Polyoxygenated sesquiterpenoids from Salvia castanea and their potential anti-Alzheime's disease bioactivities

Alantolactone improves cognitive impairment in rats with Porphyromonas gingivalis infection by inhibiting neuroinflammation, oxidative stress, and reducing Aβ levels

Neuroinflammation caused by the chronic periodontal pathogen Porphyromonas gingivalis is growing regarded as as a key factor in the pathogenesis of Alzheimer's disease (AD). Alantolactone (AL), a sesquiterpene lactone isolated from the root of Inula racemosa Hook. f, has been proven to provide various neuroprotective effects. However, whether AL can improve cognitive impairment caused by P. gingivalis infection remains unclear. In this research, a rat model of P. gingivalis infection was used to examine the neuroprotective benefits of AL. The results revealed that 6 weeks of AL treatment (50 and 100 mg/kg) shortened escape latency and increased the number of crossings over the platform location and time spent in the target quadrant of P. gingivalis-infected rats in the Morris water maze experiment. By activating the Nrf2/HO-1 pathway, AL suppressed malondialdehyde (MDA) levels and simultaneously increased the activity of total superoxide dismutase (T-SOD). Furthermore, AL lowered the presence of IL-6, IL-1β, and TNFα in the hippocampal and cortical tissues of P. gingivalis-infected rats by inhibiting astrocyte and microglial activation and NF-κB phosphorylation. AL also significantly reduced Aβ levels in the cortical and hippocampus tissues of rats infected with P. gingivalis. In conclusion, AL improved cognitive impairment in P. gingivalis-infected rats by inhibiting neuroinflammation, reducing Aβ1-42 level, and exerting antioxidative stress effects.

Sesquiterpenes from the seeds of Cichorium glandulosum and their anti- neuroinflammation activities

Three previously undescribed sesquiterpenes, along with three known ones were isolated from the seeds of Cichorium glandulosum. The structures of them were elucidated by the analysis of spectroscopic data. The isolated compounds were tested for their neuroprotective effects against LPS-induced neuroinflammation in BV-2 cells. Santamarine (5) exhibited inhibitory activity on LPS-induced NO production in BV-2 cells with IC50 of 0.89 ± 0.12 μM. The mechanism of the compound 5 was related to activating the NF-κB, MAPK and cGAS/STING pathways.

Identification of diterpenoids from Salvia castanea Diels f. tomentosa Stib and their antitumor activities

Four new diterpenoid tropolones, salvirrddones A-D (1-4), and four new icetexanes, salvirrddices A-D (9-12), along with thirteen new 11,12-seco-norabietane diterpenoids, salvirrddnor A-M (14-24, 31, 32) and sixteen known compounds (5-8, 13, 25-30, 33-37), were isolated from the roots and rhizomes of Salvia castanea Diels f. tomentosa Stib. Their structures were elucidated by comprehensive spectroscopic analyses, quantum chemical calculations, and X-ray crystallography. Structurally, compounds 1-8 represent a class of rare natural products featuring a unique cyclohepta-2,4,6-trienone moiety with diterpenoid skeletons. Bioassays showed that only diterpenoid tropolones 3, 5, 6, and 7 exhibited significant activity against several human cancer cell lines with IC50 values ranging from 3.01 to 11.63 μM. Additionally, 3 was shown to inhibit Hep3B cell proliferation, block the G0/G1 phase of the cell cycle, induce mitochondrial dysfunction and oxidative stress, promote apoptosis, as well as inhibit migration and invasion in vitro. Meanwhile, 3 demonstrated anti-proliferative, pro-apoptotic, and migration-inhibitory effects in the Hep3B xenograft zebrafish model in vivo. Network pharmacological analysis and molecular docking results suggested that 3 may treat hepatocellular carcinoma (HCC) through the PI3K-Akt signaling pathway, as well as by binding PARP1 and CDK2 targets. Overall, the present results extremely expand the repertoire of diterpenoids from natural products and may provide a novel chemical scaffold for the discovery of new antitumor drugs.

Components in SLPE Alleviate AD Model Nematodes by Up-Regulating Gene gst-5

Salvia leucantha is a perennial herb of the genus Salvia in the family Labiatae, which has a wide range of biological activities, mainly including inhibition of acetylcholinesterase, antibacterial, and anti-inflammatory activity. To explore the protective effects and mechanism of action of S. leucantha on Alzheimer's disease (AD), the anti-AD activity of SLE (extracts of S. leucantha) was determined by using a transgenic Caenorhabditis elegans (C. elegans) model (CL4176). Analyses included paralysis assay, phenotypic experiments, transcriptome sequencing, RNA interference (RNAi), heat shock assays, and gas chromatography-mass spectrometry (GC-MS). SLPE (S. leucantha petroleum ether extract) could significantly delay CL4176 paralysis and extend the longevity of C. elegans N2 without harmful effects. A total of 927 genes were significantly changed by SLPE treatment in C. elegans, mainly involving longevity regulatory pathways-nematodes, drug metabolism-cytochrome P450, and glutathione metabolic pathways. RNAi showed that SLPE exerted its anti-AD activity through up-regulation of the gene gst-5; the most abundant compound in SLPE analyzed by GC-MS was 2,4-Di-tert-butylphenol (2,4-DTBP), and the compound delayed nematode paralysis. The present study suggests that active components in S. leucantha may serve as new-type anti-AD candidates and provide some insights into their biological functions.

Two Undescribed Germacrane-Type Sesquiterpenoids from Salvia cavaleriei var. simplicifolia Stib. and Their Anti-Alzheimer's Disease Activity

Two undescribed germacrane-type sesquiterpenoids, salcasins A (1) and B (2), together with three known compounds (3-5) were isolated and identified from the whole plant of Salvia cavaleriei var. simplicifolia Stib. The structures of the undescribed compounds were elucidated on the basis of spectroscopic methods, such as HR-ESI-MS, 1D and 2D NMR data. The relative configurations of 1 and 2 were established by analyzing their NOESY spectra as well as by 13C NMR calculations with DP4+ probability analyses. The absolute configurations of 1 and 2 were determined by comparing experimental and calculated ECD spectra. Furthermore, the in vivo anti-Alzheimer's disease activities of 1-5 were evaluated using Caenorhabditis elegans AD pathological model. Among all isolated compounds, salcasin A (1) significantly delayed AD-like symptoms of worm paralysis, which may be a potential anti-AD candidate agent.

Changes in secondary metabolites contents and stress responses in Salvia miltiorrhiza via ScWRKY35 overexpression: Insights from a wild relative Salvia castanea

Salvia castanea Diels, a close wild relative to the medicinal plant, Salvia miltiorrhiza Bunge, primarily grows in high-altitude regions. While the two species share similar active compounds, their content varies significantly. WRKY transcription factors are key proteins, which regulate plant growth, stress response, and secondary metabolism. We identified 46 ScWRKY genes in S. castanea and found that ScWRKY35 was a highly expressed gene associated with secondary metabolites accumulation. This study aimed to explore the role of ScWRKY35 gene in regulating the accumulation of secondary metabolites and its response to UV and cadmium (Cd) exposure in S. miltiorrhiza. It was found that transgenic S. miltiorrhiza hairy roots overexpressing ScWRKY35 displayed upregulated expression of genes related to phenolic acid synthesis, resulting in increased salvianolic acid B (SAB) and rosmarinic acid (RA) contents. Conversely, tanshinone pathway gene expression decreased, leading to lower tanshinone levels. Further, overexpression of ScWRKY35 upregulated Cd transport protein HMA3 in root tissues inducing Cd sequestration. In contrast, the Cd uptake gene NRAMP1 was downregulated, reducing Cd absorption. In response to UV radiation, ScWRKY35 overexpression led to an increase in the accumulation of phenolic acid and tanshinone contents, including upregulation of genes associated with salicylic acid (SA) and jasmonic acid (JA) synthesis. Altogether, these findings highlight the role of ScWRKY35 in enhancing secondary metabolites accumulation, as well as in Cd and UV stress modulation in S. miltiorrhiza, which offers a novel insight into its phytochemistry and provides a new option for the genetic improvement of the plants.

UBC Gene Family Analysis in Salvia castanea and Roles of ScUBC2/5 Genes under Abiotic Stress

Salvia castanea Diels, a relative of the medicinal plant Salvia miltiorrhiza Bunge, belongs to the genus Salvia and family Lamiaceae. Ubiquitin-conjugating enzyme E2 (UBC) is an important ubiquitin-binding enzyme in protein ubiquitination. This study aimed to analyze the regulatory role of UBC genes, particularly ScUBC2/5, on the growth and adaptation of S. castanea to extreme environments including cold or drought stress. We identified nine UBC genes in S. castanea and found that these genes were extremely stable and more highly expressed in the roots than other tissues. This suggested that UBC genes might play a role in promoting root adaptation to cold and dry environments. Further analysis of UBC gene expression in hairy roots under cold (4 °C) and UV stress also confirmed their importance under stress. The contents of tanshinone and salvianolic acid in hairy roots with the overexpression of ScUBC2/5 were increased compared to non-transgenic wild type, and the cold and UV resistance of hairy roots was increased compared with that of wild type. Together, these findings highlighted the role of ScUBC2/5 in enhancing secondary metabolite accumulation and regulation in response to cold and ultraviolet stress in S. castanea, providing a new perspective for genetic improvement in its phytochemistry.

Structure-diversified terpenoids from Salvia prattii and their protective activity against alcoholic liver diseases

Eleven previously unreported compounds (1-11), including five diterpenoids (1-5) and six sesquiterpenoids (6-11), together with two known diterpenoids (12-13), have been isolated from the roots of Salvia prattii. Their structures were comprehensively elucidated through spectroscopic methods, and their configurations were established using computational 13C nuclear magnetic resonance and electronic circular dichroism. Compound 1 was found to be an abietane-type diterpenoid with a novel rearrangement generated from the cleavage of the C-4/5 chemical bond, 20-methyl shift, and the rearrangement of the C-10 side chain. Compounds 2-3 were the third and fourth examples of arrangement seco-norabietanes with a spiro-lactone ring. We evaluated all compounds for their protective effects against alcoholic liver diseases (ALD). Compound 2 exhibited potential protective activity and hence can be used as a novel anti-ALD candidate.

Neuroprotective and acetylcholinesterase inhibitory activities of alkaloids from Solanum lyratum Thunb.: An in vitro and in silico analyses

The n-BuOH extract from the herb of Solanum lyratum Thunb. (Solanaceae) was purified by various chromatographic methods, which led to the isolation of seven undescribed alkaloids ((-)-(7'S)-N-feruloyltyramine A, (+)-(7'R)-N-feruloyltyramine A, (+)-(7'S)-N-solanamide A, (-)-(7'R)-N-solanamide A, 7'S-perillascens, solanpyrrole A, and (Z)-asmurratetra A) and 13 known alkaloids, including four pairs of enantiomers. Extensive spectroscopic data and electronic circular dichroism (ECD) calculations were applied to determine the structures of the undescribed compounds. In in vitro biological activity assays, (-)-(7'S)-N-feruloyltyramine A and (+)-(7'R)-N-feruloyltyramine A exhibited pronounced neuroprotective effects against SH-SY5Y cell damage with survival rates of 75.98% and 76.61%, respectively, at 50 μM. Additionally, (-)-(7'S)-N-feruloyltyramine A and N-cis-feruloyl-3'-methoxy-tyramine displayed acetylcholinesterase (AChE) inhibitory effects with IC₅₀ values of 7.41 ± 1.76 μM and 9.21 ± 0.89 μM, respectively. Molecular docking simulations revealed that (-)-(7'S)-N-feruloyltyramine A had a binding site for AChE. These findings reveal the structural diversity of the bioactive compounds in S. lyratum and provides insights into the use of this information for the production of functional components in the pharmaceutical industry.

Highly oxygenated germacrane-type sesquiterpenoids from the whole plant of Salvia cavaleriei H.Lév. and their biological activities

The entire plant Salvia cavaleriei H.Lév. (Lamiaceae) is used as a traditional Chinese herbal medicine. Its leaves are edible, and the flowers can be soaked in water to make a health-care tea. In an effort to find natural bioactive chemical components, twelve undescribed germacrane-type sesquiterpenoids, salcavalins A-L, were isolated from the whole plant of S. cavaleriei and were identified as analogs. This is the first study to isolate highly oxygenated germacrane-type sesquiterpenoids from this plant. The structures of these undescribed compounds were elucidated by various spectroscopic methods, and their absolute configurations were confirmed by single-crystal X-ray diffraction analysis with Cu Kα radiation and electronic circular dichroism calculations. The biological activity of these undescribed compounds on the production of tumor necrosis factor-alpha in lipopolysaccharide induced NR8383 cells was evaluated, and salcavalins I and K showed anti-inflammatory activity to some extent. Salcavalins A-C, F and L were found to be neuroprotective with antiparkinsonic potential in a nematode (Caenorhabditis elegans) model. In addition, salcavalins F and I displayed marked phytotoxic activity against radish seeds at a low concentration of 50 ppm. Our findings provide scientific justification to show that bioactive sesquiterpenoids from the edible herb have anti-inflammatory in vitro, neuroprotective and phytotoxic activities.

Insights into accumulation of active ingredients and rhizosphere microorganisms between Salvia miltiorrhiza and S. castanea

Salvia miltiorrhiza is an important traditional herbal medicine, and its extracts could be used for treating cardiovascular disease. Although these medicinal compounds are functionally similar, their wild relative, S. castanea, produces significantly different concentrations of these compounds. The reason for their differences is still unknown. In a series of soil and plant-based analyses, we explored and compared the rhizosphere microbiome of S. miltiorrhiza and S. castanea. To further investigate the geographical distribution of S. castanea, MaxEnt models were used to predict the future suitable habitat areas of S. castanea in China. Results revealed the distributions and structure of the rhizosphere microbial community of S. miltiorrhiza and S. castanea at different times. In addition, differences in altitude and soil moisture resulting from changes in climate and geographical location are also critical environmental factors in the distribution of S. castanea. The findings of this study increase our understanding of plant adaptation to their geographical environment through secondary metabolites. It also highlights the complex interplay between rhizospheric factors and plant metabolism, which provides the theoretical basis for the cultivation of S. miltiorrhiza and the use of S. castanea resources.

Caesalpinbondin A, a Novel Diterpenoid Lactone With an Unprecedented Carbon Skeleton from the Seeds of Caesalpinia bonduc

One novel diterpenoid lactone named caesalpinbondin A (1) that possesses an unprecedented tetracyclic ring system in which a 6/6/5-fused tricyclic ring and a 4,5-dimethyldihydrofuran-2(3H)-one were connected by a C-C single bond comprising a 5-(naphtho [2,3-b]furan-7-yl)dihydrofuran-2(3H)-one moiety was isolated from the seeds of Caesalpinia bonduc. Its chemical structure was established by extensive spectroscopic methods, and its absolute configuration was further determined by single-crystal X-ray diffraction analysis and electronic circular dichroism calculation. The biological evaluation suggested that compound 1 demonstrated potent anti-Alzheimer’s disease (AD) bioactivity, which could delay paralysis of transgenic AD Caenorhabditis elegans. A possible biogenetic pathway of 1 was also proposed.

Natural Bioactive Products and Alzheimer’s Disease Pathology: Lessons from Caenorhabditis elegans Transgenic Models

Alzheimer’s disease (AD) is an age-dependent, progressive disorder affecting millions of people. Currently, the therapeutics for AD only treat the symptoms. Although they have been used to discover new products of interest for this disease, mammalian models used to investigate the molecular determinants of this disease are often prohibitively expensive, time-consuming and very complex. On the other hand, cell cultures lack the organism complexity involved in AD. Given the highly conserved neurological pathways between mammals and invertebrates, Caenorhabditis elegans has emerged as a powerful tool for the investigation of the pathophysiology of human AD. Numerous models of both Tau- and Aβ-induced toxicity, the two prime components observed to correlate with AD pathology and the ease of performing RNA interference for any gene in the C. elegans genome, allow for the identification of multiple therapeutic targets. The effects of many natural products in main AD hallmarks using these models suggest promising health-promoting effects. However, the way in which they exert such effects is not entirely clear. One of the reasons is that various possible therapeutic targets have not been evaluated in many studies. The present review aims to explore shared therapeutical targets and the potential of each of them for AD treatment or prevention.