists. Combinations of the following keywords were used: S. crispa, Sparassis Latifolia, Cauliflower mushroom, Hanaratake, medical applications, immune stimulating activity, anti-tumor, anti-cancer, anti-microbial, anti-melanin, anti-metastatic, anti-inflammatory, anti-fungal, antioxidant, anti-viral, anti-diabetic, and anti-hypertensive activity. The respective reference lists of the identified papers also were searched. All articles were written in English, Korean or Japanese.

Data Extraction
The bibliographic reference list was screened and manually selected from eligible studies from the electronic database for the meta-analysis, according to the criteria of associations between medical applications of S. crispa and human therapeutics. The following information from each article was obtained: article title, the name of first author, location, study year, publication year, study design, number of participants, dosage and administration, type of treatment and outcomes. These items were selected based on the presence and short descriptions of important study characteristics (e.g., title, abstract, study design, experimental object, and kind of medical application). The criteria included in the quantitative meta-analysis were empirical data that could be used to calculate the SMDs of treatments.

Exclusion Criteria
Articles were excluded based on the following criteria: no data presentation (e.g., review articles and editorials), incomplete data, repeated and similar studies.

Meta-Analysis
For each analysis, we determined the effect size (SMD) and 95% CI for the comparison between control and S. crispa groups. The SMD was obtained by dividing the mean difference between the two groups by the pooled variance, with adjustment for small samples. We considered SMDs about 0.2 or less as small values, 0.5 as moderate values, and 0.8 or greater values as large [54]. We quantified the extension to which the observed variability between studies was due to true differences between studies using the I 2 statistic. Heterogeneity was considered to be small when I 2 was less than 25%, moderate when 25-50%, and large when greater than 50% [54]. The subgroup analysis assessed the overall effects in the subgroups according to the model type, kind(s) of treatment(s), and symptoms. The value of p < 0.05 was considered statistically significant, and bias was examined using a funnel plot.
All these analyses were performed using Review Manager [46] (version 5.3, Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2014).

Limitation of Study
The limitation of this study is the number of individual studies, which are not as large as our expectation in some respect (i.e., anti-inflammatory, anti-fungal, and antioxidant activity) leading to estimations not highly significant. Especially in the sensitivity assessment, the results might be not high accuracy because of a very small quantity of those that have the same test conditions for consideration of the sensitivity.

Conclusions
Briefly, this investigation determined that S. crispa is useful in medical therapeutics, each extract showed their properties and specific applications. Particularly, a meta-analysis revealed that β-glucan, which is known as the primary ingredient of S. crispa extract, plays an important part in the treatment of cancer and diabetes. Additionally, the analysis confirmed that β-glucan and other constituents (i.e., phthalide compounds, low-molecular-weight ingredients, and anti-bacterial substances) are used in anti-inflammatory activities, as well as antioxidant and anti-fungal immunotherapies. However, recent studies have focused on the clinical application of S. crispa [3,12,13,26,31,35,44]. To support our analysis, further studies to improve the statistical significance is necessary.