Water extract of Acer tegmentosum reduces bone destruction by inhibiting osteoclast differentiation and function

Isolation and Characterization of an Anti-Osteoporotic Compound from Melia toosendan Fructus

Melia toosendan fructus, traditionally employed in traditional Chinese and Korean herbal medicine, exhibits diverse biological properties encompassing anti-tumor, anti-inflammatory, and anti-viral effects. However, its influence on bone metabolism remains largely unexplored. In this study, we investigated the impact of an ethanolic extract of Melia toosendan fructus (MTE) on osteoclast differentiation and characterized its principal active constituent in osteoclast differentiation and function, as well as its effects on bone protection. Our findings demonstrate that MTE effectively inhibits the differentiation of osteoclast precursors induced by receptor activator of nuclear factor κB ligand (RANKL). Utilizing a bioassay-guided fractionation approach coupled with UHPLC-MS/MS analysis, we isolated and identified the triterpenoid compound toosendanin (TSN) as the active constituent responsible for MTE's anti-osteoclastogenic activity. TSN treatment downregulated the expression of nuclear factor of activated T cells c1, a pivotal osteoclastogenic transcription factor, along with molecules implicated in osteoclast-mediated bone resorption, including tumor necrosis factor receptor-associated factor 6, carbonic anhydrase II, integrin beta-3, and cathepsin K. Furthermore, treatment of mature osteoclasts with TSN impaired actin ring formation, acidification, and resorptive function. Consistent with our in vitro findings, TSN administration mitigated trabecular bone loss and reduced serum levels of the bone resorption marker, C-terminal cross-linked telopeptides of type I collagen, in a mouse bone loss model induced by intraperitoneal injections of RANKL. These results suggest that TSN, as the principal active constituent of MTE with inhibitory effects on osteoclastogenesis, exhibits bone-protective properties by suppressing both osteoclast differentiation and function. These findings imply the potential utility of TSN in the treatment of diseases characterized by excessive bone resorption.

Therapeutic Effect of Acer tegmentosum Maxim Twig Extract in Bile Duct Ligation-Induced Acute Cholestasis in Mice

Cholestatic liver disease, or cholestasis, is a condition characterized by liver inflammation and fibrosis following a bile duct obstruction and an intrahepatic accumulation of bile acids. Inhibiting inflammation is a promising therapeutic strategy for cholestatic liver diseases. Acer tegmentosum Maxim extract (ATE) is best known for its anti-inflammatory and antioxidative properties. In this study, we investigated the effects of ATE on liver injury and fibrosis in mice with bile duct ligation (BDL)-induced cholestasis through analysis of gene expression, cytokines, and histological examination. Oral administration of ATE (20 or 50 mg/kg) for 14 days significantly attenuated hepatocellular necrosis compared to vehicle-treated BDL mice, which was accompanied by the reduced level of serum bile acids and bilirubin. We determined that ATE treatment reduced liver inflammation, oxidative stress, and fibrosis. These beneficial effects of ATE were concurrent with the decreased expression of genes involved in the NF-κB pathway, suggesting that the anti-inflammatory effect of ATE could be a possible mechanism against cholestasis-associated liver injury. Our findings substantiate ATE's role as an alternative therapeutic agent for cholestasis-induced liver injury and fibrosis.

Identification and pharmacokinetics of bioavailable anti-resorptive phytochemicals after oral administration of Psoralea corylifolia L

Osteoporosis and resulting bone fractures are the major health issues associated with morbidity in the aging population; however, there is no effective treatment that does not cause severe side effects. In East Asia, dried seeds of Psoralea corylifolia L. (PC) have traditionally been used as an herbal medicine to manage urinary tract, cutaneous, and gastrointestinal disorders, as well as bone health. However, the mechanism of action and active biocomponents of PC are unclear. Here, we adopted a pharmacokinetic (PK) study aiming to identify the bioavailable phytochemicals in aqueous and ethanolic extracts of PC (APC) and (EPC), respectively. In addition, we aimed to determine anti-resorptive constituents of PC, which accounted for its beneficial effects on bone health. To this end, we used ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). A rapid, sensitive, and reliable UPLC-MS/MS method was developed and determined the 17 PC ingredients. In the PK study, nine components (two chalcones, two coumarins, one coumestan, two flavonoids, and two isoflavonoids) were observed between 36 and 48 h after oral administration of APC or EPC. Among the bioavailable ingredients, four PC constituents (psoralidin, isobavachin, corylifol A, and neobavaisoflavone) inhibited M-CSF-and RANKL-induced osteoclast differentiation in bone marrow-derived macrophages. In addition, two chalcones and two isoflavonoids markedly inhibited cathepsin K activity, and their binding modes to cathepsin K were determined by molecular docking. In summary, our data suggest that bioavailable multicomponents of PC could contribute to the management of bone health.

Safety Assessment of Acer tegmentosum Maxim. Water Extract: General Toxicity Studies in Sprague-Dawley Rats and Beagle Dogs With Re-evaluation of Genotoxic Potentials

Acer tegmentosum Maxim., commonly known as Manchurian stripe maple, is a deciduous tree belonging to the family of Aceraceae and has been traditionally used in folk medicine for its remedial effects in liver diseases and traumatic bleedings. With a growing body of experimental evidence for its pharmacological efficacies, such as neuroprotective, hepatoprotective, antioxidant, and anti-inflammatory activities, A. tegmentosum has gradually gained popularity as a health supplement and functional food. However, the large part of essential toxicity information still remained lacking despite the possibility of mutagenic potentials as previously suggested, posing safety concerns for human consumption. In this study, we evaluated 90-day repeated oral toxicity of A. tegmentosum Maxim. water extract (ATWE) in SD rats with acute toxicity assessment in beagle dogs, and reevaluated genotoxicity using a combination of in vitro and in vivo assays. During the oral study period, ATWE did not cause toxicity-related clinical signs and mortality in rodents without adverse effects observed in the analysis of hematology, serum biochemistry, and histopathology, establishing >5,000 mg/kg BW as the NOAEL. In addition, doses up to 5,000 mg/kg BW did not cause acute toxicity in beagle dogs. When assessed for genotoxicity using bacterial reverse mutation, chromosome aberration, and micronucleus formation, ATWE showed lack of mutagenicity and clastogenicity. These results demonstrated that AWTE was safe in the present preclinical study for systemic toxicity and genotoxicity at the tested doses, providing a guideline for safe use in humans.

Ethanol Extract of Amomum tsao-ko Ameliorates Ovariectomy-Induced Trabecular Loss and Fat Accumulation

In Asia, Amomum tsao-ko has long been used as a spice or seasoning in food to stimulate digestion. In the present study, we evaluated the effects of ethanol extract of Amomum tsao-ko (EEAT) on menopausal osteoporosis and obesity. After the administration of EEAT in ovariectomy (OVX) mice models for five weeks, microcomputed tomography and a histological analysis were performed to assess, respectively, the trabecular structure and the fat accumulation in adipose, liver, and bone tissues. We also examined the effects of EEAT on a bone marrow macrophage model of osteoclastogenesis by in vitro stimulation from the receptor activator of nuclear factor-kappa Β ligand (RANKL) through real-time PCR and Western blot analysis. In addition, ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with authentic standards was applied to characterize the phytochemical profiling of EEAT. We found that EEAT significantly decreased OVX-induced body weight gain and fat accumulation, significantly prevented OVX-induced deterioration of bone mineral density and microstructure of trabecular tissues, and significantly inhibited osteoclast differentiation by downregulating NF-κB/Fos/NFATc1 signaling in osteoclasts. Furthermore, UHPLC-MS/MS identified eight beneficial phytochemicals in EEAT. Collectively, these results suggest that EEAT might be an effective nutraceutical candidate to attenuate menopausal osteoporosis by inhibiting osteoclastogenesis and to prevent obesity by suppressing fat accumulation.

Optimization of Extraction Conditions for Antioxidant Activity of Acer tegmentosum Using Response Surface Methodology

Extraction from edible plants is a highly important process that has various biological functions. To maximize biological activity, extraction methods should facilitate optimal extraction of functional phytochemicals. In this study, the optimal hydrothermal extraction conditions of Acer tegmentosum were determined using response surface methodology (RSM), and HepG2 cells were treated with optimized extract and hydrogen peroxide. In a central composition design, the independent variables were extraction temperature (X1: 70–90 °C), extraction time (X2: 2–6 h), and solvent-to-solid ratio (X3: 50–150). The maximum total phenolic contents (276.70 ± 10.11 mg GAE/g) and DPPH (2,2-diphenyl-1-pictylhydrazyl) activity (33.45 ± 2.20%) of A. tegmentosum were estimated at optimized extraction conditions, as follows: X1: 89.34 °C, X2: 7.36 h, X3: 184.09. Using the calculated extraction conditions, functional phytochemicals were extracted by hydrothermal extraction and freeze-dried. A. tegmentosum treatment (>10 μg/mL) of HepG2 cells remarkably attenuated hydrogen-peroxide-inducible hepatic cellular death and reactive oxygen species production in vitro.

Selective activation of the estrogen receptor-β by the polysaccharide from Cynanchum wilfordii alleviates menopausal syndrome in ovariectomized mice

The menopausal syndrome caused by rapid changes in hormone levels greatly influences the quality of life of women. Though hormone replacement therapy (HRT) is widely used to treat the menopausal syndrome, it exhibits many side effects, including the risk of thrombosis, cardiovascular diseases, and increased incidence of breast cancer; thus, diversifying the interest for phytotherapy-based materials as alternatives to HRT. Here, we isolated a crude polysaccharide fraction (CWPF) from Cynanchum wilfordii root that alleviated the ovariectomy-induced uterine atrophy and bone loss without changes in plasma estradiol concentration in mice. Increased plasma levels of follicle-stimulating hormone (FSH), alkaline phosphatase (ALP), osteocalcin (OC) in ovariectomized mice were also reduced to normal levels by CWPF administration. We found that the inhibitory effects of CWPF on menopausal symptoms were mediated by the estrogen receptor β (ER-β) specific activation, not ER-α. Moreover, CWPF treatment suppressed the phosphorylation of Akt, suggesting that CWPF alleviates post-menopausal symptoms by regulating ER-β related Akt signaling pathway. These results demonstrate that the polysaccharides corresponding to CWPF among the water-soluble extracts of CW could be used as a beneficial herbal alternative for the development of therapeutic agents to prevent menopausal syndrome in women.

Water Extract of Agastache rugosa Prevents Ovariectomy-Induced Bone Loss by Inhibiting Osteoclastogenesis

Estrogen deficiency in postmenopausal women causes homeostatic imbalance of bone, resulting in bone loss and osteoporosis. Agastache rugosa, a plant belonging to the Lamiaceae family, is an aromatic herb, and the leaves of this herb are widely used as food ingredients. Extracts of A. rugosa have various bioactivities including anti-HIV integration, anti-inflammatory, and anti-atherogenic properties. However, the beneficial effect of A. rugosa on bone has not been studied. Therefore, we investigated the effects of water extract of A. rugosa (WEAR) on osteoclast differentiation and estrogen deficiency-induced bone loss in ovariectomized (OVX) mice as an animal model for postmenopausal osteoporosis. The oral administration of WEAR remarkably improved OVX-induced trabecular bone loss and fat accumulation in the bone marrow. WEAR suppressed receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation in osteoclast precursor cells, subsequently inhibiting resorption activity on a bone mimetic surface. WEAR inhibited the expression of cellular oncogene fos (c-Fos) and nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), key osteoclastogenic transcription factors, by decreasing RANKL-induced activation of mitogen-activated protein kinases (MAPKs), and nuclear factor-κB (NF-κB) pathways. We also identified seventeen phytochemicals present in WEAR, including five phenols and twelve flavonoids, and found eleven bioactive constituents that have anti-osteoclastogenic effects. Collectively, these results suggest that WEAR could be used to treat and prevent postmenopausal osteoporosis by suppressing osteoclastogenesis.

Water Extract of Lysimachia christinae Inhibits Trabecular Bone Loss and Fat Accumulation in Ovariectomized Mice

In Asia, extracts of Lysimachia christinae have been used for liver or urinogenital system-related diseases in traditional medicine. In this study, we investigated the effects of the water extract of L. christinae (WELC) on receptor activator of nuclear factor-kappa Β ligand (RANKL)-induced osteoclastic differentiation of bone marrow macrophages, and on osteoporosis and obesity in ovariectomy mice. RANK signaling pathways related to osteoclast differentiation were examined by real-time polymerase chain reaction (PCR) and western blot analysis. Additionally, we performed micro-computed tomography to assess trabecular bone loss, histological analysis for fat accumulation in adipose, liver, and bone tissues, and phytochemical profiling for WELC characterization. WELC significantly inhibited osteoclast differentiation by downregulating RANKL-induced mitogen-activated protein kinase (MAPK)/c-Fos/nuclear factor of activated T-cells (NFAT) signaling in osteoclast precursors and ovariectomy-induced trabecular loss by suppressing osteolcastic bone resorption. WELC markedly decreased ovariectomy-induced body weight gain and fat accumulation in adipose, liver, and bone tissues. Furthermore, ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS) identified 16 phytochemicals in WELC when compared with the mass fragmentation of standard chemicals. Collectively, these results suggest that WELC might possess beneficial effects on postmenopausal osteoporosis by inhibiting osteoclast differentiation and obesity by suppressing fat accumulation.

Poria Cocos Ameliorates Bone Loss in Ovariectomized Mice and Inhibits Osteoclastogenesis In Vitro

Estrogen deprivation in postmenopausal women causes disruption of bone homeostasis, resulting in bone loss and osteoporosis. Conventional therapies can exert adverse effects. The sclerotum of Poria cocos has been used in traditional medicine and as a nutritional supplement and to treat various diseases. However, the effects of P. cocos on the bone remain largely undetermined. In this study, we examined the effects of P. cocos hydroethanolic extract (PC) on osteoclast differentiation and estrogen-deprivation-induced bone loss in an ovariectomized mouse model of postmenopausal osteoporosis. PC-mediated inhibition of receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation and resorption activity suppressed RANKL-induced expression of nuclear factor of activated T cells cytoplasmic 1 (NFATc1), which is a crucial transcription factor for osteoclast differentiation. In ovariectomized mice, PC markedly alleviated trabecular bone loss and reduced the accumulation of lipid droplets in the bone marrow. We additionally identified ten triterpenoid constituents of PC using UPLC-MS/MS analysis. Our results indicate that PC negatively regulated osteoclast differentiation and function, and can potentially be used to manage postmenopausal osteoporosis.

Forsythia suspensa Protects against Bone Loss in Ovariectomized Mice

In traditional oriental medicine, the fruit of Forsythia suspensa has been used as a nutritional supplement to alleviate inflammation and treat gastrointestinal diseases. However, there is no information available on its beneficial effects on bone. We investigated the beneficial effects of F. suspensa water extract (WFS) on osteoclast differentiation and bone loss. The microarchitecture of trabecular bone was analyzed by micro-computed tomography. Osteoclast differentiation was evaluated based on tartrate-resistant alkaline phosphatase activity, and bone resorption activity was examined on a bone-like mineral surface. The mechanism of action of WFS was assessed by evaluating the expression and activation of signaling molecules. Phytochemical constituents were identified and quantitated by ultrahigh-performance liquid chromatography-tandem mass spectrometry. WFS reduced ovariectomy-induced trabecular bone loss and inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation and resorption activity. WFS suppressed RANKL-induced expression of nuclear factor of activated T cells cytoplasmic 1, a crucial transcription factor for osteoclast differentiation by decreasing c-Fos protein levels and suppressing the activation of p38 and c-Jun-N-terminal kinase. We also identified 12 phytochemicals in WFS including lignans, phenylethanoids, and flavonoids. Collectively, these results suggest that WFS inhibits osteoclast differentiation and can potentially be used to treat postmenopausal osteoporosis.

Hepatoprotective effects of an Acer tegmentosum Maxim extract through antioxidant activity and the regulation of autophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Acer tegmentosum Maxim (AT), the East Asian stripe maple, is an herb used to treat liver disease and is approved as a functional food in Korea. AT protects against hepatic disorders, atopic dermatitis, and diabetes mellitus.

AIM OF THE STUDY

We explored the mechanism of the hepatoprotective effects of AT extract in in vitro and in vivo levels.

MATERIALS AND METHODS

AT extract from Acer tegmentosum Maxim was extracted by hot water. Hepatoprotective effects of AT extract were confirmed using carbon tetrachloride (CCl₄)- or alcohol-induced mouse model, and H₂O₂- or alcohol-induced HepG2 (liver hepatocellular carcinoma cell line) cells by measuring GOT, GPT, TG, and MDA levels. Hematoxylin and eosin (H&E) staining was used to observe the pathological analysis. Cytotoxicity or protective effect of AT extract was confirmed using MTT assay in HepG2 cells. Antioxidant effect of AT extract was measured using DPPH or H₂DCFDA assay. Mechanism study of antioxidant and autophagy was carried out using western blotting and immunofluorescence analysis.

RESULTS

AT extract increased the viability of HepG2 cells treated with H₂O₂ and ethanol, and protected the liver against damage induced by CCl₄ and alcohol. The AT extract increased the levels of nuclear respiratory factor 2 (Nrf2) and heme oxygenase-1 (HO-1). The level of microtubule-associated protein light chain 3 (LC3)-Ⅱ, beclin-1, autophagy-related genes (Atg) such as Atg3 and Atg12-5 as markers of autophagy activation was also increased. Moreover, the AT extract increased activation of mitogen-activated protein kinase (MAPK), which regulated autophagy and HO-1.

CONCLUSION

Therefore, these results indicate that the AT extract has a hepatoprotective effect by increasing antioxidant activity and inducing autophagy.

Anti-Osteoporotic Effects of Polysaccharides Isolated from Persimmon Leaves via Osteoclastogenesis Inhibition

Persimmon (Diospyros kaki L.f.) leaves have traditionally been used as a phytomedicine, in health beverages to treat cardiovascular and respiratory disease and to promote maternal health in East Asia. In particular, polysaccharides from persimmon are known to have anti-coagulant, anti-oxidant, and immune-stimulatory activities. However, their beneficial effects against osteoporosis have not been reported. In the present study, we investigated the anti-osteoporotic effects of polysaccharides from persimmon leaves (PLE0) using an in vivo model of ovariectomy (OVX)-induced bone loss and an in vitro system of receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation. In the OVX mouse model, PLE0 remarkably improved OVX-induced trabecular bone loss by suppressing osteoclast activity. In primary bone marrow-derived macrophages (BMMs), PLE0 dose-dependently inhibited osteoclast differentiation. In addition, PLE0 down-regulated RANKL-induced activation of mitogen-activated protein kinases (MAPKs) such as p38, ERK, and JNK resulting in suppression of nuclear factor of activated T cells cytoplasmic 1 (NFATc1) expression. Our results indicate that PLE0 has anti-osteoporotic effects in OVX-induced bone loss via inhibition of osteoclast differentiation. Taken together, PLE0 from persimmon may prevent postmenopausal bone loss and osteoporotic bone fragility.

Poligoni Multiflori Radix enhances osteoblast formation and reduces osteoclast differentiation

Poligoni Multiflori Radix (PMR) is a traditional Korean medicinal herb that is known to have various pharmacological effects, including antihyperlipidemic, anticancer, and anti-inflammatory effects. However, the effects of PMR on bone metabolism have not been elucidated to date. The present study aimed to investigate the in vitro and in vivo effect of PMR water extract on the regulation of osteoblast and osteoclast activity. Effects of PMR water extract on receptor activator of nuclear factor-kB ligand (RANKL)-induced osteoclast differentiation and survival of mouse bone marrow macrophages (BMMs) obtained from femurs were investigated by tartrate-acid resistant acid phosphatase (TRAP)-positive cells and XTT assay. Expression of osteoclast-related genes was assayed by western blot analysis and reverse transcription-quantitative polymerase chain reaction. Additionally, the effects of PMR water extract on osteoblastic proliferation and differentiation were investigated by alkaline phosphatase (ALP) activity assay, alizarin red staining, and levels of mRNA encoding known osteoblast markers. Furthermore, the effects of PMR water extract on lipopolysaccharide (LPS)-induced bone loss were examined in a mouse model. PMR inhibited RANKL-induced osteoclast differentiation of BMMs in a dose-dependent manner without significant cytotoxicity, and suppressed expression of the main osteoclast differentiation markers Fos proto-oncogene and nuclear factor of activated T-cell. In addition, PMR decreased the mRNA expression levels of NFATc1 target genes, including TRAP, osteoclast-associated receptor, ATPase H⁺ transporting, lysosomal 38 kDa V0 subunit d2, and Cathepsin K. These inhibitory effects were mediated by the p38 and extracellular signal-regulated kinase/nuclear factor-κB pathway. Simultaneously, PMR enhanced the differentiation of primary osteoblasts, and increased the mRNA expression of runt-related transcription factor 2, ALP, osterix, and osteocalcin. Notably, PMR improved LPS-induced trabecular bone loss in mice. Collectively, the present findings demonstrated that PMR may regulate bone remodeling by reducing osteoclast differentiation and stimulating osteoblast formation. These results suggest that PMR may be used for the treatment of bone diseases, such as osteoporosis and rheumatoid arthritis.

Ethanolic Extract of Rubus coreanus Fruits Inhibits Bone Marrow-Derived Osteoclast Differentiation and Lipopolysaccharide-Induced Bone Loss

The inhibition of osteoclast differentiation/bone resorption is a well-known therapeutic strategy for controlling pathological and postmenopausal bone loss. Natural products that specifically inhibit osteoclastogenesis could therefore be developed as antiresorptive drugs for the treatment of metabolic bone disorders characterized by excessive osteoclastic bone resorption. We therefore examined the effects of Rubus coreanus extract (eeRc) on receptor activator of nuclear factor kappa-B ligand (RANKL)-induced differentiation of bone marrow macrophages (BMMs) into osteoclasts and pit formation in vitro. Additionally, the in vivo effects of the eeRc were observed in mice with lipopolysaccharide (LPS)-induced bone erosion. In this study, we found that the ethanolic extract of Rubus coreanus fruits considerably suppressed the RANKL-induced differentiation of primary BMMs into osteoclasts and bone-resorbing activity of mature osteoclasts. Oral administration of eeRc attenuated LPS-induced bone loss in vivo, as demonstrated by the reversal of LPS-induced reduction in bone volume per tissue volume, bone mineral density, and trabecular number to some extent in eeRc-treated mice. In addition, eeRc slightly decreased the serum levels of C-terminal telopeptide fragments of type I collagen, the collagen-breakdown product generated by osteoclasts. Collectively, our results indicate that eeRc has the potential to inhibit bone loss by blocking osteoclast differentiation and could therefore be a promising natural product for the prevention and/or treatment of inflammatory bone loss.

The RANK/RANKL/OPG system in tumorigenesis and metastasis of cancer stem cell: potential targets for anticancer therapy

The molecular triad involving receptor activator of nuclear factor kβ (RANK)/RANK ligand (RANKL)/osteoprotegerin cytokine system has been well implicated in several physiological and pathological processes including bone metabolism, mammary gland development, regulation of the immune function, tumorigenesis and metastasis of cancer stem cell, thermoregulation, and vascular calcification. However, this review aimed to summarize several original and up-to-date articles focusing on the role of this signaling system in cancer cell development and metastasis as well as potential therapeutic agents targeting any of the three tumor necrotic factor super family proteins and/or their downstream signaling pathways. The RANK/RANKL axis has direct effects on tumor cell development. The system is well involved in the development of several primary and secondary tumors including breast cancer, prostate cancer, bone tumors, and leukemia. The signaling of this triad system has also been linked to tumor invasiveness in the advanced stage. Bone is by far the most common site of cancer metastasis. Several therapeutic agents targeting this system have been developed. Among them, a monoclonal antibody, denosumab, was clinically approved for the treatment of osteoporosis and cancer-related diseases.

Traditional uses, phytochemistry, and pharmacology of the genus Acer (maple): A review

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Acer (Aceraceae), commonly known as maple, comprises approximately 129 species that primarily grow in the northern hemisphere, especially in the temperate regions of East Asia, eastern North America, and Europe. These plants have been traditionally used to treat a wide range of diseases in East Asia and North America. Moreover, clinical studies have shown that medicinal plants belonging to Acer are highly effective in the treatment of rheumatism, bruises, hepatic disorders, eye disease, and pain, and in detoxification. This review provides a systematic and constructive overview of the traditional uses, chemical constituents, and pharmacological activities of plants of the genus Acer.

MATERIAL AND METHODS

This review is based on a literature study of scientific journals and books from libraries and electronic sources such as SciFinder, ScienceDirect, Springer, PubMed, CNKI, Google Scholar, Baidu Scholar, and Web of Science. The literature in this review related to chemical constituents and pharmacological activities dates from 1922 to the end of October 2015. Furthermore, ethnopharmacological information on this genus was obtained from libraries and herbaria in China and USA.

RESULTS

In traditional medicine, 40 species, 11 subspecies, and one varieta of the genus Acer are known to exhibit a broad spectrum of biological activities. To date, 331 compounds have been identified from 34 species of the genus Acer, including flavonoids, tannins, phenylpropanoids, diarylheptanoids, terpenoids, benzoic acid derivatives, and several other types of compounds, such as phenylethanoid glycosides and alkaloids. Preliminary pharmacological studies have shown that the extracts and compounds isolated from this genus exhibit a broad spectrum of biological activities such as antioxidant, antitumor, anti-inflammatory, antidiabetic, hepatoprotective, and antiobesity activities, as well as promoting osteoblast differentiation. To date, reports on the toxicity of Acer species to humans are very limited, and the major safety concern of these plants is in the veterinary field.

CONCLUSIONS

Based on our systematic review, Acer species can be used to treat rheumatism, hepatic disorders, eye disease, pain, etc. effectively. Some indications from ethnomedicine have been validated by pharmacological activities, such as the anti-inflammatory and hepatoprotective activities of the species. The available literature showed that most of the activities of these species can be attributed to flavonoids and tannins. To ensure the safety and efficacy in clinical practice in the future, studies identifying active molecules and clarifying their pharmacological mechanisms as well as toxicity are needed.

Effect of Acer tegmentosum bark on atopic dermatitis-like skin lesions in NC/Nga mice

ETHNOPHARMACOLOGICAL RELEVANCE

Atopic dermatitis (AD) is a chronic and relapsing inflammatory condition characterized by pruritic and eczematous skin lesions that requires safe and effective pharmacological therapy. The bark of Acer tegmentosum Maxim trees has been used in Korean folk and traditional medicine to treat abscesses, surgical bleeding, liver diseases, and AD.

AIM OF STUDY

To investigate the therapeutic effect of A. tegmentosum, on a mouse model of Dermatophagoides farinae (Df)-induced AD.

METHODS

Development of AD-like skin lesions was induced by repetitive skin contact with barrier-disrupted backs of NC/Nga mice with Df body ointment, and the effects of A. tegmentosum were evaluated on the basis of histopathological skin assessment results, ear swelling, and cytokine production in the dorsal skin. The component of A. tegmentosum, salidroside, inhibited the production of TSLP in KCMH-1 cells, which indicated that its production could be pharmacologically regulated.

RESULTS

Topical application of A. tegmentosum for 1 week after Df body ointment challenge significantly reduced ear swelling and improved dorsal skin lesions. Suppression of dermatitis by combined therapy was accompanied by a decrease in the skin level of Th2 cytokines, such as interleukin (IL)-4, IL-5 and IL-13, plasma levels of thymus and activation-regulated chemokine, and IgE. Induction of thymic stromal lymphopoietin, which leads to a systemic Th2 response, was also reduced in in vivo and in vitro by A. tegmentosum and salidroside.

CONCLUSIONS

Our findings suggest that A. tegmentosum treatment has a significant therapeutic effect on Df-induced AD-like skin lesions on NC/Nga mice through inhibition of thymic stromal lymphopoietin and IgE via a mechanism that may inhibit Th2-mediated immune responses. These results suggest that A. tegmentosum and salidroside may be useful tools for the treatment of AD.

Aconitum pseudo-laeve var. erectum inhibits receptor activator of nuclear factor kappa-B ligand-induced osteoclastogenesis via the c-Fos/nuclear factor of activated T-cells, cytoplasmic 1 signaling pathway and prevents lipopolysaccharide-induced bone loss in mice

Aconitum pseudo-laeve var. erectum (APE) has been widely shown in herbal medicine to have a therapeutic effect on inflammatory conditions. However, there has been no evidence on whether the extract of APE is involved in the biological bone metabolism process, particularly osteoclast-mediated bone resorption. In this study, we confirmed that the administration of APE could restore normal skeletal conditions in a murine model of lipopolysaccharide (LPS)-induced bone loss via a decrease in the receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin (OPG) ratio and osteoclast number. We then investigated the effect of APE on the RANKL-induced formation and function of osteoclasts to elucidate its underlying molecular mechanisms. APE suppressed the formation of tartrate-resistant acid phosphatase (TRAP)-positive cells, as well as the bone-resorbing activity of mature osteoclasts. Furthermore, APE attenuated nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) and c-Fos without affecting any early signal pathway of osteoclastogenesis. Subsequently, APE significantly downregulated the expression of various genes exclusively expressed in osteoclasts. These results demonstrate that APE restores LPS-induced bone loss through a decrease of the serum RANKL/OPG ratio, and inhibits osteoclast differentiation and function, suggesting the promise of APE as a potential cure for various osteoclast-associated bone diseases.