Exogenous methylglyoxal alleviates drought-induced 'plant diabetes' and leaf senescence in maize.

Drought-induced leaf senescence is associated with high sugar levels, which bears some resemblance to the syndrome of diabetes in humans; however, the underlying mechanisms of such 'plant diabetes' on carbon imbalance and the corresponding detoxification strategy are not well understood. Here, we investigated the regulatory mechanism of exogenous methylglyoxal (MG) on 'plant diabetes' in maize plants under drought stress applied via foliar spraying during the grain-filling stage. Exogenous MG delayed leaf senescence and promoted photoassimilation, thereby reducing the yield loss induced by drought by 14%. Transcriptome and metabolite analyses revealed that drought increased sugar accumulation in leaves through inhibition of sugar transporters that facilitate phloem loading. This led to disequilibrium of glycolysis and overaccumulation of endogenous MG. Application of exogenous MG up-regulated glycolytic flux and the glyoxalase system that catabolyses endogenous MG and glycation end-products, ultimately alleviating 'plant diabetes'. In addition, the expression of genes facilitating anabolism and catabolism of trehalose-6-phosphate was promoted and suppressed by drought, respectively, and exogenous MG reversed this effect, implying that trehalose-6-phosphate signaling in the mediation of 'plant diabetes'. Furthermore, exogenous MG activated the phenylpropanoid biosynthetic pathway, promoting the production of lignin and phenolic compounds, which are associated with drought tolerance. Overall, our findings indicate that exogenous MG activates defense-related pathways to alleviate the toxicity derived from 'plant diabetes', thereby helping to maintain leaf function and yield production under drought.

Retracted: MD-1 Deficiency Accelerates Myocardial Inflammation and Apoptosis in Doxorubicin-Induced Cardiotoxicity by Activating the TLR4/MAPKs/Nuclear Factor kappa B (NF-κB) Signaling Pathway.

This publication has been retracted by the Editor due to the identification of non-original figure images and manuscript content that raise concerns regarding the credibility and originality of the study and the manuscript. Reference: Ying-Jun Zhang, He Huang, Yu Liu, Bin Kong, Guangji Wang. MD-1 Deficiency Accelerates Myocardial Inflammation and Apoptosis in Doxorubicin-Induced Cardiotoxicity by Activating the TLR4/MAPKs/Nuclear Factor kappa B (NF-kappaB) Signaling Pathway. Med Sci Monit, 2019; 25: 7898-7907. DOI: 10.12659/MSM.919861.

Plant growth-promoting bacteria modulate gene expression and induce antioxidant tolerance to alleviate synergistic toxicity from combined microplastic and Cd pollution in sorghum.

Microplastics (MPs) can act as carriers for environmental pollutants; therefore, MPs combined with heavy metal pollution are attracting increasing attention from researchers. In this study, the potential of the plant growth-promoting bacterium Bacillus sp. SL-413 to mitigate the stress caused by exposure to both MPs and cadmium (Cd) in sorghum plants was investigated. The effects of inoculation on sorghum biomass were investigated using hydroponic experiments, and evaluation of Cd accumulation and enzyme activity changes and transcriptomics approaches were used to analyze its effect on sorghum gene expression. The results showed that combined polyethylene (PE) and Cd pollution reduced the length and the fresh and dry weights of sorghum plants and thus exerted a synergistic toxic effect. However, inoculation with the strains alleviated the stress caused by the combined pollution and significantly increased the biomass. Inoculation increased the dry weights of the aboveground and belowground parts by 11.5-44.6% and 14.9-38.4%, respectively. Plant physiological measurements indicated that inoculation reduced the reactive oxygen species (ROS) content of sorghum by 10.5-27.2% and thereby alleviated oxidative stress. Transcriptome sequencing showed that exposure to combined Cd+MP contamination induced downregulation of gene expression, particularly that of genes related to amino sugar and nucleotide sugar metabolism, starch and sucrose metabolism, and plant hormone signal transduction, in sorghum. However, inoculation with Bacillus sp. SL-413 resulted in an increase in the proportion of upregulated genes involved in signal transduction, antioxidant defense, cell wall biology, and other metabolic pathways, which included the phenylpropanoid biosynthesis, photosynthesis, flavonoid biosynthesis, and MAPK signaling pathways. The upregulation of these genes promoted the tolerance of sorghum under combined Cd+MP pollution stress and alleviated the stress induced by these conditions. This study provides the first demonstration that plant growth-promoting bacteria can alleviate the stress caused by combined pollution with MPs and Cd by regulating plant gene expression. These findings provide a reference for the combined plant-microbial remediation of MPs and Cd.

Engineering of formate dehydrogenase for improving conversion potential of carbon dioxide to formate.

Formate dehydrogenase (FDH) is a D-2-hydroxy acid dehydrogenase, which can reversibly reduce CO2 to formate and thus act as non-photosynthetic CO2 reductase. In order to increase catalytic efficiency of formate dehydrogenase for CO2 reduction, two mutants V328I/F285W and V354G/F285W were obtained of which reduction activity was about two times more than the parent CbFDHM2, and the formate production from CO2 catalyzed by mutants were 2.9 and 2.7-fold higher than that of the parent CbFDHM2. The mutants had greater potential in CO2 reduction. The optimal temperature for V328I/F285W and V354G/F285W was 55 °C, and they showed increasement of relative activity under 45 °C to 55 °C compared with parent. The optimal pH for the mutants was 9.0, and they showed excellent stability in pH 4.0-11.5. The kcat/Km values of mutants were 1.75 times higher than that of the parent. Then the molecular basis for its improvement of biochemical characteristics were preliminarily elucidated by computer-aided methods. All of these results further established a solid foundation for molecular modification of formate dehydrogenase and CO2 reduction.

Anti-metastatic effects of 1,2,3,4,6-Penta-O-galloyl-ß-D-glucose in colorectal cancer: Regulation of cathepsin B-mediated extracellular matrix dynamics and epithelial-to-mesenchymal transition.

Despite significant advances in the diagnosis and treatment of colorectal cancer (CRC), metastatic colorectal cancer still poses serious threat to CRC patients. The natural gallotannin 1,2,3,4,6-penta-O-galloyl-ß-D-glucose (PGG) has been shown to possess anti-tumor effects on colon cancer cells, but its anti-metastatic effect is yet to be investigated. In this study, the effects of PGG on cell proliferation, colony formation ability, motility, migration were investigated in colon cancer cells using BrdU, colony formation, scratch, and transwell assays, respectively. Western blot assay was used for assessing protein expression. The orthotopic colon tumor-bearing mouse model and human colon cancer metastatic mouse model were employed to evaluate the anti-metastatic effects of PGG. Results showed that PGG exhibited not only anti-proliferative and colony formation inhibitory effects, but also inhibition on cell adhesion, motility, and migration in both HCT116 and colon 26-M01 cells via modulating protein expression of cathepsin B, FAK, cofilin, and epithelial-to-mesenchymal transition related proteins. In addition, PGG (10 or 15 mg/kg, i.p.) could significantly inhibit liver and lung metastasis in colon cancer metastatic mice models. Furthermore, PGG could regulate the populations of T cells, macrophages, and MDSCs, while the levels of IL-2, IL-6, IL-10, IFN-γ, and TNF-α were altered after PGG treatment in metastatic CRC mice. This is the first report of the anti-metastatic effects of PGG by regulating cathepsin B-mediated extracellular matrix dynamics and epithelial-to-mesenchymal transition process in CRC. Our findings suggested that PGG has great potential to be developed as an anti-metastatic agent for metastatic CRC.

New cytotoxic dichapetalins in the leaves of Phyllanthus acidus: Identification, quantitative analysis, and preliminary toxicity assessment.

The young leaves of Phyllanthus acidus (Euphorbiaceae) are commonly used as edible vegetables in Indonesia, Thailand, and India, and their water infusions as dieting aids for people trying to remain slim. However, it is regarded as a poisonous plant in Malaya, and current researches are insufficient to provide a conclusion on its toxicity and safety under large doses. In this study, we firstly found that the refined nonpolar extracts of P. acidus leaves showed significant cytotoxic effect against BEAS-2B and L02 normal cell lines with IC50 values of 2.15 and 1.64 mg/mL, respectively. Further bioactivity-guided isolation produced four new rare dichapetalins (pacidusins A-D) from the most active fraction. Their structures including absolute configurations were elucidated by extensive spectroscopic data and X-ray diffraction analysis. All the isolated dichapetalins exhibited moderate cytotoxicity against, BEAS-2B and L02 normal cell lines with IC50 values ranging from 12.44 to 22.55 µM, as well as five human cancer cell lines with IC50 values ranging from 3.38 to 22.38 µM. Furthermore, the content of the main dichapetalins in the leaves were determined by analytical HPLC, which showed that the leaves contained a very high amount of the four isolated dichapetalins with a total yield of 0.488 mg/g of dry plant material. These toxic dichapetalins may lead to adverse health effects in higher doses. Our findings indicate that the dichapetalin containing leaves may not be suitable for consumption in large quantities as food, but demonstrate their potency as anti-cancer agents for new drug discovery.

Miscanthus cultivation shapes rhizosphere microbial community structure and function as assessed by Illumina MiSeq sequencing combined with PICRUSt and FUNGUIld analyses.

Soil microbes play important roles in plant growth and in the biogeochemical cycling of earth's elements. However, the structure and functions of the microbial community associated with the growth of second-generation energy crops, such as Miscanthus, remain unclear. Thus, in this study, the composition and function of the bacterial and fungal communities associated with Miscanthus cultivation were analyzed by MiSeq sequencing combined with PICRUSt and FUNGUIld analyses. The results of community composition and diversity index analyses showed that Miscanthus cultivation significantly altered the bacterial and fungal community composition and reduced bacterial and fungal diversity. In addition, Miscanthus cultivation increased the soil organic matter (SOM) and total nitrogen (TN) contents. The correlation analysis between microbial community composition and environmental factors indicated that SOM and TN were the most important factors affecting bacterial and fungal communities. Miscanthus cultivation could enrich the abundances of Pseudomonas, Rhizobium, Luteibacter, Bradyrhizobium, Phenylobacterium and other common plant-promoting bacteria, while also increasing Cladophialophora, Hymenula, Magnaporthe, Mariannaea, etc., which predicted corresponded to the saprotrophic, plant pathogenic, and pathotrophic trophic modes. The PICRUSt predictive analysis indicated that Miscanthus cultivation altered the metabolic capabilities of bacterial communities, including the metabolism of carbon, nitrogen, and phosphorus cycle. In addition, FUNGUIld analysis indicated that Miscanthus cultivation altered the fungal trophic mode. The effects of Miscanthus on the communities and function of bacteria and fungi varied among Miscanthus species. Miscanthus specie Xiangdi NO 1 had the greatest impact on soil bacterial and fungal communities, whereas Miscanthus specie Wujiemang NO 1 had the greatest impact on soil bacteria and fungi functions. The results of this study provide a reference for the composition and function of microbial communities during the growth of Miscanthus.

Ten new glycosides, carissaedulosides A-J from the root barks of Carissa edulis and their cytotoxicities.

Ten previously undescribed glycosides, carissaedulosides A-J (1-10) referring to six apiosylated phenylpropanoids (1-6), one coumarin-secoiridoid hybrid (7), and three furofuran lignans (8-10) were isolated from the root barks of Carissa edulis, together with 13 known analogues (11-23). Their structures were elucidated by spectroscopic analysis, ECD computational methods, and chemical derivations for configurations of sugar moieties. The new lignan bisdesmoside, 10, exhibited significant cytotoxicity against A549 (IC50 = 3.87 ± 0.03 µM) and MCF-7 (IC50 = 9.231 ± 0.290 µM) cell lines, while the known lignan monodesmoside, 12, showed impressive cytotoxic efficacy (IC50 = 5.68 ± 0.180 µM) against only MCF-7 cell line. It is noted that a known cardenolide, 11, displayed strong cytotoxic potency against HL-60, A549, MCF-7 and SW480 cell lines with IC50 values ranging from 0.023 to 0.137 µM. Moreover, compound 11 induced dose-dependent apoptosis on SW480 cell, but not explicit dose-dependent apoptosis on HL-60 cells.

The M476W/Q482H mutation of procaspase-8 restored caspase-8-mediated apoptosis.

Caspase-8 is an initiator of apoptotic signalling, and aberrations in procaspase-8 have been verified to be associated with malignant tumours. In previous studies, various procaspase-8 mutants were identified in AML patients, such as Q482H and M476W/Q482H mutations. The Q482H mutation can abolish caspase-8-mediated apoptosis by attenuating the dimerization of procaspase-8 protein monomers, causing AML patients carrying the Q482H mutation to develop resistance to chemotherapeutics. The patients with the M476W/Q482H mutation were sensitive to chemotherapy. Nevertheless, the underlying molecular mechanism is still unclear in regard to how the M476W/Q482H mutation restored caspase-8-mediated apoptosis. In this study, apoptosis was detected in the cells overexpressing the WT or mutant procaspase-8 with or without TRAIL treatment. Western blotting was devoted to detect the cleavage of procaspase-8 or the expression of proteins downstream in the apoptotic cascade and CO-IP was employed to analyze the dimerization of WT and mutant procaspase-8 proteins. Results demonstrated cells carrying the M476W/Q482H mutation restored caspase-8-mediated and TRAIL-induced apoptosis. The M476W/Q482H mutation recovered the dimerization of procaspase-8. Taken together, the M476W/Q482H mutation have restored caspase-8-mediated apoptosis resulting from the recovery of procaspase-8 dimerization.

MD-1 Deficiency Accelerates Myocardial Inflammation and Apoptosis in Doxorubicin-Induced Cardiotoxicity by Activating the TLR4/MAPKs/Nuclear Factor kappa B (NF-κB) Signaling Pathway.

BACKGROUND Myocardial apoptosis and inflammation play important roles in doxorubicin (DOX)-caused cardiotoxicity. Our prior studies have characterized the effects of myeloid differentiation protein 1(MD-1) in pathological cardiac remodeling and myocardial ischemia/reperfusion (I/R) injury, but its participations and potential molecular mechanisms in DOX-caused cardiotoxicity remain unknown. MATERIAL AND METHODS In the present study, MD-1 knockout mice were generated, and a single intraperitoneal injection of DOX (15 mg/kg) was performed to elicit DOX-induced cardiotoxicity. Cardiac function, histological change, mitochondrial structure, myocardial death, apoptosis, inflammation, and molecular alterations were measured systemically. RESULTS The results showed that the protein and mRNA levels of MD-1 were dramatically downregulated in DOX-treated cardiomyocytes. DOX insult markedly accelerated cardiac dysfunction and injury, followed by enhancements of apoptosis and inflammation, all of which were further aggravated in MD-1 knockout mice. Mechanistically, the TLR4/MAPKs/NF-kappaB pathways, which were over-activated in MD-1-deficient mice, were significantly increased in DOX-damaged cardiomyocytes. Moreover, the abolishment of TLR4 or NF-kappaB via a specific inhibitor exerted protective effects against the adverse effects of MD-1 loss on DOX-caused cardiotoxicity. CONCLUSIONS Collectively, these findings suggest that MD-1 is a novel target for the treatment of DOX-induced cardiotoxicity.

Albocycline-type Macrolides with Antibacterial Activities from Streptomyces sp. 4205.

The actinomycete genus Streptomyces is characterized by producing bioactive secondary metabolites, including antibiotics. In this study, chemical and biological investigations were carried out on Streptomyces strain 4205 isolated from the paddy soil, leading to the identification and characterization of 10 albocycline-type macrolides, among which 4 compounds were new, namely albocyclines A-D (1-4). The structures of 1-10 were identified according to the 1D- and 2D-NMR spectroscopic data. Furthermore, compounds 1-10 were evaluated for antimicrobial activity. Compounds 5-7 displayed antimicrobial activities against Candidaalbicans ATCC 90028 with the same MIC value of 10.0 mg/mL and the IC50 values of 1.5, 1.0, and 1.0 mg/mL, respectively. Thus, the research on Streptomyces sp. is of vital significance for developing new antibiotic agents.

Cytotoxic Effects of Compounds Isolated from Ricinodendron heudelotii.

This study was designed to explore the in vitro anticancer effects of the bioactive compounds isolated from Ricinodendron heudelotii on selected cancer cell lines. The leaves of the plant were extracted with ethanol and partitioned in sequence with petroleum ether, ethyl acetate, and n-butanol. The ethyl acetate fraction was phytochemically studied using thin layer chromatography (TLC) and column chromatography (CC). Structural elucidation of pure compounds obtained from the ethyl acetate fraction was done using mass spectra, ¹H-NMR, and 13C-NMR analysis. The isolated compounds were subsequently screened using five different cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7, SW-480, and normal lung epithelial cell line, BEAS-2B, to assess their cytotoxic effects. Nine compounds were isolated and structurally elucidated as gallic acid, gallic acid ethyl ester, corilagin, quercetin-3-O-rhamnoside, myricetin-3-O-rhamnoside, 1,4,6-tri-O-galloyl glucose, 3,4,6-tri-O-galloyl glucose, 1,2,6-tri-O-galloyl glucose, and 4,6-di-O-galloyl glucose. Corilagin exhibited the most cytotoxic activity with an IC50 value of 33.18 µg/mL against MCF-7 cells, which were comparable to cisplatin with an IC50 value of 27.43 µg/mL. The result suggests that corilagin isolated from R. heudelotii has the potential to be developed as an effective therapeutic agent against the growth of breast cancer cells.

Cytotoxic withanolides from the aerial parts of Tubocapsicum anomalum.

Ten new withanolides (1-10) and three artificial withanolides (11-13) were isolated from the aerial parts of Tubocapsicum anomalum, together with five known analogues (14-18). Their structures were determined on the basis of extensive spectroscopic and chemical methods. They include seven acnistin-type (1-4, 11, 14 and 15), three withajardin-type (5-7), and eight normal-type (8-10, 12, 13 and 16-18) withanolides. Of normal-type withanolides, a chemical conversion from the 16α,17α-epoxywithanolide (16) to Δ13,14-16α-hydroxywithanolide (18) was achieved by Wagner-Meerwein rearrangement. All isolates were evaluated for their cytotoxicity against four human tumor cell lines (HCT-116, HepG2, MCF-7 and A375). Among them, compounds 1-3, 6-8, 14, 16-18 showed cytotoxic activity with IC50 values of 0.24-8.71 µM.

Antifungal Amide Alkaloids from the Aerial Parts of Piper flaviflorum and Piper sarmentosum.

Sixty-three amide alkaloids, including three new, piperflaviflorine A (1), piperflaviflorine B (2), and sarmentamide D (4), and two previously synthesized ones, (1E,3S)-1-cinnamoyl-3- hydroxypyrrolidine (3) and N-[7'-(4'-methoxyphenyl)ethyl]-2-methoxybenzamide (5), were isolated from the aerial parts of Piper flaviflorum and Piper sarmentosum. Their structures were elucidated by detailed spectroscopic analysis and, in case of 3, by single-crystal X-ray diffraction. Most of the isolates were tested for their antifungal and antibacterial activities. Ten amides (6-15) showed antifungal activity against Cryptococcus neoformans ATCC 90 113 with IC50 values in the range between 4.7 and 20.0 µg/mL.

Phenolic Compounds from the Rhizomes of Smilax china L. and Their Anti-Inflammatory Activity.

A new triflavanoid, kandelin B-5 (1), was isolated from the rhizomes of Smilax china L., together with six known phenylpropanoid substituted flavan-3-ols (2-7), nine flavonoids (8-16), two stilbenoids (17, 18), and two other compounds (19, 20). The structure of compound 1 was determined on the basis of 1D, 2D NMR and HR-ESI-MS data, as well as chemical method. Compounds 2-5, 8-12, 15, 17, and 19 were evaluated for anti-inflammatory activity. Only compounds 10, 15 and 17 showed slightly IL-1ß expression inhibitory activities on LPS induced THP-1 cells, with inhibition rate of 15.8%, 37.3%, and 35.8%, respectively, at concentration of 50 µg/mL.

Characterization of the new GII.17 norovirus variant that emerged recently as the predominant strain in China.

Human noroviruses are the most important viral pathogens causing epidemic acute gastroenteritis, in which the GII.4 viruses have been predominant worldwide for the past decades. During 2014-2015 winter season, a new GII.17 variant emerged as the predominant virus in China surpassing the GII.4 virus in causing significantly increased acute gastroenteritis outbreaks. Genome sequences of the new GII.17 variant was determined and compared with other GII.17 noroviruses, revealing residue substitutions at specific locations, including the histo-blood group antigen-binding site and the putative antigenic epitopes. Further study of GII.17 outbreaks focusing on host susceptibility showed that the new GII.17 variant infected secretor individuals of A, B, O and Lewis types. Accordingly, the P particles of the new GII.17 variant bound secretor saliva samples of A, B, O and Lewis types with significantly higher binding signals than those of the P particles of the previous GII.17 variants. In addition, human sera collected from the outbreaks exhibited stronger blockade against the binding of the new GII.17 P particles to saliva samples than those against the binding between the P particles of previous GII.17 variants and saliva samples. Taken together, our data strongly suggested that the new GII.17 variant gained new histo-blood group antigen-binding ability and antigenic features, which may contribute to its predominance in causing human norovirus epidemics.

Theagalloflavic Acid, a New Pigment Derived from Hexahydroxydiphenoyl Group, and Lignan Oxidation Products Produced by Aerobic Microbial Fermentation of Green Tea.

Chinese ripe pu-erh tea is produced by aerobic microbial fermentation of green tea. To clarify the microbial degradation of tea polyphenols, Japanese commercial green tea was mixed with Chinese ripe pu-erh tea, which retains microorganisms, and fermented for 5 d. Chromatographic separation yielded a novel water-soluble yellow pigment termed theagalloflavic acid. Spectroscopic and chemical evidence suggested that this pigment was produced by oxidative ring cleavage of hexahydroxydiphenoyl esters. In addition, two new oxygenated lignin metabolites, (+)-5,5'-dihydroxypinoresinol and 5-hydroxydihydrodehydrodiconiferyl alcohol, were also isolated together with known degradation products of quercetin and tea catechins.

Steroidal saponins from the rhizomes of Polygonatum prattii.

Seven steroidal saponins including two new furostanol glycosides were isolated from the rhizomes of Polygonatum prattii collected from Panzhihua, Sichuan province of China. The new compounds were determined as 26-O-ß-d-glucopyranosyl-(25R)-3ß,22ξ-dihydroxy-furost-5-en-7-one (pratioside G) and 26-O-ß-D-glucopyranosyl-(25R)-22ξ-hydroxy-furost-5-en-3ß-O-ß-D-glucopyranosyl-(1→2)-ß-D-glucopyranosyl-(1→2)-[ß-D-xylopyranosyl-(1→3)]-ß-D-glucopyranosyl-(1→4)-ß-D-galactopyranoside (pratioside H), on the basis of detailed spectroscopic and chemical analysis.

Chemical constituents from Piper hainanense and their cytotoxicities.

Two new compounds, (Z,R)-1-phenylethylcinnamate (1) and (1R,2R,3R,6S)-pipoxide (2) were isolated from the aerial part of Piper hainanense, along with 12 known compounds, including nine benzene derivatives (4-11), one isobutylamide (12), and two polyoxygenated cyclohexene derivatives (13-14). Their structures were elucidated on the basis of the HRESIMS, 1D and 2D NMR spectroscopic analyses, and ECD in cases of 2 and 3. The absolute configuration of ellipeiopsol B (3) was determined for the first time. All these compounds 1-14 were reported from the titled plant for the first time. Most of the isolates were tested for their cytotoxicities against five human cancer cell lines. Four of which, 2, 3, 9, 14 showed moderate bioactivities. Among them, the new compound 2 showed potential cytotoxicity against SMMC-7721, MCF-7, and SW-480 with IC50 values of 9.7, 15.0, and 13.2 µM, respectively.

Triterpenoids with Promoting Effects on the Differentiation of PC12 Cells from the Steamed Roots of Panax notoginseng.

The roots of Panax notoginseng, an important Chinese medicinal plant, have been used traditionally in both the raw and processed forms, due to the different chemical constituents and bioactivities found. Thirty-eight dammarane-type triterpenoid saponins were isolated from the steam-processed roots of P. notoginseng, including 18 new substances, namely, notoginsenosides SP1-SP18 (1-18). The structures of 1-18 were determined on the basis of spectroscopic analysis and acidic hydrolysis. The absolute configuration of the hydroxy group at C-24 in 1-4, 19, and 20 was determined in each case by Mo2(AcO)4-induced circular dichroism. The new compounds were found to feature a diversity of highly oxygenated side chains, formed by hydrolysis of the C-20 sugar moiety followed by dehydration, dehydrogenation, epoxidation, hydroxylation, or methoxylation of the main saponins in the raw roots. The new saponins 1, 2, 6-8, 14, and 17 and the known compounds 20-27 showed promoting effects on the differentiation of PC12 cells, at a concentration of 10 µM.